G-protein effects on retrograde axonal transport.

Movements of medium and large sized membranous organelles (0.5-1 microns in diameter) were visualized within segments of the crab walking leg nerve with Nomarski differential interference contrast optics and subjected to video contrast enhancement. Accessibility to the axoplasm was demonstrated by intra-axonal fluorescence following addition of rhodamine conjugated to 40 kDa dextran to the external medium. Perfusion of the axons with a 1 microM solution of the 20 kDa G-protein, cp20, but not control solutions, reduced the number of organelles moving in the retrograde direction per unit time, but not the number of organelles moving in the anterograde direction. Such alteration of organelle movement may contribute to memory-specific changes of neuronal morphology.