A study of inputs to antidromically identified neurons of the locus coeruleus

Abstract

1. (1) Electrophysiological techniques were used to investigate inputs to the locus coeruleus (LC) in rats anesthetized with urethane. 2. (2) Neurons, histologically verified as being in the LC, were activated antidromically by stimulation of the supracallosal bundle. Some LC neurons were also activated antidromically by stimulation of the olfactory bulb and the bed nucleus of the stria terminalis. 3. (3) Stimulation of the vagus nerve produced mainly inhibition of LC neurons and inhibition followed by excitation. Stimulation of the splanchnic nerve and sciatic nerve produced mainly excitation of LC neurons. 4. (4) Stimulation of the bed nucleus of the stria terminalis and the olfactory bulb produced mainly inhibition and inhibition followed by excitation of LC neurons. Stimulation of the preoptic region and ventromedial nucleus of the hypothalamus produced inhibition-excitation and excitation-inhibition of LC neurons. 5. (5) Convergence of inputs to neurons of the LC were demonstrated with stimulation of sciatic nerve and splanchnic nerve, stimulation of vagus nerve and splanchnic nerve and stimulation of sciatic nerve and vagus nerve. Convergence of inputs was also observed with stimulation of olfactory bulb and bed nucleus of stria terminalis, stimulation of preoptic region and ventromedial hypothalamus, and stimulation of bed nucleus of stria terminalis and ventromedial nucleus of hypothalamus. 6. (6) The demonstration of multiple umputs to the neurons of the LC, which in turn projects diffusely to hippocampus, cerebral cortex, and cerebellum, is consistent with previous reports implicating the LC in a variety of physiological and behavioral responses.