GABA modulates baroreflex in the ventral tegmental area in rat

There are some reports demonstrating the cardiovascular functions of the ventral tegmental area (VTA). About 20–30% of the VTA neurons are GABAergic, which might play a role in baroreflex modulation. This study was performed to find the effects of GABA_A, GABA_B receptors and reversible synaptic blockade of the VTA on baroreflex. Drugs were microinjected into the VTA of urethane anesthetized rats, and the maximum change of blood pressure and the gain of the reflex bradycardia in response to intravenous phenylephrine (Phe) injection were compared with the preinjection and the control values. Microinjection of bicuculline methiodide (BMI, 100 pmol/100 nl), a GABA_A antagonist, into the VTA strongly decreased the Phe‐induced hypertension, indicating that GABA itself attenuated the baroreflex. Muscimol, a GABA_A agonist (30 mM, 100 nl), produced no significant changes. Baclofen, a GABA_B receptor agonist (1000 pmole/100 nl), moderately attenuated the baroreflex, however phaclofen, a GABA_B receptor antagonist (1000 pmole/100 nl), had no significant effect. In conclusion, for the first time, we demonstrated that GABA_A receptors of the VTA strongly attenuate and GABA_B receptors of the VTA moderately attenuate baroreflex in rat. Synapse 69:592–599, 2015 . © 2015 Wiley Periodicals, Inc.