Neuronal distribution of melanin-concentrating hormone, cocaine- and amphetamine-regulated transcript and orexin B in the brain of the Djungarian hamster (Phodopus sungorus)
Introduction
Djungarian hamsters (Phodopus sungorus) undergo a pronounced seasonal cycle in food intake, energy expenditure and body mass triggered by acclimation to short photoperiod (Morgan et al., 2003). During the entire cycle precise adjustment of seasonally appropriate food intake, energy expenditure and body mass according to a hypothetical sliding-set point (Steinlechner et al., 1983) may require communication between neuronal components controlling energy balance, photoperiodic time measurement and circadian rhythms (Klingenspor et al., 1996, Adam et al., 2000, Mercer et al., 2000, Klingenspor et al., 2000).
The primary neuronal networks integrating and coordinating the control of energy balance are mostly located in hypothalamic structures including the arcuate nucleus (ARC), the dorsomedial hypothalamic nucleus (DMH), the ventromedial hypothalamic nucleus (VMH), the lateral hypothalamic area (LHA) and the paraventricular hypothalamic nucleus (PVN). Neuronal components of the circadian timing system are distributed throughout the brain, forming a network coordinating the temporal organization of physiological processes and behavior. The primary nodes of this network include the suprachiasmatic nucleus (SCN), the intergeniculate leaflet (IGL), the median raphe nucleus (MR) and the dorsal raphe nucleus (DR). The SCN as the pacemaker of the circadian timing system receives photic input from the retina through the retinohypothalamic tract (RHT) and from the IGL through the geniculohypothalamic tract (GHT). In addition, MR and DR influence circadian rhythmicity through innervations of the SCN and IGL, respectively (Morin and Blanchard, 1995, Meyer-Bernstein and Morin, 1996).
Chemical lesions of the ARC do not have a major impact on short day mediated downregulation of food intake and body mass (Ebling et al., 1998), whereas lesions of the SCN abolish this response (Bittman et al., 1991). Hence, the circadian timing system plays an important role in the regulation of seasonal body mass cycles through communication with the hypothalamic neuronal networks controlling energy balance. Notably, direct projections from the SCN to perikarya of neurons in the LHA producing the orexigenic peptides melanin-concentrating hormone (MCH) and orexin A (OXA) and orexin B (OXB) were found in rat and human (Abrahamson et al., 2001). Recently, the neuroanatomical basis for the possible interaction of orexins and the circadian timing system was reported in the Syrian hamster (Mesocricetus auratus) and Djungarian hamster (McGranaghan and Piggins, 2001, Mintz et al., 2001). Several studies of OXA and OXB which are derived from a common pro-orexin precursor, suggest a stronger orexigenic potential of OXA (Edwards et al., 1999). The neuroanatomical tracing of differential innervation patterns for these neuropeptides may increase our understanding of functional divergence. OXA and OXB display a similar distribution pattern in rats (Sakurai et al., 1998, Edwards et al., 1999, Sahu, 2002), but no information is available on OXB in a seasonal mammal like the Djungarian hamster.
Furthermore, neurons in the LHA receive projections from the neuropeptide network of the ARC, of which anorexigenic cocaine- and amphetamine-regulated transcript (CART) represents a key factor in the regulation of seasonal body mass cycles (Adam et al., 2000, Mercer et al., 2000, Mercer et al., 2003, Mercer and Speakman, 2001). Whether the neuronal network of MCH, CART, OXA and OXB known to regulate energy balance also exerts influence on circadian behavior requires further investigation, specifically, in seasonal mammals.
The present study aimed to investigate the immunohistochemical distribution of MCH, CART and OXB in Djungarian hamsters within selected brain areas implicated in the control of food intake and circadian timekeeping processes. In addition, dual-labeling immunostaining was performed to examine the relationship between these neuropeptides.
Section snippets
Tissue preparation
Adult male Djungarian hamsters (Phodopus sungorus, n = 10) were kept at room temperature in a natural photoperiod and were housed individually in Macrolon cages with free access to water and standard breeding chow diet (Altromin 7014; Altromin, Lage, Germany). Brains were collected in the month of May (14:10 light:dark) when hamsters weighed 47–55 g and had fully developed their dark-gray summer pelage. Hamsters were killed by CO2 exposure between 13:00 and 14:00 h. Brains were dissected, fixed in
Antibody specificity
In control sections incubated with pre-adsorbed antibodies or without primary antibodies, the MCH-, CART- and OXB-ir were absent (Fig. 1a, Fig. 2a and Fig. 3a). In addition, comparing immunofluorescence and HRP-peroxidase detection a similar staining pattern was observed for all antisera. However the immunoreactivity for fibers and axon terminals appeared stronger by immunofluorescence.
MCH immunoreactivity
MCH-ir cell profiles were distributed exclusively within the hypothalamus including LHA, DMH, zona incerta
Discussion
The distribution of MCH-, CART- and OXB-ir elements as well as their neuroanatomical relationship was examined in the Djungarian hamster, a seasonal photoperiodic mammal. We focused on selected brain regions harbouring neuroendocrine pathways involved in the control of either energy balance or circadian rhythmicity.
