Gastric mucosal erosion produced by NMDA microinfusions in the lateral hypothalamus: effect of selective knife cuts.

Bilateral infusions of N-methyl-D-aspartate (NMDA) into the lateral hypothalamus (LH) produce gastric erosions in rats. The present study attempted to determine the neural pathways that mediate this effect. In order to interrupt axonal transmission, knife cuts (KC) were made in different planes adjacent to the LH. In separate groups of rats, KC were made anterior, posterior or lateral to the LH just prior to bilateral NMDA infusions (20 micrograms/microliter). The incidence of gastric erosions was measured 24 h after NMDA infusions. Animals receiving sham KC and infused with NMDA exhibited significantly more gastric erosions than those infused with vehicle. Lateral parasagittal KC blocked the occurrence of gastric erosions produced by NMDA, whereas anterior coronal KC significantly increased the incidence of erosions produced by NMDA. Posterior coronal KC did not alter the incidence of gastric erosions produced by NMDA infusions into the LH. These results suggest that intrinsic LH neurons with gastric function project axons laterally and probably descend through the internal capsule to brainstem medullary nuclei. The results of the anterior KC suggest that the LH sends and/or receives inhibitory projections from neural structures (possibly the amygdaloid complex) anterior to the plane of the KC.