Abstract

1. Sympathetic effects on the mechanical sensitivity of frogcutaneous mechanoreceptors were examined in vivo. 2. Functionallyidentified units were tested with repetitive mechanical stimuli ofthreshold intensity during electrical stimulation of the sympathetictrunk. 3. Sympathetic activity resulted in increased sensitivity forthree classes of afferents; slowly adapting compression receptors,slowly adapting stroke receptors, and rapidly adapting strokereceptors. Decreased sensitivity was produced in the fourth class,rapidly adapting compression receptors. 4. Preliminary tets of severalpossible modes of sympathetic influence indicated that blood flowchanges, changes in probe‐skin coupling and changes in tissuecompliance could not account for the observed changes in receptorsensitivity. Na+ and Cl‐ ions, secreted by cutaneous mucous glandswere found to be possible contributors to the decreased sensitivity ofrapidly adapting compression receptors. Direct neurotransmitter actionon the receptors, a likely mechanism of sympathetic action, was nottested. 5. The data indicate that systematic changes in cutaneoussensibility occur with modest changes in sympathetic efferentactivity. Possible mechanisms of these sympathetic effects arediscussed. © 1981 The Physiological Society.