The expression and localization of serine proteinase inhibitor PI-6 mRNA in developmental and ischemic mouse brain

A serine proteinase inhibitor, PI-6, is a member of the serine proteinase i nhibitor (serpin) superfamily. In the present study, we investigated the de velopmental expression of PI-6 in the mouse brain and the effect of experim ental ischemia on the expression of PI-6 in the adult brain. Northern blot analysis showed a high level of expression of PI-6 mRNA in brain stem and d iencephalon as compared with other regions in the adult brain. The expressi on of PI-6 mRNA in the whole brain was increased gradually until II days af ter birth and was decreased again in the adult brain. In situ hybridization analysis revealed that the mRNA was localized in pyramidal cell layer of t he post-natal hippocampus, especially in CA3 region, and in layer V of the cerebral cortex. In the brain stem, two specific motor nuclei, the facial n ucleus and the motor nucleus of trigeminal nerve, which are important to ac tive feeding, were strongly positive for PI-6 mRNA. Brain ischemia induced by bilateral ligation of the common carotid artery led to an increase in PI -6 mRNA expression in the whole brain, accompanied by the degeneration of h ippocampal pyramidal cells. These results indicate distinct temporal and sp atial expression of PI-6 in the mouse brain and suggest the involvement of PI-6 in the maturation of neurons and degenerative and regenerative process ed. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.