title: Strain differences in the distribution of arginine-vasopressin- and neuropeptide Y-immunoreactive neurons in the suprachiasmatic nucleus of laboratory rats.
abstract: We have studied the number of arginine-vasopressin (AVP)-immunoreactive (ir) somata and the area size of AVP- and neuropeptide Y (NPY)-ir fibers in the suprachiasmatic nuclei (SCN) of three strains of laboratory rats exhibiting a strong unimodal (ACI), a bimodal (BH), and a weak multimodal pattern (LEW) of wheel running activity. In all three strains, AVP-ir somata and fibers were located predominantly in the dorsomedial SCN. Significant strain-differences were found for the area size of AVP-ir fibers as well as for the number and density of AVP-ir somata. The total number of AVP-ir somata was significantly higher in strain ACI (2238 +/- 164) than in strains BH (1552 +/- 137) and LEW (1426 +/- 110), whereas the mean area of AVP-ir fibers was significantly larger in strain LEW (50779 +/- 2202 microns2) than in strains ACI (39034 +/- 2095 microns2) and BH (28052 +/- 1728 microns2). Consequently, the density of AVP-ir somata was significantly lower in LEW rats, which have a weak multimodal activity pattern, than in BH and ACI rats, which have a bimodal and unimodal activity pattern, respectively. These data suggest that AVP neurons may be part of SCN output pathways controlling circadian activity rhythms. NPY-ir fibers have been identified mainly in the ventral part of the SCN. The mean area of NPY-ir fibers was smallest in BH rats (26100 +/- 1822 microns2), which show a rather scattered activity onset, and larger in ACI (29934 +/- 2468 microns2) and LEW rats (31889 +/- 2728 microns2), which have rather precise activity onsets. The inbred strains ACI, BH, and LEW may prove to be suitable models to further study distinct neuronal substrates of the SCN functionally correlated with characteristic parameters of circadian rhythms.
authors.affiliation: Dept. of Biology, University of Konstanz, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Wollnik
authors.forename: S
authors.initials: S
authors.lastname: Bihler
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology; D007150:Immunohistochemistry; D008297:Male; D009412:Nerve Fibers / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D009478:Neuropeptide Y / Q000502:physiology*; D051381:Rats; D011917:Rats, Inbred Lew; D011919:Rats, Inbred Strains; D013045:Species Specificity; D013493:Suprachiasmatic Nucleus / Q000166:cytology* / Q000378:metabolism
chemical_list: D009478:Neuropeptide Y; D001127:Arginine Vasopressin