Rat Cognitive Functions During and After Treatment with the Cannabinoid Agonist, HU 210

To ascertain whether the cannabinoid agonist HU 210 (25, 50 or 100μ kg−1, i.p.) influenced rat spatial learning, animal performance was examined using the Morris water maze during and after treatments. Vocalization and wall-hugging, examples of unlearned behaviour, were examined also. HU 210 at 50 or 100μ kg−1 (once daily for four days, 60 min before a daily session) impaired learning; wall-hugging and enhanced vocalization were also displayed by the animals in the fourth session. When the drug treatment was discontinued, the effects produced by 50μ kg−1 HU 210 reversed in three days, while disruption of acquisition and vocalization caused by 100μ kg−1 HU 210 remained after seven days' abstinence. Rats sub-chronically treated with 100μ kg−1 HU 210 for ten days and then submitted to the water-maze task thirty days after last injection, did not differ with respect to controls in learning, memory, vocalization and wall-hugging. The anxiety-like state may be a specific factor contributing to the reversible impairment of spatial learning induced by HU 210.