A descriptive and quantitative morphometric study of long-term mouse adrenal medulla grafts implanted into the putamen: effect of nerve growth factor injected at grafting.

Mouse adrenal medulla grafts were evaluated morphologically and quantitatively after implantation into the mouse putamen, either alone or with nerve growth factor (NGF) injected at grafting. Specific antibodies were used to determine the expression of neurofilaments, dopamine (DA) and phenylethanolamine-N-methyl transferase (PNMT). Three months after grafting, the survival rate and size volume of chromaffin cells were significantly greater in the grafts containing NGF, and increasing numbers of intermediate cell types (e.g. chromaffin cells transforming into neurons), and of neuron-like cells seemed to have formed. Chromaffin cells stained positively for DA and PNMT, but only a few chromaffin-like processes stained for neurofilaments. A neuronal network of adrenal medulla grafts was observed, consisting of non-myelinated nerve fibers, nerve terminals and chromaffin-like processes. In all grafts the synapses on chromaffin cells were mainly small, symmetrical or asymmetrical (about 1-2 microns in diameter) with round, small clear synaptic vesicles. Nerve terminals were not immunoreactive to dopamine or PNMT. These results show that a single injection of NGF at grafting influences the survival and differentiation of chromaffin cells. This study suggests that adrenal medulla grafts may integrate into the putamen.