Endogenous GABA in the commissural subnucleus of the NTS inhibits the carotid chemoreceptor reflex via GABA A receptors in rats.
Using urethane-chloralose anesthetized rats, we investigated which GABA receptor is responsible for the action of endogenous GABA on the carotid chemoreceptor reflex in the commissural subnucleus of the nucleus tractus solitarius (commNTS). Microinjection of the selective GABA uptake inhibitor nipecotic acid (40 nmol) into the commNTS attenuated the increases in respiration (respiratory movement and rate) and the elevation in arterial blood pressure elicited by carotid chemoreceptor stimulation. These effects were completely antagonized by premicroinjection of the GABA(A) antagonist bicuculline (20 pmol), but not of the GABA(B) antagonist 2-OH-saclofen (400 pmol), into the same site. These findings suggest that endogenous GABA mainly acts on GABA(A) receptors, and inhibits the chemoreceptor reflex in the commNTS in rats.
Suzuki
M
M
Department of Pharmacology, Saitama Medical School, Saitama, Japan. mhzusuki@saitama-med.ac.jp
Nishina
M
M
Nakamura
S
S
Maruyama
K
K
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002339:Carotid Arteries / Q000187:drug effects / Q000502:physiology*; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D058787:GABA-A Receptor Antagonists; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009557:Nipecotic Acids / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000502:physiology*; D017552:Solitary Nucleus / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D058787:GABA-A Receptor Antagonists; D009557:Nipecotic Acids; D011963:Receptors, GABA-A; C030278:nipecotic acid; D005680:gamma-Aminobutyric Acid