FMR1 and fragile X syndrome: Although systemic drug administration cannot determine exact mechanisms for the differences we observe in Fmr1-/Y mice, our current findings replicate those of other behavioral and electrophysiological studies reporting that Fmr1 deletion affects the dopaminergic, glutamatergic, and cholinergic neurotransmitter systems and extend these differences to the regulation of brain reward, which may have clinical implications for patients with FXS.