Influence of brain stem on intra-abdominal pressure reflex of pelvic nerve origin

Abstract

Inhibitory and facilitory actions of the brain stem on the intra-abdominal pressure response to pelvic nerve stimulation (pelvicoabdominal reflex) were studied in anesthetized cats. Transection in the upper pons slightly caudal to the inferior colliculus suppressed the reflex, while transection in the medulla oblongata rostral to the apex of the ala cinerea caused release of the reflex from a tonic inhibition. Upon stimulating the brain stem, inhibitory points were found to be distributed widely in the preoptic region, subthalamus, hypothalamus, central graymatter, midbrain tegmentum, pontile tegmentum, bulbar reticular formation, and the region of the spinal tract of the trigeminal nerve. The lateral reticular formation at the level of the inferior olive, which produces an increase in the intra-abdominal pressure upon direct stimulation, proved to be inhibitory of the reflex. Facilitatory points were obtained only in the medulla; occasionally in areas lateral to the superior olive, near the solitary tract, and the raphe rostral to the obex; and invariably in the region corresponding to the medial longitudinal fascicle caudal to the obex.