Excitation-contraction coupling in skeletal muscle fibers from adult domestic honeybee

Claude Collet (1)

1 AE - Abeilles et Environnement

Excitation–contraction coupling was characterized in enzymatically isolated adult honeybee skeletal muscle fibers. The voltage-dependent Ca2+ current (ICa) underlies action potential (AP) depolarization phase in honeybee muscle. A single AP leads to rapid and transient cytoplasmic Ca2+ increase (“Ca2+ transient”), which afterwards returns toward baseline following an exponential time course. Trains of APs elicit a staircase increase of Ca2+, as a result of multiple Ca2+ transient summation. Surprisingly, the nifedipine- sensitive ICa is blocked by allethrin, a pyrethroid insecticide, revealing myotoxic effects of this neurotoxic insecticide for honeybees. Ca2+ transients are under the control of Ca2+ entry through voltage-activated Ca2+ channels. Indeed, Ca2+ transient amplitude depends on extracellular Ca2+ concentration, and bell-shaped relationships are obtained for both ICa integral and the Ca2+ transient peak in response to depolarizations of increasing amplitude. The slow inactivation kinetics of ICa induces long-lasting Ca2+ transients that tend to reach a plateau and to return toward a resting level after the end of the stimulation. A Ca2+-induced Ca2+ release mechanism is suggested by two results. First, caffeine (≥5 mM) and 4-cmc (>0.4 mM), two activators of the sarcoplasmic reticulum Ca2+ release channels (CRCs), induce Ca2+ elevations in the absence of extracellular Ca2+. Second, ryanodine (5 μM) a plant alkaloid that binds specifically to CRCs, depresses voltageinduced Ca2+ transients. Honeybee muscle fibers represent a valuable model to study invertebrate excitation–contraction coupling and insecticide myotoxicity toward useful insects

Mots clés: HONEYBEE; SOCIAL INSECT; POLLINATOR; ADULT; SKELETAL MUSCLE; EXCITATION-CONTRACTION COUPLING; MYOTOXICITY; HISTOLOGY; TRANSMISSION ELECTRON MICROSCOPY; ELECTROPHYSIOLOGY; CALCIUM IMAGING; APIS MELLIFERA; APIDAE; HYMENOPTERA; PATCH-CLAMP; INSECTE SOCIAL; ADULTE; CALCIUM; MYOTOXICITE; HISTOLOGIE; ACTION POTENTIAL

Mots clés: RYANODINE RECEPTOR; CALCIUM TRANSIENT; CONFOCAL MICROSCOPY; ION CURRENT; APIFORMES; RECEPTEUR A LA RYANODINE; IMAGERIE CALCIQUE; FLUORESCENCE; VARIATION TRANSITOIRE CALCIQUE; MICROSCOPIE CONFOCALE; ULTRASTUCTURE; COURANT IONIQUE; POTENTIEL D'ACTION; ABEILLE DOMESTIQUE; POLLINISATEUR; MUSCLE SQUELETTIQUE; COUPLAGE EXCITATION-CONTRACTION; INSECTICIDE; MICROSCOPIE ELECTRONIQUE A TRANSMISSION; ELECTROPHYSIOLOGIE

Domaines: Sciences du Vivant [q-bio]

Claude Collet. Excitation-contraction coupling in skeletal muscle fibers from adult domestic honeybee. Pflügers Archiv European Journal of Physiology, 2009, 458 (3), pp.601-612. ⟨10.1007/s00424-009-0642-6⟩. ⟨hal-02661011⟩