Post on 30-Jan-2016
description
Light →SCN: -direct via the retinohypothalamic (RHT) pathway -indirect via geniculohypothalamic (GHT) pathway
SCN: some morphological features
• Parvocellular, paired structure, ~16-20,000 neurons in rodent, miniscule in man
• Phenotypes: multiple potential transmitters– most express GABA (1993 proposal: SCN output is inhibitory)
– Peptides: • vasoactive intestinal peptide (VIP) in cells in ventrolateral part;
receives retinal input; forms part of the output projection • vasopressin (VP) in cells in dorsomedial part; forms part of the
output projection• somatostatin (SS) in cells whose axons remain intrinsic to SCN
Lets consider the neural connections of SCN
A schematic outline from Ibata et al
Frontiers in Neuroendocrinology
20: 241-268, 1999
Notes:1 -Based on
immunocytochemical grounds, SCN can be
subdivided into dorsomedial (shell) and
ventrolateral (core) segments
2 -Retinal input is to the VIPergic neurons in the
ventrolateral SCN3 -output pathways arise from both VIPergic and
vasopressinergic neurons in SCN
4 -most projections are local, to hypothalamic
sites (exceptions: LGB,
TPV)
SCN: techniques to define input-output pathways
• Using retrograde and/or anterograde transport of suitable markers e.g. wheat germ agglutin (WGA)
SCN: techniques to define input-output pathways
• Using retrograde and anterograde transport of suitable markers e.g. WGA
• Using viral retrograde transneuronal traceing (pseudorabies)
Retrograde transneuronal labeling with pseudorabies virus (PRV) injected in the adrenal gland
SCN: techniques to define input-output pathways
• Using retrograde and/or anterograde transport of suitable markers e.g. WGA
• Using viral retrograde transneuronal tracing (PRV)
• Using double label immunocytochemistry to define phenotype (peptides)
PRV (green)
A-C: in PVN oxytocin (red)
D-E: in SCNvasopressin
(red)
F: in SCNVIP (red)
Anatomical and functional demonstration of a multisynaptic suprachiasmatic nucleus adrenal (cortex) pathway
European Journal of Neuroscience 11: 15351544, 1999RM Buijs, J Wortel, JJ van Heerikhuize, MGP Feenstra, GJ Ter Horst,HJ Romijn, A Kalsbeek
Suprachiasmatic nucleus (SCN)
• Brain Res. 1972 Jul 13;42(1):201-6.–
Loss of a circadian adrenal corticosterone rhythm following suprachiasmatic lesions in the rat.
Moore RY, Eichler VB.