Limitations of presynaptic adrenoceptor theory: the characteristics of the effects of noradrenaline and phenoxybenzamine on stimulation-induced efflux of [3H]noradrenaline in vas deferens.

摘要: The effects of noradrenaline and phenoxybenzamine on the stimulation-induced efflux 3H-transmitter were examined in guinea-pig vasa deferentia to assess how they conform expectations presynaptic receptor theory. stimulated transmurally with 0.5, 1.0, 3.0 10.0 Hz two different train lengths (10 50 pulses), presence either agonist or antagonist. Noradrenaline (3 X 10(-7) M) depressed overflow tritium by about 60% at each test frequency 10 pulses 30% pulses, except 0.5 Hz. Phenoxybenzamine 10(-5) increased a diminishing extent increasing frequency, both effect was not sensitive length. finding that decreased essentially independent suggests these compounds do function as antagonist adrenoceptor regulating transmitter output. Further, distinctly profiles for phenoxybenzamine, length, raises possibility have common mechanism site action achieving their effects.