| Abstract: | ED50 values for analgesia (tail-clip method) at 30 min after heroin HCl administered i.v. or s.c. in groups of Swiss-Webster mice were not significantly different. Nor was the duration of the analgesia following various doses of heroin significantly different after i.v. or s.c. injections, although there was a tendency for the latter route to have a longer effect. Hyperactivity (mean levels in groups of 5 mice, measured by an Activity Meter), though variable, was increased after s.c. injections of heroin in a dose-related manner up to doses of 10 mg/kg. Larger doses progesssively prolonged the peak levels of hyperactivity. Because the degree and duration of both analgesia and hyperactivity were parallel over a wide range of doses of heroin HCl in these mice, a close relationship between the two underlying mechanisms seems very likely. |
