Synaptic reorganization induced by selective photoablation of an identified neuron

The maintenance of synaptic strength and specificity in the CNS may depend on interactions among postsynaptic dendrites. We examined the effect of rem oving a neuron on synaptic organization. A single identified postsynaptic n euron in the adult cercal system of the cockroach was removed with photoabl ation. After a 30 d recovery period, the synaptic connectivity and morpholo gy of the intact presynaptic and postsynaptic neurons were analyzed. The sy naptic connectivity was reorganized in a manner that was consistent with fu nctional plasticity. To associate anatomical changes with this reorganization, we analyzed the m orphology of the presynaptic and postsynaptic neurons by quantitative morph ometry. Both presynaptic and intact postsynaptic neurons maintained a stabl e morphology after removal of a neighboring postsynaptic neuron. Using the Hausdorff Match method (HM) (Mizrahi et al. 2000), we found that the spatia l organization of the intact dendritic and axonal trees after ablation of a postsynaptic neuron remained stable. Thus, interactions with neighboring n eurons were not necessary for maintaining dendritic morphology in the adult nervous system. However, adult central synapses were capable of adjusting to maintain normal function.