Role of GABAergic Inhibition in the Coding of Interaural Time Differences of Low-Frequency Sounds in the Inferior Colliculus

• Published in: Journal of neurophysiology 2005-06, Vol.93 (6), p.3390-3400
• Main Authors: D'Angelo, W. R, Sterbing, S. J, Ostapoff, E.-M, Kuwada, S
• Format: Article
• Language: English
• Subjects: Acoustic Stimulation - methods; Action Potentials - drug effects; Action Potentials - radiation effects; Animals; Auditory Pathways - drug effects; Auditory Pathways - physiology; Auditory Pathways - radiation effects; Auditory Threshold - physiology; Bicuculline - pharmacology; Brain Mapping; Dose-Response Relationship, Radiation; Female; Functional Laterality; GABA Antagonists - pharmacology; gamma-Aminobutyric Acid - metabolism; Glutamic Acid - pharmacology; Inferior Colliculi - drug effects; Inferior Colliculi - physiology; Inferior Colliculi - radiation effects; Iontophoresis - methods; Neural Inhibition - drug effects; Neural Inhibition - physiology; Neural Inhibition - radiation effects; Rabbits; Sound; Sound Localization - drug effects; Sound Localization - physiology; Sound Localization - radiation effects; Time Perception - drug effects; Time Perception - physiology; Time Perception - radiation effects
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00956.2004

Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut Submitted 14 September 2004; accepted in final form 31 December 2004 A major cue for the localization of sound in space is the interaural time difference (ITD). We examined the role of inhibition in the shaping of ITD responses in the inferior colliculus (IC) by iontophoretically ejecting -aminobutyric acid (GABA) antagonists and GABA itself using a multibarrel pipette. The GABA antagonists block inhibition, whereas the applied GABA provides a constant level of inhibition. The effects on ITD responses were evaluated before, during and after the application of the drugs. If GABA-mediated inhibition is involved in shaping ITD tuning in IC neurons, then applying additional amounts of this inhibitory transmitter should alter ITD tuning. Indeed, for almost all neurons tested, applying GABA reduced the firing rate and consequently sharpened ITD tuning. Conversely, blocking GABA-mediated inhibition increased the activity of IC neurons, often reduced the signal-to-noise ratio and often broadened ITD tuning. Blocking GABA could also alter the shape of the ITD function and shift its peak suggesting that the role of inhibition is multifaceted. These effects indicate that GABAergic inhibition at the level of the IC is important for ITD coding. Address for reprint requests and other correspondence: S. Kuwada, Department of Neuroscience, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030 (E-mail: shig{at}neuron.uchc.edu )