GABAergic mechanisms that shape the temporal response to odors in moth olfactory projection neurons

Thomas A. Christensen, Brian R. Waldrop, John G. Hildebrand

Research output: Contribution to journalArticle

33 Scopus citations

Abstract

Mitral/tufted cells in the olfactory bulb and projection neurons (PNs) in the insect antennal lobe are involved in complex synaptic interactions with inhibitory interneurons to help shape their odor-evoked responses. In the moth Manduca sexta, both γ-aminobutyric acid (GABA) and the GABA(A) receptor agonist muscimol hyperpolarize and lower input resistance in many PNs, often blocking ongoing spike traffic. The GABA response mimics a short-latency, chloride-mediated inhibitory postsynaptic potential (IPSP) evoked in PNs by electrical or odor stimulation of afferent inputs, and the classical GABA(A) receptor antagonist bicuculline methiodide (BMI) quickly and reversibly blocks this IPSP. Focal injection of BMI (100 μM) immediately preceding a GABA pulse blocks the hyperpolarization evoked by GABA, but a similar injection of BMI preceding an acetylcholine (ACh) pulse fails to block the depolarization evoked by ACh. Moreover, the temporal pattern of odor-evoked activity in moth PNs is also strongly and reversibly altered by BMI. Importantly, the temporal pattern of the response depends on the temporal characteristics of the stimulus: continuous stimulation evokes more complex, rhythmic responses, whereas a pulsatile stimulus can be copied with a discrete burst of spikes for each pulse. Collectively our results indicate that PNs in the moth antennal lobe possess GABA receptors that share certain characteristics in common with vertebrate GABA(A) receptors. These receptors are largely responsible for helping PNs integrate information about both the molecular features and the timing of olfactory input to the brain.

Original languageEnglish (US)
Pages (from-to)475-481
Number of pages7
JournalAnnals of the New York Academy of Sciences
Volume855
DOIs
StatePublished - Jan 1 1998

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ASJC Scopus subject areas

  • Neuroscience(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • History and Philosophy of Science

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