Single-sided Deafness Leads to Changes in Vesicular Synaptic Transporters and Matrix Metalloproteinase 9 in the Primary Auditory Cortex.

Changes in perineuronal nets (PNNs) after hearing loss were described in previous studies. The present study aimed to examine how single-sided deafness (SSD) affects the expression of excitatory and inhibitory synaptic transporters and PNNs in the primary auditory cortex (A1). Sprague-Dawley rats (8-week-old females, n = 30) were divided into three groups: (1) the SSD 2-week group (n = 10), (2) the SSD 4-week group (n = 10), and (3) the 4-week control group (n = 10). The expression levels of vesicular glutamate transporter 1 (VGLUT1), VGLUT2, vesicular GABA transporter (VGAT), and genes related to PNNs were measured using quantitative reverse transcription-polymerase chain reaction. The A1 was immunostained for VGLUT1, glutamate acid decarboxylase (GAD) 67, neurocan, aggrecan, brevican, and Wisteria floribunda agglutinin (WFA). The expression levels of VGLUT1, VGLUT2, and VGAT were elevated in the A1 on the ipsilateral side in the SSD groups compared with those in the control groups. Aggrecan expression was elevated in the A1 on the contralateral side in the SSD 2-week group. The SSD groups had elevated expression levels of metalloproteinase (MMP) 9 on the contralateral side. The presynaptic glutamatergic and GABAergic transporters were increased in the A1 on the ipsilateral side after induction of SSD. Changes in the cortical auditory nervous system accompanied changes in the PNNs and their degradation enzymes MMP9 and MMP14.