GABA-mediated synaptic inhibition of projection neurons in the antennal lobes of the sphinx moth, Manduca sexta

Brian Waldrop, Thomas A. Christensen, John G Hildebrand

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Abstract

1. Responses of neurons in the antennal lobe (AL) of the moth Manduca sexta to stimulation of the ipsilateral antenna by odors consist of excitatory and inhibitory synaptic potentials (Fig. 2A). Stimulation of primary afferent fibers by electrical shock of the antennal nerve causes a characteristic IPSP-EPSP synaptic response in AL projection neurons (Fig. 2B). 2. The IPSP in projection neurons reverses below the resting potential (Fig. 3), is sensitive to changes in external (Fig. 4) and internal (Fig. 5) chloride concentration, and thus is apparently mediated by an increase in chloride conductance. 3. The IPSP is reversibly blocked by 100 μM picrotoxin (Fig. 6) or bicuculline (Fig. 7). 4. Many AL neurons respond to application of GABA with a strong hyperpolarization and an inhibition of spontaneous spiking activity (Fig. 8). GABA responses are associated with an increase in neuronal input conductance (Fig. 9) and a reversal potential below the resting potential (Fig. 11). 5. Application of GABA blocks inhibitory synaptic inputs (Fig. 12 A) and reduces or blocks excitatory inputs (Fig. 12B). EPSPs can be protected from depression by application of GABA (Fig. 12B). 6. Muscimol, a GABA analog that mimics GABA responses at GABAA receptors but not at GABAB receptors in the vertebrate CNS, inhibits many AL neurons in the moth (Fig. 13).

Original languageEnglish (US)
Pages (from-to)23-32
Number of pages10
JournalJournal of Comparative Physiology A
Volume161
Issue number1
DOIs
StatePublished - Jan 1987

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antennal lobe
Manduca
Sphingidae
Moths
Manduca sexta
moth
gamma-Aminobutyric Acid
neurons
chloride
Neurons
Inhibitory Postsynaptic Potentials
odor
antenna
vertebrate
membrane potential
Excitatory Postsynaptic Potentials
moths
chlorides
Membrane Potentials
Chlorides

ASJC Scopus subject areas

  • Behavioral Neuroscience
  • Neuroscience(all)
  • Physiology (medical)
  • Physiology
  • Animal Science and Zoology
  • Medicine(all)

Cite this

GABA-mediated synaptic inhibition of projection neurons in the antennal lobes of the sphinx moth, Manduca sexta. / Waldrop, Brian; Christensen, Thomas A.; Hildebrand, John G.

In: Journal of Comparative Physiology A, Vol. 161, No. 1, 01.1987, p. 23-32.

Research output: Contribution to journalArticle

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N2 - 1. Responses of neurons in the antennal lobe (AL) of the moth Manduca sexta to stimulation of the ipsilateral antenna by odors consist of excitatory and inhibitory synaptic potentials (Fig. 2A). Stimulation of primary afferent fibers by electrical shock of the antennal nerve causes a characteristic IPSP-EPSP synaptic response in AL projection neurons (Fig. 2B). 2. The IPSP in projection neurons reverses below the resting potential (Fig. 3), is sensitive to changes in external (Fig. 4) and internal (Fig. 5) chloride concentration, and thus is apparently mediated by an increase in chloride conductance. 3. The IPSP is reversibly blocked by 100 μM picrotoxin (Fig. 6) or bicuculline (Fig. 7). 4. Many AL neurons respond to application of GABA with a strong hyperpolarization and an inhibition of spontaneous spiking activity (Fig. 8). GABA responses are associated with an increase in neuronal input conductance (Fig. 9) and a reversal potential below the resting potential (Fig. 11). 5. Application of GABA blocks inhibitory synaptic inputs (Fig. 12 A) and reduces or blocks excitatory inputs (Fig. 12B). EPSPs can be protected from depression by application of GABA (Fig. 12B). 6. Muscimol, a GABA analog that mimics GABA responses at GABAA receptors but not at GABAB receptors in the vertebrate CNS, inhibits many AL neurons in the moth (Fig. 13).

AB - 1. Responses of neurons in the antennal lobe (AL) of the moth Manduca sexta to stimulation of the ipsilateral antenna by odors consist of excitatory and inhibitory synaptic potentials (Fig. 2A). Stimulation of primary afferent fibers by electrical shock of the antennal nerve causes a characteristic IPSP-EPSP synaptic response in AL projection neurons (Fig. 2B). 2. The IPSP in projection neurons reverses below the resting potential (Fig. 3), is sensitive to changes in external (Fig. 4) and internal (Fig. 5) chloride concentration, and thus is apparently mediated by an increase in chloride conductance. 3. The IPSP is reversibly blocked by 100 μM picrotoxin (Fig. 6) or bicuculline (Fig. 7). 4. Many AL neurons respond to application of GABA with a strong hyperpolarization and an inhibition of spontaneous spiking activity (Fig. 8). GABA responses are associated with an increase in neuronal input conductance (Fig. 9) and a reversal potential below the resting potential (Fig. 11). 5. Application of GABA blocks inhibitory synaptic inputs (Fig. 12 A) and reduces or blocks excitatory inputs (Fig. 12B). EPSPs can be protected from depression by application of GABA (Fig. 12B). 6. Muscimol, a GABA analog that mimics GABA responses at GABAA receptors but not at GABAB receptors in the vertebrate CNS, inhibits many AL neurons in the moth (Fig. 13).

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