| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Rudolf Magnus Institute of Neuroscience, Department of Pharmacology and Anatomy, University Medical Centre Utrecht, Universiteitsweg 100, 3584 CG, Utrecht, The Netherlands
(Requests for offprints should be addressed to R A H Adan; Email: RAHAdan{at}med.uu.nl)
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and methodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
There are at least two different populations of first-order neurons in the ARC. One population contains the orexigenic neuropeptides agouti-related protein (AgRP) and neuropeptide Y (NPY). Expression of AgRP and NPY is suppressed in states of positive energy balance when leptin and insulin levels are high.
In contrast, leptin and insulin stimulate the expression of pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART), which are co-expressed in the second group of first-order neurons in the ARC. POMC is the precursor of the melanocortin peptide 
-melanocyte-stimulating hormone (-MSH), which, like CART, has an inhibitory effect on food intake (reviewed in Hillebrand et al. 2002, Leibowitz & Wortley 2004).
AgRP and NPY mRNA expression is increased during 1–7 days of fasting and after food restriction in mice (Hahn et al. 1998, Mizuno et al. 1998, Mizuno & Mobbs 1999, Morton et al. 2004) and rats (Brady et al. 1990, Korner et al. 2001, Bertile et al. 2003, Bi et al. 2003, Wolden-Hanson et al. 2004). Both AgRP and NPY are upregulated in the leptin-deficient ob/ob mouse (Shutter et al. 1997, Mizuno et al. 1998, Mizuno & Mobbs 1999, Yamamoto et al. 1999, Tritos et al. 2001). The effects of fasting on arcuate POMC and CART expression are less pronounced. POMC and CART expression is unchanged or decreased after 1–7 days of fasting in rats (Brady et al. 1990, Kristensen et al. 1998, Kaneda et al. 2001, Korner et al. 2001, Li et al. 2002, Savontaus et al. 2002, Bertile et al. 2003, Bi et al. 2003, Wolden-Hanson et al. 2004). In ob/ob mice, POMC and CART levels are decreased relative to wild-type mice (Mizuno et al. 1998). Also nociceptin, a neuropeptide with orexigenic properties, is expressed in the ARC (reviewed in Olszewski & Levine 2004). However, nociceptin expression is not increased after a 16 h fast (Rodi et al. 2002). Taken together, first-order neurons are strongly regulated by disturbances in energy balance, which is most explicit in the increased AgRP and NPY expression during fasting and the increased POMC and CART expression by leptin.
Neuropeptides expressed in second-order neurons include CART (PVN, LHA & DMH), melanin-concentrating hormone (MCH; co-expressed with CART in the LHA), orexins (LHA), corticotropin-releasing hormone (CRH; PVN) and nociceptin (PVN, LHA, VMH and DMH). MCH, orexins and nociceptin stimulate food intake (although less when compared with NPY), whereas CRH is an anorexigenic neuropeptide (Hillebrand et al. 2002, Leibowitz & Wortley 2004, Olszewski & Levine 2004).
The regulation of neuropeptide expression in second-order neurons by disturbances in energy balance is less prominent than in first-order neurons. Fasting results in elevated or unchanged expression of MCH and orexin in the LHA (Presse et al. 1996, Qu et al. 1996, Herve & Fellmann 1997, Sakurai et al. 1998, Cai et al. 1999, Lopez et al. 2000, Swart et al. 2001, Tritos et al. 2001, Bertile et al. 2003, Akiyama et al. 2004, Morton et al. 2004). In ob/ob mice MCH expression is upregulated, whereas orexin expression has been reported to be either downregulated or unaffected (Qu et al. 1996, Yamamoto et al. 1999, 2000, Tritos et al. 2001). As in the ARC, nociceptin expression in the PVN and the LHA was unchanged after a 16 h fast (Rodi et al. 2002). Expression of anorexigenic CRH in the PVN was either decreased or unchanged following fasting or food restriction (Brady et al. 1990, Kiss et al. 1994, Ahima et al. 1999, Fekete et al. 2000, Kaneda et al. 2001). Also CART expression in the PVN is decreased after fasting, whereas CART expression in the LHA remains unaffected (Li et al. 2002, Wolden-Hanson et al. 2004). The discrepancies in the nature and extent of regulation of neuropeptide expression following fasting suggest that factors other than energy balance per se influence gene regulation of these neuropeptides. These discrepancies may be explained by differences in the animals like strain, sex or age, and differences in experimental conditions, which besides the length of the fasting period may include single or group housing, circadian time of killing animals and environmental conditions such as the presence of a running-wheel.
