Hypoxia and fluoxetine in newborn female rats increase the performance of spatial long-term memory and reactivity of the hypothalamic-pituitary-adrenocortical system in adulthood

Abstract

The study investigated the effects of 1) acute normobaric hypoxia with a reduced oxygen concentration in inhaled air and 2) the selective serotonin reuptake inhibitor fluoxetine in newborn female rat pups on spatial learning, the performance of spatial short-term and long-term memory and reactivity of the hypothalamic-pituitary-adrenal axis (the HPA axis) in adult rats. The newly obtained data indicate a deterioration in the ability for spatial learning only in the first out of five training days. Hypoxia did not change the performance of memory in the test "recognition of a new object" and caused an improvement in long-term memory in the Morris water maze. This was combined with a higher content of corticosterone in blood plasma after testing long-term memory. Fluoxetine did not change the performance indicators of memory or hormonal indicators in either control or hypoxic adult rats. Fluoxetine normalized the latent period of reaching the platform in hypoxic rats when testing learning, and did not reduce the indicator of long-term memory improved by hypoxia. The obtained results suggest that neonatal normobaric hypoxia under certain conditions helps improving memory, while fluoxetine has a protective effect on cognitive abilities and the HPA axis in adult female rats.