Evidence for sympathetic, purinergic transmission in the iris dilator muscle of the rabbit.
Electrical transmural stimulation of isolated iris dilator muscle of the rabbit produced a transient contraction that consisted of adrenergic and nonadrenergic components. In contrast to the adrenergic component, the nonadrenergic component was resistant to prazosin and other adrenoceptor antagonists. However, both components were completely blocked by guanethidine or tetrodotoxin. Among some tested compounds including neuropeptide Y, both ATP and 2-methylthio ATP produced a transient contraction in the dilator muscle and the sustained treatment with each markedly attenuated the nonadrenergic responses to electrical stimulation and to ATP. Suramin had no effect on and alpha,beta-methylene ATP potentiated the responses to electrical stimulation and to ATP. These results suggest that the nonadrenergic contraction induced by electrical transmural stimulation is a sympathetic purinergic response that may be mediated through unique purinoceptors.
Muramatsu
I
I
Department of Pharmacology, Fukui Medical School, Japan.
Kigoshi
S
S
Oda
Y
Y
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D004558:Electric Stimulation; D005260:Female; D006145:Guanethidine / Q000494:pharmacology; D066298:In Vitro Techniques; D007498:Iris / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009478:Neuropeptide Y / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011817:Rabbits; D011983:Receptors, Purinergic / Q000187:drug effects / Q000502:physiology*; D013498:Suramin / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D009478:Neuropeptide Y; D011983:Receptors, Purinergic; D013873:Thionucleotides; D013779:Tetrodotoxin; D013498:Suramin; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D011224:Prazosin; C008501:2-methylthio-ATP; D006145:Guanethidine