Baseline spike activity of neurons in the locus coeruleus of the rat after lesions to a number of medulla oblongata nuclei.

Bilateral lesioning of the presublingual nucleus (nucleus praepositus hypoglossi) of the medulla oblongata induced significant changes in the nature of baseline spine activity in the locus coeruleus. After lesioning, the mean frequency of spike activity of locus coeruleus neurons decreased more than two-fold. The numbers of neurons with train-grouped activity and polymodal neurons increased significantly. Exclusion of the solitary tract nucleus led to an increase in the number of neurons with regular activity and some decrease in the mean discharge frequency in locus coeruleus neurons. These data support the suggestion that the presublingual nucleus plays a significant role in the transmission of afferent influences on the activity of locus coeruleus neurons.