Characterization of dopamine release and metabolism in the prefrontal cortex of C57BL/6L and BALB/c mice

Abstract

The prefrontal cortex (PFC) has been implicated in the integration of emotional, cognitive and autonomic influences and, in turn, in the coordination of behavioral responses. PFC functioning is under the strong control of the dopaminergic system. A complex balance between the amount of neurotransmitter synthesized, stored, released, metabolized and recaptured determines the intensity of monoaminergic signalling. In the present study, we, therefore, investigated neurochemical aspects of dopaminergic signalling in the PFC of two inbred mouse strains, C57BL/6J (B6J) and BALB/c (BALB). In a series of experiments, we observed strain differences in prefrontal dopaminergic signalling. By means of in vivo microdialysis, extracellular levels of dopamine (DA) and its metabolites were found to be higher in the BALB strain compared to B6J animals. Furthermore, metabolism of DA by measuring the activity of MAO type B in the PFC is lower in the BALB strain. We next determined the amount of dopamine transporter (DAT) in the PFC with BALB mice expressing lower levels of DAT indicating a decreased monoamine reuptake, while increased extracellular DA concentrations. Importantly, DA signalling within the PFC has been reported to play a major role in the extinction of aversive memories. Thus, fear extinction experiments are currently performed to establish a mechanistic correlate between the intensity of monoaminergic signalling in the PFC and the behavioral processing of emotional memories.