Epinephrine facilitates neurogenic responses in isolated segments of dog mesenteric arteries.
Epinephrine (EPI) bitartrate (10(-9)-10(-8) M) significantly enhanced tension development in response to electrical field stimulation in isolated segments of dog mesenteric arteries. Responses to exogenous norepinephrine (NE) were generally unaffected, indicating that the EPI-induced increases in response to field stimulation are not explicable in terms of changes in postjunctional sensitivity. The facilitatory effects of EPI (5 X 10(-9) M) were unaffected by atenolol (10(-6) M) but were completely abolished by timolol (2 X 10(-7) M), suggesting an involvement of beta 2-adrenoreceptors in mediating the EPI-induced facilitation of neurogenic responses. Responses to exogenous NE were usually unaffected by either beta-adrenoreceptor antagonist. The results suggest that release of endogenous sympathetic neurotransmitter, measured in terms of postjunctional effects on vascular smooth muscle tone, appears to be modulated by prejunctional facilitatory beta 2-adrenoreceptors and that these receptors may be a physiologic site of action of EPI.
Borkowski
K R
KR
Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
Kwan
C Y
CY
Daniel
E E
EE
D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D004285:Dogs; D004558:Electric Stimulation; D004837:Epinephrine / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000294:innervation / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000294:innervation / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology; D013999:Timolol / Q000494:pharmacology
D001262:Atenolol; D013999:Timolol; D009638:Norepinephrine; D004837:Epinephrine