Castration modulates singing patterns and electrophysiological properties of RA projection neurons in adult male zebra finches.

Songhua Wang,Dongfeng Li,Shaoyi Liu,Fengling Li,Congshu Liao,Wei Meng

doi:10.7717/peerj.352

Abstract

Castration can change levels of plasma testosterone. Androgens such as testosterone play an important role in stabilizing birdsong. The robust nucleus of the arcopallium (RA) is an important premotor nucleus critical for singing. In this study, we investigated the effect of castration on singing patterns and electrophysiological properties of projection neurons (PNs) in the RA of adult male zebra finches. Adult male zebra finches were castrated and the changes in bird song assessed. We also recorded the electrophysiological changes from RA PNs using patch clamp recording. We found that the plasma levels of testosterone were significantly decreased, song syllable’s entropy was increased and the similarity of motif was decreased after castration. Spontaneous and evoked firing rates, membrane time constants, and membrane capacitance of RA PNs in the castration group were lower than those of the control and the sham groups. Afterhyperpolarization AHP time to peak of spontaneous action potential (AP) was prolonged after castration.These findings suggest that castration decreases song stereotypy and excitability of RA PNs in male zebra finches.

Highlights

Steroid sex hormones change oscines song behavior and modulate the underlying neural substrates in adulthood
We examined the effect of castration on singing patterns and electrophysiological properties of RA projection neurons (PNs) in adult male zebra finches
High testosterone levels are associated with song stability, which reduces the potential for vocal plasticity (Williams, Connor & Hill, 2003)

Summary

Introduction

Steroid sex hormones change oscines song behavior and modulate the underlying neural substrates in adulthood. Testosterone can increase the stability of song (Meitzen et al, 2009a; Sizemore & Perkel, 2011), the size of song nuclei (Brenowitz et al, 1998; Brenowitz et al, 1991; Dloniak & Deviche, 2001; Hall & Macdougall-Shackleton, 2012; Meitzen & Thompson, 2008), the expression of androgen receptor mRNA (Fraley et al, 2010; Wacker et al, 2010) and the excitability in song-control neurons (Meitzen et al, 2007a; Meitzen, Perkel & Brenowitz, 2007b) in seasonally breeding songbirds. How to cite this article Wang et al (2014), Castration modulates singing patterns and electrophysiological properties of RA projection neurons in adult male zebra finches. RA activity is significantly correlated with variations in the spectral entropy of syllables (Sober, Wohlgemuth & Brainard, 2008), and RA shows accurately timed and structured bursts of activity that are associated with specific syllables (Yu & Margoliash, 1996)

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