Environmental enrichment reverses memory impairment in B3-ARKO mice

Abstract

Norepinephrine plays an important role in modulating the processes of memory consolidation and evocation through its beta-adrenergic receptors (Adr{beta}), which are expressed in the hippocampus and amygdala. Several studies have shown that all three subtypes of Adr{beta} ({beta}1, {beta}2 and {beta}3) play an important role in cognition. Environmental enrichment (EE), a technique initially used to decrease the stress of animals held in captive environments, has also been shown to produce cognitive benefits in both healthy and sick animals. In this study, we hypothesized that EE would reverse the memory impairment induced by the absence or Adr{beta}3. To test this, 21- and 86-day-old Adr{beta}3KO mice were exposed to an EE protocol for 8 weeks. The study showed that the EE protocol is able to correct the memory impairment when applied to Adr{beta}3KO animals immediately after weaning but has no effect when applied to adult animals. We also found that aging worsens the memory of Adr{beta}3KO mice. Our results suggest that a richer and more diverse environment helps to correct memory impairment in Adr{beta}3KO animals. They also reinforce the idea that noradrenergic signaling is involved in the cognitive impairment observed late in life, as aging led to a worsening in the memory of the Adr{beta}3KO animals that was not corrected by the environmental enrichment protocol.