Cardiovascular effects of flesinoxan in anaesthetized and conscious dogs

Stimulation of 5-HT1A receptors is known to decrease the arterial blood pressure in anaesthetized rats, cats and dogs. We investigated the hypotensive activity of flesinoxan (0.1 + 0.2 + 0.7 mumol/kg), a 5-HT1A-receptor agonist, in dogs anaesthetized with either morphine and pentobarbital or enflurane and also in the conscious state. Flesinoxan led to a decrease in arterial blood pressure in anaesthetized, but not in conscious dogs. In the conscious state the marked increase in heart rate, which can be taken as an indicator of sympathetic tone, may have masked the consequences of vasodilatation. These different haemodynamic responses to flesinoxan may be dependent on side effects of the drug in the conscious dogs, in particular hyperventilation and salivation combined with anxiety, and on the magnitude of the decrease in baroreceptor reflex activity during anaesthesia with morphine and pentobarbital on the one hand and enflurane on the other hand.