Comparative distribution of mRNA encoding the growth hormone secretagogue-receptor (GHS-R) in Microcebus murinus (Primate, Lemurian) and rat forebrain and pituitary

The forebrain and pituitary sites of synthesis of growth hormone secretagog ue-receptor mRNA were identified in four adult lemurs (Microcebus murinus) by in situ hybridisation performed with a radiolabeled cRNA probe transcrib ed from human Growth Hormone Secretagogue-Receptor cDNA. The cRNA sense and antisense probes were hybridised to cryostat sections containing structure s extending from the rostral hypothalamus to its caudal Limit as defined by the mammillary bodies. The pituitary gland and areas adjacent to the hypot halamus were also analyzed. For comparative purposes, sections from five ad ult rats containing these structures were hybridised with the same probes. The results point to a widespread distribution of Growth Hormone Secretagog ue-Receptor mRNA in the hypothalamus, hippocampal formation, and cerebellar cortex of both lemurs and rats. As in the rat, specific hybridisation was particularly dense in the arcuate nucleus. Significant species differences were observed in the periventricular nucleus, the ventromedial nucleus, the lateral hypothalamic area, and the pituitary gland. In contrast to the rat , the lemur exhibited marked labelling in the infundibular nucleus, the per iventricular nucleus and the pars tuberalis of the pituitary gland, whereas no labeling was detectable in the ventromedial nucleus and the lateral hyp othalamic area. These results are discussed in terms of difference between the control of growth hormone secretion, feeding behaviour and seasonal rhy thmicity among murine species and primates. J. Comp. Neurol. 429:469-489, 2 001. (C) 2001 Wiley-Liss, Inc.