The effects of bilateral microinjections of a new potent and highly se
lective delta-opioid receptor agonist pCl-DPDPE (0.00, 0.1, 1.0, or 2.
5 mu g/side) were tested in rats for 60 min in activity monitors. The
durations of horizontal movement time, rearing time, and stereotypy ti
me were measured during six consecutive 10-min time blocks. The pCl-DP
DPE resulted in short-lived biphasic effects of attenuation followed b
y potentiation for the three measures. These data in part replicate th
e behavioral effects of other delta-opioid receptor agonists.