Stress induced changes in transmitter release from sympathetic varicosities of the mouse vas deferens

Activation of the sympathetic nervous system is an important component of t he response to stress, but the effects of prolonged stress on sympathetic n eurotransmission have not been assessed. In the present study we have exami ned the effect of 3 to 10 days exposure to stress induced by frequent handl ing and sham injections on neurotransmitter release from sympathetic varico sities of the mouse vas deferens. DiOC(2)(5)-fluorescence was used to visua lise the sympathetic varicosities so that extracellular electrodes could be placed over known numbers of varicosities to monitor transmitter release u sing electrophysiological techniques. The frequency of excitatory junction currents (EJCs) increased with increasing duration of exposure to stress. T he mean and maximum EJC amplitude significantly increased by 107% and 43%, respectively after 10 days of exposure to stress. The density of sympatheti c varicosities innervating smooth muscle of the mouse vas deferens was not changed throughout the duration of the exposure to stress. The findings fro m this study demonstrate that the efficacy of transmitter release from the sympathetic varicosities is altered by repeated exposure of mice to stressf ul stimuli, such as handling and sham injections. Since such procedures are routine in many pharmacological experiments, it is important that investig ators are aware of these changes so that due consideration is given when in terpreting the data obtained from animals treated in this way. (C) 1999 Els evier Science B.V. All rights reserved.