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Morphology and dendritic maturation of developing principal neurons in the rat basolateral amygdala

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Abstract

The basolateral nucleus of the amygdala (BLA) assigns emotional valence to sensory stimuli, and many amygdala-dependent behaviors undergo marked development during postnatal life. We recently showed principal neurons in the rat BLA undergo dramatic changes to their electrophysiological properties during the first postnatal month, but no study to date has thoroughly characterized changes to morphology or gene expression that may underlie the functional development of this neuronal population. We addressed this knowledge gap with reconstructions of biocytin-filled principal neurons in the rat BLA at postnatal days 7 (P7), 14, 21, 28, and 60. BLA principal neurons underwent a number of morphological changes, including a twofold increase in soma volume from P7 to P21. Dendritic arbors expanded significantly during the first postnatal month and achieved a mature distribution around P28, in terms of total dendritic length and distance from soma. The number of primary dendrites and branch points were consistent with age, but branch points were found farther from the soma in older animals. Dendrites of BLA principal neurons at P7 had few spines, and spine density increased nearly fivefold by P21. Given the concurrent increase in dendritic material, P60 neurons had approximately 17 times as many total spines as P7 neurons. Together, these developmental transitions in BLA principal neuron morphology help explain a number of concomitant electrophysiological changes during a critical period in amygdala development.

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Acknowledgments

The authors would like to thank Prof. Todd Preuss for resources for the analysis of neuron morphology and the Emory University Institute for Quantitative Theory and Methods for assistance with statistical analyses. This work was funded by the following grants from the National Institutes of Health: MH 069852 to D.G.R., base grant RR 00165 to the Yerkes National Primate Research center, and MH 090729 to D.E.E.

Conflict of interest

The authors would like to declare no conflicts of interest.

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  1. Department of Psychiatry and Behavioral Sciences, Division of Behavioral Neuroscience and Psychiatric Disorders, Yerkes Research Center, Emory University School of Medicine, 954 Gatewood Rd., Atlanta, GA, 30033, USA

    Steven J. Ryan, David E. Ehrlich & Donald G. Rainnie

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  1. Steven J. Ryan
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  2. David E. Ehrlich
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  3. Donald G. Rainnie
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Correspondence to Donald G. Rainnie.

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S. J. Ryan and D. E Ehrlich contributed equally.

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Ryan, S.J., Ehrlich, D.E. & Rainnie, D.G. Morphology and dendritic maturation of developing principal neurons in the rat basolateral amygdala. Brain Struct Funct 221, 839–854 (2016). https://doi.org/10.1007/s00429-014-0939-x

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