The effects of corticosterone on persistence of attention in Mus musculus

Abstract

It is widely believed that corticosterone plays a role in psychological, and ultimately behavioural adaptation during stress. The aim of this thesis was to examine the nature of the adaptation brought about by corticosterone. The hypothesis under test was that corticosterone enhances the persistence of attention. This was primarily suggested by the known actions of the hippocampus - which is the site of the major concentration of the receptors for corticosterone in the brain. The experimental strategy was to examine the effects of exogenous corticosterone on various facets of behaviour believed to relate to the persistence of attention. Both adrenally intact and adrenalectomised animals were used. In the runway distractability test no effect of corticosterone was detectable, either to a relevant or to an irrelevant stimulus, or to two stimuli presented in succession. Neither did corticosterone produce an effect on the habituation of a response to a novel object or to a hole-poke response. In discrimination problems, corticosterone impaired shifting, regardless of whether the problem was a reversal or a non-reversal shift. Passive avoidance was also impaired, but only as assessed by the comparison between delayed and immediate testing under high doses of corticosterone. Active avoidance responding correlated positively with plasma corticosterone levels, but also only under certain circumstances. Overall these results are inconclusive, giving only very limited support to the working hypothesis.