VOLTAGE-SENSITIVE DYE RECORDING USING RETROGRADELY TRANSPORTED DYE INTHE CHICKEN SPINAL-CORD - STAINING AND SIGNAL CHARACTERISTICS

We describe a novel method for retrogradely labeling specific neuronal populations using voltage-sensitive dyes. Styryl dyes were injected i nto the Ventral roots of the isolated embryonic chick spinal cord. Aft er waiting several hours, the dye labeled motoneurons and autonomic pr eganglionic neurons. Neuronal cell bodies, dendrites and axons were la beled; we presume that the dye traveled either by retrograde transport or by diffusion within the membrane of the axon to which the dyes wer e initially applied. Using either a photodiode array or a photomultipl ier, fluorescence changes could be recorded from motoneurons following antidromic or synaptic activation. Several characteristics of the flu orescence changes were measured indicating that the signals did indeed reflect changes in the motoneuron membrane potential. The best labeli ng and optical signals were obtained using the relatively hydrophobic dyes di-8-ANEPPQ and di-12-ANEPEQ. In the great majority of cases thes e dyes responded with an increase in fluorescence of 1-3% (Delta F/F) in response to synaptic or antidromic depolarization of the motoneuron s. We anticipate that these techniques should be useful in the mapping of activity patterns and connectivity in neural networks within a def ined population of neurons.