Influence of temperature on stimulus-secretion coupling in the sympathetic nerves and on neuromuscular transmission, in guinea-pig vas deferens.
In guinea-pig isolated vas deferens moderate cooling (within the range 16-41 degrees C) improved, while further cooling depressed, sympathetic neuromuscular transmission. Moderate cooling: (a) enhanced the contractile responses both to electrical nerve stimulation and (although less strongly) to exogenous noradrenaline or to the adenosine 5'-triphosphate (ATP) analogue, alpha, beta-methylene ATP; (b) enhanced the overflow of [3H]noradrenaline evoked by electrical nerve stimulation at 1-8 Hz, but not that caused by direct depolarization of varicosities with 80 mM potassium; (c) reduced the depressing effect of exogenous noradrenaline, as well as the enhancing effect of the alpha-adrenoceptor blocking agent phentolamine, on the secretory responses to electrical nerve stimulation; (d) while not altering the maximal secretion of tracer noradrenaline at infinitely high frequency or external calcium, lowered the frequency or calcium concentration required for half-maximal secretion, both in the absence and in the presence of phentolamine.


CONCLUSIONS
moderate cooling improves sympathetic neuromuscular transmission in guinea-pig vas deferens, both prejunctionally, by enhancing transmitter secretion, and post-junctionally, by increasing the responsiveness of the smooth muscle to transmitter.
Stjärne
L
L
Alberts
P
P
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004558:Electric Stimulation; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009469:Neuromuscular Junction / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism* / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism; D010646:Phentolamine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects; D013696:Temperature; D014649:Vas Deferens / Q000294:innervation*
D000317:Adrenergic alpha-Antagonists; D018377:Neurotransmitter Agents; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine; D010646:Phentolamine