Alpha-adrenoceptors and facilitation at a sympathetic neuroeffector junction.
Excitatory junction potentials were recorded from the mouse vas deferens following 5 stimuli at 1Hz and a single stimulus at times from 100 msec to 9 sec later. E.j.ps facilitate and facilitation decayed over a biexponential time course, with time constants of 120 msec and 4.3 sec. Clonidine (10(-8)-10(-7) M) depressed e.j.p. amplitude, and also accelerated both phases of the decay of facilitation. Yohimbine (10(-7) M) and piperoxan (10(-7)-10(-6) M) increased the amplitude of all but the first e.j.p. in a train, and slowed both phases of the decay of facilitation. One way in which prejunctional modulation by alpha-adrenoceptors may occur is therefore by modifying the carry-over of facilitation from one stimulus to the next.
D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009130:Muscle, Smooth / Q000187:drug effects; D009431:Neural Conduction / Q000187:drug effects; D009451:Neuroeffector Junction / Q000187:drug effects*; D010883:Piperoxan / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D010883:Piperoxan; D003000:Clonidine