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GABA-induced response in spiral ganglion cells acutely isolated from guinea pig cochlea.

Nakagawa T, Yamashita M, Hisashi K, Usami SI, Kakazu Y, Shibata S, Nakashima T, Koike K, Kubo K, Komune S

Department of Otorhinolaryngology, Faculty of Medicine, Kyushu University, 3-1-1 Maidashi Higashi-ku, Fukuoka 812-8582, Japan. nakataka@qent.med.kyshu-u.ac.jp

The physiological and pharmacological properties of gamma-aminobutyric acid (GABA)-induced responses were investigated in acutely isolated spiral ganglion cells (SGCs) of guinea pig by using either a nystatin-perforated patch recording configuration or a conventional whole-cell patch recording mode combined with rapid drug application. GABA and GABA(A) subtype receptor agonist, muscimol, induced inward currents in a concentration-dependent manner in 74% of all cells. The current-voltage relationship for the GABA response indicated the GABA-induced current in SGCs is carried by Cl-. Bicuculline (BIC), strychnine (STR), and picrotoxin (PTX) suppressed the GABA response in a concentration-dependent manner. BIC and STR, and PTX blocked the GABA response in a competitive manner and in a non-competitive manner, respectively. For inorganic antagonists, Cd2+ and Ni2+ also inhibited the GABA response. On the other hand, Zn2+ failed to suppress the GABA response in SGCs. An antibiotic, benzylpenicillin, suppressed the GABA response. The GABA response was augmented by both a barbiturate derivative, pentobarbital (PB), and a benzodiazepine derivative, diazepam. The results suggest clearly that the physiological and pharmacological characteristics of GABA(A) receptor on acutely isolated guinea pig SGCs are quite similar to the common GABA(A) receptor found in other sensory ganglion cells.

Published 22 November 2005 in Neurosci Res, 53(4): 396-403.
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