Distribution and synaptology of vasoactive intestinal polypeptide (VIP) immunoreactive structures in the rat periaqueductal grey

C. Paspalas, B. Gerics, K. Halasy, G. Papadopoulos, F. Hajós

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2 Citations (Scopus)


Light microscopic analysis of the rat midbrain periaqueductal grey (PAG) showed vasoactive intestinal polypeptide immunore-active (VIP-ir) neurons localized at the lateral and ventral walls of the aqueduct. Some varicose VIP-ir elements were detected closely associated with the ependyma. While several VIP-ir elements were encountered immediately under the ependyma, in a few cases, VIP-ir cell bodies were seen on the luminal surface of the ependymal cells lining the aqueduct. Electron microscopy revealed that most of these cells possessed the characteristics of a local circuit neuron. All VIP-ir cells had indented nuclei. Two types were distinguished: One with rounded cell body receiving numerous axo-somatic synapses established by VIP-negative axons. The other cell type was fusiform and its surface was almost fully isolated from axonal contacts by a glial sheath. The VIP-ir processes were interconnected with other periaqueductal cells by a variety of synaptic contacts. VIP-ir axon terminals formed asymmetric synapses with immunonegative dendritic shafts often in glomerulus-like assemblies. The postsynaptic immunonegative dendrites were of the aspinous, beaded type. We suggest that VIP-ir cells and processes in the midbrain PAG establish connections between the longitudinal functional columns of this region. On the basis of their morphology, VIP-ir cells in the PAG appear to be excitatory, terminating on inhibitory interneurons. Thus, a VIP-stimulated inhibition may be instrumental in the coordination of responses evoked by the stimulation of PAG columns.

Original languageEnglish
Pages (from-to)541-549
Number of pages9
JournalJournal of Neurocytology
Issue number8
Publication statusPublished - Jan 1 2000

ASJC Scopus subject areas

  • Anatomy
  • Neuroscience(all)
  • Histology
  • Cell Biology

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