Use of the radial maze in studies of phencyclidine and other drugs of abuse

Effects of drugs known to disrupt performance in an 8-arm radial maze are reported in terms of changes caused in the pattern of arm entry. Phencyclidine (PCP) and N-allyl-N-normetazocine (SKF-10,047) alter the pattern of arm entry in a way which distinguishes their actions from those of scopolamine and certain serotonergic agonists. The apparent rank order of potencies for causing this effect is (+)SKF-10,047 > PCP > (-)SKF-10,047. Results of previous radial maze studies evaluating the interactions of clonidine and verapamil with PCP are summarized. Data are reported which indicate that the ability of verapamil to potentiate PCP's behavioral effects stems from an alteration of the pharmacokinetics of PCP; when verapamil (20 mg/kg, IP) was administered 15 minutes before [³H]PCP (40μCi/kg, IP), brain levels of tritium were increased by 154 to 225 percent. Finally, possible advantages of using a 4-arm radial maze in studies of PCP and related drugs are discussed.