Cardiovascular and drinking responses elicited by central administration of angiotensin II: Differential effects of GABA injected into the ventral tegmental area and spiperone injected into the nucleus accumbens

Abstract

The ventral tegmental area and its dopamine projections to the nucleus accumbens have been shown to be involved in goal-directed behavior. This study investigated the contribution of GABAergic input to the ventral tegmental area and dopaminergic input to the nucleus accumbens to the drinking and cardiovascular responses elicited by central administration of angiotensin II. Injections of 25 ng of angiotensin II into a lateral cerebral ventricle of the conscious rat elicited water intakes averaging 8 ml in 15 min with latencies usually less than 3 min. Pretreatment of the nucleus accumbens with spiperone, a dopamine antagonist, or the ventral tegmental area with γ-amino butyric acid (GABA) produced dose-dependent reductions in water intake and number of laps taken while increasing the latency to drink. Injections of spiperone into the nucleus accumbens in anesthetized animals failed to alter the cardiovascular response elicited following the central administration of angiotensin II. However, administration of GABA into the ventral tegmental of urethane anaesthetized animals attenuated the pressor response normally elicited by central administration of angiotensin II. These findings suggest that GABA input to the ventral tegmental area is involved in both the cardiovascular and drinking responses elicited following central administration of angiotensin II. The dopamine projections to the nucleus accumbens appear only to be involved in the drinking response elicited by central injections of angiotensin II. Divergence of the signals separately accessing the skeletal motor behavioral component and the cardiovascular component elicited by central administration of angiotensin II must occur before the involvement of these dopamine pathways.