ON THE INFLUENCE OF THE PERINEURONAL MICROENVIRONMENT ON THE OUTGROWTH OF PERIKARYAL PROJECTIONS OF SPINAL GANGLION NEURONS

While the outgrowth of the slender projections from the perikaryon of spinal ganglion neurons is an intrinsic property of these neurons, it is also influenced by the surrounding microenvironment. To obtain evid ence concerning whether the outgrowth of these projections is influenc ed by one or both components of the perineuronal microenvironment (sat ellite cells plus extracellular matrix) we have taken advantage of a r are arrangement of these neurons. In the spinal ganglia of adult anima ls nerve cell bodies are occasionally arranged in pairs, the two nerve cell bodies of the pair being separated by a satellite cell sheet lac king a basal lamina, while along the remaining portions of their surfa ces they are enveloped by a satellite cell sheath, in turn surrounded by a basal lamina and connective tissue. By studying these paired nerv e cells we have been able to compare, in the same nerve cell body, the extent of the perikaryal projections in surface domains associated on ly with satellite cells and in surface domains associated with both sa tellite cells and extracellular matrix. In spinal ganglia of the rat a nd lizard we have found that the overall development of the perikaryal projections does not differ significantly in either of these surface domains. This finding suggests that neuron-satellite cell interactions rather than factors in the extracellular matrix play a role in promot ing the outgrowth of perikaryal projections from spinal ganglion neuro ns.