Effects of chronic cocaine self-administration on norepinephrine transporters in the nonhuman primate brain

Abstract

Rationale: While cocaine blocks dopamine and serotonin transporters, considerably less emphasis has been placed on its effects following blockade of the norepinephrine transporter (NET). To date, no studies have made a systematic investigation of the effects of chronic cocaine on primate NET density.

Objective: We previously reported increases in NET density in portions of the monkey bed nucleus of stria terminalis after 100 days of cocaine self-administration. In the present study we extend these findings and assess the changes in [3H]nisoxetine binding in additional brain regions of rhesus monkeys chronically self-administrating cocaine.

Results: [3H]Nisoxetine binding sites in the A1 noradrenergic cell group were significantly higher after 5 days of cocaine exposure. One hundred days of self-administration also induced a higher density of NET binding within the A1 cell group; however, in addition, the effects extended to the nucleus prepositus, as well as forebrain regions such as hypothalamic nuclei, basolateral amygdala, parasubiculum, and entorhinal cortex.

Conclusions: These data demonstrate that cocaine self-administration alters the noradrenergic system of nonhuman primates. Although cocaine affected NET binding sites in the forebrain projections of both the ventral (VNAB) and dorsal (DNAB) noradrenergic bundles, the alteration in the A1 cell group at the early time-point suggests that the VNAB appears to be more sensitive than the DNAB to the effects of cocaine. Given the role of norepinephrine in arousal and attention, as well as mediating responses to stress, long-term exposure to cocaine is likely to result in significant changes in the way in which information is perceived and processed by the central nervous system of long-term cocaine users.