The CRH1 antagonist CP154,526 failed to alter ischemia-induced neurodegeneration and spatial memory deficits in rats but inhibited behavioral activity in the novel open field

Abstract

Corticotropin-releasing hormone (CRH) has been implicated in ischemia-induced neurotoxicity, due in part to excitatory effects at the hippocampus, and the demonstrated neuroprotective effects of centrally administered, non-specific CRH antagonists. However, a number of issues remain to be clarified from these studies, including the relative contribution of CRH receptor subtypes, and the efficacy of these compounds to alter ischemia-induced behavioral impairments. In the current study, a highly selective, systemically administered CRH1 antagonist (CP154,526) failed to reverse global ischemia-induced cell death in hippocampal CA1 neurons or spatial memory impairments as assessed in the radial arm maze. Similarly, central administration of α-helical CRH failed to confer protection against ischemic damage. Interestingly, CRH1 antagonism reversed ischemia-induced hyperactivity in a novel open field, suggesting that modulation of this behavior is independent of effects on hippocampal CA1 cell loss. Failure of the current study to demonstrate neuroprotective effects of either the selective or non-selective CRH antagonists tested challenges the proposed neurotoxic role of CRH in global ischemia. These findings are discussed in relationship to recent findings reconsidering the participation of CRH in excitotoxic-mediated cellular damage.