Abstract
In anesthetized rats, responses of extracellular dopamine release in the nucleus accumbens to innocuous and noxious mechanical cutaneous stimulation of the back were investigated. Coaxial microdialyis probe was stereotaxically implanted in the nucleus accumbens and dialysed with artificial cerebrospinal fluid at a speed of 2 μl/min. Dialysate output from the probe was directly injected into the high liquid chromatograph and the amount of dopamine released from the nucleus accumbens for 5 min was consecutively measured with electro-chemical detector. Innocuous stroking stimulation for 5 min applied to the bilateral back significantly increased dopamine release for 10 min after the onset of stimulation. The increase in dopamine release was observed by stroking of the contralateral, but not iplilateral back. Bilateral noxious pinching stimulation had no effect on dopamine release in the nucleus accumbens. These results indicate that excitation of the innocuous mechanical afferents can stimulate dopamine release without emotional influence. [J Physiol Sci. 2006;56 Suppl:S213]
