Effects of vagotomy on neurotransmitter receptors in the rat dorsal vagal complex

The dorsal vagal complex contains many different neurotransmitter receptors. The cyto-architectural localizations of some of these receptors remain largely unknown. In rats, vagotomy was performed to destroy vagal afferents terminating in the nucleus of the solitary tract and to produce chromatolysis of preganglionic motoneurons in the dorsal motor nucleus of the vagus. Quantitative receptor autoradiography was then employed to determine the effect of vagotomy upon the distribution of receptors for thyrotropin-releasing hormone, substance P, and serotonin within individual regions and subnuclei of the entire dorsal vagal complex. Vagotomy reduced the concentrations of thyrotropin-releasing hormone and substance P, but not serotonin 1A or serotonin 1B, receptors in the dorsal motor nucleus of the vagus. Within the nucleus of the solitary tract, substance P receptors were reduced in only the medial and central subnuclei after vagotomy. In contrast, no effect was observed upon the concentrations of thyrotropin-releasing hormone, serotonin 1A, or serotonin 1B receptors in any subnuclei of the solitary tract following vagotomy. These results suggest that in the dorsal motor nucleus of the vagus, thyrotropin-releasing hormone and substance P receptors are localized upon vagal preganglionic motoneurons, while serotonin 1A and serotonin 1B receptors are present upon interneurons or other neuronal elements. These results also suggest that thyrotropin-releasing hormone, substance P, serotonin 1A, and serotonin 1B receptors in the nucleus of the solitary tract are localized upon internuncial neurons in the nucleus of the solitary tract.