title: Chronic 2G exposure affects c-Fos reactivity to a light pulse within the rat suprachiasmatic nucleus.
abstract: This study examined the effect of the hyperdynamic environment on the function of the retinohypothalamic tract. Rats were exposed to either 2 days or 21 days of 2G via centrifugation. During the last hour of 2G exposure, one series of rats was exposed to a 1 hour phase-shifting light pulse while the second series of rats did not receive a light pulse. In addition a groups of 1G controls was exposed to the same 1 hour lighting paradigm. All animals were processed for c-Fos within the SCN. The 1G controls showed the normal response to light in which significantly greater numbers of c-Fos positive neurons were found in the SCN of the light pulsed rats relative to that of the nonlight pulsed rats. However, rats exposed to 2 days of 2G did not show the same response to light. Light pulsed rats and nonlight pulsed rats exhibited few c-Fos positive neurons within the SCN. A recovery in the effect of light to induce c-Fos reactivity within SCN neurons occurred in the rats exposed to 21 days of 2G. These results suggest that exposure to 2G can temporarily suppress the responsiveness of the SCN to the phase-shifting effects of light mediated by the retinohypothalamic tract.
authors.affiliation: Section of Neurobiology, Physiology, and Behavior, University of California Davis, 95616-8519, USA. dmmurakami@ucdavis.edu
authors.forename: D M
authors.initials: DM
authors.lastname: Murakami
authors.forename: I H
authors.initials: IH
authors.lastname: Tang
authors.forename: C A
authors.initials: CA
authors.lastname: Fuller
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D002498:Centrifugation; D002940:Circadian Rhythm / Q000502:physiology* / Q000528:radiation effects; D015870:Gene Expression; D016762:Genes, fos; D006112:Gravitation; D018471:Hypergravity; D007031:Hypothalamus / Q000502:physiology / Q000528:radiation effects; D007150:Immunohistochemistry; D008027:Light; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000502:physiology / Q000528:radiation effects; D013493:Suprachiasmatic Nucleus / Q000502:physiology* / Q000528:radiation effects