INTRASEPTAL MICROINJECTION OF BETA-FUNALTREXAMINE BLOCKED A MICROWAVE-INDUCED DECREASE OF HIPPOCAMPAL CHOLINERGIC ACTIVITY IN THE RAT

Acute (45 min) exposure to pulsed (2 mu s pulse width, 500 pulses per second) 2450-MHz microwaves at a power density of 1 mW/cm(2) (whole bo dy specific absorption rate 0.6 W/kg) microwaves caused a decrease in cholinergic activity in the hippocampus of the rat as measured by the sodium-dependent high-affinity choline uptake. Microinjection of beta- funaltrexamine (1 mu g) into the septum before microwave exposure bloc ked this effect. These data indicate that mu-opioid receptors in the s eptum mediate a microwave-induced decrease in cholinergic activity in the hippocampus and support our hypothesis that microwaves at a whole body SAR of 0.6 W/kg can activate endogenous opioids in the brain.