Systemic magnesium chloride administration fails to produce phencyclidine-like discriminative stimulus effects in rats.

Systemic administration of magnesium chloride was evaluated for phencyclidine (PCP)-like discriminative stimulus effects. Six rats were trained to discriminate PCP (1.25 mg/kg, i.p.) from saline under a two-lever fixed-ratio 32 schedule of food reinforcement. Magnesium chloride (10-80 mg/kg, i.p.) failed to substitute for PCP, with no dose producing greater than an average of 21% PCP-lever responding. At doses greater than 40 mg/kg, magnesium chloride decreased rates of responding, providing evidence that it was evaluated over a behaviorally-relevant dose range. The results provide further evidence for differences in the behavioral effects of drugs which antagonize N-methyl-D-aspartate receptor-mediated neurotransmission by different mechanisms.