Memory deficits induced by chronic cannabinoid exposure are prevented by adenosine A2AR receptor antagonism

Abstract

Patients under cannabis-based therapies are usually chronically exposed to cannabinoids. Chronic treatment with a cannabinoid receptor agonist, WIN 55,212-2, affects brain metabolism and modifies functional connectivity between brain areas responsible for memory and learning. Therefore, it is of uttermost importance to discover strategies to mitigate the negative side-effects of cannabinoid-based therapies. Previously, we showed that a single treatment with the synthetic cannabinoid WIN 55,212-2 disrupts recognition memory, an effect mediated by cannabinoid receptor 1 (CB₁R) and cancelled by concomitant administration of adenosine A_2A receptor (A_2AR) antagonists. We herein evaluate if memory deficits induced by chronic exposure to WIN 55,212-2 can also be reverted by A_2AR antagonism, and assessed the synaptic mechanisms that could be involved in that reversal. We show that chronic administration of KW-6002 (istradefylline) (3 mg/kg/28days) reverts memory deficits (evaluated through the Novel Object Recognition Test) induced by chronic cannabinoid exposure (WIN 55,212-2, 1 mg/kg/28 days). Long Term Potentiation (LTP) of synaptic potentials recorded from the CA1 area of the hippocampus was impaired by WIN 55,212-2 (300 nM), an effect partially rescued by the A_2AR antagonist, SCH 58261 (100 nM). Chronic administration of KW-6002 or WIN 55,212-2 did not affect A_2AR or CB₁R binding in the hippocampus and in the prefrontal cortex. These results, showing that A_2AR antagonism can still revert memory deficits after chronic administration of a cannabinoid, an effect that involves mitigation of synaptic plasticity impairment, strongly indicate that adenosine A_2ARs are appropriate targets to tackle side-effects of putative therapies involving the activation of cannabinoid receptors.

Keywords: Adenosine A(2A) receptor; Cannabinoid receptor 1; KW-6002; LTP; Memory; Novel object recognition.