Pathway From the Zona Incerta to the Superior Colliculus in the Rat

J Comp Neurol. 1992 Jul 22;321(4):555-75. doi: 10.1002/cne.903210405.

Abstract

In order to test the proposal that the zona incerta contributes to the generation of orienting movements, we examined the synaptic relationships between the incertotectal pathway and the cells of origin of the predorsal bundle. The predorsal bundle cells give rise to the major premotor pathway from the superior colliculus to the brainstem gaze centers. First, cytochrome oxidase histochemistry, gamma-aminobutyric acid (GABA), and glutamic acid decarboxylase (GAD) immunocytochemistry, and the axonal transport of markers were used to define the borders of a ventral subdivision of the zona incerta. This subdivision projects topographically to the same sublamina of the intermediate grey layer of the superior colliculus that contains the vast majority of the predorsal bundle cells. Experiments in which incertotectal cells were labeled by both retrograde transport and immunocytochemistry showed that this pathway is GABAergic. Retrograde and anterograde experiments also showed that this pathway is reciprocated by a pathway from the intermediate grey layer of the superior colliculus to the same ventral subdivision of the zona incerta. Finally, experiments combining axonal transport and electron microscopic methods showed that the incertotectal pathway is the source of a monosynaptic GABAergic input to the cells of origin of the predorsal bundle. The ventral subdivision of the zona incerta is contrasted with a second source of GABAergic input to the predorsal bundle cells, the substantia nigra pars reticulata.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Afferent Pathways / anatomy & histology
  • Afferent Pathways / cytology
  • Afferent Pathways / physiology
  • Animals
  • Axonal Transport
  • Efferent Pathways / anatomy & histology
  • Efferent Pathways / cytology
  • Efferent Pathways / physiology
  • Electron Transport Complex IV / analysis
  • Glutamate Decarboxylase / analysis
  • Histocytochemistry
  • Horseradish Peroxidase
  • Immunohistochemistry
  • Microscopy, Electron
  • Motor Activity
  • Nerve Fibers / physiology
  • Nerve Fibers / ultrastructure
  • Orientation
  • Periaqueductal Gray / anatomy & histology
  • Periaqueductal Gray / cytology
  • Periaqueductal Gray / physiology*
  • Rats
  • Superior Colliculi / anatomy & histology
  • Superior Colliculi / cytology
  • Superior Colliculi / physiology*
  • Synapses / physiology*
  • Synapses / ultrastructure
  • Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate
  • Wheat Germ Agglutinins
  • gamma-Aminobutyric Acid / analysis

Substances

  • Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate
  • Wheat Germ Agglutinins
  • gamma-Aminobutyric Acid
  • Horseradish Peroxidase
  • Electron Transport Complex IV
  • Glutamate Decarboxylase