Morphine: exogenous endorphin?

Abstract

There is now increasing evidence that the multiple pharmacological actions of morphine are mediated by different sites in the central nervous system (CNS). For example, the periaqueductal gray (PAG) is now known to mediate the analgesic action of morphine (Jacquet and Lajtha, 1976), as well as the explosive motor behavior (EMB) observed following local morphine administration (Jacquet and Lajtha, 1974). Some morphine abstinence signs such as wet-dog shakes, teeth chattering, and so on, were found to be mediated by sites adjacent to the lateral ventricle (Herz, 1972), and body temperature changes induced by morphine were found to be mediated by hypothalamic sites (Lotti, 1973). However, other characteristic morphine effects such as opiate immobility have not yet been localized to any specific CNS site.