In the current study, MCH-ir perikarya were present in several hypothalamic structures implicated in the regulation of energy balance including LHA, ZI, DMH and PHA. A similar
Acknowledgment
This study was supported by the Deutsche Forschungsgemeinschaft (KL973-5) and the Danish Research Agency.
References (46)
Hypothalamic cocaine- and amphetamine-regulated transcript (CART) neurons: histochemical relationship to thyrotropin-releasing hormone, melanin-concentrating hormone, orexin/hypocretin and neuropeptide Y
Brain Res.
(1999)- et al.
Short photoperiod reduces leptin gene expression in white and brown adipose tissue of Djungarian hamsters
FEBS Lett.
(1996) - et al.
Independent feeding and metabolic actions of orexins in mice
Biochem. Biophys. Res. Commun.
(1998) - et al.
Orexin A-like immunoreactivity in the hypothalamus and thalamus of the Syrian hamster (Mesocricetus auratus) and Siberian hamster (Phodopus sungorus), with special reference to circadian structures
Brain Res.
(2001) - et al.
Early regulation of hypothalamic arcuate nucleus CART gene expression by short photoperiod in the Siberian hamster
Regul. Pept.
(2003) - et al.
Hypothalamic neuropeptide mechanisms for regulating energy balance: from rodent models to human obesity
Neurosci. Biobehav. Rev.
(2001) - et al.
Distribution of hypocretin-(orexin) immunoreactivity in the central nervous system of Syrian hamsters (Mesocricetus auratus)
J. Chem. Neuroanat.
(2001) - et al.
Defense of a lowered weight maintenance level by lateral hypothamically lesioned rats: evidence from a restriction-refeeding regimen
Physiol. Behav.
(1977) - et al.
Distribution of orexin neurons in the adult rat brain
Brain Res.
(1999) - et al.
Effects of cocaine- and amphetamine-regulated transcript peptide, leptin and orexins on hypothalamic serotonin release
Eur. J. Pharmacol.
(2001)
Interactions of neuropeptide Y, hypocretin-I (orexin A) and melanin-concentrating hormone on feeding in rats
Brain Res.
Orexins and orexin receptors: implication in feeding behavior
Regul. Pept.
Orexins and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior [see comments]
Cell
Actions of cocaine- and amphetamine-regulated transcript (CART) peptide on regulation of appetite and hypothalamo–pituitary axes in vitro and in vivo in male rats
Brain Res.
The contribution of the median preoptic nucleus to renal sympathetic nerve activity increased by intracerebroventricular injection of hypertonic saline in the rat
Brain Res.
The suprachiasmatic nucleus projects to posterior hypothalamic arousal systems
Neuroreport
Photoperiod regulates growth, puberty and hypothalamic neuropeptide and receptor gene expression in female Siberian hamsters
Endocrinology
Orexin receptor-1 (OX-R1) immunoreactivity in chemically identified neurons of the hypothalamus: focus on orexin targets involved in control of food and water intake
Eur. J. Neurosci.
Suprachiasmatic and paraventricular control of photoperiodism in Siberian hamsters
Am. J. Physiol.
Seasonal neuroendocrine rhythms in the male Siberian hamster persist after monosodium glutamate-induced lesions of the arcuate nucleus in the neonatal period
J. Neuroendocrinol.
The effect of the orexins on food intake: comparison with neuropeptide Y, melanin-concentrating hormone and galanin
J. Endocrinol.
Characterization of CART neurons in the rat and human hypothalamus
J. Comp. Neurol.
The Edinger-Westphal nucleus: sources of input influencing accommodation, pupilloconstriction, and choroidal blood flow
J. Comp. Neurol.
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2013, Journal of Chemical NeuroanatomyCitation Excerpt :A small number of orexinergic neurons have been reported in this region in kangaroo (Yamamoto et al., 2006), a range of rodent species (Broberger et al., 1998; Cutler et al., 1999; Novak and Albers, 2002; Nixon and Smale, 2007; Bhagwandin et al., 2011a), cat (Wagner et al., 2000), sheep (Iqbal et al., 2001), pig (Ettrup et al., 2010), rock hyrax (Gravett et al., 2011), giraffe and harbour porpoise (Dell et al., 2012), four-toed sengi and giant otter shrew (Calvey et al., 2013), and human (Thannikal et al., 2007). Interestingly, the orexinergic neurons forming the optic tract cluster were not observed in the brains of hamsters (Mintz et al., 2001; McGranaghan and Piggins, 2001; Khorooshi and Klingenspor, 2005; Vidal et al., 2005), or in any of the microchiropteran species studied previously (Kruger et al., 2010a). Thus, the phylogenetic variance in the occurrence of these neurons lends support to the concept of assigning these neurons as a specific nucleus.