ACTIVATION OF LOCUS-COERULEUS BY PREFRONTAL CORTEX IS MEDIATED BY EXCITATORY AMINO-ACID INPUTS

We examined the role of excitatory amino acids (EAAs) in activation of noradrenergic locus coeruleus (LC) neurons evoked by electrical stimu lation of the medial prefrontal cortex (mPFC) in halothane-anesthetize d rats. Microinfusion of the specific N-methyl-D-aspartate antagonist 2-amino-5-phosphonopentanoic acid (AP5, 50 or 100 mu M) into the LC si gnificantly suppressed LC responses evoked by mPFC stimulation. Microi nfusion of the selective non-NMDA antagonist 6-cyano-7-nitroquinoxalin e-2,3-dione (CNQX, 25 or 50 mu M) also significantly reduced evoked LC responses. Simultaneous microinfusion of both AP5 and CNQX considerab ly increased the proportion of LC neurons which exhibited complete sup pression of evoked responses (81%), compared to either AP5 or CNQX alo ne (similar to 50% each). These results indicate that LC activation by mPFC stimulation is mediated by both MMDA- and non-NMDA-type EAA chan nels. (C) 1997 Elsevier Science B.V.