Abstract
The retinal ganglion cells (RGCs) have diverse morphology and physiology. Although some studies show that correlations between morphological properties and physiological properties exist in cat RGCs, these properties are much less distinct and their correlations are unknown in mouse RGCs. In this study, using three-dimensional digital neuron reconstruction, we systematically analyzed twelve morphological parameters of mouse RGCs as they developed in the first four postnatal weeks. The development of these parameters fell into three different patterns and suggested that contact from bipolar cells and eye opening might play important roles in RGC morphological development. Although there has been a general impression that the morphological parameters are not independent, such as RGCs with larger dendritic fields usually have longer but sparser dendrites, there was not systematic study and statistical analysis proving it. We used Pearson's correlation coefficients to determine the relationship among these morphological parameters and demonstrated that many morphological parameters showed high statistical correlation. In the same cells we also measured seven physiological parameters using whole-cell patch-clamp recording, focusing on intrinsic excitability. We previously reported the increase in intrinsic excitability in mouse RGCs during early postnatal development. Here we showed that strong correlations also existed among many physiological parameters that measure the intrinsic excitability. However, Pearson's correlation coefficient revealed very limited correlation across morphological and physiological parameters. In addition, principle component analysis failed to separate RGCs into clusters using combined morphological and physiological parameters. Therefore, despite strong correlations within the morphological parameters and within the physiological parameters, postnatal mouse RGCs had only limited correlation between morphology and physiology. This may be due to developmental immaturity, or to selection of parameters.
Highlights
The retina has long been a model system in which to study neuronal morphology and physiology, i.e. neuron structure and function [1,2,3,4,5,6,7]
To determine the developmental progression of retinal ganglion cells (RGCs) morphology, 175 RGCs from mice aged between P4 and P24 were patchfilled with fluorescent dye, imaged and digitally reconstructed
We previously described the development of intrinsic excitability in mouse RGCs and that intrinsic excitability was similar among mouse ON, OFF and multistratified RGCs during the first three postnatal weeks [28]
Summary
The retina has long been a model system in which to study neuronal morphology and physiology, i.e. neuron structure and function [1,2,3,4,5,6,7]. Physiological categorizations of retinal ganglion cells (RGCs) were based on light responses, such as ON versus OFF responses and large versus small receptive fields [6,8,9,10], but other physiological parameters affect function and have been used to categorize RGCs [4,11,12,13,14]. Cat RGCs can be divided into three physiological types (X, Y and W) based on different light responses. These three different physiological types correspond to three morphological classes (beta, alpha and gamma) based on soma size, dendritic field size and dendritic branching pattern [2,6,15,16,17,18]. This high level of specificity between morphology and physiology in cat RGCs is partially lost in rat RGCs [20]
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