Effects of neonatal 6-hydroxydopamine treatment upon morphological organization of the posteromedial barrel subfield in mouse somatosensory cortex

Eric P. Loeb, Fen-Lei Chang, William T. Greenough

Research output: Contribution to journalArticle

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Abstract

While recent studies indicate that proposed regulation of visual cortex plasticity by norepinephrine (NE) probably involves 6-hydroxydopamine (6-OHDA) effects other than NE depletion, reports of diminished neuronal maturation and reduced postweaning sensitivity to environmental conditions in animals treated with anti-adrenergic compounds continue to suggest a role for NE in neocortical development. To assess its possible role in development of a highly organized neocortical structure, the effects of postnatal 6-OHDA administration upon development of the somatosensory cortical posteromedial barrel subfield (PMBSF), which subserves the large facial whiskers, were observed in mice with whiskers in the middle row of the face removed unilaterally. Treatment with 6-OHDA caused 96-98% depletion of NE in parietal cortex. There were no effects of (or lesion interactions with) 6-OHDA treatment on barrel size in measures of Nissl-stained neurons, and 6-OHDA effects on numerical measures of dendritic branching of Golgi-impregnated non-pyramidal neurons in PMBSF were negligible. There were, however, effect of 6-OHDA treatment upon the highly ordered arrangement of dendrites within barrels. In 6-OHDA-treated animals, the class I (spiny and sparsely spined) cell dendrites were less attracted to the barrel hollow. In controls, for class I cells with their somata within the barrel wall, there was a high correlation between the distance from the soma to the hollow and the amount of dendrite in the wall, reflecting the distance the dendrite traverses to the hollow. In 6-OHDA-treated animals, this correlation was absent, i.e., cells at any distance from the hollow tended to have a high percentage of dendrite in the wall. For cells in the hollow, in controls, a relatively constant majority of dendrite stayed in the hollow. In 6-OHDA-treated animals, the amount of dendrite that hollow cells extended into the wall increased as the somata became closer to the wall, suggesting a loss of systematic governance of the orientation of dendrites by the overall pattern of the barrel. Thus the effect of 6-OHDA administration was to reduce enforcement of the normal rules of barrel organization. Two other findings related to the spread of dendrites into septa and neighboring barrels. It was found that 6-OHDA treatment increased the frequency of class II cells (smooth cells) having significant amounts of their dendrites extending outside the original barrel. Similarly, the drug treatment increased the number of class I cells extending their dendrites into adjacent denervation-induced barreloids. Given evidence that afferent activity is involved in postnatal organization of the PMBSF, all 3 findings accord with the proposal that the physiological effects of NE are to suppress background activity and to potentiate specific afferent activity, which might attract or selectively retain dendrites growing in regions of highest thalamic afferent density.

Original languageEnglish (US)
Pages (from-to)113-120
Number of pages8
JournalBrain Research
Volume403
Issue number1
DOIs
StatePublished - Feb 10 1987
Externally publishedYes

Fingerprint

Somatosensory Cortex
Oxidopamine
Dendrites
Norepinephrine
Carisoprodol
Vibrissae
Neurons
Parietal Lobe
Adrenergic Antagonists
Denervation
Visual Cortex

Keywords

  • 6-Hydroxydopamine
  • Development
  • Posteromedial barrel subfield
  • Somatosensory cortex

ASJC Scopus subject areas

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

Cite this

Effects of neonatal 6-hydroxydopamine treatment upon morphological organization of the posteromedial barrel subfield in mouse somatosensory cortex. / Loeb, Eric P.; Chang, Fen-Lei; Greenough, William T.

In: Brain Research, Vol. 403, No. 1, 10.02.1987, p. 113-120.

Research output: Contribution to journalArticle

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