DISTRIBUTION OF NEUROPEPTIDE-Y RECEPTOR EXPRESSION IN THE RAT SUPRACHIASMATIC NUCLEUS

Neurones of the suprachiasmatic nucleus constitute the mammalian circa dian clock which receives photic information via the retino-hypothalam ic tract and to some extent non-photic information via the geniculo-hy pothalamic tract. The majority of neurones in the geniculo-hypothalami c tract contains neuropeptide Y and both in vitro and in vivo physiolo gical experiments have demonstrated that neuropeptide Y administered d irectly into the suprachiasmatic nucleus has the capacity to phase-shi ft the endogenous circadian rhythm of these neurones. The recent cloni ng of multiple mammalian neuropeptide Y receptors enabled us to perfor m an in situ hybridization histochemical study identifying expression of distinct neuropeptide Y receptor encoding mRNAs in the suprachiasma tic nucleus. It was seen that Y1 and Y5 receptor mRNA is highly expres sed in neurones of the ventrolateral portion of the suprachiasmatic nu cleus while neither Y2 nor Y4 receptor mRNA could be detected in the n ucleus. These experiments demonstrate that post-synaptic neuropeptide Y mediated events in the suprachiasmatic nucleus are likely to be medi ated by either of these receptors. (C) 1998 Elsevier Science B.V. All rights reserved.