Activity-based anorexia (ABA) is an animal model that is used to study aspects of anorexia nervosa. In this model, rats are given free access to a running-wheel and are at the same time exposed to a restricted feeding schedule. As a consequence, rats become hyperactive and decrease their food intake (Routtenberg & Kuznesof 1967). Depending on, amongst others, the severity of the feeding schedule, rats lose more than 25% of their body weight within a week upon exposure to the ABA model (Burden et al. 1993, Kas et al. 2003) and eventually will not survive (Routtenberg & Kuznesof 1967, Kas et al. 2003). A hallmark of ABA is not only the development of hyperactivity, but also the shift in activity patterns. ABA rats display substantial activity during the period preceding scheduled feeding. This food-anticipatory activity (FAA) seems crucial for the development of ABA (Dwyer & Boakes 1997). ABA also results in activation of the hypothalamo–pituitary–adrenal (HPA) axis, which manifests itself in increased adrenal weight and plasma corticosterone levels (Burden et al. 1993). As yet there is no conclusive theory explaining the mechanism behind the paradox of self-starvation and hyperactivity leading to physical collapse in ABA.
Little is known about the regulation of the hypothalamic neuropeptides that are involved in the regulation of feeding behaviour and energy balance (e.g. candidate neuropeptides) during ABA. After a week of exposure to the ABA model, POMC expression in the ARC is decreased whereas arcuate AgRP expression in strongly upregulated (Kas et al. 2003). CRH expression in the PVN is unchanged when rats are exposed to ABA until they reach a relative body weight of 75% (Burden et al. 1993). The problem is that in both of those studies rats had already developed severe ABA. The aim of the present study was to investigate the regulation of candidate hypothalamic neuropeptides in first- and second-order neurons during the earlier stages of the development of ABA and to compare these results with those of sedentary food-restricted rats. To this extent, rats were killed at the end of the fourth day of exposure to the ABA model, before they entered a state of severe emaciation. Neuropeptide mRNA expression levels were then measured using quantitative real-time PCR (qPCR) on punches containing separate hypothalamic regions.
|
Materials and methods |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Female outbred Wistar WU rats (n=32, synchronised for oestrous cycle; Harlan, Horst, The Netherlands) weighing approximately 160 g upon arrival were individually housed under a 12 h light:12 h darkness cycle in a room with constant ambient temperature (21 ± 2 °C). Rats were allowed to habituate to this environment for 2 weeks, during which food and water were available freely. After these 2 weeks, 16 rats were placed in cages containing a running-wheel for a 10 day adaptation period while the 16 other rats were left in their home cages. Food and water remained available freely. After this 10 day adaptation period, both running and sedentary rats were divided into two groups matched for 4 day running-wheel activity (RWA; average days –4/–1: 5730 ± 753 revolutions) and body weight (average day –1: 215–1.6 g). For both running and sedentary rats, one group retained free access to food and water while the other group was exposed to a feeding schedule in which food was available for 1 h at the onset of the dark phase only. Figure 1
shows a schedule of the experiment. Body weight was measured just before the onset of the dark phase, and just before food access in the food-restricted groups. RWA was continuously monitored using a Cage Registration program (Department of Biomedical Engineering, UMC Utrecht, The Netherlands). Rats were sacrificed by decapitation at the end of the light phase of day 3. Trunk blood was collected into tubes containing lithium-heparin (Sarstedt, Nümbrecht, Germany) with 83 µmol EDTA and 1 mg aprotonin. Tubes were collected on ice until centrifugation (20 min at 2600 g at 4 °C); subsequently plasma was stored at –20 °C until further processing. Brains were quickly removed, frozen in cold isopentane and stored at –80 °C. Retroperitoneal white adipose tissue (WAT) and WAT surrounding the oviducts, interscapular brown adipose tissue (BAT) and adrenals were collected and weighed.
|
RIAs
Plasma leptin and insulin were measured using commercially available rat RIA kits, according to the manufacturer’s protocol (Linco Research, St Charles, MO, USA).
