Summary
Synaptic junctions located on the dendrites of lamprey (Petromyzon marinus) reticulospinal neurons labelled with intracellularly-injected horseradish peroxidase were studied. The normal ultrastructure of the synaptic junctions was defined and several quantitative measures made from each junction in order to test the hypothesis that distally-located synapses are ultrastructurally different from those located at proximal dendritic sites. A total of 820 contacts from one neuron and 279 from a second neuron ranging from 20 to 340 μm from the soma were quantified. The vast majority of the presynaptic endings contained round, clear-cored vesicles and formed an asymmetrical membrane differentiation with the postsynaptic dendrite. A small fraction of the population contained flattened or pleomorphic vesicles and these synapses were equally distributed with respect to distance from the soma. Many of the terminals contained a few large dark- and clear-cored vesicles. Four quantitative measures of each synaptic contact were made. These included vesicle number, length of differentiated membrane, vesicle area and terminal area. Four ratios relating the different quantitative measures were also calculated. Each ratio or measurement from the synaptic junctions was plotted as a function of distance from the soma to determine if differences existed at any distance. It was found that synaptic junctions are uniformly similar and that distal junctions did not differ significantly (P > 0.05) from those at proximal dendritic sites. It is concluded that if distal synapses do compensate for their remote location they do this in some other way, possibly by increasing the number of synaptic contacts made by each presynaptic axon.
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References
Burke, R. E. andTen Bruggencate, G. (1971) Electrotonic characteristics of motoneurons of varying size.Journal of Physiology 212, 1–20.
Cajal, S. R. y (1911)Histologie du Système Nerveux de l'Homme et des Vertébrés. Vol. II. Paris: Maloine.
Christensen, B. N. (1976) Morphological correlates of synaptic transmission in lamprey spinal cord.Journal of Neurophysiology 39, 197–212.
Christensen, B. N. andEbner, F. E. (1978) The synaptic architecture of neurons in opossum somatic sensory-motor cortex: A combined anatomical and physiological study.Journal of Neurocytology 7, 39–60.
Christensen, B. N. andTeubl, W. P. (1979a) Estimates of cable parameters in lamprey spinal cord neurones.Journal of Physiology (in press).
Christensen, B. N. andTeubl, W. P. (1979b) Localization of a synaptic input on dendrites of a lamprey giant interneurone from cable parameters.Journal of Physiology (in press).
Colonnier, M. (1968) Synaptic patterns of cell types in the different laminae of the cat visual cortex. An electron microscopic study.Brain Research 9, 268–87.
Eide, E., Fedina, L., Jansen, J., Lundberg, A., andVyklicky, L. (1969) Unitary components in the activation of Clarke's column neurones.Acta physiologica scandinavica 77, 145–58.
Iansek, R. andRedman, S. (1973a) An analysis of the cable properties of spinal motoneurones using a brief intracellular current pulse.Journal of Physiology 234, 613–36.
Iansek, R. andRedman, S. (1973b) The amplitude, time course and charge of unitary excitatory post-synaptic potentials.Journal of Physiology 234, 655–88.
Iles, J. F. (1976) Central terminations of muscle afferents on motoneurones in the cat spinal cord.Journal of Physiology 262, 91–118.
Jack, J. J. B., Miller, S., Porter, R. andRedman, S. J. (1971) The time course of minimal excitatory postsynaptic potentials evoked in spinal motoneurones by group Ia afferent fibres.Journal of Physiology 215, 353–80.
Jack, J. J. B. andRedman, S. J. (1971) An electrical description of the motoneurone, and its application to the analysis of synaptic potentials.Journal of Physiology 215, 321–52.
Jones, E. G. andPowell, T. P. S. (1970) Electron microscopy of the somatic sensory cortex of the cat. I. Cell types and synaptic organization.Philosophical Transactions of the Royal Society of London B257, 1–11.
Kreuter, F., Richter, D. W., Camerer, H. andSenekowitsch, R. (1977) Morphological and electrical description of medullary neurons of the cat.Pflügers Archiv 372, 7–16.
Kuno, M. (1964) Quantal components of excitatory synaptic potentials in spinal motoneurones.Journal of Physiology 175, 81–99.
Kuno, M. (1971) Quantum aspects of central and ganglionic synaptic transmission in vertebrates.Physiological Reviews 51, 647–8.
Kuno, M. andMiyahara, J. (1968) Factors responsible for multiple discharge of neurons in Clarke's column.Journal of Neurophysiology 31, 624–38.
Kuno, M., Turkanis, S. A. andWeakly, J. N. (1971) Correlation between nerve terminal size and transmitter release at the neuromuscular junction of the frog.Journal of Physiology 213, 545–56.
Kuno, M., Munoz-Martinez, E. J. andRandic, M. (1973) Synaptic action on Clarke's column neurones in relation to afferent terminal size.Journal of Physiology 228, 343–60.
Lux, H. D., Schubert, P. andKreutzberg, G. (1970) Direct matching of morphological and electrophysiological data in cat spinal motoneurons. InExcitatory Synaptic Mechanisms (edited byAndersen, P. andJansen, J. K. S.), pp. 189–198. Oslo: Universitetsforlaget.
Nelson, P. G. andLux, H. D. (1970) Some electrical measurements of motoneuron parameters.Biophysics Journal 10, 55–73.
Rall, W. (1962a) Electrophysiology of a dendritic neuron model.Biophysics Journal 2, 145–69.
Rall, W. (1962b) Theory of physiological properties of dendrites.Annals of the New Yor Academy of Sciences 96, 1071–92.
Rall, W. (1964) Theoretical significance of dendritic trees for neuronal input-output relations. InNeural Theory and Modelling (edited byReiss, R. F.), pp. 73–97. Stanford University Press.
Rall, W. (1967) Distinguishing theoretical synaptic potentials computed for different soma-dendritic distributions of synaptic input.Journal of Neurophysiology 30, 1138–68.
Rall, W. (1969) Time constants and electrotonic length of membrane cylinders and neurons.Biophysics Journal 9, 1483–508.
Rall, W. (1970) Cable properties of dendrites and effects of location. InExcitatory Synaptic Mechanisms (edited byAndersen, P. andJansen, J. K. S.), pp. 175–188. Oslo: Universitetsforlaget.
Rall, W., Burke, R. E., Smith, T. G., Nelson, P. G. andFrank, K. (1967) Dendritic location of synapses and possible mechanisms for the monosynaptic epsp in motoneurons.Journal of Neurophysiology 30, 1169–93.
Redman, S. J. (1973) The attenuation of passively propagating dendritic potentials in a motoneurone cable model.Journal of Physiology 234, 637–64.
Snow, P. J., Rose, P. K. andBrown, A. G. (1976) Tracing axons and axon collaterals of spinal neurons using intracellular injection of horseradish peroxidase.Science 191, 312–3.
Uchizono, K. (1965) Characteristics of excitatory and inhibitory synapses in the central nervous system of the cat.Nature 207, 642–3.
Uchizono, K. (1966) Excitatory and inhibitory synapses in the cat spinal cord.Japanese Journal of Physiology 16, 570–5.
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Christensen, B.N., Quinn, J. The relationship between some measures of synaptic ultrastructure as a function of distance from the soma on lamprey reticulospinal neurons. J Neurocytol 8, 737–750 (1979). https://doi.org/10.1007/BF01206673
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DOI: https://doi.org/10.1007/BF01206673