Long-Evans hooded rats maintained on a fixed-ratio (FR15) schedule of food reinforcement were given 0.3, 1.5 or 2.9 nmole (1, 5 or 10 μg) of synthetic camel β-endorphin. This produced a dose-related suppression of FR15 responding during the 30 min behavioral session with an ED50 of 0.7 nmole. On a molar basis, β-endorphin is 21 times more potent than morphine in suppressing fixed-ratio responding.
|Original language||English (US)|
|Pages (from-to)||No. 355|
|State||Published - Jan 1 1977|