Structure-function correlation in transient amacrine cells of goldfish retina: Basic and multifractal analyses of dendritic trees in distinct synaptic layers

Amacrine cells generating light-evoked transient ON-OFF responses were stai ned by intracellular injection of horseradish peroxidase after determining their input-output (voltage response vs. light intensity) profiles. Ten cel ls specifically having bistratified dendritic trees were analyzed. The cros s-sectional area of the dendrites in each sublamina (a and b) of the inner plexiform layer was initially measured. Although some variability was obser ved, there was no statistically significant overall difference in the cross -sectional areas of the dendritic trees in sublaminae a and b. Also, the am plitudes of the ON and OFF responses, generated by a midrange criterion sti mulus, could not be correlated with the cross-sectional areas or the number of branches of the dendrites in sublaminae b and a, respectively. On the o ther hand, determination of the generalized fractal spectra revealed that t he negative (up to -3) and zero-order fractal dimensions of the dendritic t rees in sublamina a were consistently higher than those for sublamina b. Fu rthermore, there was a positive correlation between response amplitude and some part of the generalized fractal dimension in the respective parts of t he dendritic trees. It is concluded that dendritic tree characteristics dif fer in the two halves of the inner plexiform layer and that these can be re lated to the cells' light-evoked response amplitudes. Furthermore, generali zed fractal analysis appears to be a useful method for correlating structur e and function in retinal amacrine cells with complex dendritic trees. (C) 2001 Wiley-Liss, Inc.