Experiments were performed on groups of rats after acute and sub-chronic treatment (once daily for 9 days) with the cannabinoid agonist HU 210 (25-100 µg kg(-1), i.p.) as well as 24 h and 7 days after the last drug injection. The animals underwent three behavioural tests in novel environments. In the observation cages (Test 1), rat locomotor activity was found to be dose-dependently reduced after acute and sub-chronic treatment at all doses and virtually unchanged during abstinence; grooming was potently inhibited by acute treatment but potentiated by the sub-chronic one at doses of 50 and 100 µg kg(-1), the effect of the higher dose persisting after 24 h and 7 days abstinence. Vocalization in animals in response to a tactile stimulus was highest after HU 210 at 100 µg kg(-1)in all experimental modes except after 7 days abstinence. In the X-maze (Test 2), sub-chronic HU 210 dose- dependently enhanced rat natural aversion for open arms, and this behaviour persisted during abstinence after the highest dose. Grooming in the X-maze was completely absent in rats acutely injected with HU 210 but potentiated in those sub-chronically treated or abstinent. In the swimming test (Test 3) rats sub-chronically treated at 50 and 100 pg kg(-1)displayed relevant wall-hugging and the same occurred 24 h after last injection. On the whole, our results are indicative of an anxiogenic-like effect of sub-chronic HU 210 at high doses and reflect the persistence of enhanced emotional response to novel environments when the treatment is discontinued.
THE CANNABINOID AGONIST HU 210 MODIFIES RAT BEHAVIOURAL RESPONSES TO NOVELTY AND STRESS / Giuliani, Daniela; Ferrari, Francesca; Ottani, Alessandra. - In: PHARMACOLOGICAL RESEARCH. - ISSN 1043-6618. - STAMPA. - 41:1(2000), pp. 45-51. [10.1006/phrs.1999.0560]