Inhibition of medullary raphé/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 raphé/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, raphé/parapyramidal neurons constitute an important brainstem center for mediating cutaneous vasoconstriction initiated by alerting stimuli and by cold exposure.