Impulse activity of the rat medulla oblongata in response to stimulation of taste receptors and visceral chemoreceptors

The unit activity from the medulla oblongata was extracellularly recorded during stimulation of taste receptors and visceral chemoreceptors of small intestine with the solutions of hydrochloric acid and sodium chloride. Neurons responding to the chemical stimulation are at the caudal part of nucleus tractus solitarius. Responses of taste, viscerochemical and convergence units are tonic and their discharge rates are low. The ability for chemical stimulus graduation analysis characterizes each group of units. Increased concentration of the solutions in intestine brings about the increase in the number of viscerochemical neurons with inhibited background activity. This may be the index of satiation and serve as a starting link in the mechanism of food rejection.