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Focal cerebral ischemia induces CRH mRNA in rat cerebral cortex and amygdala
M L Wong1, S A Loddick, P B Bongiorno
1Clinical Neuroendocrinology Branch, NIMH, NIH, Bethesda, Maryland 20892-1284, USA.
Abstract:
Corticotropin-releasing hormone (CRH) antagonism has neuroprotective effects in models of ischemia. We examined CRH mRNA by in situ hybridization in a well-established rat model of focal cerebral ischemia caused by permanent middle cerebral artery occlusion (MCAo). In ischemic cortex CRH mRNA levels were elevated 2.6-fold 60 min after MCAo, compared with sham operated animals. CRH mRNA was also induced in the amygdala, 60 min following ischemia, in a pattern which was qualitatively different from that of sham operated animals. This rapid and profound increase in CRH mRNA levels during focal cerebral ischemia is likely to be associated with neurotoxicity, as CRH antagonism has been reported to cause a significant reduction in neuronal loss during ischemia.
Insights
Corticotropin-releasing hormone (CRH) mRNA rapidly increases in the brain after focal cerebral ischemia. This suggests CRH may contribute to neurotoxicity, as blocking it offers neuroprotection.
Area of Science:
- Neuroscience
- Molecular Biology
- Pathophysiology
Background:
- Corticotropin-releasing hormone (CRH) antagonism demonstrates neuroprotective potential in ischemia models.
- Focal cerebral ischemia, induced by middle cerebral artery occlusion (MCAo), is a significant cause of brain injury.
Purpose of the Study:
- To investigate the expression of CRH mRNA in a rat model of permanent focal cerebral ischemia.
- To determine the temporal and spatial changes in CRH mRNA levels following MCAo.
Main Methods:
- Utilized in situ hybridization to quantify CRH mRNA levels in rat brain tissue.
- Employed a permanent middle cerebral artery occlusion (MCAo) model to induce focal cerebral ischemia.
- Compared CRH mRNA expression in ischemic cortex and amygdala with sham-operated controls.
Main Results:
- CRH mRNA levels in the ischemic cortex were significantly elevated (2.6-fold) at 60 minutes post-MCAo compared to sham animals.
- CRH mRNA induction was also observed in the amygdala 60 minutes after ischemia, with a distinct pattern compared to sham controls.
- These findings indicate a rapid and substantial increase in CRH mRNA during the acute phase of focal cerebral ischemia.
Conclusions:
- The rapid and pronounced upregulation of CRH mRNA following focal cerebral ischemia suggests a potential role in neurotoxicity.
- CRH antagonism's known neuroprotective effects further support the hypothesis that CRH contributes to ischemic neuronal damage.
- Targeting CRH pathways may represent a therapeutic strategy for mitigating brain injury after stroke.