Dopamine release and uptake are greater in female than male rat striatum as measured by fast cyclic voltammetry
Section snippets
Subjects
Adult male and female Sprague–Dawley rats were purchased from Charles River Laboratories (Raleigh, NC, U.S.A.). They were segregated by sex and were housed in plastic cages under a 12:12 h light:dark cycle with lights on at 06.00. Food and water were provided ad libitum. The average weights (± standard error) for all animals used in these experiments were 263±5 g (range 227–328 g) for females and 383±15 g (range 290–468 g) for males. Animal care was in accordance with the Guide for the Care and Use
Stimulation current vs dopamine release
Figure 1 shows representative dopamine overflow curves in the caudate nucleus of anesthetized male and female rats following 60 Hz 2 s electrical stimulations of the medial forebrain bundle at varying current intensities. More extracellular dopamine was elicited by increasing stimulation current up to a maximum of 300 μA in each sex. Each stimulation intensity evoked more dopamine release in females than males, with the disparity being greatest between 100 and 200 μA.
Figure 2 shows group averages
Discussion
The present studies report robust sex differences in dopaminergic neurotransmission. In vivo and in vitro experiments indicated that both dopamine release and uptake rates were greater in female caudate nucleus although transporter affinity was the same in males and females. Dopamine release in vivo was greater in female than male caudate nucleus over a range of stimulation current intensities tested. Dopamine release and uptake did not vary across phases of the female estrous cycle.
Release and
Conclusions
This work shows that dopamine release and uptake are greater in female than male rat striatum and provides a framework to understand sex differences in behavioral responses of animals to psychostimulants. Dopamine release and uptake kinetics did not vary across the female estrous cycle. This finding of fundamental sex differences in extracellular dopamine regulation may have implications for drug abuse and neurological disorders.
Acknowledgements
The authors thank Dr Paul Garris for helpful discussions regarding these experiments. This work was supported by grant no. 09079 (CMK) and NS 15841 (RMW).
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