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Simultaneous measurement of contractile effects in the circular and longitudinal smooth muscle of the rat vas deferens by drugs perfused externally or via the lumen
Author(s) -
Busatto Pedro A.,
Jurkiewicz Aron
Publication year - 1985
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1985.tb11071.x
Subject(s) - vas deferens , isometric exercise , perfusion , lumen (anatomy) , muscle contraction , anatomy , medicine , chemistry , phenoxybenzamine , endocrinology , biology , propranolol
1 The effects of noradrenaline and barium chloride were studied in the rat isolated vas deferens by perfusion of drugs either externally or through the lumen of the organ. Two effects were recorded simultaneously in the same preparation: (a) isometric contractions, due to the tension elicited by drugs on the external (longitudinal) smooth muscle layer and (b) pressure of internal perfusion, due to contractions of the internal (circular) smooth muscle layer. 2 It was found with the longitudinal muscle that: (a) the potency, expressed as pD 2 values, and the maximum response to noradrenaline were lower if the drug was perfused internally rather than externally; (b) the differences in maximum effects were pronounced on the prostatic half but were not observed on the epididymal half; (c) the maximum response obtained by internal perfusion could be increased by simultaneously adding the same dose of drug externally; (d) when barium chloride was used instead of noradrenaline no significant differences were observed on pD 2 values, but differences on maximal responses were similar to that observed for noradrenaline; (e) it was possible to block completely the effect of internal or external noradrenaline on the longitudinal muscle, by perfusing external phenoxybenzamine. In these conditions the responses of the circular muscle to the agonist were only partly blocked. 3 With the circular muscle, the differences related to internal and external perfusion were less marked than in the longitudinal muscle. However, unlike the latter, the circular layer was slightly more sensitive to drugs applied internally, in relation to pD 2 values. 4 It is suggested that the difference in pD 2 values may be due to the removal of noradrenaline by the neuronal uptake process, whereas the difference in maximal effect is due to the inaccessibility of part of the receptor population when drugs are added through the lumen.