Increased expression of cutaneous α₁-adrenoceptors after chronic constriction injury in rats

α₁-Adrenoceptor expression on nociceptors may play an important role in sympathetic-sensory coupling in certain neuropathic pain syndromes. The aim of this study was to determine whether α₁- adrenoceptor expression was upregulated on surviving peptidergic, nonpeptidergic, and myelinated nerve fiber populations in the skin after chronic constriction injury of the sciatic nerve in rats. Seven days after surgery, α₁-adrenoceptor expression was upregulated in the epidermis and on dermal nerve fibers in plantar skin ipsilateral to the injury but not around blood vessels. This α₁-adrenoceptor upregulation in the plantar skin was observed on all nerve fiber populations examined. However, α₁-adrenoceptor expression was unaltered in the dorsal hind paw skin after the injury. The increased expression of α₁- adrenoceptors on cutaneous nociceptors in plantar skin after chronic constriction injury suggests that this may be a site of sensory-sympathetic coupling that increases sensitivity to adrenergic agonists after nerve injury. In addition, activation of upregulated α₁-adrenoceptors in the epidermis might cause release of factors that stimulate nociceptive signaling. Perspective Our findings indicate that peripheral nerve injury provokes upregulation of α₁-adrenoceptors on surviving nociceptive afferents and epidermal cells in the skin. This might contribute to sympathetically maintained pain in conditions such as complex regional pain syndrome, painful diabetic neuropathy, and postherpetic neuralgia.