Neurite-specific Ca2+ dynamics underlying sound processing in an auditory interneurone.
Concepts on neuronal signal processing and integration at a cellular and subcellular level are driven by recording techniques and model systems available. The cricket CNS with the omega-1-neurone (ON1) provides a model system for auditory pattern recognition and directional processing. Exploiting ON1's planar structure we simultaneously imaged free intracellular Ca(2+) at both input and output neurites and recorded the membrane potential in vivo during acoustic stimulation. In response to a single sound pulse the rate of Ca(2+) rise followed the onset spike rate of ON1, while the final Ca(2+) level depended on the mean spike rate. Ca(2+) rapidly increased in both dendritic and axonal arborizations and only gradually in the axon and the cell body. Ca(2+) levels were particularly high at the spike-generating zone. Through the activation of a Ca(2+)-sensitive K(+) current this may exhibit a specific control over the cell's electrical response properties. In all cellular compartments presentation of species-specific calling song caused distinct oscillations of the Ca(2+) level in the chirp rhythm, but not the faster syllable rhythm. The Ca(2+)-mediated hyperpolarization of ON1 suppressed background spike activity between chirps, acting as a noise filter. During directional auditory processing, the functional interaction of Ca(2+)-mediated inhibition and contralateral synaptic inhibition was demonstrated. Upon stimulation with different sound frequencies, the dendrites, but not the axonal arborizations, demonstrated a tonotopic response profile. This mirrored the dominance of the species-specific carrier frequency and resulted in spatial filtering of high frequency auditory inputs.
Baden
T
T
Department of Zoology, University of Cambridge, Cambridge, United Kingdom. tb283@cam.ac.uk
Hedwig
B
B
D000161:Acoustic Stimulation / Q000379:methods; D000818:Animals; D001522:Behavior, Animal; D002118:Calcium / Q000378:metabolism*; D002490:Central Nervous System / Q000166:cytology*; D004307:Dose-Response Relationship, Radiation; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D005260:Female; D006135:Gryllidae; D007395:Interneurons / Q000166:cytology* / Q000502:physiology / Q000528:radiation effects; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009433:Neural Inhibition / Q000502:physiology; D016501:Neurites / Q000378:metabolism*; D017711:Nonlinear Dynamics
D004533:Egtazic Acid; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium