GLUCOSE ATTENUATES A MORPHINE-INDUCED DECREASE IN HIPPOCAMPAL ACETYLCHOLINE OUTPUT - AN IN-VIVO MICRODIALYSIS STUDY IN RATS

Systemic injections of morphine impair performance in memory tests. Gl ucose administration ameliorates memory deficits produced by morphine treatment. The memory impairments induced by morphine may be related t o opioid inhibition of acetylcholine release with reversal of this eff ect by glucose. The present experiment determined whether: (1) systemi c morphine treatment decreases acetylcholine output in the hippocampal formation; and (2) systemic glucose administration attenuates the eff ect of morphine treatment. Employing microdialysis, samples were colle cted at 12-min intervals and assayed for acetylcholine using HPLC with electrochemical detection. Morphine (10 mg/kg)/saline injections resu lted in an immediate decrease in acetylcholine output (20-35%) that wa s observed up to the third postinjection sample (36 min). Glucose (100 mg/kg) administered concurrently with morphine attenuated the reducti on in acetylcholine output in the second and third samples. These find ings suggest that glucose may attenuate morphine-induced memory impair ments by reversing a decrease in acetylcholine output produced by morp hine.