Receptive fields of unmyelinated ventral root afferent fibres in the cat.

Abstract

SUMMARY1. The receptive fields were determined for 118 afferent fibres in the S2, S3 and Ca (caudal) 1 ventral roots of the cat. Of these fibres, ninety-three were unmyelinated, another eleven were probably unmyelinated, and fourteen were myelinated, according to estimates of their conduction velocities.2. Confirmation that the recordings were from ventral root filaments came from electron microscopic inspection of ten of the filaments from which recordings of the activity of unmyelinated afferents were made.3. Receptive fields were demonstrated for twelve unmyelinated afferent fibres in the distal stumps of the S2 and S3 ventral roots which had been sectioned 3 weeks previously, indicating that the cell bodies giving rise to these fibres were not in the spinal cord.4. The action potentials of some of the unmyelinated ventral root afferent fibres were complex, suggesting branching of the afferents within the ventral root.5. One third of the unmyelinated ventral root afferents had receptive fields in somatic structures: the skin and deep tissues.6. Two thirds of the unmyelinated ventral root afferents had receptive fields in the viscera of the pelvis: the bladder, urethra, vagina, and lower bowel.7. Many of the unmyelinated afferents in the ventral roots, especially those with cutaneous receptive fields, had high thresholds and may participate in nociception.8. It is concluded that the cat ventral root contains a major sensory component and that the Law of Bell and Magendie is not an accurate description of the organization of the ventral root in this animal. L. CLIFTON AND OTHERS

Inhibitory interactions between colonic and vesical afferents in the micturition reflex of the cat.

“…This feature also contrasts with recurrent inhibition since the latter was found to have a prolonged time course which sometimes lasted several minutes. Myelinated and unmyelinated afferents from the colon have been found in sacral dorsal roots by Floyd & Lawrenson (1979) and in sacral ventral roots by Clifton, Coggeshall, Vance & Willis (1975) and Floyd, Koley & Morrison (1976). De Groat & Krier (1978) have described a role for unmyelinated afferents from the colon in eliciting reflex discharges in colonic efferent fibres of the cat pelvic nerve, but the myelinated afferents appear to play little or no role in that response.…”

Sensory blockade of S3 dermatome prevents pain during bladder catheterization

“…5,6 In animals, two different types of sensory afferents from the urethra have been reported; myelinated afferent fibres in the pelvic nerve which respond to movements of the urethral catheter, 7 and unmyelinated afferent fibres in the sacral ventral root which respond to distension of the urethra, 8 and both are thought to be responsible for urethral pain. In humans, the sensory and motor innervation of the urinary bladder has been reported in the management of detrusor reflex and pain in patients with neurogenic bladder, 9,10 however, the transmission of urethral pain remains unclear.…”

The central control of the lumbar sympathetic pathway to the large intestine of the cat.

“…It was not determined whether these afferent fibres have their peripheral receptive fields in the colon. However, many of the afferent fibres which enter the sacral ventral roots have their receptive fields in the distal colon and rectum (Clifton et al 1976). Thus, it seems reasonable to assume that similar inputs would exist at the lumbar level.…”