Benzodiazepine-sensitive GABA(A) receptors in the commissural subnucleus of the NTS are involved in the carotid chemoreceptor reflex in rats.
We studied the role of benzodiazepine (BDZ) receptors in the commissural subnucleus of the nucleus tractus solitarius (commNTS) in chemoreceptor reflex in urethane-anesthetized, pancronium-immobilized, artificially ventilated and bilaterally vagotomized rats. A BDZ agonist, diazepam (1-4 micromol/kg), administered intravenously reduced resting phrenic nerve activity (PNA) and blood pressure (BP). Stimulation of carotid chemoreceptors induced an increase in PNA and an increase in BP. Diazepam inhibited this chemoreceptor reflex. The effects of intravenous injection of diazepam (4 micromol/kg) on the chemoreceptor reflex were antagonized by microinjection of the BDZ antagonist flumazenil (100 pmol) into the commNTS. Microinjection of flumazenil (100 pmol) alone had no effect on the basal PNA and BP, and the chemoreceptor reflex. These results suggest that BDZ receptors are present in the carotid chemoreceptor reflex pathway in the commNTS and potentiate GABA(A) transmission.
Suzuki
Masahiko
M
Department of Pharmacology, Saitama Medical School, Moroyama, Iruma-gun, Saitama 350-0495, Japan. nhsuzuki@saitama-med.ac.jp
Nishina
Masami
M
Nakamura
Shinichi
S
Maruyama
Kei
K
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002339:Carotid Arteries / Q000294:innervation* / Q000502:physiology; D002628:Chemoreceptor Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D003975:Diazepam / Q000494:pharmacology; D005442:Flumazenil / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D008297:Male; D010791:Phrenic Nerve / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism*; D012018:Reflex / Q000187:drug effects / Q000502:physiology; D017552:Solitary Nucleus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D017833:Visceral Afferents / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018756:GABA Antagonists; D011963:Receptors, GABA-A; D005442:Flumazenil; D005680:gamma-Aminobutyric Acid; D003975:Diazepam