Abstract
The aim of the present study was to examine whether the LC/SC modulates visceromotor function. An electromyogram (EMG) of the external abdominal oblique muscle evoked by colorectal distention was measured as a visceromotor response, and inhibitory effects of LC/SC stimulation were estimated by the decrease of EMG activity. Under halothane anesthesia (1% in air), graded colorectal distentions (30, 60, or 80 mmHg) were produced by inflating a balloon inside the descending colon and rectum. Colorectal distention at a pressure of 30 mmHg did not evoke any EMG activity in the external abdominal oblique muscle in all rats tested. Electrical stimulation of the LC/SC (30, 50 and 70 μA, 100 Hz, 0.1 ms pulses) reduced EMG responses evoked by colorectal distention to 60 and 80 mmHg. LC/SC stimulation was effective both ipsilaterally and contralaterally indicating a bilateral effect. EMG responses decreased with an increase of LC/SC stimulation intensity. Following recordings of the inhibitory effects of LC/SC stimulation, lesions of the LC/SC ipsilateral to the EMG recording site were induced. LC/SC stimulation did not reduce the EMG responses when stimulation was applied to the lesiond LC/SC, whereas EMG responses were observed by stimulation of the intact LC/SC contralateral to the EMG recording site. From lesion experiments, it could be considered that suppression of the visceromotor response to colorectal distention is due to activation of the LC/SC. The results suggest that the visceromotor function is under the control of the centrifugal pathways from the LC/SC. [Jpn J Physiol 55 Suppl:S157 (2005)]
