Administration of dexfenfluramine in pregnant rats: effect on brain serotonin parameters in offspring

Impaired spatial and sequential learning in rats treated neonatally with D-fenfluramine

D-Fenfluramine, a serotonin releaser, was administered to neonatal rats on postnatal days 11-20 (a stage of hippocampal development analogous to third trimester human ontogeny). As adults, the D-fenfluramine-treated offspring exhibited dose-related impairments of sequential and spatial learning and reference memory in the absence of sensorimotor impairments. Procedures to minimize stress and to control for other performance effects prior to testing for spatial learning demonstrated that nonspecific factors did not account for the selective effects of D-fenfluramine on learning and memory. Developmental D-fenfluramine-induced spatial and sequential learning deficits are similar to previous findings with developmental MDMA treatment. By contrast, recent findings with developmental D-methamphetamine treatment showed spatial learning deficits while sparing sequential learning. The spatial learning effects common to all three drugs suggest that they may share a common mechanism of action, however, the effects are not related to long-lasting changes in hippocampal 5-HT levels as no differences were found in adulthood. Whether the cognitive deficits are related to the effects of substituted amphetamines on corticosteroids, other aspects of the 5-HT system, or some unidentified neuronal substrates is not known, but the data demonstrate that these drugs are all capable of inducing long-term adverse effects on learning.

Effects of antihistamines on fenfluramine-induced depletion of indoles in the brain of rats

Various effects of chlorpheniramine (CPA), diphenhydramine (DIPH), tripelennamine (TRIP), and pyrilamine (PYRI) on fenfluramine (FEN)-induced depletion of serotonin in the brain of rats were observed to be dependent on body temperature. Levels of 5-HT and 5-HIAA in the frontal cortex, hippocampus, and striatum of rats treated with FEN (10 mg/kg, once or twice daily x 4 days) decreased to approximately 30% (P < 0.01) that of controls with no significant changes after CPA, DIPH, TRIP, and PYRI. Treatment with FEN plus CPA (5, 10, 20 mg/kg) and FEN plus DIPH (20 mg/kg), but not FEN plus TRIP (20 mg/kg) and FEN plus PYRI (20 mg/kg), increased brain serotonin levels 2- to 3-fold more than those treated with FEN plus saline. Treatment with FEN plus CPA and FEN plus DIPH, but not FEN plus TRIP and FEN plus PYRI, decreased rectal temperature with no significant change after FEN. The antihistamines alone decreased temperature at a 1-hour period and enhanced FEN-induced reduction in body weight. Possible mechanisms of the different effects of antihistamines on FEN-induced depletion of serotonin are discussed.

Effects of prenatal co-administration of phentermine and dexfenfluramine in rats

Pregnant rats were infused with phentermine plus dexfenfluramine from days 3 through 17 of gestation. Control rats were either pair-fed or were fed ad libitum. There were no effects of prenatal drug treatment on number of offspring, their birth weights, or on their motor coordination assessed at 11 days of age. Mothers and pups were sacrificed 21 days postpartum. Drug-treated mothers, but not their pups, showed a reduced density of serotonergic axons in the hippocampus compared with controls. 25% of the pups from the prenatal drug group showed mitral valve thickening.