The spatio-temporal characteristics of release of acetylcholinesterase from the in vivo substantia nigra can now be described using a chemiluminescent reaction. Electrical stimulation of the striatum caused an increase in release of acetylcholinesterase within the ipsilateral substantia nigra; however, this increase in release of protein was non-uniform and pulsatile. The findings suggest that release of acetylcholinesterase within the substantia nigra has a fine space-time resolution never before appreciated.