Central injections of spiperone and GABA: attenuation of angiotensin II stimulated thirst

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Abstract
This study investigated the effects of injecting spiperone or γ-aminobutyric acid (GABA) into the brain on drinking induced by angiotensin II injected into a lateral cerebral ventricle of the rat. Injections of 12.5 pM of angiotensin II elicited water intakes averaging 10 mL in 15 min with latencies of less than 3 min. Spiperone, a dopamine antagonist injected into the nucleus accumbens produced dose-dependent reductions in water intake and number of laps while increasing the latency to drink. Injections of GABA into the ventral tegmental area produced dose-dependent reductions in water intake and number of laps without altering latency to drink or lap volume. GABA injected into the globus pallidus reduced drinking in a manner similar to that described for spiperone injected into the nucleus accumbens when angiotensin II was the dipsogenic agent but was totally without effect on drinking induced by carbachol injections. These results indicate that a proposed neuronal circuit composed of GABA input to ventral tegmental area neurons, dopamine input from the ventral tegmental area to nucleus accumbens neurons, and subsequent GABA input from the nucleus accumbens to globus pallidus neurons may interact with the goal-directed behaviour, drinking, elicited by central angiotensin II administration. Further, they provide evidence that this neuronal circuit may be part of a functional interface for response initiation.