Brain transplants enhance rather than reduce the impairment of spatial memory and olfaction in bulbectomized rats.

Abstract

The possibility to compensate the loss of olfactory and non-olfactory functions due to removal of the olfactory bulb by embryonal brain grafts was investigated in adult rats. Spatial working memory was examined in an 8-arm radial water maze task 6 weeks after bulbectomy. During 15 daily trials, performance gradually improved in bulbectomized controls (n = 10) and in rats with olfactory bulb transplants (n = 9), but did not attain that of intact controls (n = 10). No improvement was observed in the rats with substantia nigra grafts (n = 8). Eleven weeks after bulbectomy, the same rats were tested in the water tank navigation task. The performance improved during ten 12-trial sessions in bulbectomized rats less than in intact controls, but more than in the transplanted rats. The olfactory food retrieval test performed 14 weeks after bulbectomy revealed almost full recovery of smell in bulbectomized rats, but not in the transplanted animals. It is concluded that the spatial memory deficit is probably due to bulbectomy-induced interference with septohippocampal function which is not alleviated, but rather enhanced by transplantation. The results suggest that the effect of brain grafting is not always beneficial.

Mesenchymal Stem Cells Preserve Working Memory in the 3xTg-AD Mouse Model of Alzheimer’s Disease

“…The triple transgenic mouse model of AD (3xTg-AD) generated by LaFerla and colleagues [ 25 ] harbors three transgenes of Presenilin 1 (PS1, M146V), tau (P301L) and Amyloid precursor protein (APP, SWE) and manifests the two major pathological features seen in AD patients, namely A β plaques and neurofibrillary tangles. Extracellular amyloid plaques are observed in 3xTg-AD animals in the frontal cortex at six months of age and in the hippocampus by 12 months followed by neurofibrillary tangles, leading to a memory deficit measurable in the Morris water maze (MWM) test [ 1 , 26 , 27 ].…”

Effects of transplantation of fetal hippocampal or hindbrain tissue into the brains of adult rats with hippocampal lesions on water maze acquisition.

“…This recovery did not occur in rats that received fetal mesencephalic tissue grafts. Amemori et al (1989) and Choulli et al hypothesized that the reinnervation of the host brain by the transplanted tissue disrupted processes within the host brain that occurred in the nontransplanted rats and were beneficial to behavioral recovery. These processes could include either unmasking of previously silent circuits or anatomical reorganization such as takes place during reactive synaptogenesis.…”

“…In addition to the experiment by Dalrymple-Alford et al (1988), at least four other studies have noted transplant–induced behavioral impairment, and all have observed that this impairment was relative to rats with lesions that showed some amount of time-related behavioral recovery. Amemori et al (1989) observed that bulbectomized rats exhibit deficits in spatial learning tasks. Some recovery occurred in these animals with time, but this recovery was not evident in bulbectomized rats that received fetal transplants.…”

An Olfactory Bulbectomy Model to Study Plasticity of the Nervous System in Rat: A Review Focused on Published Data From the Slovak Republic

“…The authors suggested that the adverse effect of OB and corpus striatum transplants was probably due to their poor connectivity with the host brain, which prevented the regenerating olfactory axons from reaching higher olfactory centers. In the next study of Amemori et al (1989) the possibility to compensate the loss of olfactory and non-olfactory functions, induced by the removal of the OB, by embryonal OB grafts was investigated in adult rats. Spatial working memory of the animals was examined in the radial water maze task 6 weeks after bulbectomy/transplantation.…”