Synaptic connections of enkephalin-immunoreactive nerve terminals in the neostriatum: a correlated light and electron microscopic study
- 1 October 1982
- journal article
- research article
- Published by Springer Nature in Journal of Neurocytology
- Vol. 11 (5), 779-807
- https://doi.org/10.1007/bf01153519
Abstract
Summary Two different antisera to leucine-enkephalin were used to study the localization of enkephalin-like immunoreactive material in the neostriatum and globus pallidus of the rat, by means of the unlabelled antibody-enzyme method. Thin immunoreactive varicose fibres are scattered throughout the neostriatum. In the ventral striatum, fibres come together and follow a relatively straight course for several micrometers, forming tube-like structures which can be traced to cell bodies; these cell bodies are completely surrounded by immunoreactive fibres. Occasional immunoreactive varicose fibres are also found close to another type of neuron throughout the whole neostriatum. Examination by electron microscopy of immunoreactive structures that had been identified first in the light microscope, showed that each of the nearly 200 varicosities examined was a vesicle-containing bouton that formed a synaptic contact. Rarely were asymmetrical synaptic contacts found between immunoreactive boutons and dendritic spines. All other synapses formed by enkephalin-immunoreactive boutons were symmetrical. Two types of postsynaptic neuron were identified; the first type was a medium-sized neuron with the ultrastructural features of a typical striatal spiny neuron. The second type had a larger perikaryon surrounded by numerous immunoreactive varicosities that were found to be boutons forming symmetrical synapses. The long dendrites of this second type of neuron likewise received a dense input of immunoreactive boutons forming symmetrical synapses; such ensheathed dendrites were found to be the tube-like structures seen in the light microscope. The ultrastructural features of these neurons, notably a highly indented nucleus, were those of a rare type of striatonigral neuron. In the globus pallidus, all the enkaphalin-immunoreactive boutons studied formed symmetrical synapses with ensheathed dendrites and perikarya that were similar to the latter type of postsynaptic neuron in the neostriatum. Axo-axonic synapses involving immunoreactive boutons were not seen in our material. The results are consistent with the view that enkephalin-like substances may be synaptic transmitters in the neostriatum and that they may have different actions according to the nature of the postsynaptic target. The finding that one type of neostriatal neuron, and a very similar neuron in the globus pallidus, receives multiple enkephalin-immunoreactive boutons all over its perikaryon and along its dendrites indicates a potentially important role of enkephalin in the convergence of information within the neostriatum and pallidum on to output neurons.Keywords
This publication has 52 references indexed in Scilit:
- Ontogeny of the leucine-enkephalin neuron system of the rat: Immunohistochemical analysis. I. Lower brainstemJournal of Comparative Neurology, 1982
- Changes in the activity of nigral neurones induced by morphine and other opiates in rats with an intact brain and after prenigral decerebrationNaunyn-Schmiedebergs Archiv für experimentelle Pathologie und Pharmakologie, 1981
- Ultrastructure of Golgi-impregnated and gold-toned spiny and aspiny neurons in the monkey neostriatumJournal of Neurocytology, 1980
- Regional distribution of methionine-enkephalin- and beta-endorphin-like immunoreactivity in human brain and pituitaryBrain Research, 1979
- Minireview opiates, opioid peptides and single neuronesLife Sciences, 1979
- ENDOGENOUS OPIOID PEPTIDES IN NEURONS OF THE HUMAN BRAINThe Lancet, 1978
- Experimental demonstration of intrinsic synapses in cat's caudate nucleusNeuroscience Letters, 1977
- Possible actions of opiates upon synapsesProgress in Neurobiology, 1976
- Identification of two related pentapeptides from the brain with potent opiate agonist activityNature, 1975
- Morphine Action at Central Nervous System Sites in Rat: Analgesia or Hyperalgesia Depending on Site and DoseScience, 1973