This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by LeSauter, J. Articles by Silver, R. Search for Related Content PubMed PubMed Citation Articles by LeSauter, J. Articles by Silver, R. Social Bookmarking                         What's this?

Attachment Site of Grafted SCN Influences Precision of Restored Circadian Rhythm

Department of Psychology, Barnard College of Columbia University, New York, NY 10027

P. Romero

Department of Psychology, Barnard College of Columbia University, New York, NY 10027

M. Cascio

Department of Psychology, Barnard College of Columbia University, New York, NY 10027

R. Silver

Department of Psychology, Barnard College of Columbia University, New York, NY 10027

Fetal hypothalamic grafts containing the suprachiasmatic nucleus (SCN) restore circadian locomotor rhythmicity when implanted into the third ventricle of SCN-lesioned hamsters. However, the quality of restored rhythms is variable, and the locomotor rhythms of grafted animals are generally less robust than those of intact animals. The present study explored whether anatomical features of the graft predict the quality of the recovered rhythm and whether such information might provide insight as to the target of the signal from the SCN that controls locomotor rhythmicity. The following graft parameters were assessed: distance between the attachment site of the graft and potential targets for the output signal from the SCN, number and overall size of SCN clusters, the size of the cluster closest to the SCN lesion site, and extent of vasoactive intestinal polypeptide (VIP) and vasopressin-associated neurophysin (NP) positive fiber outgrowth from the graft. The restored circadian activity rhythm was assessed by quantifying the precision of activity onset and the amount, period, and robustness of rhythmicity. The results indicate a significant positive correlation between the precision of activity onset and the proximity of the closest SCN cluster to the site of the lesioned host SCN. A more detailed analysis of the spatial location of the graft indicates that proximity of the graft in the dorsal and caudal directions, but not the rostral direction, is positively correlated with the precision of the recovered rhythm. This suggests two possibilities: the coupling signal may act on a site very near the SCN and travel preferentially in a rostro-caudal direction. Alternatively, the coupling signal may act on a site rostral to the SCN. That the site is not far rostral to the SCN was suggested by the lack of a correlation between the precision of the restored rhythm and the rostrally lying anterior medial preoptic nucleus. Finally, evaluation of NP- and VIP-ergic fibers in nuclei known to receive input from the SCN indicates that the extent of such innervation by graft efferents does not predict either the occurrence of recovery or the precision of the recovered rhythm. Overall, these results suggest that the target(s) of SCN pacemakers regulating locomotor rhythmicity lie in the hypothalamus, close to or rostral to the SCN.

Key Words: circadian rhythms • coupling signals • suprachiasmatic nucleus • neural trans plantation • hamster

Journal of Biological Rhythms, Vol. 12, No. 4, 327-338 (1997)
DOI: 10.1177/074873049701200405


CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				U. Schibler, J. Ripperger, and S. A. Brown Peripheral Circadian Oscillators in Mammals: Time and Food J Biol Rhythms, June 1, 2003; 18(3): 250 - 260. [Abstract] [PDF]

				T. Reischig and M. Stengl Ectopic transplantation of the accessory medulla restores circadian locomotor rhythms in arrhythmic cockroaches (Leucophaea maderae) J. Exp. Biol., June 1, 2003; 206(11): 1877 - 1886. [Abstract] [Full Text] [PDF]