ACTIVATION OF OUTWARD CURRENT BY PITUITARY ADENYLATE-CYCLASE ACTIVATING POLYPEPTIDE IN MOUSE MICROGLIAL CELLS

In order to investigate the interaction between the nervous and immune systems, we have analyzed title effect of one of the neuropeptides, p ituitary adenylate cyclase activating polypeptide (PACAP), on microgli a; cells by the patch-clamp?mp method, Puff application of PACAP38 ont o mouse microglial sells induced an outward current in a dose-dependen t manner, Reversal potentials of the outward current were dependent on external K+ concentrations ([K+](o)) and independent of [Cl-](o). Ion channel) blockers of potassium currents, quinine) (1, mM), tetraethyl ammonium (TEA, 20 mM) and 4-aminopyridine) (4-AP, 5 mM), suppressed th e outward current with a potency order of quinine>TEA>4-AP., PACAP27 a lso induced outward current less effectively than PACAP38. A fragment of PACAP38 [PACAP(6-38)], known as an inhibit-or for PACAP38, suppress ed the outward current. These data suggest that PACAP38 activates a qu inine-sensitive K+ outward current and modulates activities in microgl ia., They indicate that. the immune system in the brain can be modulat ed bt neurotransmitters;, the mediators of neurons, (C) 1998 Wiley-Lis s, Inc.