The origin of the afferent supply to the mediodorsal thalamic nucleus: Enhancement of HRP transport by selective lesions

Allan Siegel, Takeo Fukushima, Richard Meibach, Leonard Burke, Henry Edinger

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79 Scopus citations


This experiment attempted to identify the cell bodies of origin of axons in the forebrain which supply the mediodorsal thalamic nucleus (MD). Injections of horseradish peroxidase (HRP) were placed into MD in 60 rats. Survival times varied from 1-4 days. Following injections placed into different portions of MD, HRP positively labeled cells were observed in a variety of forebrain structures which lie rostral to the injection sites. Discrete injections of HRP placed into the midline of MD labeled cells situated exclusively in the extreme ventromedial aspect of central levels of the reticular nucleus. HRP injections which included anterior levels of MD labeled cells situated principally in layers V-VI of the sulcal prefrontal cortex, while injections which involved more posterior and lateral portions of MD labeled cells in the deepest layers of the dorsomedial prefrontal cortex. Injections of this region of MD also labeled cells in adjacent portions of the deepest layers of anterior cingulate gyrus, polymorphic cell layer of prepyriform cortex and olfactory tubercle and sites immediately lateral to the vertical limb of the diagonal band and dorsal to its horizontal limb. Positively labeled cells were observed in the cortical, medial, basolateral and basomedial amygdaloid nuclei and adjacent pyriform cortex only when ablations of prefrontal cortex preceded HRP injections of MD. This findings indicates that lesions of the prefrontal cortex dramatically enhance the HRP labeling process in the amygdala and suggests the possibility that the technique involving the placement of selective lesions may be used to advangate in other anatomical systems which receive multiple inputs from widely distributed sources.

Original languageAmerican English
Pages (from-to)11-23
Number of pages13
JournalBrain Research
Issue number1
StatePublished - Oct 21 1977

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology


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