Release of endogenous ATP from the vasa deferentia of the rat and guinea-pig by the indirect sympathomimetic tyramine.
1. Adenosine 5'triphosphate (ATP) as well as [3H]-noradrenaline ([3H]-NA) is released by perfusion of the vas deferens with the indirect sympathomimetic tyramine (100 microM); this result is consistent with the concept of sympathetic cotransmission. 2. While tyramine produced a strong contraction in the vas deferens of the rat, it had little mechanical action in the guinea-pig vas deferens. This appears to be largely because tyramine induces considerably lower levels of release of both ATP and NA from the guinea-pig vas deferens compared to that of the rat. Furthermore, NA released by tyramine appears to release ATP from a secondary pool in the rat vans deferens, but not that of the guinea-pig, since prazosin reduced the tyramine-induced release of ATP in the rat vas deferens. 3. alpha,beta-Methylene ATP (alpha,beta-meATP) increased both the spontaneous release of ATP and the tyramine-evoked efflux of ATP and [3H]-NA. The basal and tyramine-induced efflux of [3H]-NA was also enhanced by the alpha 1-adrenoceptor antagonist, prazosin, suggesting that prejunctional alpha 1-adrenoceptors may modulate neurotransmitter release.
Kirkpatrick
K A
KA
Department of Anatomy and Developmental Biology, University College London, UK.
Burnstock
G
G
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009638:Norepinephrine / Q000378:metabolism; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism; D014439:Tyramine / Q000494:pharmacology*; D014649:Vas Deferens / Q000187:drug effects / Q000378:metabolism*
D018340:Receptors, Adrenergic, alpha-1; D000255:Adenosine Triphosphate; D009638:Norepinephrine; D014439:Tyramine; D011224:Prazosin