Cannabinoid agonist WIN55,212-2 prevents scopolamine-induced impairment of spatial memory in rats

Abstract

The endocannabinoid system is involved in diverse processes, like learning and memory, governed by cholinergic neurotransmission. Recent research demonstrates that in a rat model of dementia derived from basal forebrain cholinergic degeneration, WIN55,212-2, a potent cannabinoid receptor agonist, improves cognition through increased cortical choline levels. However, the effect of cannabinoids on cholinergic deficits is still under investigation. In this work, we studied the effect of this treatment in a pharmacological rat model of transient cholinergic hypofunction by the acute administration of the muscarinic antagonist, scopolamine (2 mg/kg), in spatial, recognition and aversive memory tests. Scopolamine induced memory impairment was observed in the three tests and, importantly, the cannabinoid subchronic treatment with low doses of WIN55,212-2 (0.5 mg/kg) prevented this deleterious effect in spatial memory when evaluated in Barnes maze test. Autoradiographic studies indicate that, following the WIN55,212-2 treatment, cannabinoid receptor density increased in the motor and somatosensory cortices. In layers I-V of the motor cortex, the activity of cannabinoid and muscarinic receptors also increased. These results suggest that WIN55,212-2, through the activation of cannabinoid receptors, indirectly elevates the muscarinic tone in key cortical areas for learning and memory, preventing the memory deficits induced by scopolamine specifically in spatial memory. This highlights the importance of the crosstalk between the endocannabinoid and the cholinergic system for learning and memory processes and suggest that cannabinoid agonists might be an alternative for the treatment of cognitive deficits associated with cholinergic dysfunction.