Cutaneous vascular bed is not involved in arterial pressure changes elicited by increasing or decreasing the activity of inhibitory vasomotor neuronsin caudal ventrolateral medulla in rabbits

We determined whether caudal ventrolateral medulla (CVLM) vasodepressor neu rons tonically inhibit vasomotor tone in the ear in anesthetized rabbits, I njection of L-glutamate (10 nmol in 100 nl) into the CVLM decreased arteria l pressure and increased superior mesenteric conductance. Ear conductance d ecreased (0.43 +/-. 0.06 to 0.33 +/- 0.05 cm s(-1) per mmHg, n = 15 injecti ons, 12 rabbits, P < 0.01). Conversely, bilateral injection of gamma-aminob utyric acid (100 nmol in 100 nl) increased arterial pressure and decreased superior mesenteric conductance. At the same time ear conductance increased (0.39 +/- 09 to 0.48 +/- 0.27 cm s(-1) per mmHg, n = 8 injections, eight r abbits, P < 0.05). Results suggest that ear vessels are not tonically inhib ited by the CVLM vasodepressor neurons. Presympathetic motoneurons regulati ng cutaneous flow may be excited, rather than inhibited, by the CVLM neuron s. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.