APStracts 4:0103N, 1997.

Cholecystokinin Activates CCKB-Receptor Mediated Ca-Signaling in HippocampalAstrocytes Wolfgang MŸller, Uwe Heinemann, and Karin Berlin Institut fŸr Physiologie der CharitŽ, Abt. Neurophysiologie AG Molekulare Zellphysiologie, Tucholskystr. 2, D-10117 Berlin, Germany.

APStracts 4:0103N, 1997.

ABSTRACT
Cholecystokinin-8S (CCK-8S) is the most abundant neuropeptide in the mammalian cortex and the limbic system, however, its physiological functions remained largely obscure. We studied effects of CCK on astrocytic Ca-signaling, that has met considerable interest as a second messenger in astrocytic-neuronal signaling, by digital ratio-imaging of Fura-2/AM loaded rat and mouse hippocampal astrocytes in dissociated culture. Superfusion of CCK-8S (5-50nM for 2 min) evoked repetitive Ca-increases of several hundred nM in a subpopulation of astrocytes. Mouse astrocytes appeared to be more responsive to CCK than rat cells with respect to the fraction of cells responding as well as to the amplitudes of Ca-increases. The Ca-responses persisted in the absence of extracellular Ca, indicating that release of Ca from intracellular stores is the primary source of these Ca- increases. The CCK-8S-induced Ca-increases were blocked by the CCKB receptor antagonist PD135158 (100 nM) but not by the CCKA-antagonist lorglumide (100 nM). We surmise that astrocytes might be a major primary target for CCK in the central nervous system.

Received 15 January 1997; accepted in final form 17 June  1997.
APS Manuscript Number J037-7
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 15 July 1997