A synergistic interaction between histamine and vasoactive intestinal peptide (VIP) on cyclic AMP production in the...

The effects of vasoactive intestinal peptide (VIP) and histamine, alone and in combination, on cyclic AMP formation have been studied in selected tissues of the central nervous system (CNS) of chick. VIP strongly stimulated cyclic AMP production in the pineal gland, moderately in the retina (maintained in "eye-cup" preparations), and had no effect in cerebral cortical slices. Combination of VIP with forskolin produced a synergistic response in the pineal gland; in the cerebral cortex VIP did not influence the elevation of cyclic AMP production evoked by forskolin, histamine and isoprenaline. Histamine stimulated cyclic AMP synthesis in the all tested CNS tissues, showing the following order 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 in the pineal gland clearly more than additive; such a synergistic interaction was antagonized by aminopotentidine, an accepted in mammals H2-histamine receptor blocker. It is concluded that both VIP and histamine can be considered as functionally important neuromodulators in avians (similar to mammalian species). These two substances may play in concert to regulate the pineal physiology in avian species.