Microdissection
Coronal sections of 300 µm thickness were cut from frozen rat brains in a cryostat at approximately –8 °C, transferred to a flexible black rubber strip and immediately covered with RNAlater reagent (Ambion Europe, Huntingdon, UK). Punches containing the selected hypothalamic regions were taken with a stainless steel punch needle of 2 mm diameter (Zivic Laboratories, Pittsburgh, PA, USA). For each region, punches were pooled for each individual rat. Specific sections from which punches were taken based on the rat brain atlas coordinates of Paxinos & Watson (1998). PVN punches (n=4 per rat) were taken from two adjacent sections between –1.7 and –2.4 mm relative to bregma. ARC punches (n=3 per rat) were taken from three subsequent sections between –2.6 and –3.8 mm relative to bregma. LHA punches (n=4 per rat) were taken from two adjacent sections between –3.0 and –3.8 mm relative to bregma, from the same sections as from which ARC punches were taken. Punches were stored at 4 °C in RNAlater for a maximum of 48 h until further processing.
RNA isolation and cDNA synthesis
RNA was extracted using TRIzol reagent (Invitrogen, Carlsbad, CA, USA) according to the manufacturer’s instructions. The quality of the RNA was determined by agarose gel electrophoresis. RNA quality of samples was regarded acceptable for further use if the 18S and 28S ribosomal RNAs appeared intact. cDNA was synthesised from total RNA that had been treated with RNase free DNaseI (Roche, Mannheim, Germany) using SuperScript II reverse transcriptase and oligo dT12–18 primers (Invitrogen). No dithiothreitol was used in the reaction as it may negatively influence the efficiency of the subsequent PCRs (Lekanne Deprez et al. 2002).
qPCR
qPCR was performed using a LightCycler instrument and the LightCycler FastStart DNA Master SYBR Green I reaction mix (Roche), according to the manufacturer’s instructions. Reactions were performed in a total volume of 10 µl containing 2 µl cDNA, 2–5 mM MgCl2, 0.5 µM of each primer and 1 µl of the SYBR Green reaction mix. Primer sequences were taken from the literature or designed with Primer3 software using settings recommended in the LightCycler manual. For each primer pair, annealing temperature and MgCl2 concentration were optimised. PCR efficiencies were obtained from standard curves of serial cDNA dilutions over three to four orders of magnitude. Primer sequences, annealing temperatures, MgCl2 concentrations and PCR efficiencies are listed in Table 1. Specificity of the PCRs were verified using melting curve analysis and agarose gel electrophoresis, confirming the formation of a single PCR product of the expected length. cDNA samples from separate nuclei from single rats were measured in duplicate. Cycle threshold values were obtained using the second derivative maximum method in the LightCycler software. Gene expression was calculated as normalised ratio (Rn), which is a measure of the amount of cDNA present in a sample relative to a calibrator sample measured in the same qPCR experiment and normalised to a reference gene. For each nucleus studied, a pool from cDNAs from that nucleus was used as calibrator sample. Cyclophilin was used as reference gene (Medhurst et al. 2000).
|
All data are presented as means ± S.E.M. Statistical analysis was performed using SPSS 11.5 software. Total RWA, food intake, food intake on day 3, WAT and BAT weights and relative adrenal weights were analysed by ANOVA using Bonferroni’s post-hoc test. Relative body weight was analysed by GLM repeated-measures analysis followed by ANOVA and Bonferroni’s post-hoc test. Except for nociceptin, neuropeptide mRNA expression levels between freely fed and food-restricted rats were analysed using a one-sided t-test as expression of these neuropeptides has been shown to be consistently either up- or downregulated upon fasting or food restriction. Nociceptin levels were compared using a two-sided t-test. Plasma leptin and insulin levels between freely fed vs food-restricted rats, as well as between freely fed sedentary vs running rats, were analysed using a one-sided t-test. Differences were considered significant at P<0.05. Correlations between physiological parameters and neuropeptide expression levels were determined using Pearson’s bivariate correlation analysis.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Rats with access to running-wheels developed anticipatory activity before the scheduled hour of feeding (Fig. 2), while total RWA over the food restriction period was not significantly increased (P=0.163, t-test) in food-restricted rats relative to freely fed running rats (Table 2). Over the 4 days during which rats were subjected to the model, as well as in the last feeding period before the experiment was stopped, rats in running-wheels did not eat less than food-restricted sedentary rats (Table 2). The relative body weights of food-restricted rats decreased over time. This effect was stronger in running rats than in sedentary rats (Fig. 3). Available WAT and BAT stores decreased following food restriction. WAT stores were also decreased in freely fed running rats as compared with freely fed sedentary rats. Relative adrenal weight was increased following food restriction in running rats. Relative adrenal weight was also increased in freely fed running rats as compared with freely fed sedentary rats (Table 2).
