Inhibition of medullary raphe/parapyramidal neurons prevents cutaneous vasoconstriction elicited by alerting stimuli and by cold exposure in conscious rabbits

In conscious rabbits, microinjection of muscimol into the medullary raphe/parapyramidal region decreased fluctuation (coefficient variation) of resting ear blood flow (from 62 8 to 25 +/- 4%, P < 0.01, n = 8). The muscimol injection also prevented falls in ear blood flow that normally occur in response to alerting stimuli and to cold exposure. Thus, raphe/parapyramidal neurons constitute an important brainstem center for mediating cutaneous vasoconstriction initiated by alerting stimuli and by cold exposure. (c) 2005 Elsevier B.V All rights reserved.