Abstract
Local interneurons (LNs) play important roles in shaping and modulating the activity of output neurons in primary olfactory centers. Here, we studied the morphological characteristics, odor responses, and neurotransmitter content of LNs in the antennal lobe (AL, the insect primary olfactory center) of the moth Manduca sexta. We found that most LNs are broadly tuned, with all LNs responding to at least one odorant. 70% of the odorants evoked a response, and 22% of the neurons responded to all the odorants tested. Some LNs showed excitatory (35%) or inhibitory (33%) responses only, while 33% of the neurons showed both excitatory and inhibitory responses, depending on the odorant. LNs that only showed inhibitory responses were the most responsive, with 78% of the odorants evoking a response. Neurons were morphologically diverse, with most LNs innervating almost all glomeruli and others innervating restricted portions of the AL. 61 and 39% of LNs were identified as GABA-immunoreactive (GABA-ir) and non-GABA-ir, respectively. We found no correlations between odor responses and GABA-ir, neither between morphology and GABA-ir. These results show that, as observed in other insects, LNs are diverse, which likely determines the complexity of the inhibitory network that regulates AL output.
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Abbreviations
- AL:
-
Antennal lobe
- GABA-ir:
-
GABA-immunoreactive
- ISF:
-
Instantaneous spike frequency
- LN:
-
Local interneuron
- MGC:
-
Macroglomerular complex
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Acknowledgments
This work was supported by NIH grant R01-DC-02751 to JGH and a NIH Training grant (through the Center for Insect Science) 1 K12 Gm00708 to AMD. CER thanks N.T. Davis for his dedicated teaching of immunocytochemistry methods. The authors thank the members of the Hildebrand laboratory for many helpful discussions, M. Marez for rearing M. sexta, P. Jansma for advice in confocal microscopy, and two anonymous reviewers for many helpful comments and suggestions that greatly improved this manuscript.
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Reisenman, C.E., Dacks, A.M. & Hildebrand, J.G. Local interneuron diversity in the primary olfactory center of the moth Manduca sexta . J Comp Physiol A 197, 653–665 (2011). https://doi.org/10.1007/s00359-011-0625-x
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DOI: https://doi.org/10.1007/s00359-011-0625-x