|
|
|
As shown in Fig. 4, AgRP and NPY mRNA expression levels in the ARC were significantly increased in both sedentary and running food-restricted rats as compared with freely fed rats. This effect was stronger in the running animals, in which AgRP and NPY were increased 4.8- and 5.4-fold respectively vs 2.3- and 1.7-fold in the sedentary groups.
|
for all experimental groups. The anorexigenic neuropeptides in the ARC, POMC and CART were both significantly downregulated in restricted running rats (2.1- and 1.5-fold respectively), but only CART was significantly downregulated in restricted sedentary rats (1.6-fold) as compared with freely fed rats. Expression levels of nociceptin in the ARC, as well as expression levels of CART, CRH and nociceptin in the PVN and of prepro-orexin and CART in the LHA were not significantly different in both sedentary and running food-restricted animals as compared with freely fed rats. A small but significant upregulation of MCH (1.3-fold) was found in the LHA of food-restricted running rats but not in food-restricted sedentary rats. Both plasma leptin and insulin levels were reduced in food-restricted groups. In freely fed running rats, plasma leptin and insulin levels were lower than in freely fed sedentary rats (Fig. 4
).
|
The variations in gene expression levels of AgRP and NPY were especially large in the group of food-restricted running rats (Fig. 4). In order to investigate to what extent variability in AgRP and NPY mRNA expression were explained by differences in body weight loss between rats, correlation analysis was performed within this group. AgRP and NPY gene expression levels showed a strong negative correlation with relative body weight and WAT mass (Table 3), but not with insulin, whereas correlation analysis with plasma leptin levels did not reach significance (P=0.051 for AgRP and P=0.054 for NPY). Moreover, expression levels of AgRP and NPY were strongly correlated (r=0.995, P<0.001, n=8) within the group of food-restricted running rats, as well as in the other groups (data not shown).
|
Expression levels of MCH and CART, which are co-localised in second-order neurons in the LHA, were significantly correlated in all groups except the food-restricted running rats (Table 4).
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Body composition was different between freely fed sedentary rats and freely fed running rats, the latter having less WAT, but equal body weight (Table 2, Fig. 3). Therefore, the effects of food restriction were compared within the running and sedentary groups separately.
In both running and sedentary food-restricted rats, AgRP and NPY mRNAs were increased. The upregulation was stronger in the running rats, reflecting a stronger negative energy balance in these animals. Correlation analysis within the group of running food-restricted rats showed that both AgRP and NPY expression levels are negatively correlated with relative body weight and WAT. This indicates that AgRP and NPY expression is dependent on the availability of energy stores. The fact that we found no correlation between AgRP or NPY mRNA levels and plasma insulin and leptin levels within this group of rats, may have been caused by the fact that all rats within this group had similarly low levels of these hormones. The negative correlation between the expression of AgRP and NPY and WAT correlates with a strong reduction in the level of circulating leptin, which is produced by adipose tissue (reviewed in Mohamed-Ali et al. 1998) and is reduced in ABA (Hillebrand et al. 2005). There was also a strong correlation between AgRP and NPY expression levels in all groups. Taken together, it can be concluded that the expression of AgRP and NPY is co-regulated and increases during the development of ABA, which is an adequate response to negative energy balance. Interestingly, AgRP and NPY expression levels in the ARC did not differ between running and sedentary freely fed rats, despite significant differences in plasma leptin and insulin levels between these groups. This indicates that factors other than leptin and insulin regulate expression of these mRNAs.
Expression of the anorexigenic neuropeptides POMC and CART was downregulated in the ARC of food-restricted running rats. Thus, as for AgRP and NPY, expression of POMC and CART in the ARC appears to be regulated in an adequate manner during the development of ABA. However, although POMC and CART are co-localised in the same arcuate neurons, only CART was significantly downregulated in the ARC of food-restricted sedentary rats and expression levels of POMC and CART did not correlate in any of the groups. This suggests that regulation of expression between POMC and CART is more differentiated than regulation of AgRP and NPY, which are strongly co-regulated by leptin and energy balance. Interestingly, plasma leptin levels were positively correlated with CART mRNA but not with POMC mRNA in the ARC when data from all groups were pooled together. Thus, other factors besides energy balance and leptin may regulate POMC expression in the ARC. One such factor may be the serotonin system, since POMC/CART neurons are activated by stimulation of the serotonin 5HT2C receptors that are expressed on the majority of these neurons (Heisler et al. 2002).
