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This Article Full Text Full Text (PDF) All Versions of this Article: 93/4/1949    most recent 01050.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Mercer, A. R. Articles by Hildebrand, J. G. Search for Related Content PubMed PubMed Citation Articles by Mercer, A. R. Articles by Hildebrand, J. G.

Plateau Potentials in Developing Antennal-Lobe Neurons of the Moth, Manduca sexta

¹Department of Zoology, University of Otago, Dunedin, New Zealand; ²Arizona Research Laboratories Division of Neurobiology, University of Arizona, Tucson, Arizona; and ³Zoologisches Institut II, Lehrstuhl Tierphysiologie, Universität zu Köln, Germany

Submitted 6 October 2004; accepted in final form 9 November 2004

Using whole cell recordings from antennal-lobe (AL) neurons in vitro and in situ, in semi-intact brain preparations, we examined membrane properties that contribute to electrical activity exhibited by developing neurons in primary olfactory centers of the brain of the sphinx moth, Manduca sexta. This activity is characterized by prolonged periods of membrane depolarization that resemble plateau potentials. The presence of plateau potential–generating mechanisms was confirmed using a series of tests established earlier. Brief depolarizing current pulses could be used to trigger a plateau state. Once triggered, plateau potentials could be terminated by brief pulses of hyperpolarizing current. Both triggering and terminating of firing states were threshold phenomena, and both conditions resulted in all-or-none responses. Rebound excitation from prolonged hyperpolarizing pulses could also be used to generate plateau potentials in some cells. These neurons were found to express a hyperpolarization-activated inward current. Neither the generation nor the maintenance of plateau potentials was affected by removal of Na⁺ ions from the extracellular medium or by blockade of Na⁺ currents with TTX. However, blocking of Ca²⁺ currents with Cd²⁺ (5 x 10^–4 M) inhibited the generation of plateau potentials, indicating that, in Manduca AL neurons, plateau potentials depend on Ca²⁺. Examining Ca²⁺ currents in isolation revealed that activation of these currents occurs in the absence of experimentally applied depolarizing stimuli. Our results suggest that this activity underlies the generation of plateau potentials and characteristic bursts of electrical activity in developing AL neurons of M. sexta.

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