STIMULATED RELEASE OF ACETYLCHOLINESTERASE IN RAT STRIATUM REVEALED BY IN-VIVO MICROSPECTROPHOTOMETRY

The microspectrophotometric technique allows a direct in vivo measurem ent of brain extracellular acetylcholinesterase. An optical probe asso ciated with electrodes for stimulation was implanted in striatum of an aesthetized rats to determine the effects of neuronal excitation on th e acetylcholinesterase activity. Electrical stimulations induced a rev ersible increase in acetylcholinesterase activity of about 30 to 50%, with a recovery to baseline occurring after 1 or 2 h. Furthermore, ite rative electrical stimulation induced a progressive fading of this phe nomenon. An enhancement of acetylcholinesterase activity was also obse rved by stimulations with potassium injections through a canal of the probe. These results suggest mainly an intracellular origin of the rel eased enzyme and estimate its contribution at about 40% of the whole e xtracellular enzyme activity.