In the present study, expression of nociceptin in the ARC was not changed during chronic food restriction. This is in line with the effect of short term (16 h) food restriction, which does not lead to changed nociceptin expression either (Rodi et al. 2002). However, correlation analysis showed that arcuate nociceptin expression was negatively correlated with relative body weight and WAT mass in food-restricted running rats. This may indicate that arcuate nociceptin expression is upregulated during strong negative energy balance, although this effect is not as strong as the regulation of AgRP and NPY.
MCH in the second-order neurons in the LHA was selectively upregulated during food restriction in running rats but not in sedentary rats, indicating that MCH expression is increased in situations of severe negative energy balance. This has also been shown by Bertile et al.(2003) who found that MCH expression during fasting was not increased until after more than 4 days of fasting. Nociceptin expression was modestly increased in the LHA of food-restricted running rats, but expression of the other neuropeptides studied in the LHA, CART and prepro-orexin, was not changed during food restriction in either sedentary or running rats. This is in accord with data obtained after 48 and 16 h of fasting for CART and nociceptin respectively (Li et al. 2002, Rodi et al. 2002) and with reports on prepro-orexin regulation during food restriction (Cai et al. 1999, Akiyama et al. 2004). Thus, in contrast to first-order neurons in the ARC, in second-order neurons in the LHA, only MCH expressions and nociceptin are regulated by strong negative energy balance. Strong negative energy balance also dissociates the regulation of MCH and CART in the LHA. Therefore, factors other than energy status may play a more important role in regulating neuropeptides in second-order neurons in the LHA. For instance, MCH expression is inhibited by oestrogen (Murray et al. 2000, Mystkowski et al. 2000).
Food restriction did not result in changes in expression levels of CART, nociceptin and CRH in the PVN. For CART, this is in contrast with the effects of 48–72 h fasting, which decreases CART expression in the PVN (Li et al. 2002, Wolden-Hanson et al. 2004). For nociceptin this corresponds with the effect of 16 h of fasting (Rodi et al. 2002). Unchanged expression levels of CRH in the PVN in ABA have been reported before (Burden et al. 1993, Wong et al. 1993). Interestingly, CRH expression in the PVN was negatively correlated with POMC expression in the ARC in the food-restricted running animals. This is unexpected regarding previous findings. -MSH prevents fasting-induced suppression of CRH expression in the PVN (Fekete et al. 2000) and the melanocortin agonist MTII induces c-Fos expression in the PVN (Thiele et al. 1998). These findings suggest a positive correlation between POMC and CRH expression. During development of ABA, the control of CRH activation through POMC may thus be disrupted.
None of the neuropeptides that were investigated in first- and second-order neurons correlated with RWA or FAA. Since the atypical antipsychotic olanzapine, which amongst others acts on 5HT2A/C receptors, strongly reduces RWA in ABA rats (Hillebrand et al. 2005) it is likely that other systems such as the serotonin system are involved in the development of hyperactivity seen in ABA.
In conclusion, during the development of ABA, the expression of orexigenic and anorexigenic neuropeptides in primary and secondary neurons in the ARC, PVN and LHA are regulated in a way that is expected in response to negative energy balance. Kas et al.(2003) have described that the expression of melanocortin receptors in the ventromedial hypothalamus is increased during ABA. Therefore, this study does not rule out involvement of the neuropeptides that were investigated here per se in the development of ABA, since it is possible that changes in neuropeptide receptor density rather than neuropeptide expression itself contribute to the development of ABA.
|
Acknowledgements |
|---|
|
References |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Akiyama M, Yuasa T, Hayasaka N, Horikawa K, Sakurai T & Shibata S 2004 Reduced food anticipatory activity in genetically orexin (hypocretin) neuron-ablated mice. European Journal of Neuroscience 20 3054–3062.[CrossRef][Web of Science][Medline]
Berthoud HR 2004 Mind versus metabolism in the control of food intake and energy balance. Physiology and Behavior 81 781–793.[CrossRef][Medline]
Bertile F, Oudart H, Criscuolo F, Maho YL & Raclot T 2003 Hypothalamic gene expression in long-term fasted rats: relationship with body fat. Biochemical and Biophysical Research Communications 303 1106–1113.[CrossRef][Web of Science][Medline]
Bi S, Robinson BM & Moran TH 2003 Acute food deprivation and chronic food restriction differentially affect hypothalamic NPY mRNA expression. American Journal of Physiology. Regulatory, Integrative and Comparative Physiology 285 R1030–R1036.
