Ralph L. Kitchell

Electrophysiologic studies of penile mechanoreceptors in the rat

Abstract The neural activity of afferent fibers in the dorsal nerve of the penis was studied in 16 barbiturate-anesthetized rats. Sixty-one single units responsive to mechanical stimulation were isolated. Each receptor was tested for critical displacement, force, and velocity thresholds as well as its sinusoidal stimulation frequency-following characteristics and fiber conduction velocity. Based on adaptation responses to sustained mechanical stimuli, 36 of the 61 fibers were classified as rapidly adapting (RA) units and 25 as slowly adapting (SA) units, whereas previous workers did not find any slowly adapting receptors. We believe our ability to find SA units is due to mechanical and thermal stabilization of the penis and to our use of a wellcontrolled mechanostimulator.

Brood patch innervation and its role in the onset of incubation in the Turkey hen

The source of innervation to the brood patch in turkey hens was determined by recording the electrophysiological activity of cutaneous nerves while manually stimulating various regions of the skin. The entire area of the brood patch was innervated by eight nerves, arising from thoracic vertebra 3 to synsacrothoracic vertebra 1. To determine whether afferent input from the brood patch influenced egg production or incubation behavior, hens were bilaterally denervated prior to photoinduced egg production. Denervated hens visited nests the same number of times, but stayed on the nest for less total time than controls by the fourth week of photostimulation. Serum prolactin levels rose in control hens but not in denervated hens. Egg production was maintained in the denervated hens but not in controls. None of the denervated hens displayed incubation behavior. This experiment supports the view that peripheral nervous input plays a role in the onset of incubation behavior.

Rapidly and slowly adapting mechanoreceptors in the glans penis of the cat

Sixty-one single mechanoreceptive fibers were surgically isolated from the dorsal nerve of the penis in anesthetized, mature, and sexually intact male cats. Impulse activity was recorded extracellularly. Receptive fields on the glans penis were stimulated with an accurate computer controlled mechanostimulator. Thirty-four units were categorized as rapidly adapting (RA) based on the absence of a response to sustained skin displacement. The remaining were slowly adapting (SA) units responding to sustained displacement. Most of the SA units were located in the distal smooth glans whereas RA units predominated in the proximal spiny glans. Displacement thresholds were significantly lower for RA units. All units encoded indentation velocity although the SA units were better suited to discriminate slowly moving stimuli. In addition, SA units encoded sustained displacement amplitude. Male cats with a denervated glans penis display disoriented mounting behavior disabling intromission. The presence of distally located SA mechanoreceptors suggests they may be the primary penile proprioceptors, mediating, along with the RA mechanoreceptors, successful completion of intromission.

Spinal Nerve Root Origin of the Median, Ulnar and Musculocutaneous Nerves and their Muscle Nerve Branches to the Canine Forelimb

The contribution individual ventral spinal nerve roots made to the canine median nerve, ulnar nerve, musculocutaneous nerve, and their muscle nerve branches was determined electrophysiologically. Each spinal nerve root was sequentially stimulated. Utilizing quantitative signal averaging techniques, the evoked potential was measured at each tested peripheral nerve. Evoked potential to the median nerve originated from the seventh cervical sinal root (C7) through the second thoracic spinal root (T2) with most input from C8 and TI. The ulnar nerve received evoked potential from C7‐T2. Although T1 provided the major input to both the median and ulnar nerves, the relative contribution of T1 was greater in the ulnar nerve. The musculocutaneous nerve received input from ventral spinal roots C6‐Tl with C6 and C7 providing most of the evoked potential. The ventral spinal roots which supplied the bulk of the evoked potential to a particular muscle nerve were consistent between individual dogs. Variation of evoked potential input was greatest from spinal roots which supplied less than 10% of the total potential.

Spinal Root Origin of the Radial Nerve and Nerves Innervating Shoulder Muscles of the Dog

The ventral spinal root origin of the radial nerve, its muscle branches, and brachial plexus nerves which supply shoulder and thoracic musculature was determined in the dog. Electrophysiological signal averaging techniques measured evoked potential from specific ventral spinal roots to individual muscle nerves. The entire radial nerve received input from the sixth cervical (C6) through the second thoracic (T2) spinal roots. The most significant (p < .05) input to triceps brachii came from C8 while the deep ramus of the radial nerve received its largest input from C7. The brachiocephalicus, suprascapular, and subscapular nerves all received their most significant (p < .05) innervation from C6. Approximately 90 % of the evoked potential to the axillary nerve originated from C7. The thoracodorsal nerve received most of its innervation from ventral roots C7 and C8. The lateral thoracic nerve which innervates the cutaneous trunci muscle was supplied by ventral roots C8–T2. Examination of innervation patterns suggests that only modest variation of spinal root input to specific nerves occurred between individual dogs.

Electrophysiological Studies of the Cutaneous Innervation of the External Genitalia of the Male Dog

The external genitalia and perineum of the male dog receive cutaneous innervation from the caudal cutaneous femoral, superficial perineal and genitofemoral nerves and the dorsal nerve of the penis. In addition the cranial and caudal iliohypogastric nerves occasionally supply the prepuce. Considerable overlaop between adjacent cutaneous areas, particularly on the prepuce, is noted and the extent of all cutaneous areas is greater and more expansive than previosly described. Only the cutaneous area of the genitofemoral nerve is reduced from earlier accounts, being restricted to the prepuce, inguinal region, and medial thigh but never supplying the scrotum.

Dorsal Nerve Root Origins of the Cutaneous Nerves of the Feline Pelvic Limb

The dorsal root origins of cutaneous nerves supplying the feline pelvic limb were determined electrophysiologically in 11 cats. Cutaneous nerves were surgically exposed and the presence or absence of an evoked potential in response to stimulation of individual dorsal roots was noted. The dorsal cutaneous branches of L3–L5 and S3, and the lateral cutaneous branch of L3 each arose solely from their parent spinal nerves. The L7, SI, and S2 dorsal cutaneous branches had multiple dorsal root origins. The lateral cutaneous femoral nerve originated from L3–L6 dorsal roots in 4 patterns of origin, and the saphenous nerve originated from L4–L6 dorsal roots in 2 patterns of origin. The lateral and caudal cutaneous sural nerves originated from L6–SI roots in 2 and 3 patterns, respectively. The lateral and medial plantar nerves arose from L6–S2 roots in 4 and 2 patterns, respectively. The superficial and deep peroneal nerves originated from L6–SI roots in 2 and 3 patterns, respectively. The caudal cutaneous femoral nerve or its branches arose from L7–S3 in 8 origin patterns. The dorsal nerve of the penis and the superficial perineal nerve arose from L.7–S3 and SI –S3 roots, respectively, each in 4 patterns. A subtle correlation between plexus type and dorsal root origins of the cutaneous nerves was noted.

Sexual behavior of male dairy goats: effects of deafferentation of the genitalia

The following study examines the effects of deafferentation of the penis, scrotum, prepuce and adjacent cutaneous surfaces on the development of mounting behavior in male dairy goats. Ten males underwent surgical deafferentations and 10 males received sham operations at 8 to 12 weeks of age. Mounting and other sexual behaviors were monitored while subjects were cohabiting with male and female penmates and when individually exposed to estrous females. Denervated males mounted penmates less frequently than sham controls and lacked vigorous thrusting behavior. When exposed to estrous females denervated goats did not exhibit the normal progression from shallow to deep thrusting with successive mounts and failed to attain intromissions and ejaculations. However, frequency of mounting was similar to that of controls when the latter were prevented from attaining intromissions. It was concluded that sensory feedback from the genitalia and surrounding cutaneous areas is not required for the initiation of leg-kicking behavior in male dairy goats but plays an important role in the development and maintenance of normal patterns of thrusting behavior. Because it was not possible to determine the rate at which reinnervation occurred, the extent to which mounting behavior depends on sensory feedback could not be determined.

Binocular Dissecting Microscopic Studies on the Density of Toruli Tactile in the La Mancha Goat

The Merkel cells and associated nervous terminal plates have been called toruli tactiles (TT). These structures can be ubiquitously seen on the shaved hairy skin after staining with a methylene blue solution. Four La Mancha goats of both sexes were examined for the density of TT. TT were visually located under a binocular dissecting microscopic (14 ×) and then the number of TT in the field was directly counted. The density of TT in different corporal areas of the body surface was estimated from the mean of several two‐cm square samples of skin.

Afferent and Efferent Fibres in the Putative Caudal Cutaneous Femoral Nerve in the Sheep

Anatomical dissections supported by neurophysiological recordings have shown the putative caudal cutaneous femoral nerve in the sheep, when present, to contain afferent and efferent nerve fibres passing in both directions between the pudendal and sciatic nerves. Fascicles from the ventral branches of one or more sacral spinal nerves may join this interconnection directly: other fascicles either bypass the interconnection, or arise from it, and pass distally to innervate muscle and/or skin. We suggest that the interconnection should be regarded simply as part of the lumbosacral plexus.