The development of non-retinal afferent projections to the frog optic tectum and the substance P immunoreactivity of tectal connections

Elizabeth A. Debski, Martha Constantine-Paton

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14 Scopus citations


Accessibility in early development and the presence of a retinotopic map have made the amphibian optic tectum a popular system for exploration of the role of synaptic function in central map refinement. Although a great deal is known about the development of retinal innervation of the tectum, little information exists about the development of non-retinal tectal inputs. Since these other afferent systems may contribute to the synaptic drive of developing tectal cells and thereby be involved in the activity-dependent refinement of the retinotectal map, we sought to determine whether these inputs are present at the early tadpole stages when the first retinal axons refine their synaptic order within the tectal neuropil. Rhodamine-labelled latex beads, retrogradely transported from injection sites in the optic tecta, were used to identify tectal afferent projections. Projection patterns in very young tadpoles were identical to those found in juvenile frogs and heavily labelled regions included areas of the posteroventral tegmental field, the posterior tuberculum, the ventromedial thalamic nucleus, the ventral part of the ventrolateral thalamic nucleus, the suprachiasmatic nucleus and discrete regions within the central and anterior thalamic nuclei. Ipsilateral nucleus isthmi cells were also labelled, indicating the existence of an isthmo-tectal projection in even the youngest animals examined. Additionally, substance P-like immunoreactive tecto-isthmal fibers were traced from the optic tectum to the nucleus isthmi. The presence of these connections suggests that feedback from the nucleus isthmi and/or input from the other brain areas projecting to the tectum may play a role in modulating the cellular mechanisms that underlie the formation of the visual map.

Original languageEnglish
Pages (from-to)21-39
Number of pages19
JournalDevelopmental Brain Research
Issue number1
StatePublished - Mar 19 1993

Bibliographical note

Funding Information:
Acknowledgements. We would like to thank Doug Kankel for use of his three-dimensional reconstruction facilities and Karen Stark for instruction in the use of the PC3D program. In addition we would like to thank Jonathan Rothberg, Susan Diaz, Steve Montal and Vickie Borah for technical assistance during various phases of this project. Finally, we thank Trish Steen for the care and shipping of histological material. This work was supported by National Institutes of Health Grants EY05829 and EY06039.


  • Nucleus isthmi
  • Rana pipiens
  • Tectal afferent
  • Topographic map
  • Visual development

ASJC Scopus subject areas

  • Developmental Neuroscience
  • Developmental Biology


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