Dopaminergic inhibition of sympathetic activity in the cat
Abstract:
The influence of dopaminergic agonists on the spontaneous and evoked activity of the sympathetic postganglionic renal efferent fibres was studied in lightly anaesthetized cats (urethane, 600 mg/kg, ip). Apomorphine, bromocriptine and piribedil (0.2, 0.07 and 0.4 mg/kg iv, respectively) depressed the spontaneous activity of the renal nerve. Electrical stimulation (16 V, 0.3 ms, 2-128 Hz, 2 s) of the sciatic nerve elicited a burst of activity of the sympathetic efferents followed by a silent period. Apomorphine and piribedil (the same doses as above) prolonged the duration of the silent periods. All these effects of dopaminergic agonists were antagonized by haloperidol (0.05-0.1 mg/kg iv). The results suggest that administration of dopaminergic agonists leads to preponderance of inhibition in the somato-sympathetic reflex integration.
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