Premium
TRANSIENT EXCITATORY RESPONSES TO SUSTAINED STIMULATION OF INTRAMURAL NERVES IN ISOLATED BOVINE LYMPHATIC VESSELS
Author(s) -
McHale N. G.,
Allen J. M.,
McCarron J. G.
Publication year - 1988
Publication title -
quarterly journal of experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0144-8757
DOI - 10.1113/expphysiol.1988.sp003130
Subject(s) - stimulation , contraction (grammar) , isometric exercise , medicine , endocrinology , excitatory postsynaptic potential , muscle contraction , chemistry , extracellular , biology , inhibitory postsynaptic potential , biochemistry
Spontaneous isometric contractions were measured in 2 cm segments of bovine mesenteric lymphatics. Field stimulation at 4 Hz was applied for a 20 min period. This caused a threefold increase in contraction frequency initially but the response faded rapidly so that, within 6 min of the beginning of stimulation, contraction frequency had returned to a value which was not significantly different from control. In contrast to the effect on frequency 3 H efflux from vessels pre‐loaded with [ 3 H]noradrenaline was maintained at a value significantly higher than control for the entire stimulation period. The fade in response to exogenous noradrenaline was similar to that seen with field stimulation but with a slightly slower time course. Vessels desensitized with noradrenaline showed a greatly diminished response to field stimulation but responded normally to other agonists. Increasing the extracellular KCI concentration to 18 mM also caused a threefold increase in contraction frequency but, unlike the response to noradrenaline and field stimulation, this was maintained for the 20 min period during which [K + ] o was raised. The results suggest that the adrenoceptors on lymphatic smooth muscle exhibit very rapid homologous desensitization.