PACAP and VIP in the photoneuroendocrine system (PNES).

The presence of PACAP and VIP was demonstrated in all the four levels of the photoneuroendocrine system (PNES) with the use of immunohistochemistry (IHC), radioimmunoassay (RIA), anterograde and retrograde tracing techniques, and cell immunoblot assay (CIBA). Both peptides play a physiological role in the PNES. According to our results both PACAP and VIP are involved in the regulation of the gonadotrop hormone secretion and their inhibitory role may be mediated through the neuronal chain of the PNES.