Effect of GABAergic inhibition on odorant concentration coding in mushroom body intrinsic neurons of the honeybee
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Kenyon cells, the intrinsic neurons of the insect mushroom body, have the intriguing property of responding in a sparse way to odorants. Sparse neuronal codes are often invariant to changes in stimulus intensity and duration, and sparse coding often depends on global inhibition. We tested if this is the case for honeybees’ Kenyon cells, too, and used in vivo Ca2+ imaging to record their responses to different odorant concentrations. Kenyon cells responded not only to the onset of odorant stimuli (ON responses), but also to their termination (OFF responses). Both, ON and OFF responses increased with increasing odorant concentration. ON responses were phasic and invariant to the duration of odorant stimuli, while OFF responses increased with increasing odorant duration. Pharmacological blocking of GABA receptors in the brain revealed that ionotropic GABAA and metabotropic GABAB receptors attenuate Kenyon cells’ ON responses without changing their OFF responses. Ionotropic GABAA receptors attenuated Kenyon cell ON responses more strongly than metabotropic GABAB receptors. However, the response dynamic, temporal resolution and paired-pulse depression did not depend on GABAA transmission. These data are discussed in the context of mechanisms leading to sparse coding in Kenyon cells.
KeywordsKenyon cells Ca2+ imaging Olfactory coding GABA receptors OFF responses
Clawed Kenyon cell
Region of interest
We are grateful to Drs. Silke Sachse, Melanie Haehnel and Nobuhiro Yamagata for their help and advice during the experiments. The work was supported by a grant of the Deutsche Forschungsgemeinschaft (Me 365/31-1).
- Enell L, Hamasaka Y, Kolodziejczyk A, Nässel DR (2007) gamma-Aminobutyric acid (GABA) signaling components in Drosophila: immunocytochemical localization of GABA(B) receptors in relation to the GABA(A) receptor subunit RDL and a vesicular GABA transporter. J Comp Neurol 505:18–31PubMedCrossRefGoogle Scholar
- Krofczik S, Menzel R, Nawrot MP (2009) Rapid odor processing in the honeybee antennal lobe network. Front Comput Neurosc 2:9Google Scholar