In utero exposure to cocaine delays postnatal synaptic maturation of glutamatergic transmission in the VTA.

Maternal exposure to cocaine may perturb fetal development and affect synaptic maturation in the offspring. However, the molecular mechanism underlying such changes remains elusive. We focused on the postnatal maturation of glutamatergic transmission onto ventral tegmental area dopamine neurons in the mouse. We found that, during the first postnatal week, transmission was dominated by calcium-permeable AMPA receptors and GluN2B-containing NMDA receptors. Subsequently, mGluR1 receptors drove synaptic insertion of calcium-impermeable AMPA receptors and GluN2A-containing NMDAR. When pregnant mice were exposed to cocaine, this glutamate receptor switch was delayed in offspring as a result of a direct effect of cocaine on the fetal dopamine transporter and impaired mGluR1 function. Finally, positive modulation of mGluR1 in vivo was sufficient to rescue maturation. These data identify the molecular target through which in utero cocaine delays postnatal synaptic maturation, reveal the underlying expression mechanism of this impairment and propose a potential rescue strategy.