Cutaneous vascular bed is not involved in arterial pressure changes elicited by increasing or decreasing the activity of inhibitory vasomotor neurons in caudal ventrolateral medulla in rabbits.
We determined whether caudal ventrolateral medulla (CVLM) vasodepressor neurons tonically inhibit vasomotor tone in the ear in anesthetized rabbits. Injection of L-glutamate (10 nmol in 100 nl) into the CVLM decreased arterial pressure and increased superior mesenteric conductance. Ear conductance decreased (0.43+/-0.06 to 0. 33+/-0.05 cm s(-1) per mmHg, n=15 injections, 12 rabbits, P<0.01). Conversely, bilateral injection of gamma-aminobutyric 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 rabbits, P<0.05). Results suggest that ear vessels are not tonically inhibited by the CVLM vasodepressor neurons. Presympathetic motoneurons regulating cutaneous flow may be excited, rather than inhibited, by the CVLM neurons.
Departments of Physiology and Medicine, Centre for Neuroscience, Flinders University, S.A. 5042, Bedford Park, Australia. w.w.blessing@flinders.edu.au
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D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000294:innervation* / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D004423:Ear / Q000098:blood supply / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism / Q000494:pharmacology; D008526:Medulla Oblongata / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017538:Mesenteric Artery, Superior / Q000187:drug effects / Q000294:innervation / Q000378:metabolism; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011817:Rabbits; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D012867:Skin / Q000098:blood supply* / Q000187:drug effects / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D014666:Vasomotor System / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism / Q000494:pharmacology
D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid