Postnatal Development of the Mechanical Response of the Isolated Rat Vas Deferens to Nerve Stimulation

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Abstract
Isolated vas deferens preparations from rats aged 2–22 days were stimulated transmurally in a superfusion bath. The first responses to postganglionic nerve stimulation appeared in preparations from animals 3 days of age whereas responses to exogenous noradrenaline (NA) and direct stimulation of the smooth muscle cells were obtained one day earlier. Preparations of all ages responded readily to low concentrations of exogenous NA (0.2–5.0, μg/ml) while acetylcholine (ACh) had to be added in much higher concentrations (10–100, μg/ml) to give equal direct responses.a‐receptor blockers (phentolamine or phenoxybenzamine, 0.2–2.0, μg/ml) totally inhibited the contractions of preparations from animals up to about 10 days of age, but thereafter the effect was changed into potentiation of the responses. Atropine (0.5–2.0, μg/ml) generally caused a slight decrease of contractions of preparations up to about 15 days of age, but at later stages it was without effect.It is concluded that the major part of the motor innervation of the rat vas deferens is adrenergic but that subtreshold amounts of ACh probably are liberated from some source within the organ on transmural stimulation. The most probable explanation for the greater sensitivity of the young vas deferens preparations to the specific receptor blockers seem to be a greater accessibility of the junctional receptors, perhaps in combination with relatively smaller amounts of transmitter liberated at these early ages.

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