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Differential effects of THC- or CBD-rich cannabis extracts on working memory in rats

2004; Elsevier BV; Volume: 47; Issue: 8 Linguagem: Inglês

10.1016/j.neuropharm.2004.08.009

1873-7064

Paola Fadda, Lianne Robinson, Walter Fratta, Roger G. Pertwee, Gernot Riedel,

Sleep and Wakefulness Research

Cannabinoid receptors in the brain (CB1) take part in modulation of learning, and are particularly important for working and short-term memory. Here, we employed a delayed-matching-to-place (DMTP) task in the open-field water maze and examined the effects of cannabis plant extracts rich in either Δ9-tetrahydrocannabinol (Δ9-THC), or rich in cannabidiol (CBD), on spatial working and short-term memory formation in rats. Δ9-THC-rich extracts impaired performance in the memory trial (trial 2) of the DMTP task in a dose-dependent but delay-independent manner. Deficits appeared at doses of 2 or 5 mg/kg (i.p.) at both 30 s and 4 h delays and were similar in severity compared with synthetic Δ9-THC. Despite considerable amounts of Δ9-THC present, CBD-rich extracts had no effect on spatial working/short-term memory, even at doses of up to 50 mg/kg. When given concomitantly, CBD-rich extracts did not reverse memory deficits of the additional Δ9-THC-rich extract. CBD-rich extracts also did not alter Δ9-THC-rich extract-induced catalepsy as revealed by the bar test. It appears that spatial working/short-term memory is not sensitive to CBD-rich extracts and that potentiation and antagonism of Δ9-THC-induced spatial memory deficits is dependent on the ratio between CBD and Δ9-THC.