GABAergic Mechanisms and Cardiovascular Function

Abstract

It has been reported that GABA affects the regulation of cardiovascular function through both the peripheral GABAergic system and central GABAergic mechanisms. Intracerebral or intraventricular administration of GABA agonists or GABA transaminase inhibitors has been shown to lower blood pressure and heart rate via central GABAergic mechanisms [1, 4, 5, 16, 19, 25]. Intravenous administration of GABA was found to lower blood pressure and to induce bradycardia in dogs [6]. In this case, it is most likely that peripheral GABA actions were responsible for changes in cardiovascular funetion, since GABA is unable to cross the blood-brain barrier [11]. In in vitro experiments, GABA inhibited the stimulation evoked release of norepinephrine from the rat atria [2]. It has been proposed that GABA induces a release of noncholinergic and nonadrenergic substance [13]. However, evidence of the presence of GABAergic neurons in the heart has not been reported. The role of central GABAergic mechanisms in cardiovascular funetion has been reviewed in detail and is not addressed here. Of relevance to this chapter are those studies that implicate a peripheral cardiovascular function for GABA and a possible neurotransmitter role for GABA in the sinus node of the heart.