α<sub>2</sub>-adrenoceptors control the release of noradrenaline but not neuropeptide Y from perivascular nerve terminals
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Date
2002
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Abstract
Neuropeptide Y (NPY) and noradrenaline (NA) are co-transmitters at many sympathetic synapses, but it is not yet clear if their release is independently regulated. To address this question, we quantified the electrically evoked release of these co-transmitters from perivascular nerve terminals to the mesenteric circulation in control and drug-treated rats. 6-Hydroxydopamine reduced the tissue content and the electrically evoked release of ir-NPY and NA as well as the rise in perfusion pressure. A 0.001 mg/kg reserpine reduced the content of ir-NPY and NA, but did not modify their release nor altered the rise in perfusion pressure elicited by the electrical stimuli. However, 0.1 mg/kg reserpine reduced both the content and release of NA but decreased only the content but not the release of ir-NPY; the rise in perfusion pressure was halved. Clonidine did not affect the release of ir-NPY while it lowered the outflow of NA, not altering the rise in perfusion pressure elicited by the electrical stimuli. Yohimbine, did not modify the release of ir-NPY but increased the NA outflow, it antagonized the clonidine effect. Therefore, presynaptic alpha(2)-adrenoceptors modulate the release of NA but not NPY, implying separate regulatory mechanisms. (C) 2002 Elsevier Science Inc. All rights reserved.
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neuropeptide Y (NPY) release, noradrenaline (NA) release, sympathetic co-transmitter release, reserpine, 6-hydroxydopamine, alpha(2)-presynaptic receptors, presynaptic regulation, alpha(2)-autoreceptors