Myelinated afferent nerve fibers from the skin of the rabbit ear

SUMMARY1. The receptive field properties and conduction velocities of single dorsal root axons, activated from the sural and cutaneous branches of the posterior tibial (medial plantar) nerves, were examined in anaesthetized rabbits.2. The sural nerve sample included all types of units previously recorded from the saphenous nerve . In particular it was shown that electrical stimulation of the sural nerve at strengths up to 1-3T produced a volley of impulses in a pure population of slowly adapting units (Type I units).3. The medial plantar sample showed an absence of Type I slowly adapting units and Type T hair follicle units. Corresponding to this there were no touch corpuscles or tylotrich hairs in the skin of the hind foot and the fastest medial plantar axons conducted at 60-70 m/sec as opposed to 80-85 m/sec for the sural nerve. Stimulation of the medial plantar nerve at stimulus strengths close to threshold produced a volley of impulses in a nearly pure population of Type G hair follicle units.

Section: Discussionsupporting

confidence: 63%

Section: Discussionsupporting

confidence: 63%

The distribution of cutaneous receptors in the rabbit's hind limb and differential electrical stimulation of their axons

Brown¹,

Hayden²

1971

“…Experiments will be necessary to test capsaicin's action on slowly adapting A mechanoreceptors, which are not present in the rabbit ear (Brown et al 1967), on specific warm fibres, which were not encountered in the present survey, and on subcutaneous sense organs, which were not studied.…”

Section: Discussionmentioning

confidence: 99%

Selective responsiveness of polymodal nociceptors of the rabbit ear to capsaicin, bradykinin and ultra‐violet irradiation.

Szolcsányi

1987

172

SUMMARY1. The activity of single C-and A-fibre cutaneous sensory units was recorded from the great auricular nerve of anaesthetized rabbits to compare the effects of chemical with other forms of stimulation under several experimental conditions. Chemical agents were delivered by close arterial injection.2. Small intra-arterial injections of bradykinin (0-2 ,ug) and a substantial range of capsaicin doses (2-200 ,sg) consistently activated C polymodal nociceptors without exciting other types of C-or A-fibre cutaneous sense organs.3. Topical application of xylene to the receptive field of polymodal nociceptors evoked a strong excitation which lasted several minutes.4. The responses of polymodal nociceptors to mechanical, chemical (bradykinin, xylene) and noxious thermal stimuli were suppressed or abolished after large intra-arterial doses of capsaicin. Capsaicin desensitization of polymodal nociceptors to one kind of stimulation often was not paralleled by similar changes in responsiveness to other stimuli. However, on the average, capsaicin desensitization altered responses to thermal, chemical and mechanical stimuli without afferent selectivity.5. Background discharge developed in C polymodal nociceptors of the rabbit ear following ultra-violet irradiation sufficient to produce evidence of delayed inflammation. Noxious heat and bradykinin injection (0-2 ,ug) evoked more activity from C polymodal nociceptors in the irradiated ears than from control units.

“…However, the possibility that the skin spot units excited by stimulation of the dorsal ear skin were associated with hairs in the ventral skin could not be excluded, since the ventral surface of the ear was set in plaster of Paris to achieve the necessary rigidity for recording. The problem is discussed further in subsequent papers (Miller, 1966;Brown et at. 1966).…”

Section: Discussionmentioning

confidence: 99%

“…The guard hair units display a high selective sensitivity to mechanical stimuli and do not respond to warm stimuli. The use of rods for applying cold stimuli masked a weak dynamic response to cold stimuli, which Brown et al (1966) have since confirmed using a different type of thermode. In the absence of any other type of terminal it would be tempting to associate skin spot units with 'free' nerve endings.…”

Section: Discussionmentioning

confidence: 99%

Mechanoreceptors in rabbit ear skin innervated by myelinated nerve fibres

Miller¹,

Weddell²

1966

Self Cite

SUMMARY1. The activity of single myelinated fibres innervating mechanosensitive units in the dorsal skin of the ears of New Zealand White and Chinchilla rabbits has been recorded with glass micropipette electrodes, inserted into intact bundles of the great auricular nerve.2. Only two types of afferent unit were observed: hair units, sensitive to hair displacement, and skin spot units, sensitive to deformation of spotlike areas of skin between the hair orifices. Hair units were more numerous and no unit contained receptors of both types. Up to nine hairs or six skin spots composed each hair or skin spot unit, respectively. Both types were rapidly adapting.3. The areas of the receptive fields of the hair units were significantly larger in the New Zealand White than in the Chinchilla strain.4. In the hair units from the Chinchilla rabbits: (a) there was no correlation between the receptive field areas and the conduction velocities of the afferent fibres; (b) the areas and conduction velocities of the units showed no significant topographical distribution over the ear; (c) the extent of the overlap of the receptive fields was estimated and the sum of the areas is shown to be about 40 times the area of the ear. INTRODIUCTIONIn studies on the innervation of rabbit ear skin (Weddell, Pallie & Palmer, 1955;Weddell & Pallie, 1955;Weddell, Taylor & Williams, 1955) it was observed that about three quarters of the myelinated afferent fibres to the ear were related to hair follicles and that each follicle was innervated by the branches of at least two myelinated fibres. From counts of the hair follicles and myelinated dorsal-root fibres and on the assumption of a random uniform distribution it was calculated that each fibre innervates on average about eighty follicles, the branches of up to six fibres supplying a single follicle. The overlapping of afferent units predicted from these calculations was partly confirmed by the considerable coincidence of the I9-2