“Dose-addition analysis and the interaction index indicated that combinations of PE and MA were either additive or sub-additive in their reinforcing effects.”
“However, PE produces centrally-mediated dopaminergic effects that are linked to the reinforcing effects of MA and other illicit psychostimulants and has been reported to function as a positive reinforcer in non-human primates.”
“These results suggest that, while MA is a more potent reinforcer than PE , the two drugs are comparable in terms of reinforcing strength.”