| Popis: |
It is well-known that ketamine (Kt) anaesthesia produces a rise in blood pressure and heart rate in man. These cardiostimulatory effects were adscribed to several factors such as: a) increased sympathetic nervous system activity by direct stimulation of central nervous structures, b) increased catecholamine release from the peripheral sympathetic system, c) high plasmatic renin levels. However, the quantitative participation of these mechanisms in the cardiovascular effects of this anaesthetic agent is unknown. While some authors have shown a major rise in serum renin activity in experimental anaesthesia, others have been unable to confirm these results. The present study was undertaken to assess if the cardiostimulatory effects of Kt anaesthesia were due to an activation of renin-angiotensin system or to increased sympathetic activity. In consequence we used rats treated with enalapril (an angiotensin-converting enzyme inhibitor) or propranolol prior to anaesthetic procedures. Thirty male Wistar and six spontaneously hypertensive rats (SHR) weighing 240-300 g were used in all the experiments. The rats were randomly grouped into six groups. I- Non-anaesthetized rats, II- Anaesthetized rats (trained in the experimental procedures), III- Anaesthetized rats (without training), IV- Anaesthetized rats previously treated with enalapril, V- Anaesthetized rats pretreated with propranolol, VI- SHR treated with enalapril. The rats of groups IV and VI received enalapril p.o. for three weeks (25 mg/Kg body wt). The animals of group V were submitted to acute beta-adrenergic blockade. Propranolol dose: 10 mg/Kg body wt, was given i.p. 15 min before Kt anaesthesia. Blood pressure and heart rate were measured with a sphygmomanometer and photoelectric sensors and recorded.(ABSTRACT TRUNCATED AT 250 WORDS) |
