Dose-response effects of beta-phenylethylamine on stereotyped behavior in pargyline-pretreated rats.

We studied the dose-response and the time-course effect of beta-phenylethylamine (4.0-64.0 mg/kg, ip) on stereotyped behavior and motor activity in male Sprague-Dawley rats pretreated 2 hr eariler with pargyline (0.25-8.0 mg/kg, iv). Stereotyped behavior, defined as repetitive, nongoal-directed head movements and sniffing, and changes in motor activity were observed immediately after injection of beta-phenylethylamine for a 1 hr period. With increasing doses of pargyline pretreatment, beta-phenylethylamine produced, in a dose-response relationship, progressively more stereotyped behavior accompanied by increased motor activity. Without pargyline pretreatment, only 64.0 mg/kg beta-phenylethylamine induced behavioral changes. Stereotyped behavior and increased motor activity had an onset at 4-6 min after the injection of beta-phenylethylamine, peak at 10-30 min, and gradual decline in the next 10-20 min. These results are discussed in terms of a possible relationship with the degree of inhibition of Type a and Type B monoamine oxidase acused by the different doses of pargyline.