Caudate-putamen and nucleus accumbens extracellular acetylcholine responses to methamphetamine binges.

ABSTRACT

Exposure of experimental animals to an escalating dose, multiple binge pattern of methamphetamine administration results in the progressive emergence of a unique behavioral profile, which includes a significant decrease in the duration of the stereotypy phase as well as a profound increase and qualitative change in the locomotor activation. This behavioral profile is associated with a selective decrease in the caudate-putamen but not nucleus accumbens extracellular dopamine response. Since the acetylcholine interneurons in these regions are partly under the control of the mesostriatal and mesoaccumbens dopamine inputs, changes in the activation of these interneurons should parallel the regionally differential dopamine responses during multiple binge treatment. Therefore, we characterized the caudate-putamen and nucleus accumbens extracellular acetylcholine responses to escalating-dose, multiple binge methamphetamine administration. An acute methamphetamine binge decreased acetylcholine levels in caudate-putamen, but had no effect on levels in nucleus accumbens. Furthermore, corresponding to the selective decrease in the dopamine response, the caudate-putamen but not nucleus accumbens extracellular acetylcholine response exhibited tolerance with repeated binge exposures; i.e. the decrease in acetylcholine associated with the acute methamphetamine binge was attenuated with multiple binge exposure. These results are consistent with our hypothesis and suggest that the regionally differential acetylcholine responses reflect one functional consequence of the escalating-dose, multiple binge stimulant treatment.