Effect of acute nitric oxide synthase inhibition in the modulation of heart rate in rats

Brazilian Journal of Medical and Biological Research

A.l. Fellet¹  C. Di Verniero¹  P. Arza¹  A. Tomat¹  A. Varela¹  C. Arranz¹  A.m. Balaszczuk¹ 

[1] ,Universidad de Buenos Aires Facultad de Farmacia y Bioquímica Cátedra de FisiologíaBuenos Aires,Argentina

关键词: Nitric oxide;    Nitric oxide synthase;    Autonomic nervous system;    Heart rate;    Heart;   

DOI  :  10.1590/S0100-879X2003000500015

来源: SciELO

【 摘 要 】

Acute nitric oxide synthase inhibition with N G-nitro-L-arginine methyl ester (L-NAME) on chronotropic and pressor responses was studied in anesthetized intact rats and rats submitted to partial and complete autonomic blockade. Blood pressure and heart rate were monitored intra-arterially. Intravenous L-NAME injection (7.5 mg/kg) elicited the same hypertensive response in intact rats and in rats with partial (ganglionic and parasympathetic blockade) and complete autonomic blockade (38 ± 3, 55 ± 6, 54 ± 5, 45 ± 5 mmHg, respectively; N = 9, P = NS). L-NAME-induced bradycardia at the time when blood pressure reached the peak plateau was similar in intact rats and in rats with partial autonomic blockade (43 ± 8, 38 ± 5, 46 ± 6 bpm, respectively; N = 9, P = NS). Rats with combined autonomic blockade showed a tachycardic response to L-NAME (10 ± 3 bpm, P<0.05 vs intact animals, N = 9). Increasing doses of L-NAME (5.0, 7.5 and 10 mg/kg, N = 9) caused a similar increase in blood pressure (45 ± 5, 38 ± 3, 44 ± 9 mmHg, respectively; P = NS) and heart rate (31 ± 4, 34 ± 3, 35 ± 4 bpm, respectively; P = NS). Addition of L-NAME (500 µM) to isolated atria from rats killed by cervical dislocation and rats previously subjected to complete autonomic blockade did not affect spontaneous beating or contractile strength (N = 9). In vivo results showed that L-NAME promoted a tachycardic response in rats with complete autonomic blockade, whereas the in vitro experiments showed no effect on intrinsic heart rate, suggesting that humoral mechanisms may be involved in the L-NAME-induced cardiac response.

【 授权许可】

CC BY   
 All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License