Age-related changes in electrotonic coupling ratio of two identified neurons in Lymnaea stagnalis were studied together with the underlying changes in the steady-state conductance properties of the network. Two phases were distinguished in the development of coupling ratio across lifespan. During the first phase (age of 3-13 months), coupling ratio decreased from decreased from 60% to 30%. The second phase (age 13-20 months) was characterized by an increase in coupling ratio. Values of up to 60% were reached again in the oldest animals. Voltage clamp measurements showed that the biphasic trend of the age-related changes in coupling ratio is paralleled by changes in conductance properties of the junction between VD1 and RPD2. During the first phase junctional conductance decreased, whereas during the second phase junctional conductance increased. In addition to the decrease in junctional conductance, a growth-related increase in non-junctional conductance of VD1 and RPD2 contributed to the decrease in coupling ratio observed during the first phase. Thus our results indicate that in Lymnaea junctional connections between neurons may undergo considerable and discontinuous changes after sexual maturation. In addition to these changes in steady-state electrical properties, indications were obtained that age-related changes of kinetically slower conductance(s) may occur in the non-junctional membrane of VD1 and RPD2.
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http://dx.doi.org/10.1016/0006-8993(91)90578-j | DOI Listing |
Sci Total Environ
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Department of Chemistry, Physics, Environmental and Soil Sciences, University of Lleida - AGROTECNIO-CERCA Center, Rovira Roure 191, 25198 Lleida, Spain.
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Department of Inorganic Chemistry, Physical Chemistry and Electrochemistry, National University of Science and Technology Politehnica Bucharest, 1-7 Gheorghe Polizu St., 011061 Bucharest, Romania. Electronic address:
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