Transient up-regulation of ciliary neurotrophic factor receptor-alpha mRNA in axotomized rat septal neurons.

Using non-radioactive in situ hybridization we investigated the effect of fimbria-fornix transection on the expression of ciliary neurotrophic factor receptor alpha (CNTFR alpha) mRNA in axotomized septohippocampal neurons of the rat septal complex. Whereas CNTFR alpha expression was undetectable in the medial septal nucleus/diagonal band complex (MSDB) of control animals, specific up-regulation was observed in MSDB neurons after fimbria-fornix transection. CNTFR alpha expression was maximal 7-10 days after the lesion and had returned to control levels after 3 weeks. Following unilateral fimbria-fornix transection, CNTFR alpha up-regulation was restricted to the MSDB ipsilateral to the lesion. When cholinergic septal neurons were selectively eliminated by immunolesioning with 192 IgG-saporin prior to fimbria-fornix transection, the lesion-induced expression of CNTFR alpha was still observed in many medial septal nucleus neurons. These results demonstrate that after fimbria-fornix transection CNTFR alpha expression is transiently induced in axotomized, non-cholinergic neurons of the medial septal nucleus, suggesting a postlesion function of locally supplied CNTF.