Long-term effects on cortical glutamate release induced by prenatal exposure to the cannabinoid receptor agonist (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinyl-methyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone: an in vivo microdialysis study in the awake rat.

The aim of the present in vivo microdialysis study was to investigate whether prenatal exposure to the CB(1) receptor agonist WIN55,212-2 mesylate (WIN; (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinyl-methyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone), at a dose of 0.5 mg/kg (s.c. from the fifth to the 20th day of gestation), that causes neither malformations nor overt signs of toxicity, influences cortical glutamate extracellular levels in adult (90-day old) rats. Dam weight gain, pregnancy length and litter size at birth were not significantly affected by prenatal treatment with WIN. Basal and K(+)-evoked dialysate glutamate levels were lower in the cerebral cortex of adult rats exposed to WIN during gestation than in those born from vehicle-treated mothers. In both group of animals WIN (0.1 mg/kg, i.p.) increased dialysate glutamate levels. However, while the blockade of the CB1 receptors with the selective receptor antagonist SR141716A completely counteracted the WIN-induced increase in those rats exposed to vehicle during gestation, it failed to antagonise the increase in those born from WIN-treated dams. These findings suggest that prenatal exposure to the CB1 receptor agonist WIN, at a concentration which is not associated with gross malformations and/or overt signs of toxicity, induces permanent alterations in cortical glutamatergic function. The possibility that these effects might underlie, at least in part, some of the cognitive deficits affecting the offspring of marijuana users is discussed.