QUIPAZINE AND LIGHT HAVE SIMILAR EFFECTS ON C-FOS INDUCTION IN THE RAT SUPRACHIASMATIC NUCLEUS

The effects of the serotonin agonist, quipazine, on the induction of c -fos in the suprachiasmatic nucleus of the rat was examined at differe nt times of the 24 h cycle. Quipazine administered at night induced Fo s production in a dose dependent manner (1, 3, 10, 30 mu mol/kg) in th e ventrolateral portion of the suprachiasmatic nucleus at ZT18. Admini stration of the highest dose at other times resulted in c-fos inductio n at ZT15 but not at other times of the day or subjective day examined (CT6 and ZT12). When compared to the effects of light pulses (2 lux/1 min), quipazine only caused c-fos induction at times when light cause d induction. Our results support a role of serotonergic pathways in th e transmission or modulation of photic information from the retina to the suprachiasmatic nucleus of the rat. (C) 1997 Elsevier Science B.V.