Reactive Sprouting (Pruning Effect) is Altered in the Brain of Rats Perinatally Exposed to Morphine

Abstract

Recent publications have suggested that the endogenous opioid system may be involved in the natural process of brain growth and development (1). When opioids such as morphine, heroin, or methadone are supplied exogenously to man and laboratory animals, there is a reduced somatic and neuronal development (1, 2, 3, 4). In addition if opioids are added to the culture media of neurons and cell lines, the process of growth and differentiation is altered (3, 4). These effects are apparently mediated by the opioid receptor since the administration of specific antagonists prevents the opioid-induced alterations (3, 4). Also opioid antagonists as naltrexone alter brain and body development when administered to pregnant mothers (1). The diffusion of opiates from the mother blood stream to the fetus brain occurs without apparent difficulties (3, 4). The “opiate foetal syndrome”, encountered in children of mothers addicted to opiates, is apparently becoming widespread with an incidence superior to other neonatal problems such as those caused by alcoholic mothers, or cancer and Down syndrome (3, 4). It is unclear to what extent the brain of neonates from opiate addicted mothers is altered, and furthermore no molecular and cellular clues are available for understanding such damage.