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The nigral projection to predorsal bundle cells in the superior colliculus of the rat.

Publication ,  Journal Article
Bickford, ME; Hall, WC
Published in: J Comp Neurol
May 1, 1992

Predorsal bundle cells give rise to the major efferent pathway from the superior colliculus to the premotor centers of the brainstem and spinal cord responsible for initiating orienting movements. The activity of predorsal bundle cells is profoundly influenced by an inhibitory pathway from substantia nigra pars reticulata that uses gamma aminobutyric acid (GABA) as a neurotransmitter. The present study examines the morphological basis for this influence of substantia nigra on predorsal bundle cells in the rat. In the first experiments, the laminar distributions of the nigrotectal tract terminals and the predorsal bundle cells were compared. The predorsal bundle cells were labeled by the retrograde axonal transport of horseradish peroxidase from either the decussation of the predorsal bundle or the cervical spinal cord, while the terminations of the pathway from substantia nigra pars reticulata were labeled by anterograde axonal transport from the substantia nigra. Either horseradish peroxidase, wheat germ agglutinin conjugated to horseradish peroxidase, or Phaseolus vulgaris leucoagglutinin were used as anterograde tracers. The results showed that the distributions of both the predorsal bundle cells and the nigrotectal terminals are restricted almost entirely to the intermediate grey layer and that they overlap extensively. Predorsal bundle cells varied in size. Within the areas of maximum overlap, the majority, regardless of size, was closely apposed by nigrotectal terminals. In a second series of experiments, the synaptic contacts between nigrotectal terminals and the tectospinal component of the predorsal bundle were examined in tissue in which both the terminals and the tectospinal cells were labeled for electron microscopy. In the final experiments, the distribution and fine structure of the nigrotectal terminals were compared to those of terminals that had been labeled immunocytochemically with an antibody to glutamic acid decarboxylase, the synthesizing enzyme for GABA. The results showed that nigrotectal terminals contain large numbers of mitochondria and pleomorphic vesicles, and form synaptic contacts with the somas and proximal dendrites of tectospinal cells. These synapses have modest postsynaptic densities. In both their distribution and fine structure, these terminations resemble the glutamic acid decarboxylase immunoreactive terminals that contact tectospinal cells. Taken together, these results support the view that the nigrotectal tract is an important source of GABAergic input to most, if not all, predorsal bundle cells.

Duke Scholars

Published In

J Comp Neurol

DOI

ISSN

0021-9967

Publication Date

May 1, 1992

Volume

319

Issue

1

Start / End Page

11 / 33

Location

United States

Related Subject Headings

  • gamma-Aminobutyric Acid
  • Synapses
  • Superior Colliculi
  • Substantia Nigra
  • Spinal Cord
  • Rats
  • Phytohemagglutinins
  • Neurons
  • Neurology & Neurosurgery
  • Nerve Endings
 

Citation

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Bickford, M. E., & Hall, W. C. (1992). The nigral projection to predorsal bundle cells in the superior colliculus of the rat. J Comp Neurol, 319(1), 11–33. https://doi.org/10.1002/cne.903190105
Bickford, M. E., and W. C. Hall. “The nigral projection to predorsal bundle cells in the superior colliculus of the rat.J Comp Neurol 319, no. 1 (May 1, 1992): 11–33. https://doi.org/10.1002/cne.903190105.
Bickford ME, Hall WC. The nigral projection to predorsal bundle cells in the superior colliculus of the rat. J Comp Neurol. 1992 May 1;319(1):11–33.
Bickford, M. E., and W. C. Hall. “The nigral projection to predorsal bundle cells in the superior colliculus of the rat.J Comp Neurol, vol. 319, no. 1, May 1992, pp. 11–33. Pubmed, doi:10.1002/cne.903190105.
Bickford ME, Hall WC. The nigral projection to predorsal bundle cells in the superior colliculus of the rat. J Comp Neurol. 1992 May 1;319(1):11–33.
Journal cover image

Published In

J Comp Neurol

DOI

ISSN

0021-9967

Publication Date

May 1, 1992

Volume

319

Issue

1

Start / End Page

11 / 33

Location

United States

Related Subject Headings

  • gamma-Aminobutyric Acid
  • Synapses
  • Superior Colliculi
  • Substantia Nigra
  • Spinal Cord
  • Rats
  • Phytohemagglutinins
  • Neurons
  • Neurology & Neurosurgery
  • Nerve Endings