A SYNERGISTIC INTERACTION BETWEEN HISTAMINE AND VASOACTIVE-INTESTINAL-PEPTIDE (VIP) ON CYCLIC-AMP PRODUCTION IN THE CHICK PINEAL-GLAND

The effects of vasoactive intestinal peptide (VIP) and histamine, alon e and in combination, on cyclic AMP formation have been studied in sel ected tissues of the central nervous system (CNS) of chick. VIP strong ly stimulated cyclic AMP production in the pineal gland, moderately in the retina (maintained in ''eye-cup'' preparations), and had no effec t in cerebral cortical slices. Combination of VIP with forskolin produ ced a synergistic response in the pineal gland; in the cerebral cortex VIP did not influence the elevation of cyclic AMP production evoked b y forskolin, histamine and isoprenaline. Histamine stimulated cyclic A MP synthesis in the all tested CNS tissues, showing the following orde r of sensitivity to the amine: pineal gland > cerebral cortex > retina . The effects of histamine were stronger in the presence of forskolin. A combination of VIP and histamine produced the cyclic AMP response i n the pineal gland clearly more than additive; such a synergistic inte raction was antagonized by aminopotentidine, an accepted in mammals H- 2-histamine receptor blocker. It is concluded that both VIP and histam ine can be considered as functionally important neuromodulators in avi ans (similar to mammalian species). These two substances may play in c oncert to regulate the pineal physiology in avian species.