Cocaine exposure during the brain growth spurt: studies of neonatal survival, somatic growth, and brain development

Neonatal Sprague-Dawley rat pups were assigned to one of five groups. Three cocaine-treated groups were injected SC with either 40, 60, or 80 mg/kg/day of cocaine from postnatal day (PND) 4 through 9. Control groups were either injected with equivalent volumes of sterile dH2O (vehicle control) or received no injections (normal control) from PND 4 through 9. This early postnatal period, corresponding to the third trimester of pregnancy in humans, is characterized as a period of rapid development within the central nervous system (CNS), generally termed the brain growth spurt. The survival rate, somatic growth, and brain development in response to the various dosages of postnatal cocaine administration were assessed. There was a dose-dependent relationship between cocaine administration and survival rate. Furthermore, significantly reduced somatic growth, assessed in terms of body weight, was found in animals given 80 mg/kg cocaine daily, as compared with controls. With respect to brain weight, no significant differences were obtained among the various doses of cocaine-treated and control animals and there was no evidence of regional vulnerability (forebrain, cerebellum, or brainstem) to the cocaine insult. Additionally, neither an effect of gender, nor the interactions of gender with various doses of cocaine treatment was found on somatic growth and brain development. Taken together, the present results suggest that the brain exhibits a greater resistance to the cocaine insults than does somatic growth. Several possible explanations regarding the somatic growth retardation are discussed.