Impulse pattern, innervation density and two point discrimination of skin and mucosal afferents in humans. Considerations for a sensory reinnervation of urinary bladder and anal canal in spinal cord lesions. IV (IV).
1. Single fiber action potentials (Ap's) were recorded with 2 pairs of wire electrodes from a coccygeal nerve root. Simultaneous impulse patterns of 3T0 + 6T1 + 3T2 + 11T3 + 5T4 and 4P single skin afferent units were separated by their different Ap wave forms and conduction velocities. For a rapid touch or pin-prick the afferent units fired on average with 2 Ap's. 2. The touch units had most likely the following receptor properties. T1: rapidly adapting, medium high threshold, sensitive to skin traction over a distance of more than 10 cm. T2: rapidly adapting, high threshold. T3: slowly adapting, lowest threshold among T afferents for a light touch with no movement along the skin. T4: slowly adapting, lowest threshold among T afferents for a light touch with a movement component parallel to the skin surface. The T1 to T4 afferent receptors are the PC, RA, SAI and SAII receptors respectively. The correspondence is not safe. 3. With nerve fibre diameter distribution histograms (morph), myelinated fibre numbers, conduction velocity distribution histograms (electro) and Ap occurrence patterns, innervations were determined. With estimated dermatome areas, innervation densities i of skin dermatomes were calculated for nerve fibre diameters larger than 5 microns: i(electro, morph; Co) = (0.6T0 + 1.2T1 + 2.8T2 + 2.4T3 + 1.2T4 + 1.6P)/cm2, i(morph; S4) = (0.4T0 + 1T1 + 0.8T2 + 1.1T3 + 0.5T4)/cm2, i(electro; S4) = 0.4T0 + 2.3T1 + 2.1T2 + 2T3 + 1.5T4)cm2, i(morph; T9) (lateral)) = (0.8 (T0 or hair follicle) + 1.7T1 + 0.9T2 + 0.7T3 + 0.4T4)/cm2. 4. Innervation densities of mucosal afferent units M of urethra, trigonum vesicae and anal canal through S3 and S4 roots had the following lower limits: i(electro; urethra + trigonum) = 2 M/cm2, i(electro; anal canal) = 3 M/cm2. The innervation density of skin like receptors of the anal canal through an S4 ventral root was with i(electro; anal canal) = (0.5T0 + 2.4T1 + 1.6T2 + 1.2T3 + 0.8T4)/cm2 at least as high as the innervation density of the S4 dermatome. The urethra possesses no skin like receptors in the mucosa. Mechanoreceptor afferents of the mucosa (M) of urethra and anal canal had thresholds similar to those of T3 and T4 afferents. 5. The two point discrimination of a volunteer was for a light touch 30 mm in the S3 and S4 dermatomes and reduced to 25 mm with faster and stronger touch. In the direction of the anus and the os coccygeum the two point discrimination reduced to 25 mm.(ABSTRACT TRUNCATED AT 400 WORDS)
Schalow
G
G
D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000344:Afferent Pathways / Q000502:physiology*; D001003:Anal Canal / Q000294:innervation / Q000503:physiopathology; D004192:Discrimination, Psychological / Q000502:physiology; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000294:innervation* / Q000503:physiopathology; D009431:Neural Conduction / Q000502:physiology; D010146:Pain / Q000503:physiopathology; D010812:Physical Stimulation; D012867:Skin / Q000294:innervation* / Q000503:physiopathology; D013118:Spinal Cord Diseases / Q000503:physiopathology*; D013126:Spinal Nerve Roots / Q000502:physiology; D001743:Urinary Bladder / Q000294:innervation* / Q000503:physiopathology