Major role of MT2 receptors in the beneficial effect of melatonin on long-term recognition memory in C57BL/6J male mice

Abstract

Melatonin, a major signal of the circadian system, is also involved in brain functions such as learning and memory. Chronic melatonin treatment is known to improve memory performances, but the respective contribution of its central receptors, MT₁ and MT₂, is still unclear. Here, we used new single receptor deficient MT₁^-/- and MT₂^-/- mice to investigate the contribution of each receptor in the positive effect of chronic melatonin treatment on long-term recognition memory. The lack of MT₂ receptor precluded memory-enhancing effect of melatonin in the object recognition task and to a lesser extent in the object location task, whereas the lack of MT₁ receptor mitigated its effect in the object location task only. Our findings support a key role of MT₂ in mediating melatonin's beneficial action on long-term object recognition memory, whereas MT₁ may contribute to the effect on object location memory.

Keywords: Long-term recognition memory; MT(1) deficiency; MT(2) deficiency; Melatonin; Object location; Object recognition.