Brady LS, Smith MA, Gold PW & Herkenham M 1990 Altered expression of hypothalamic neuropeptide mRNAs in food-restricted and food-deprived rats. Neuroendocrinology 52 441–447.[Web of Science][Medline]
Burden VR, White BD, Dean RG & Martin RJ 1993 Activity of the hypothalamic–pituitary–adrenal axis is elevated in rats with activity-based anorexia. Journal of Nutrition 123 1217–1225.
Cai XJ, Widdowson PS, Harrold J, Wilson S, Buckingham RE, Arch JR, Tadayyon M, Clapham JC, Wilding J & Williams G 1999 Hypothalamic orexin expression: modulation by blood glucose and feeding. Diabetes 48 2132–2137.[Abstract]
Dwyer DM & Boakes RA 1997 Activity-based anorexia in rats as failure to adapt to a feeding schedule. Behavioural Neuroscience 111 195–205.[Medline]
Fekete C, Legradi G, Mihaly E, Tatro JB, Rand WM & Lechan RM 2000 alpha-Melanocyte stimulating hormone prevents fasting-induced suppression of corticotropin-releasing hormone gene expression in the rat hypothalamic paraventricular nucleus. Neuroscience Letters 289 152–156.[CrossRef][Medline]
Hahn TM, Breininger JF, Baskin DG & Schwartz MW 1998 Coexpression of Agrp and NPY in fasting-activated hypothalamic neurons. Nature Neuroscience 1 271–272.[CrossRef][Web of Science][Medline]
Heisler LK, Cowley MA, Tecott LH, Fan W, Low MJ, Smart JL, Rubinstein M, Tatro JB, Marcus JN, Holstege H et al. 2002 Activation of central melanocortin pathways by fenfluramine. Science 297 609–611.
Herve C & Fellmann D 1997 Changes in rat melanin-concentrating hormone and dynorphin messenger ribonucleic acids induced by food deprivation. Neuropeptides 31 237–242.[CrossRef][Web of Science][Medline]
Hillebrand JJ, de Wied D & Adan RA 2002 Neuropeptides, food intake and body weight regulation: a hypothalamic focus. Peptides 23 2283–2306.[CrossRef][Web of Science][Medline]
Hillebrand JJ, van Elburg AA, Kas MJ, van Engeland H & Adan RA 2005 Olanzapine treatment reduces hyperactivity in activity-based anorexia: possible implications for the treatment of anorexia nervosa. Biological Psychiatry (In Press).
Johren O, Neidert SJ, Kummer M & Dominiak P 2002 Sexually dimorphic expression of prepro-orexin mRNA in the rat hypothalamus. Peptides 23 1177–1180.[CrossRef][Web of Science][Medline]
Kaneda T, Makino S, Nishiyama M, Asaba K & Hashimoto K 2001 Differential neuropeptide responses to starvation with ageing. Journal of Neuroendocrinology 13 1066–1075.[CrossRef][Web of Science][Medline]
Kas MJ, van Dijk G, Scheurink AJ & Adan RA 2003 Agouti-related protein prevents self-starvation. Molecular Psychiatry 8 235–240.[CrossRef][Web of Science][Medline]
Kiss A, Jezova D & Aguilera G 1994 Activity of the hypothalamic pituitary adrenal axis and sympathoadrenal system during food and water deprivation in the rat. Brain Research 663 84–92.[CrossRef][Web of Science][Medline]
Korner J, Savontaus E, Chua SC Jr, Leibel RL & Wardlaw SL 2001 Leptin regulation of Agrp and Npy mRNA in the rat hypothalamus. Journal of Neuroendocrinology 13 959–966.[CrossRef][Web of Science][Medline]
Kristensen P, Judge ME, Thim L, Ribel U, Christjansen KN, Wulff BS, Clausen JT, Jensen PB, Madsen OD, Vrang N et al. 1998 Hypothalamic CART is a new anorectic peptide regulated by leptin. Nature 393 72–76.[CrossRef][Medline]
