Immunoreactive substance P is not part of the retinohypothalamic tract in the rat

摘要: The retinohypothalamic tract (RHT) is a monosynaptic retinofugal pathway mediating information concerning the light/dark cycle from retina to brain's biological clock located in suprachiasmatic nucleus (SCN). Light information, which daily adjusts (entrains) rhythms of behaviour and physiology generated by SCN, mediated two neurotransmitters, viz. glutamate pituitary adenylate cyclase activating polypeptide (PACAP), co-stored RHT. Substance P (SP) modulates photic- glutamate-induced phase shifts but data on its possible presence RHT are conflicting. By labelling projection SCN with anterograde tracer cholera toxin subunit B (ChB) antibodies against PACAP, we have shown that SP immunoreaction absent PACAP/ChB-labelled nerve fibres indicating SP-immunoreactive not part may originate cell bodies within SCN. In retina, immunoreactivity occurs amacrine cells inner nuclear layer, few displaced ganglion layer dense plexus terminals plexiform layer. Double immunostaining has revealed identical PACAP-immunoreactive constitute These findings together demonstration bilateral eye enucleation does decrease number indicate neurotransmitter could be an intrinsic modulating photic input clock.