Affiliation:
1. Department of Neuroscience, University of Virginia Health Science Center, Charlottesville, VA 22908-0230, USA
Abstract
SUMMARYIn cold-blooded species the efficacy of neuromuscular function depends both on the thermal environmental of the animal's habitat and on the concentrations of modulatory hormones circulating within the animal's body. The goal of this study is to examine how temperature variation within an ecologically relevant range affects neuromuscular function and its modulation by the neurohormone serotonin (5-HT) in Homarus americanus, a lobster species that inhabits a broad thermal range in the wild. The synaptic strength of the excitatory and inhibitory motoneurons innervating the lobster dactyl opener muscle depends on temperature, with the strongest neurally evoked muscle movements being elicited at cold (<5°C) temperatures. However, whereas neurally evoked contractions can be elicited over the entire temperature range from 2 to >20°C, neurally evoked relaxations of resting muscle tension are effective only at colder temperatures at which the inhibitory junction potentials are hyperpolarizing in polarity. 5-HT has two effects on inhibitory synaptic signals: it potentiates their amplitude and also shifts the temperature at which they reverse polarity by approximately +7°C. Thus 5-HT both potentiates neurally evoked relaxations of the muscle and increases the temperature range over which neurally evoked muscle relaxations can be elicited. Neurally evoked contractions are maximally potentiated by 5-HT at warm (18°C) temperatures; however, 5-HT enhances excitatory junction potentials in a temperature-independent manner. Finally, 5-HT strongly increases resting muscle tension at the coldest extent of the temperature range tested (2°C) but is ineffective at 22°C. These data demonstrate that 5-HT elicits several temperature-dependent physiological changes in the passive and active responses of muscle to neural input. The overall effect of 5-HT is to increase the temperature range over which neurally evoked motor movements can be elicited in this neuromuscular system.)
Publisher
The Company of Biologists
Subject
Insect Science,Molecular Biology,Animal Science and Zoology,Aquatic Science,Physiology,Ecology, Evolution, Behavior and Systematics
Reference68 articles.
1. ASMFC (2005). Atlantic States Marine Fisheries Commission species profile: American lobster. Peer-reviewed stock assessment presents new opportunities and challenges for lobster management. Atl. States Mar. Fish. Comm. Fish. Focus14, 4-6.
2. Beaumont, V. and Zucker, R. (2000). Enhancement of synaptic transmission by cyclic AMP modulation of presynaptic Ih channels. Nat. Neurosci.3, 133-141.
3. Bykhovskaia, M., Hackett, J. T. and Worden, M. K.(1999). Asynchrony of quantal events in evoked multiquantal responses indicates presynaptic quantal interaction. J. Neurophysiol.81,2234-2242.
4. Bykhovskaia, M., Polagaeva, E. and Hackett, J. T.(2001). Hyperosmolarity reduces facilitation by a Ca(2+)-independent mechanism at the lobster neuromuscular junction: possible depletion of the releasable pool. J. Physiol.537,179-190.
5. Bykhovskaia, M., Polagaeva, E. and Hackett, J. T.(2004). Mechanisms underlying different facilitation forms at the lobster neuromuscular synapse. Brain Res.1019,10-21.
Cited by
16 articles.
订阅此论文施引文献
订阅此论文施引文献，注册后可以免费订阅5篇论文的施引文献，订阅后可以查看论文全部施引文献