Leibowitz SF & Wortley KE 2004 Hypothalamic control of energy balance: different peptides, different functions. Peptides 25 473–504.[CrossRef][Web of Science][Medline]
Lekanne Deprez RH, Fijnvandraat AC, Ruijter JM & Moorman AF 2002 Sensitivity and accuracy of quantitative real-time polymerase chain reaction using SYBR green I depends on cDNA synthesis conditions. Analytical Biochemistry 307 63–69.[CrossRef][Web of Science][Medline]
Li HY, Hwang HW & Hu YH 2002 Functional characterizations of cocaine- and amphetamine-regulated transcript mRNA expression in rat hypothalamus. Neuroscience Letters 323 203–206.[CrossRef][Web of Science][Medline]
Lopez M, Seoane L, Garcia MC, Lago F, Casanueva FF, Senaris R & Dieguez C 2000 Leptin regulation of prepro-orexin and orexin receptor mRNA levels in the hypothalamus. Biochemical and Biophysical Research Communications 269 41–45.[CrossRef][Web of Science][Medline]
Marie-Claire C, Laurendeau I, Canestrelli C, Courtin C, Vidaud M, Roques B & Noble F 2003 Fos but not Cart (cocaine and amphetamine regulated transcript) is overexpressed by several drugs of abuse: a comparative study using real-time quantitative polymerase chain reaction in rat brain. Neuroscience Letters 345 77–80.[CrossRef][Web of Science][Medline]
Medhurst AD, Harrison DC, Read SJ, Campbell CA, Robbins MJ & Pangalos MN 2000 The use of TaqMan RT-PCR assays for semiquantitative analysis of gene expression in CNS tissues and disease models. Journal of Neuroscience Methods 98 9–20.[CrossRef][Web of Science][Medline]
Mizuno TM & Mobbs CV 1999 Hypothalamic agouti-related protein messenger ribonucleic acid is inhibited by leptin and stimulated by fasting. Endocrinology 140 814–817.
Mizuno TM, Kleopoulos SP, Bergen HT, Roberts JL, Priest CA & Mobbs CV 1998 Hypothalamic pro-opiomelanocortin mRNA is reduced by fasting and [corrected] in ob/ob and db/db mice, but is stimulated by leptin. Diabetes 47 294–297.[Abstract]
Mohamed-Ali V, Pinkney JH & Coppack SW 1998 Adipose tissue as an endocrine and paracrine organ. International Journal of Obesity and Related Metabolic Disorders 22 1145–1158.
Morton GJ, Mystkowski P, Matsumoto AM & Schwartz MW 2004 Increased hypothalamic melanin concentrating hormone gene expression during energy restriction involves a melanocortin-independent, estrogen-sensitive mechanism. Peptides 25 667–674.[Web of Science][Medline]
Murray JF, Baker BI, Levy A & Wilson CA 2000 The influence of gonadal steroids on pre-pro melanin-concentrating hormone mRNA in female rats. Journal of Neuroendocrinology 12 53–59.[CrossRef][Medline]
Mystkowski P, Seeley RJ, Hahn TM, Baskin DG, Havel PJ, Matsumoto AM, Wilkinson CW, Peacock-Kinzig K, Blake KA & Schwartz MW 2000 Hypothalamic melanin-concentrating hormone and estrogen-induced weight loss. Journal of Neuroscience 20 8637–8642.
Olszewski PK & Levine AS 2004 Minireview: Characterization of influence of central nociceptin/orphanin FQ on consummatory behavior. Endocrinology 145 2627–2632.
Paxinos G & Watson C 1998 The Rat Brain in Stereotaxic Coordinates, edn 4. Academic Press, New York.
