Strain differences in basal and cocaine-evoked dopamine dynamics in mouse striatum

In vivo microdialysis was used to characterize basal dopamine (DA) dynamics and cocaine-evoked DA levels in the striatum of 129/Sv-ter, C57BL/6J, DBA/2J, and Swiss-Webster mice. Basal dialysate levels of DA did not differ in the four strains tested. Similarly, the no net flux method of quantitative microdialysis revealed no difference in extracellular levels between strains. However, the in vivo extraction fraction of DA was significantly less in 129/Sv-ter (53%) mice compared with C57BL/6J (68%), DBA/2J (69%), and Swiss-Webster (67%) mice, indicating a lower rate of basal DA uptake in the 129/Sv-ter strain. Perfusion of K(+) (60 and 100 mM) through the microdialysis probe significantly increased dialysate DA levels and there was no difference between strains in the magnitude of this effect. The acute administration of cocaine (5-20 mg/kg i.p.) increased DA levels in the four strains tested. Cocaine-evoked DA levels (in nanomoles) were significantly greater in 129/Sv-ter compared with C57BL/6J, DBA/2J, or Swiss-Webster mice after administration of either 5, 10, or 20 mg/kg cocaine. However, the percentage increase in DA did not differ across strains. These data demonstrate that there are strain-related differences in basal DA dynamics in the striatum of the mouse. Basal DA uptake was reduced in striatum of 129/Sv-ter mice compared with C57BL/6J, DBA/2J, or Swiss-Webster mice. In addition, the response of DA levels to cocaine may be enhanced in 129/Sv-ter compared with C57BL/6J, DBA/2J, or Swiss-Webster mice.