EXISTENCE OF GLUTAMATE IN NORADRENERGIC LOCUS-COERULEUS NEURONS OF RODENTS

This study distinguished three types of immunolabeled neurons in nucle us locus coeruleus (LC) of the rat and mouse: cells single labeled eit her for tyrosine hydroxylase-like immunoreactivity (TH-LI) or glutamat e (Glu)-LI, and those double labeled for both antigens. Although the d ouble labeled neurons tend to be located in the middle and ventral thi rds of the rat LC nucleus, throughout its rostrocaudal extent, such fe ature was not apparent in the mouse. Quantitatively a majority of neur ons cocontaining TH- and Glu-LI were commonly observed in the rat (62% ) and mouse (77%) LC. Additional studies utilizing the combined retrog rade and immunohistochemical labeling revealed that such a high incide nce of coexistence of the TH- and Glu-LI was also represented by coeru leocortical neurons in the rat (69% and 75% of all ipsilateral and con tralateral projection cells, respectively). A possible role of coerule ocortical neurons involvement in Glu- and norepinephrine-mediated targ et neuron dysfunction is discussed.