title: GABA modulates baroreflex in the ventral tegmental area in rat.
abstract: 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.
authors.affiliation: Department of Physiology School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Masoumeh
authors.initials: M
authors.lastname: Hatam
authors.affiliation: Department of Physiology School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Minoo
authors.initials: M
authors.lastname: Rasoulpanah
authors.affiliation: Department of Physiology School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Nasimi
mesh_terms: D000818:Animals; D001418:Baclofen / Q000031:analogs & derivatives / Q000494:pharmacology; D017704:Baroreflex / Q000187:drug effects*; D001640:Bicuculline / Q000494:pharmacology; D018755:GABA Agonists / Q000494:pharmacology*; D018756:GABA Antagonists / Q000494:pharmacology*; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017557:Ventral Tegmental Area / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D018755:GABA Agonists; D018756:GABA Antagonists; C052329:phaclofen; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D001418:Baclofen; D001640:Bicuculline
keywords: GABA; VTA; baroreflex gain; ventral tegmental area