Effects of Sympathetic Stimulation on Mechanoreceptors of Cat Vibrissae

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Abstract
In a previous investigation adrenergic nerve terminals were demonstrated in the hair follicles of cat vibrissae. The present study shows that electrical stimulation of the cervical sympathetic trunk produces small but repeatable changes in the dynamic responses of the slowly adapting mechanoreceptors of the vibrissae in that the number of impulses in each discharge is reduced and their latency increased. Changes in the static responses are very small. These effects were abolished by phentolamine. The receptor responses as well as effects of sympathetic stimulation remain unaffected by a brief carotid occlusion. It is concluded that the sympathetic modulation observed is a direct effect of locally released noradrenaline and is not attributable to circulatory changes or to pilomotor activity.