In three separate studies, rats were presented with a flavored solution and then injected with one of a variety of doses of morphine in the taste aversion paradigm. Presentations of the flavored water and injections were done 17 times in one study. Doses of from 2 to 20 mglkg of morphine were sufficient to suppress drinking of the flavored solution and the extent of the suppression was hardly modified across continuous injections. Furthermore, in one experiment it was demonstrated that injections following the first five injections still had capabilities of suppressing drinking. It made little difference whether the injections were subcutaneously or intraperitoneally given. There were considerable individual differences with respect to extent of suppression of drinking the flavored solution. Some rats showed almost complete suppression but others only a slight suppression.

Rats were trained to avoid footshock during three daily sessions, 100 trials/session, in an automated one-way avoidance chamber. Subsequent to training, footshock was terminated and the rats' persistence in responding was tabulated. Between training and the test of persisting avoidance, three groups of rats received a response prevention (RP) treatment and one group received no RP. RP consisted of forcing the rats to stay on the once-dangerous grid for 5 min, once a day for 4 days. Two groups received RP under the influence diazepam (25 or 50 mg/kg, p.o.). With respect to persisting avoidance, groups ordered themselves from most to least as: (1) placebo with no RP, (2) high dose of diazepam with RP, (3) low dose of diazepam with RP, and (4) placebo with RP. Because RP with placebo was the most effective treatment, it was concluded that diazepam is inefficient as an adjunctive treatment for overcoming persisting anxiety/fear/avoidance.

No abstract