Role of nitric oxide in the control of the heart rate within the nucleus ambiguus of rats.
The aim of this study was to determine whether NO plays a role in the control of heart rate (HR) within the nucleus ambiguus (NA). Experiments were performed in 29 male Wistar rats anaesthetized with urethane. Microinjections of the NO-donor sodium nitroprusside (SNP; 5 mmol) as well as of L-arginine (L-arg; 50 mmol) into functionally identified cardioinhibitory sites within the NA significantly decreased HR (-57.7 +/- 8.4 and -53.8 +/- 3.2 bpm, respectively), whereas the NO-synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) significantly increased HR (+40 +/- 2.7 bpm). Bilateral vagotomy and i.v. injection of atropine (0.5mg/kg) always abolished the HR decrease induced by SNP and L-arg, whereas propranolol did not affect the HR responses. These results demonstrated that NO mechanisms within the NA play a role in the parasympathetic control of the HR.
Ruggeri
P
P
Dipartimento di Medicina Sperimentale, Facoltà di Medicina e Chirurgia, Università di Genova, Italy.
Battaglia
A
A
Ermirio
R
R
Grossini
E
E
Molinari
C
C
Mary
D A
DA
Vacca
G
G
D000818:Animals; D001120:Arginine / Q000737:chemistry / Q000494:pharmacology; D001340:Autonomic Nerve Block; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006339:Heart Rate / Q000502:physiology*; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013237:Stereoisomerism
D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D009599:Nitroprusside; D009569:Nitric Oxide; D001120:Arginine; D019331:NG-Nitroarginine Methyl Ester