Sensory fibres in ventral roots L7 and S1 in the cat

Abstract

Receptive fields were determined for 98 unmyelinated and 132 myelinated axons in the L7 and S1 cat ventral roots. Of the 98 unmyelinated axons, 70 had their receptive fields in somatic structures, the skin and deep tissues. Of the seventy unmyelinated axons with somatic receptive fields, 35 were mechanical nociceptors, 15 were mechanical and thermal nociceptors, 11 were deep nociceptors, 6 were thermal receptors and 3 were low threshold mechanoceptors. Of the 98 unmyelinated axons, 24 had their receptive fields in visceral structures: the intestine, bladder and vagina. It was confirmed that myelinated fibers attached to peripheral receptive fields can be found in ventral roots and that the receptive fields functional qualities of these fibers are as expected of dorsal root fibers for the same segments. A previous study demonstrated that approximately 30% of the axons in the L7 and S1 cat ventral roots were unmyelinated and arose from dorsal root ganglion cells. The present study confirms that these axons are sensory and that the axons are predominantly cutaneous nociceptors and visceral afferents. The L7 and S1 cat ventral roots apparently have a major sensory component.