| Abstract: | Abstract The influence of surgical anaesthesia induced by ketamine, pentobarbital, pentobarbital-xylazine, or chloralose-urethane on blood pressure and heart rate was studied, and the effects were compared with results in conscious and pithed rats. The blood pressure was significantly decreased by pentobarbital-xylazine. The heart rate increased in all groups except in pentobarbital-xylazine anaesthetized rats. Generally, a fall in heart rate and blood pressure was observed during a two hours lasting anaesthesia as compared to the initial values. The blood pressure response to noradrenaline was significantly lowered by ketamine, pentobarbital and chloralose-urethane anaesthesia, and the response of the heart rate only by chloralose-urethane. Guanethidine 5 mg/kg intravenously significantly lowered the blood pressure in the ketamine, pentobarbital and chloralose-urethane anaesthetized groups. The guanethidine induced potentiation of the haemodynamic effects of noradrenaline was considerably influenced by the anaesthetic, the augmentation being greatest in pentobarbital and chloralose-urethane anaesthetized rats. Chloralose-urethane is considered a suitable anaesthetic in rats when studying the effects of noradrenaline and guanethidine. Following a single intraperitoneal injection a surgical anaesthesia of more than two hours' duration was obtained, and the variance of the parameters studied was less than that following administration of the other anaesthetics. It is emphasized that various effects of anaesthetics unrelated to their anaesthetic properties may obscure or even invalidate results obtained with drugs acting on the peripheral sympathetic nervous system. |
