The isolated pilomotor muscles as an in vitro preparation

Abstract

Relatively little work has been done on the physiology of the arrector pili or pilomotor muscles of the skin, and none at all appears to have been done in vitro. This is understandable, since the pilomotor muscles are discrete, microscopic, smooth-muscle bundles which cannot be dissected out easily. They are attached at one end to the hair follicles and at the other to the inner surface of the basal layer of the epidermis. Because neither of these attachments are to rigid structures a contraction produces a twofold effect; the hairs stand up and the epidermis immediately above the epidermal insertion is pulled downwards so that 'goose-skin' appears. Both manifestations occur simultaneously and each has been used to study the behaviour of the pilomotor muscles in situ (

Single follicular unit transplantation reconstructs arrector pili muscle and nerve connections and restores functional hair follicle piloerection

“…To investigate whether piloerection could be demonstrated in transplanted hairs, hair responses to neurotransmitter agents and piloerection inhibitors were evaluated as reported previously 8–10 . Agents were injected i.d.…”

“…In the rodents, a vibrissa‐type follicle is a specialized sensitive sensory organ that is connected to dense sensory nerve fibers and voluntary muscle, which is innervated by motor neurons 6,7 . Activation of sympathetic nerves stimulates the APM and initiates hair follicle piloerection in almost all human hairs and rodent coat hairs 8,9 . The APM, which is an involuntary smooth muscle, is immunopositive for α‐smooth muscle actin, α8‐integrin and calponin 10,11 .…”

“…6,7 Activation of sympathetic nerves stimulates the APM and initiates hair follicle piloerection in almost all human hairs and rodent coat hairs. 8,9 The APM, which is an involuntary smooth muscle, is immunopositive for a-smooth muscle actin, a8-integrin and calponin. 10,11 The APM connects the bulge region of a permanent portion of the hair follicle to the dermis and is innervated by adrenergic neurons, which are classified as sympathetic neurons.…”

Quantitative Pilomotor Axon Reflex Test

“…9 The mechanism whereby phenylephrine evokes axon-reflex mediated piloerection is not fully elucidated. In prior reports, piloerection was evoked with electric current in vitro using an isolated cat piloarrector muscle 10 and in vivo, in humans directly and via an axon-reflex. 1 We have evoked axon-reflex mediated piloerection with higher current intensities than those used in this study (2mAmp for 5 minutes over a 1 cm diameter region), however, the lower current intensities used to evoke axon-reflex mediated piloerection with phenylephrine in this study, when used with saline alone, did not evoke piloerection.…”

α1-AR agonist induced piloerection protects against the development of traction alopecia

“…The arrector pili is a smooth muscle, which is attached at one end to the hair follicle and at the other to the inner surface of the basal layer of epidermis. Contraction of the muscle produces two effects: hairs are erected and the epidermis immediately above the epidermal insertion is pulled downward to give the characteristic appearance of “goose bumps” . Piloerection can be stimulated directly by mechanical, thermal, electrical, or pharmacological stimuli or indirectly via an axon reflex .…”