Olfactory bulb neurons respond to gastric distension.

Single unit discharges in the olfactory bulb (OB) were recorded extracellularly in anesthetized rats during controlled gastric distension. The activity of 37 neurons in the periglomerular layer of the OB modulated by gastric distension was analyzed. Twelve of the 37 cells decreased, eight decreased and then increased in frequency, and 17 displayed more complex effects due to gastric distension. Generally, the latency of the responses to gastric distension was less than one second. All those cells which responded to gastric distension also responded to vagus nerve stimulation. This effect was abolished or attenuated by cutting the vagus nerve at the cervical level. The threshold volume by which the stomach was infused for the initial decrease in OB neuronal discharge frequency was 3.0 ml. When more than 8 ml were infused, increases in firing frequencies were always observed. The results of the present experiments indicate that the discharge frequency of the periglomerular OB neurons are modulated by visceral afferents.