Figure 6.

Correlation of ICSS facilitation in rats with (A) in vitro selectivity to promote DA versus 5-HT release and (B) break points maintained under a progressive-ratio schedule of drug self-administration in rhesus monkeys. (A) Abscissa: Log selectivity to release DA versus 5-HT expressed as the log of selectivity values shown in Table 1. Ordinate: Maximum facilitation of ICSS expressed as the maximum increase produced by any drug dose in percent pre-drug baseline number of reinforcers delivered across all brain stimulation frequencies (from Figures 1 and 3, right panels). Fenfluramine was excluded from this figure because it did not facilitate ICSS at any dose or time and because precise selectivity could not be quantified due to low potency to release dopamine. (B) Abscissa: Maximum break point maintained by any drug dose under a progressive-ratio schedule of drug self-administration in rhesus monkeys. Ordinate. Maximum facilitation of ICSS as in panel A. (–)MDMA and fenfluramine were excluded from the correlation because they did not facilitate ICSS in rats and/or did not reliably maintain self-administration in monkeys (self-administration by <50% of monkeys tested). PAL-287 and phenmetrazine were also excluded, because they have not been tested by Woolverton and colleagues under the progressive-ratio schedule of drug self-administration in rhesus monkeys.