Reduction of Corticostriatal Glutamatergic Fibers in Basic Fibroblast Growth Factor Deficient Mice is Associated with Hyperactivity and Enhanced Dopaminergic Transmission

Background: Basic fibroblast growth factor (FGF2) plays a crucial role during the development of the cerebral cortex. Mice with a knockout of the FGF2 gene have a reduced number of glutamatergic neurons within the deep layers of the cerebral cortex. Methods: We used molecular and behavioral analyses to investigate possible alterations in corticostriatal function in FGF2 / mice. Results: We found that FGF2 deficiency leads to decreased expression of presynaptic markers of integrity for glutamatergic fibers in the striatum, namely the membrane excitatory amino acid transporter 3 (EAAT3) and the vesicular glutamate transporter 1 (VGLUT1). The reduction of corticostriatal glutamatergic function in FGF2/mice is associated with enhanced locomotor activity in a novel environment and increased responsiveness to dopaminergic drugs, such as cocaine or amphetamine. The behavioral alterations of FGF2 / can be normalized by injection of a low dose of the dopaminergic agonist apomorphine (.1 mg/kg) that reduces dopamine release by acting on presynaptic receptors. Conclusions: Our data demonstrate that FGF2 / mice have an increased tone and responsiveness of the dopaminergic system and suggest that these animals might represent a model to study disorders that are characterized by an imbalance between glutamatergic and dopaminergic neurotransmission.