Neuronal expression of FOS protein in the nucleus tractus solitarii and the dorsal motor nucleus of the vagus nerve after i.p. injection of ulcerogenic aspirin.

Aspirin, a common analgesic-antipyretic and anti-inflammatory drug, often induces gastric ulcer, but its pathogenesis remains unsettled. The purpose of this study was to identify the CNS neurons that express FOS protein after i.p. injection of aspirin (100-300 mg/kg). This was done in the unanesthetized Wistar rats with careful physiological controls. Dose-dependently, many FOS-immunoreactive (FOS-ir) neurons were found in the medial part of the nucleus tractus solitarii (NTSm) and the dorsal motor nucleus of the vagus nerve (DMX) of the lower medulla, but none in the paraventricular nucleus of the hypothalamus (PVH). Distribution of FOS-ir neurons in the DMX corresponds with that of the visceromotor neurons involved in gastric secretion. This study suggests that the aspirin-induced gastric ulcer may not originate in the PVH but in the NTSm-DMX system.