High-Probability Neurotransmitter Release Sites Represent an Energy-Efficient Design.
Curr Biol
; 26(19): 2562-2571, 2016 10 10.
Article
em En
| MEDLINE
| ID: mdl-27593375
ABSTRACT
Nerve terminals contain multiple sites specialized for the release of neurotransmitters. Release usually occurs with low probability, a design thought to confer many advantages. High-probability release sites are not uncommon, but their advantages are not well understood. Here, we test the hypothesis that high-probability release sites represent an energy-efficient design. We examined release site probabilities and energy efficiency at the terminals of two glutamatergic motor neurons synapsing on the same muscle fiber in Drosophila larvae. Through electrophysiological and ultrastructural measurements, we calculated release site probabilities to differ considerably between terminals (0.33 versus 0.11). We estimated the energy required to release and recycle glutamate from the same measurements. The energy required to remove calcium and sodium ions subsequent to nerve excitation was estimated through microfluorimetric and morphological measurements. We calculated energy efficiency as the number of glutamate molecules released per ATP molecule hydrolyzed, and high-probability release site terminals were found to be more efficient (0.13 versus 0.06). Our analytical model indicates that energy efficiency is optimal (â¼0.15) at high release site probabilities (â¼0.76). As limitations in energy supply constrain neural function, high-probability release sites might ameliorate such constraints by demanding less energy. Energy efficiency can be viewed as one aspect of nerve terminal function, in balance with others, because high-efficiency terminals depress significantly during episodic bursts of activity.
Palavras-chave
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Terminações Pré-Sinápticas
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Transmissão Sináptica
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Drosophila melanogaster
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Neurônios Motores
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Junção Neuromuscular
Limite:
Animals
Idioma:
En
Revista:
Curr Biol
Assunto da revista:
BIOLOGIA
Ano de publicação:
2016
Tipo de documento:
Article
País de afiliação:
Estados Unidos