Discharge patterns in postganglionic neurones to skeletal muscle and kidney during activation of the hypothalamic and midbrain defence areas in the cat.

Electrical stimulation of hypothalamic and midbrain defence area sites eliciting a cholinergic vasodilatation in the hindlimb activates vasodilator fibres supplying skeletal muscle. Simultaneous baroreceptor mediated suppression of sympathetic vasoconstrictor activity to the muscle and postfiring depression of vasoconstrictor activity contribute to the development of the vasodilatation during and after the stimulus. The observation of a differential pattern of activation of muscle and renal vasoconstrictor fibres implies a reciprocal influence exerted on these sympathetic outflows by neurones in the defence areas of the brain.