Norepinephrine excitation of cutaneous nociceptors in adjuvant-induced inflamed rats does not depend on sympathetic neurons

To test the contribution of sympathetic postganglionic neurons (SPGNs) to adrenergic excitation of cutaneous nociceptor activities in adjuvant-inflamed rats (AI rats), we studied the effects of norepinephrine (NE) in a group of sympathectomized AI rats. Sympathectomy was complete in 4–6 weeks by guanethidine (30–50 mg/kg). NE excited polymodal receptor units in the saphenous nerve at an incidence (25–30%) similar to that in AI rats, while CH-38083 blocked such excitation. These results show that α 2-adrenoceptors in SPGNs are not involved in the norepinephrine excitation of cutaneous nociceptors in AI rats.