On 2013 Oct 23, MICHAEL TAFFE commented:

Establishing the behavioral discrimination for MDMA takes something on the order of 50-80 training exposures going by Bondareva T, 2005 from this group and Gatch MB, 2009 from another. Training doses of 1.5 mg/kg of MDMA appear to be optimal. It is not impossible that this degree of exposure might attenuate the serotonin response to MDMA. Perhaps not to the extent of a high-dose, repeated so-called "neurotoxicity" regimen but behaviorally significant (e.g., see Albaugh DL, 2011 nevertheless. If so, by the time the discrimination for MDMA was established, the subjective drug effect might be more stimulant typical, i.e., dopamine dependent. Full cocaine substitution would therefore be predicted. In contrast the cocaine trained group might not have experienced the attenuation of the serotonin response to MDMA. If this is the case then the subjective properties of the acute challenge with MDMA in cocaine trained animals would arise from a substantially different neuropharmacological effect than the effect in the MDMA-trained animals post-acquisition.

On 2013 Oct 23, MICHAEL TAFFE commented:

Establishing the behavioral discrimination for MDMA takes something on the order of 50-80 training exposures going by Bondareva T, 2005 from this group and Gatch MB, 2009 from another. Training doses of 1.5 mg/kg of MDMA appear to be optimal. It is not impossible that this degree of exposure might attenuate the serotonin response to MDMA. Perhaps not to the extent of a high-dose, repeated so-called "neurotoxicity" regimen but behaviorally significant (e.g., see Albaugh DL, 2011 nevertheless. If so, by the time the discrimination for MDMA was established, the subjective drug effect might be more stimulant typical, i.e., dopamine dependent. Full cocaine substitution would therefore be predicted. In contrast the cocaine trained group might not have experienced the attenuation of the serotonin response to MDMA. If this is the case then the subjective properties of the acute challenge with MDMA in cocaine trained animals would arise from a substantially different neuropharmacological effect than the effect in the MDMA-trained animals post-acquisition.