THE pentapeptide enkephalin interacts with opiate receptors of peripheral tissues¹ and with stereospecific opiate receptors of brain homogenates². Ejected from micropipettes in the vicinity of central neurones, it has depressant^3–5 and excitant⁶ effects. These actions, however, cannot be related specifically to the analgesic effects of systematically administered opiates. In electrophoretic experiments, tissue concentrations are unknown and hence even antagonism by electrophoretic naloxone is not necessarily a sufficient test of relevance to the effects of systemic opiates. This report is concerned with the effects of morphine when administered electrophoretically into the substantia gelatinosa. The subsequent changes in the firing of neurones within Rexed laminae IV and V can be related to the effects of this compound given svstemically. Furthermore methion-ine enkephalin had an action similar to that of morphine.