TRANSPLANTATION OF BASAL FOREBRAIN CELLS OF FETAL RATS INTO THE SUBARACHNOID SPACE - IMPROVEMENT OF DISTURBANCE OF PASSIVE-AVOIDANCE MEMORYDUE TO INJURY NUCLEUS BASALIS MAGNOCELLULARIS

Basal forebrain cells of foetal rats were transplanted into the subara chnoid space of adult rats harbouring a kainic acid-induced unilateral lesion in the nucleus basalis magnocellularis. Passive avoidance resp onse tests were performed eight weeks after the transplantation, and t he results were compared with those of lesioned but non-transplanted r ats and of non-lesioned control rats. Although acquisition impairments did not improve, retention impairments were significantly ameliorated in the transplanted rats. Histologically, transplanted foetal neurons survived and grew very well over the cortical surface, and exhibited facilitated neuritic elongation on acetylcholinesterase staining. Chol ine acetyl-transferase-immunoreactive neurons were found along the nee dle track as well as in the subarachnoid graft tissues. The results se em to indicate that not the re-innervation from the graft to the host cortex but the diffusional supply of neurotransmitters and/or their sy nthetic enzymes and neurotrophic factors were responsible for improvem ent of memory deficits. The subarachnoid space proved to be an adequat e place for growth of transplanted neuronal and glial cells for reason s of ample supply of oxygen and nutrition and of low tissue pressure.