The Journal of Neurophysiology Vol. 79 No. 5 May 1998, pp. 2408-2415
Copyright ©1998 The American Physiological Society

Picrotoxin Eliminates Frequency Selectivity of an Auditory Interneuron in a Bushcricket

Andreas Stumpner

I. Zoologisches Institut, D-37073 Gottingen, Germany

Stumpner, Andreas. Picrotoxin eliminates frequency selectivity of an auditory interneuron in a bushcricket. J. Neurophysiol. 79: 2408-2415, 1998. AN1, an auditory interneuron in the bushcricket Ancistrura nigrovittata, is narrowly tuned to the male song frequency (~15 kHz). It receives pronounced inhibitory input at frequencies below and, more prominently, above this fundamental frequency. It is also subject to side-dependent inhibition producing asymmetric response functions for left- and right-side stimulation. In addition, intensity-response functions of AN1 peak as stimulus intensities increase. Application of the GABA_A channel-blocker picrotoxin eliminates all subthreshold inhibitory postsynaptic potentials, revealing underlying excitation that is particularly obvious in the high-frequency range. Excitatory thresholds close to the song frequency remain unchanged by picrotoxin. Thus a specifically tuned neuron is shown to become broadly tuned after elimination of frequency-dependent inhibition. Although average maximum response strength is increased by 150% after picrotoxin application, at male song frequencies a slight reduction of the responses is still present at high intensities. Side-dependent inhibition remains largely unaffected by picrotoxin, suggesting that side- and frequency-dependent inhibitions are caused by different transmitters from different neurons.

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				A Stumpner An interneurone of unusual morphology is tuned to the female song frequency in the bushcricket Ancistrura nigrovittata (Orthoptera, Phaneropteridae) J. Exp. Biol., January 8, 1999; 202(15): 2071 - 2081. [Abstract] [PDF]