Met-enkephalin-induced vasoconstriction in the microcirculation of rat striated muscle.
Sprague-Dawley rats were anesthetized with pentobarbital (50 mg/kg) and the arterioles of the cremaster muscle were observed using television microscopy. Methionine (Met)-enkephalin was added to give bath concentrations of 10(-11) to 10(-7) M. Met-enkephalin caused a decrease in the diameter of first-order (127 +/- 7 microns), second-order (57 +/- 7 microns), and third-order (18 +/- 2 microns) arterioles, with the third-order arterioles showing the greatest reactivity. The effects of Met-enkephalin were attenuated by the opiate antagonist, naloxone, by the alpha-adrenergic receptor antagonists, phentolamine and prazosin, and by chemical sympathectomy with 6-hydroxydopamine. These results suggest that Met-enkephalin causes vasoconstriction in the striated muscle microcirculation by stimulating norepinephrine release from local nerve terminals.
Brock
J W
JW
Department of Physiology and Biophysics, School of Medicine, University of Louisville, KY 40292.
Joshua
I G
IG
Miller
F N
FN
Li
F
F
D000818:Animals; D001160:Arterioles / Q000187:drug effects; D004744:Enkephalin, Methionine / Q000494:pharmacology*; D008297:Male; D008833:Microcirculation / Q000187:drug effects; D009129:Muscle Tonus / Q000187:drug effects; D009132:Muscles / Q000098:blood supply*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
D014662:Vasoconstrictor Agents; D004744:Enkephalin, Methionine