Biphasic expression of TGF-beta 1 mRNA in the rat brain following permanent occlusion of the middle cerebral artery

Two patterns of transforming growth factor-beta 1 (TGF-beta 1) expression w ere identified in brains of normotensive rats following permanent occlusion of the middle cerebral artery (MCAO). First, a relative increase of TGF-be ta 1 mRNA by 37% was found at 12 h after MCAO in the ipsilateral cingulate cortex as compared to the homotopic contralateral region. The cingulate cor tex is located distant from the ischemic territory. Treatment with the glut amate receptor antagonists MK-801 and NBQX did not reduce this expression ( 34% and 26% increase, respectively). Therefore, peri-infarct depolarization waves were probably not responsible for induction. Secondly, an increase o f TGF-beta 1 mRNA by 116% was found at 7 days after MCAO within infarcted t issue. This expression was not reduced by the glutamate receptor antagonist s MK-801 (increase 140%) and NBQX (increase 137%), either. TGF-beta 1 mRNA expression in the cingulate cortex at 12 h after MCAO is possibly mediated by neurons and astroglia and may support cell survival. Expression in the i nfarcted tissue at 7 days after MCAO is most likely related to the invasion of monocytes and may be involved in the downregulation of inflammatory eve nts, in neoangiogenesis, and in formation of a glial scar around the infarc t. (C) 1999 Elsevier Science B.V. All rights reserved.