Collet Claude, Belzunces Luc
Ecologie des invertébrés, INRA, Institut National de la Recherche Agronomique, UMR406, Domaine St Paul, Site Agroparc, F-84914 Avignon cedex 9, France.
J Exp Biol. 2007 Feb;210(Pt 3):454-64. doi: 10.1242/jeb.02667.
In the hive, a wide range of honeybees tasks such as cell cleaning, nursing, thermogenesis, flight, foraging and inter-individual communication (waggle dance, antennal contact and trophallaxy) depend on proper muscle activity. However, whereas extensive electrophysiological studies have been undertaken over the past ten years to characterize ionic currents underlying the physiological neuronal activity in honeybee, ionic currents underlying skeletal muscle fibre activity in this insect remain, so far, unexplored. Here, we show that, in contrast to many other insect species, action potentials in muscle fibres isolated from adult honeybee metathoracic tibia, are not graded but actual all-or-none responses. Action potentials are blocked by Cd(2+) and La(3+) but not by tetrodotoxin (TTX) in current-clamp mode of the patch-clamp technique, and as assessed under voltage-clamp, both Ca(2+) and K(+) currents are involved in shaping action potentials in single muscle fibres. The activation threshold potential for the voltage-dependent Ca(2+) current is close to -40 mV, its mean maximal amplitude is -8.5+/-1.9 A/F and the mean apparent reversal potential is near +40 mV. In honeybees, GABA does not activate any ionic membrane currents in muscle fibres from the tibia, but L-glutamate, an excitatory neurotransmitter at the neuromuscular synapse induces fast activation of an inward current when the membrane potential is voltage clamped close to its resting value. Instead of undergoing desensitization as is the case in many other preparations, a component of this glutamate-activated current has a sustained component, the reversal potential of which is close to 0 mV, as demonstrated with voltage ramps. Future investigations will allow extensive pharmacological characterization of membrane ionic currents and excitation-contraction coupling in skeletal muscle from honeybee, a useful insect that became a model to study many physiological phenomena and which plays a major role in plant pollination and in stability of environmental vegetal biodiversity.
在蜂巢中，蜜蜂的一系列任务，如蜂巢清理、哺育、产热、飞行、觅食以及个体间通讯（摆尾舞、触角接触和交哺）都依赖于适当的肌肉活动。然而，尽管在过去十年里已经进行了广泛的电生理研究来表征蜜蜂生理神经元活动背后的离子电流，但迄今为止，这种昆虫骨骼肌纤维活动背后的离子电流仍未得到探索。在这里，我们表明，与许多其他昆虫物种不同，从成年蜜蜂后胸胫骨分离出的肌肉纤维中的动作电位不是分级的，而是实际的全或无反应。在膜片钳技术的电流钳模式下，动作电位被镉离子（Cd(2+)）和镧离子（La(3+)）阻断，但不被河豚毒素（TTX）阻断，并且在电压钳下评估时，钙离子（Ca(2+)）电流和钾离子（K(+)）电流都参与了单个肌肉纤维动作电位的形成。电压依赖性钙离子电流的激活阈值电位接近 -40 mV，其平均最大幅度为 -8.5±1.9 A/F，平均表观反转电位接近 +40 mV。在蜜蜂中，γ-氨基丁酸（GABA）不会激活来自胫骨的肌肉纤维中的任何离子膜电流，但L-谷氨酸，一种神经肌肉突触处的兴奋性神经递质，当膜电位在电压钳下接近其静息值时，会诱导内向电流的快速激活。与许多其他标本的情况不同，这种谷氨酸激活电流的一个成分没有脱敏，而是有一个持续成分，其反转电位接近0 mV，这通过电压斜坡得到了证明。未来的研究将允许对蜜蜂骨骼肌中的膜离子电流和兴奋-收缩偶联进行广泛的药理学表征，蜜蜂是一种有用的昆虫，已成为研究许多生理现象的模型，并且在植物授粉和环境植物生物多样性的稳定性中发挥着重要作用。
