Responses of group IV afferent units from skeletal muscle to stretch, contraction and chemical stimulation.

In an attempt to differentiate between nociceptive group IV muscle receptors and "ergoceptive" ones, the discharges of single group IV fibres from skeletal muscle in response to local pressure, sustained stretch, repetitive contraction and intra-arterial injections of bradykinin, 5-hydroxytryptamine (5-HT), potasssium, phosphate, and lactate were studied in anesthetized cats.