Non-invasive laser microsurgery selectively damages populations of labeled mouse neurons: dependence on incident laser dose and absorption.

Selective photothermolysis (SP) is a novel technique by which brief, unfocused laser pulses are selectively absorbed by, and cause selective thermal damage to, endogenously pigmented structures. This report describes the use of an exogenous non-fluorescent chromophore (Procion blue) to effect cellular damage by SP. Cultured dorsal root ganglia neurons were selectively labeled with Procion blue and subjected to varying doses of laser illumination. Progressive cellular damage was assessed by leakage of propidium iodide through damaged membranes. The neurons targeted via an exogenous chromophore sustained damage which was proportionate to laser dose and chromophore concentration. The results of these experiments demonstrated that the rate and extent of neuronal damage can be controlled by adjusting either the incident dose of laser energy or the amount of target chromophore within cells. Selective photothermolysis will provide an experimental tool for neurobiologists in particular and will find general use within the biomedical field.