Constriction of the ear pinna vascular bed accompanies the trigeminal depressor response in rabbits.

Electrical stimulation of the spinal tract of the trigeminal nerve at 5 Hz to elicit the trigeminal depressor response in anesthetized rabbits also causes an acute fall in ear pinna blood flow to near zero levels (from 31+/-8 to 2+/-2 kHz, n = 5, P < 0.01). This active vasoconstriction in the ear artery contrasts with the active vasodilation in femoral, renal and mesenteric arteries known to be part of the trigeminal depressor response. The selective vasoconstriction observed in the ear bed in response to noxious stimulation in anesthetized rabbits is similar to the vigorous acute vasoconstriction occurring in this cutaneous bed in conscious rabbits responding to salient environmental stimuli.