Disturbances in blood pressure homeostasis modify GABA release in the locus coeruleus

The locus coeruleus (LC) of anaesthetized rats was superfused with artificial cerebrospinal fluid through a push-pull cannula and the release of the amino acids gamma-aminobutyric acid (GABA), taurine and arginine was determined in the superfusate. Increases in blood pressure (BP) induced either by intravenous infusions of noradrenaline and phenylephrine or by blood injection enhanced the release of GABA in the LC. Decreases in BP elicited by intravenous infusion of sodium nitroprusside or by haemorrhage decreased the GABA release rate. The BP changes did not influence the release rates of taurine and arginine. These findings demonstrate that GABA release in the LC is modified by cardiovascular impulses and suggest that GABAergic neurones modulate LC activity in response to disturbances in BP homeostasis.