Castration-Modulated Electrophysiological Properties of HVC Neurons in Adult Male Zebra Finches

The nucleus HVC (high vocal center) within the avian motor cortex is the initial part of two song control pathways, which are vocal motor and anterior forebrain pathway. HVC also receive the feedback of the auditory signal. Androgens (testosterone) play an important role in control birdsong. Castration can decrease levels of plasma testosterone and change song stability. In this study, we investigated the effect of castration on electrophysiological properties of neurons in the HVC of adult male zebra finches. The bird was castrated and HVC neurons were electrophysiological recorded using patch clamp recording. We found that membrane time constants, and input resistance of HVC projection neurons (HVCRA and HVCX) in the castration group were lower than those of the control group. Afterhyperpolarization(AHP) time to peak and amplitude of action potential was prolonged after castration. These findings suggest that castration decreases excitability of HVC projection neurons and song stability in male zebra finches. In conclusion, androgen can enhance the excitability of HVC projection neurons. Androgens can activate the VMP pathway and inhibit the AFP pathway to maintain the stability of the song.