Summary
Electron microscopic examination of the monkey lateral geniculate nucleus, pars dorsalis (LGNd) reveals the occurrence of synaptic contacts between profiles belonging to interneurons (I-cells). Almost all combinations are observed, namely, axodendritic, dendrodendritic, dendrosomatic and somatodendritic, the most frequent being the dendrodentritic synapses between the presynaptic dendrites characteristic of I-cells. Quantitative analysis of 5 samples, each consisting of 200 μm2 of net LGNd neuropil, shows that presynaptic membrane specializations present in I-cell axonal and dendritic elements amount to a mean of 3.73 μm or 8.16 % of the surface of such profiles. Only 61% of this extent is in contact with principal cells (P-cells), and an unexpectedly high 39% engages other I-cell elements. Approximately 18% of the neuropil is occupied by I-cell profiles. A tentative segregation of axonal and dendritic endings revealed the following significant mean differences: dendritic terminals are more numerous and larger; axonal profiles have more of their surface occupied by synaptic sites and each contact is longer. Findings suggest the existence of a network of interconnected interneurons which are presumably inhibitory in nature. Such an arrangement can provide a certain measure of anisotropic disinhibition which may be responsible for specific transformations occurring in the LGNd depending upon the size and velocity of the stimulus as well as of the degree of synchronicity of temporal patterns.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Andersen, P., Eccles, J.C.: Inhibitory phasing of neuronal discharge. Nature (Lond.) 196, 645–647 (1962)
Burke, W., Sefton, A.J.: Inhibitory mechanisms in lateral geniculate nucleus of rat. J. Physiol. (Lond.) 187, 231–246 (1966)
Famiglietti, E.V.: Dendro-dendritic synapses in the lateral geniculate nucleus of the cat. Brain Res. 20, 181–191 (1970)
Famiglietti, E.V., Jr., Peters, A.: The synaptic glomerulus and the intrinsic neuron in the dorsal lateral geniculate nucleus of the cat. J. comp. Neurol. 144, 285–334 (1972)
Guillery, R.W.: Patterns of synaptic interconnections in the dorsal lateral geniculate nucleus of cat and monkey: A brief review. Vision Res. Suppl. 3, 211–227 (1971)
Hámori, J., Pasik, P., Pasik, T.: Postnatal differentiation of “presynaptic dendrites” in the lateral geniculate nucleus of the rhesus monkey. In: Physiology and Pathology of Dendrites, pp. 149–161. (ed. G.W. Kreutzberg). New York: Raven Press 1975
Hámori, J., Pasik, T., Pasik, P., Szentágothai, J.: Triadic synaptic arrangements and their possible significance in the lateral geniculate nucleus of the monkey. Brain Res. 80, 379–393 (1974)
Lábos, E.: Enhancement of integrative capacities by means of coupling synaptic triads in the lateral geniculate nucleus. Exp. Brain Res. 23, Suppl. 156 (1975)
Le Vay, S.: On the neurons and synapses of the lateral geniculate nucleus of the monkey and the effects of eye enucleation. Z. Zellforsch. 113, 396–419 (1971)
Lieberman, A.R.: Neurons with presynaptic perikarya and presynaptic dendrites in the rat lateral ge niculate nucleus. Brain Res. 59, 35–59 (1973)
Lieberman, A.R., Webster, K.E.: Aspects of the synaptic organization of intrinsic neurons in the dorsal lateral geniculate nucleus. An ultrastructural study of the normal and of the experimentally deafferented nucleus in the rat. J. Neurocytol. 3, 677–710 (1974)
Morest, D.K.: Dendrodendritic synapses of cells that have axons: the fine structure of the Golgi type II cell in the medial geniculate body of the cat. Z. Anat. Entwickl.-Gesch. 133, 216–246 (1971)
Pasik, P., Pasik, T., Hámori, J., Szentágothai, J.: Golgi type II interneurons in the neuronal circuit of the monkey lateral geniculate nucleus. Exp. Brain Res. 17, 18–34 (1973)
Pecci-Saavedra, J., Vaccarezza, O.L.: Synaptic organization of the glomerular complexes in the lateral geniculate nucleus of Cebus monkey. Brain Res. 8, 389–393 (1968)
Peters, A., Palay, S.L.: The morphology of laminae A and A1 of the dorsal nucleus of the lateral geniculate body of the cat. J. Anat. (Lond.) 100, 451–486 (1966)
Rafols, J.A., Valverde, F.: The structure of the dorsal lateral geniculate nucleus in the mouse. A Golgi and electron microscopic study. J. comp. Neurol. 150, 303–332 (1973)
Ralston, H.J., Herman, M.M.: The fine structure and synapses in the ventrobasal thalamus of the cat. Brain Res. 14, 77–97 (1969)
Rinvik, E., Grofová, I.: Light and electron microscopical studies of the normal nuclei ventralis lateralis and ventralis anterior thalami in the cat. Anat. Embryol. 146, 57–93 (1974)
Singer, W., Pöppel, E., Creutzfeldt, O.: Inhibitory interaction in the cat's lateral geniculate nucleus. Exp. Brain Res. 14, 210–226 (1972)
Szentágothai, J.: The structure of the synapse in the lateral geniculate body. Acta anat. (Basel) 55, 166–185 (1963)
Szentágothai, J.: Neuronal and synaptic architecture of the lateral geniculate body. In: Handbook of Sensory Physiology, Vol. VII/3B, pp. 141–176. (ed. R. Jung). Berlin-Heidelberg-New York: Springer 1973
Szentágothai, J., Hámori, J., Tömböl, T.: Degeneration and electron microscope analysis of the synaptic glomeruli in the lateral geniculate body. Exp. Brain Res. 2, 283–301 (1966)
Uchizono, K.: Characteristics of excitatory and inhibitory synapses in the central nervous system of the cat. Nature (Lond.) 207, 642–643 (1965)
Wong, M.T.T.: Somato-dendritic and dendro-dendritic synapses in the squirrel monkey lateral geniculate nucleusl. Brain Res. 20, 135–139 (1970)
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Pasik, P., Pasik, T. & Hámori, J. Synapses between interneurons in the lateral geniculate nucleus of monkeys. Exp Brain Res 25, 1–13 (1976). https://doi.org/10.1007/BF00237322
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00237322