Angiotensin II-induced depression of Purkinje cell firing and possible modulatory action on GABA responses

Effects of octapeptide angiotensin II (AII) were tested on cortical neurons of rat's cerebellum by means of microiontophoresis. It was observed that AII consistently depressed spontaneous firing of Purkinje cell, whereas other unidentified neurons were unaffected. When tested against responses of Purkinje cell to depressant putative neurotransmitters, namely, GABA, glycine, taurine, 5-hydroxytryptamine and noradrenaline, it was observed that AII specifically enhanced depressant action of GABA, while the responses to other substances were unaffected. Both AII-induced depression of cell firing and the AII-induced enhancement of GABA depression were antagonized by a specific GABA antagonist, bicuculline methochloride. We therefore suggest that AII exerts an inhibitory action on Purkinje cells through its modulatory action on bicuculline-sensitive GABA receptors.