Survival of Egg-Laying Controlling Neuroendocrine Cells During Reproductive Senescence of a Mollusc
During brain aging neuronal degradation occurs. In some neurons this may result in degeneration and cell death, still other neurons may survive and maintain their basic properties. The present study deals with survival of the egg-laying controlling neuroendocrine caudodorsal cells (CDCs) during reproductive senescence of the pond snail Lymnaea stagnalis. In senescent animals CDCs exhibited reduced branching patterns but still maintained their electrophysiological characteristics. In the isolated CNS the cells could still respond with an afterdischarge upon electrical stimulation. After an extended period of no egg laying of Lymnaea CDCs failed to exhibit an afterdischarge. In senescent CDCs that failed an afterdischarge, discharge activity could be restored by exposure to peptides released by CDCs from reproductive animals. Moreover, raising the intracellular cAMP level could induce discharge activity in CDCs with afterdischarge failure. Discharge activity also occurred during depolarization of senescent CDCs by exposure of the cells to saline with a high potassium concentration. These results indicate that in senescent CDCs the pacemaking mechanism of the afterdischarge is still intact but that the initial activation fails. Chemical (auto)transmission of CDCs in such animals was indeed reduced as indicated by the small amplitude of the depolarizing afterpotential (DAP) induced by electrical stimulation. Interestingly, CDCs of senescent animals contained a relative large amount of a particular small peptide. The artificially synthesized peptide appeared to suppress DAP induction in CDCs. Possibly, release of the peptide contributes to the prevention of afterdischarge induction in senescent CDCs. The results so far indicate that in senescent Lymnaea neurons electrophysiological functions persist even after long periods of inactivity and severe morphological reduction.
KeywordsSenescence reproduction neuroendocrine cells neuropeptides neurophysiology
Unable to display preview. Download preview PDF.
- 3.DeVlieger, T. A., Kits, K. S., TerMaat, A., Lodder, J. C. (1980) Morphology and electrophysiology of the ovulation hormone producing neuroendocrine cells of the freshwater snail Lymnaea stagnalis (L.). J. Exp. Biol. 84, 259–271.Google Scholar
- 4.Geraerts, W. P. M., TerMaat, A., Vreugdenhil, E. (1988) The peptidergic neuroendocrine control of egg laying behavior in Aplysia and Lymnaea. In: H. Laufer and G. H. Downer (eds) Endocrinology of selected invertebrate types. Vol. II. Alan R. Liss, New York, pp. 141–231.Google Scholar
- 14.Jiménez, C. R. (1997) Generation of complex peptide diversity in neuroendocrine cells of Lymnaea stagnalis and the rat. Thesis Vrije Universiteit, Amsterdam, The Netherlands.Google Scholar
- 23.Swaab, D. F., Dubelaar, E. J. G., Hofman, M. A., Scherder, E. J. A., van Someren, E. J. W., Verwer, R. W. H. (2002) Brain aging and Alzheimer’s disease; use it or lose it. Progr. Brain Res. 138, 345–373.Google Scholar
This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.