Ten days later, both groups were given "voluntary cocaine access" and were presented with a lever.
Almost all stimulants are of the amphetamine type (ATS) derived from ephedrine, pseudoephedrine, or phenylephrine; cocaine access and injection are rarely reported.
The escalation of drug intake in rats with extended cocaine access has further been shown to be under the control of micro-RNAs in the dorsal striatum (Im et al., 2010; Jonkman & Kenny, 2013).
"For a drug like cocaine, easier access and rapid delivery may lead some people into using more cocaine more often, and may make it more difficult for some users to control their use".
With regard to cocaine, extended access self-administration has been shown to produce tolerance to the locomotor-stimulating effects of cocaine, cocaine-induced dopamine overflow measured by microdialysis, and the ability of cocaine to inhibit the DAT measured by voltammetry.
Additionally, we have found that, following extended access cocaine self-administration, the ability of cocaine to augment exocytotic dopamine release is blunted (ref (32) but see ref (35)).
In support of this hypothesis, we have observed reductions in electrically evoked dopamine release following extended access cocaine self-administration (refs (12), (13), and (32− 34) but see ref (35)), suggesting that intracellular dopamine levels are reduced.
Work from our lab has shown that, following 24 h access cocaine self-administration, the ability of quinpirole, a D2-receptor agonist, to decrease dopamine release is markedly decreased and this effect remains for 7 days of abstinence.
Experimenter-delivered sensitization paradigms produce robust sensitization of AMPH-induced locomotion, similar to cocaine; however, extended access AMPH self-administration does not change the potency of AMPH at the DAT, or the ability of AMPH to increase extracellular dopamine levels as measured by microdialysis.
These results fail to support the views that increasing access to cocaine or abstinence enhances the reinforcing strength of cocaine.
In the present study, despite 3 weeks of extended access to cocaine self-administration and a large escalation of cocaine consumption [from 7.34±2.50 to 26.04±1.21 mg/day; F 16,160) = 15.98, P<0.01], rats rapidly acquired a strong and stable preference for lever S over lever C (Fig. 5b).
