[Duration-tuning of the neurons in the inferior colliculus of guinea pigs and the role of gamma-aminobutyric acid mediated inhibition].
OBJECTIVE
To evaluate duration tuning in the inferior colliculus (IC) of guinea pigs and the role of GABA-mediated inhibition on this tuning.


METHODS
Totally 23 healthy albino guinea pigs of either sex were employed in this study. After anesthesia, spikes of neurons in inferior colliculus were recorded using five-barrel glass-pipettes. The characteristic frequency was determined by recording iso-intensity response curves at moderate intensity level (40-70 dB SPL) and duration tuning was measured with signals of fixed intensity and varied durations. GABA-A receptor antagonist, bicuculline, was applied to neurons by means of in vivo micro-iontophoresis through one channel in the five-barrel glass-pipettes.


RESULTS
IC neurons of guinea pigs, especially for those who showed sustained temporal response pattern, showed stronger duration tuning in their transient response peak to signal onset. Among 207 neurons recorded, totally 93 neurons were found to show clear duration selectivity. The duration selectivity was eliminated or turned to be weaker in most of the neurons in which the effect of bicuculline was observed successfully.


CONCLUSIONS
Unlike what was reported in bats, duration selectivity may be a transient process for most of IC neurons in guinea pigs. Duration selectively of IC neurons in the guinea pig was also largely dependent on the GABAergic inhibition.
Chen
Zheng-nong
ZN
Department of Otorhinolaryngology, Affiliated Shanghai Sixth People's Hospital of Shanghai Jiaotong University, Otorhinolaryngology Institute of Shanghai Jiaotong University, Clinical Auditory Center of Shanghai, Shanghai 200233, China.
Wang
Jian
J
Feng
Yan-mei
YM
Yu
Dong-zhen
DZ
Yin
Shan-kai
SK
D000818:Animals; D005072:Evoked Potentials, Auditory; D005260:Female; D006168:Guinea Pigs; D007245:Inferior Colliculi / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D005680:gamma-Aminobutyric Acid