alpha2-Adrenoceptors control the release of noradrenaline but not neuropeptide Y from perivascular nerve terminals.
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, 0.1mg/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 alpha2-adrenoceptors modulate the release of NA but not NPY, implying separate regulatory mechanisms.
Donoso
M Veronica
MV
Departmento de Fisiologi;a y Biologi;a Celular, Facultad de Ciencias Biológicas, Centro de Regulación Celular y Patología, Instituto Milenio de Biología Fundamental y Aplicada, MIFAB, Pontificia Universidad Católica de Chile, Casilla, Santiago, Chile.
Carvajal
Andrés
A
Paredes
Alfonso
A
Tomic
Alexander
A
Koenig
Cecilia S
CS
Huidobro-Toro
J Pablo
JP
D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D004299:Dopamine beta-Hydroxylase / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007150:Immunohistochemistry; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000378:metabolism*; D009478:Neuropeptide Y / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D016627:Oxidopamine / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology*; D015424:Reperfusion; D012110:Reserpine / Q000494:pharmacology; D013997:Time Factors; D014018:Tissue Distribution; D015016:Yohimbine / Q000494:pharmacology
D009478:Neuropeptide Y; D018341:Receptors, Adrenergic, alpha-2; D015016:Yohimbine; D012110:Reserpine; D016627:Oxidopamine; D004299:Dopamine beta-Hydroxylase; D000110:Acetylcholinesterase; D003000:Clonidine; D009638:Norepinephrine