1 In the normal and
phenoxybenzamine-treated vasa deferentia of the rat the overflow of
tritium after preloading with [3H]-
noradrenaline increased with the increase in frequency of transmural stimulation. Phenozybenzamine enhanced overflow by 5 to 7 fold. 2 After
tetraethylammonium (
TEA, 10 mM), fractional
tritium overflow at 5 Hz increased from a control value of 2.8 to 53 X 10(-4), and at 0.5 Hz it reached 154 X 10(-4). Enhancement of overflow was inversely related to the frequency of stimulation. 3 Contractor responses of the vas deferens induced by transmural stimulation were markedly potentiated, both in amplitude and duration, by 10 mM
TEA. The contraction developed in the presence of 10 mM
TEA at 0.5 Hz was comparable to that obtained
at 10 Hz in normal
Krebs solution. 4 In the presence of 5 mM
TEA, contractions of the vas deferens caused by exogenous
noradrenaline were potentiated about 5 fold. 5 The overflow and contractor response induced by 45 mM K were enhanced about 5 fold in 10 mM
TEA-
Krebs solution. Facilitation of K-induced overflow by
TEA was reduced over 50% by
tetrodotoxin (TTX, 1 microM). 6 Delivery of a single
shock (1.0 ms duration) to 10 mM
TEA-treated vas deferens resulted in a 63% increase in
tritium overflow over background overflow. The fractional overflow amounted to almost 720 X 10(-4) after a single
shock, as compared to 154 X 10(-4) obtained at 0.5 Hz. 7 The vas deferens treated with 10 mM
TEA and stimulated by a single
shock developed a contraction which was greater in amplitude and duration than that seen in normal tissue
at 10 Hz. 8 Five second serial samples collected from superfused 10 mM
TEA-treated vas deferens contained maximum quantities of radioactivity in the first 5 s after a single
shock. In subsequent samples, radioactivity gradually declined, and reached prestimulation level after about 25 s. 9 The fractional overflow caused by stimulation at 0.1 Hz in 10 mM
TEA-treated tissue progressively increased as external Ca was gradually raised from 0.83 to 10 mM. 10 The mechanism of action of
TEA in enhancing the overflow of sympathetic transmitter, particularly in response to a single
shock, is discussed in relation to Ca.