Presse F, Sorokovsky I, Max JP, Nicolaidis S & Nahon JL 1996 Melanin-concentrating hormone is a potent anorectic peptide regulated by food-deprivation and glucopenia in the rat. Neuroscience 71 735–745.[CrossRef][Web of Science][Medline]
Qu D, Ludwig DS, Gammeltoft S, Piper M, Pelleymounter MA, Cullen MJ, Mathes WF, Przypek R, Kanarek R & Maratos-Flier E 1996 A role for melanin-concentrating hormone in the central regulation of feeding behaviour. Nature 380 243–247.[CrossRef][Medline]
Rodi D, Polidori C, Bregola G, Zucchini S, Simonato M & Massi M 2002 Pro-nociceptin/orphanin FQ and NOP receptor mRNA levels in the forebrain of food deprived rats. Brain Research 957 354–361.[CrossRef][Web of Science][Medline]
Routtenberg A & Kuznesof AW 1967 Self-starvation of rats living in activity wheels on a restricted feeding schedule. Journal of Comparative and Physiological Psychology 64 414–421.[CrossRef][Web of Science][Medline]
Sakurai T, Amemiya A, Ishii M, Matsuzaki I, Chemelli RM, Tanaka H, Williams SC, Richardson JA, Kozlowski GP, Wilson S et al. 1998 Orexins and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior. Cell 92 573–585.[CrossRef][Web of Science][Medline]
Savontaus E, Conwell IM & Wardlaw SL 2002 Effects of adrenalectomy on AGRP, POMC, NPY and CART gene expression in the basal hypothalamus of fed and fasted rats. Brain Research 958 130–138.[CrossRef][Medline]
Schwartz MW, Woods SC, Porte D Jr, Seeley RJ & Baskin DG 2000 Central nervous system control of food intake. Nature 404 661–671.[Medline]
Shutter JR, Graham M, Kinsey AC, Scully S, Luthy R & Stark KL 1997 Hypothalamic expression of ART, a novel gene related to agouti, is up-regulated in obese and diabetic mutant mice. Genes and Development 11 593–602.
Swart I, Overton JM & Houpt TA 2001 The effect of food deprivation and experimental diabetes on orexin and NPY mRNA levels. Peptides 22 2175–2179.[CrossRef][Medline]
Thiele TE, van Dijk G, Yagaloff KA, Fisher SL, Schwartz M, Burn P & Seeley RJ 1998 Central infusion of melanocortin agonist MTII in rats: assessment of c-Fos expression and taste aversion. American Journal of Physiology 274 R248–R254.
Tritos NA, Mastaitis JW, Kokkotou E & Maratos-Flier E 2001 Characterization of melanin concentrating hormone and preproorexin expression in the murine hypothalamus. Brain Research 895 160–166.[CrossRef][Web of Science][Medline]
Wei R & Sternberg EM 2004 IL-1 beta-mediated neuropeptide and immediate early gene mRNA induction is defective in Lewis hypothalamic cell cultures. Journal of Neuroimmunology 146 114–125.[Medline]
Wolden-Hanson T, Marck BT & Matsumoto AM 2004 Blunted hypothalamic neuropeptide gene expression in response to fasting, but preservation of feeding responses to AgRP in aging male Brown Norway rats. American Journal of Physiology. Regulatory, Integrative and Comparative Physiology 287 R138–R146.
Wong ML, Licinio J, Gold PW & Glowa J 1993 Activity-induced anorexia in rats does not affect hypothalamic neuropeptide gene expression chronically. International Journal of Eating Disorders 13 399–405.
Yamamoto Y, Ueta Y, Date Y, Nakazato M, Hara Y, Serino R, Nomura M, Shibuya I, Matsukura S & Yamashita H 1999 Down regulation of the prepro-orexin gene expression in genetically obese mice. Brain Research. Molecular Brain Research 65 14–22.[Medline]
Yamamoto Y, Ueta Y, Serino R, Nomura M, Shibuya I & Yamashita H 2000 Effects of food restriction on the hypothalamic prepro-orexin gene expression in genetically obese mice. Brain Research Bulletin 51 515–521.[CrossRef][Web of Science][Medline]
Received 19 May 2005
Accepted 6 June 2005
This article has been cited by other articles:
|
|
 |
|
  F. Remmers, L. A. W. Verhagen, R. A. H. Adan, and H. A. Delemarre-van de Waal Hypothalamic Neuropeptide Expression of Juvenile and Middle-Aged Rats after Early Postnatal Food Restriction Endocrinology, July 1, 2008; 149(7): 3617 - 3625. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Lutter, V. Krishnan, S. J. Russo, S. Jung, C. A. McClung, and E. J. Nestler Orexin Signaling Mediates the Antidepressant-Like Effect of Calorie Restriction J. Neurosci., March 19, 2008; 28(12): 3071 - 3075. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
