Descending influences from the infralimbic cortex on vago-vagal reflex control of gastric motor activity in the rat

In experiments on urethane anaesthetised rats the influence of electrical s timulation of ventral areas of the medial prefrontal cortex (mPFC) on spont aneous and vagally-mediated gastric motility were studied. Stimulation of t he mPFC resulted in gastric relaxation manifested as a fall in intragastric pressure from a baseline value of 5.0+/-0.5 cm H2O. These were most promin ent following a short latency when the infralimbic cortex (IL) was stimulat ed (27.4+/-2.5% fall in gastric pressure). Electrical stimulation of the ce ntral end of one cervical vagus nerve caused a comparable decrease in gastr ic pressure (27.1+/-2.9%). The cortical mediated relaxation was reduced by atropine and abolished by vagotomy. The cortically induced gastric relaxati on followed a shorter latency (5.9+/-1.0 s), time to nadir (20.1+/-2.7 s) a nd the half recovery time (21.5+/-4.0 s) than vagally mediated relaxations (9.9+/-2.3, 56.0+/-5.3 and 83.4+/-9.5 s, respectively). Vagally mediated re laxations were inhibited by simultaneous stimulation of the infralimbic cor tex. In this case the decrease of gastric pressure, the time to nadir and t he half recovery time were significantly decreased in comparison with the g astric relaxatory responses to vagal stimulation alone (P<0.05). We conclud e that one way in which the mPFC influences gastric motility is via cortico fugal projections from the infralimbic cortex to the brain-stem which modul ate transmission of vago-vagal reflexes. (C) 2000 Published by Elsevier Sci ence B.V.