Enhanced learning following a single, acute dose of MDA

The behavioral effects of a single, acute dose of methylenedioxyamphetamine (MDA) were assessed using the rabbit nictitating membrane (NM) preparation. Acquisition of the classically conditioned NM response was carried out in a single session under MDA at doses of 10 and 20 mumol/kg (1.79 and 3.58 mg/kg, respectively) and retention was assessed during a drug-free state 48 h later. In agreement with previous reports, MDA at a dose of 10 mumol/kg enhanced acquisition of the conditioned NM response and learning was retained in the nondrug state. However, MDA at a dose of 20 mumol/kg failed to affect either acquisition or retention. In further agreement with previous reports, MDA at 10 mumol/kg facilitated the amplitude of the unconditioned response during unpaired stimulus presentations. It is suggested that this enhanced motor response may be due to enhanced neural transmission in the afferent limb of the unconditioned reflex arc.