TY - JOUR
T1 - Chicken suprachiasmatic nuclei
T2 - II. Autoradiographic and immunohistochemical analysis
AU - Cantwell, Elizabeth L.
AU - Cassone, Vincent M.
PY - 2006/11/20
Y1 - 2006/11/20
N2 - The vertebrate circadian system is composed of multiple inputs, oscillators, pacemakers, and outputs. In birds, the pineal gland and retinae have been denned as pacemakers within this system. Evidence for a third, hypothalamic pacemaker is abundant. It has been presumed that this pacemaker is homologous to the mammalian suprachiasmatic nucleus (SCN). Two candidate structures have been referred to as the avian SCN-the medial SCN (mSCN) and the visual SCN (vSCN). Previously, we suggested that both structures are involved in a "suprachiasmatic complex." To further explore evidence for an avian SCN, the present study employed several classical techniques to assess intrinsic characteristics of the mSCN and vSCN in the chicken. First, analysis of mSCN and vSCN cytoarchitecture indicated that the mSCN is similar in location and cell population to the mammalian SCN, while the vSCN is more similar in terms of its shape. Second, intravitreal injections of tritiated proline were used to identify hypothalamic retinal terminals. The findings support previous studies identifying the vSCN as the primary retinorecipient hypothalamic structure in birds. Third, analysis of mSCN and vSCN chemoarchitecture suggests that both the mSCN and vSCN display similarity to the mammalian SCN, which displays significant interspecies variation. Finally, a unique astrocytic bridge between the mSCN and vSCN is demonstrated, suggesting that astrocytes play a role within the suprachiasmatic nuclei of birds, similar to the situation in mammals. Our previously presented working model of the avian suprachiasmatic complex is updated to include these data.
AB - The vertebrate circadian system is composed of multiple inputs, oscillators, pacemakers, and outputs. In birds, the pineal gland and retinae have been denned as pacemakers within this system. Evidence for a third, hypothalamic pacemaker is abundant. It has been presumed that this pacemaker is homologous to the mammalian suprachiasmatic nucleus (SCN). Two candidate structures have been referred to as the avian SCN-the medial SCN (mSCN) and the visual SCN (vSCN). Previously, we suggested that both structures are involved in a "suprachiasmatic complex." To further explore evidence for an avian SCN, the present study employed several classical techniques to assess intrinsic characteristics of the mSCN and vSCN in the chicken. First, analysis of mSCN and vSCN cytoarchitecture indicated that the mSCN is similar in location and cell population to the mammalian SCN, while the vSCN is more similar in terms of its shape. Second, intravitreal injections of tritiated proline were used to identify hypothalamic retinal terminals. The findings support previous studies identifying the vSCN as the primary retinorecipient hypothalamic structure in birds. Third, analysis of mSCN and vSCN chemoarchitecture suggests that both the mSCN and vSCN display similarity to the mammalian SCN, which displays significant interspecies variation. Finally, a unique astrocytic bridge between the mSCN and vSCN is demonstrated, suggesting that astrocytes play a role within the suprachiasmatic nuclei of birds, similar to the situation in mammals. Our previously presented working model of the avian suprachiasmatic complex is updated to include these data.
KW - Antigen distribution
KW - Astrocytes
KW - Avian
KW - Circadian
KW - Retinohypothalamic
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U2 - 10.1002/cne.21124
DO - 10.1002/cne.21124
M3 - Article
C2 - 16998905
AN - SCOPUS:33749988693
SN - 0021-9967
VL - 499
SP - 442
EP - 457
JO - Journal of Comparative Neurology
JF - Journal of Comparative Neurology
IS - 3
ER -