FOS EXPRESSION IN RAT PONTINE TEGMENTAL NEURONS FOLLOWING ACTIVATION OF THE MEDIAL PREOPTIC AREA

Fos immunohistochemistry was used to map the distribution of pontine n eurons excited by activation of the medial preoptic area (MPO). Althou gh we have previously shown that Barrington's nucleus receives a very dense focal input from the MPO, electrical stimulation of the preoptic area unexpectedly induced very little Fos expression in Barrington's neurons. These results suggest that the MPO --> Barrington's projectio n utilizes a transmitter(s) that does not involve transduction of the Fos protein; alternatively, MPO afferents to Barrington's nucleus may be inhibitory in nature. As Barrington's nucleus plays a critical role in micturition, MPO projections to Barrington's nucleus may regulate voiding reflexes during sexual behavior. Interestingly, while the locu s coeruleus (LC) proper receives only a sparse projection from the MPO , extensive Fos expression was present in LC. The finding of Fos immun oreactive LC neurons suggests that the excitatory influence of MPO may regulate LC neuronal activity and NE release during reproductive beha viors. (C) 1998 Elsevier Science B.V.