Circadian activity rhythms in selectively bred ethanol-preferring and nonpreferring rats

Rosenwasser, Alan M.; Fecteau, Matthew E.; Logan, Ryan W.; Reed, Jeffrey D.; Cotter, Shawnia J.N.; Seggio, Joseph A.

doi:10.1016/j.alcohol.2005.07.001

Next »Alcohol
Volume 36, Issue 2 , Pages 69-81, June 2005

Circadian activity rhythms in selectively bred ethanol-preferring and nonpreferring rats

Alan M. Rosenwasser
- Department of Psychology, University of Maine, Orono, ME 04469, USA
- Department of Biological Sciences, University of Maine, Orono, ME 04469, USA
- Corresponding author. Department of Psychology, 5742 Little Hall, University of Maine, Orono, ME 04469-5742, USA. Tel.: +1-207-581-2035; fax: +1-207-581-6128.
Matthew E. Fecteau
- Department of Psychology, University of Maine, Orono, ME 04469, USA
Ryan W. Logan
- Department of Psychology, University of Maine, Orono, ME 04469, USA
Jeffrey D. Reed
- Department of Psychology, University of Maine, Orono, ME 04469, USA
Shawnia J.N. Cotter
- Department of Psychology, University of Maine, Orono, ME 04469, USA
Joseph A. Seggio
- Department of Biological Sciences, University of Maine, Orono, ME 04469, USA

Received 10 February 2005; received in revised form 9 May 2005; accepted 13 July 2005.

Abstract

Chronic alcohol intake is associated with dramatic disruptions in sleep and other circadian biological rhythms in both humans and experimental animals. In human alcoholics, these disruptions persist during extended abstinence and appear to promote relapse to drinking. Whereas chronic ethanol intake alters fundamental properties of the circadian pacemaker in unselected rats, nothing is known concerning circadian pacemaker function in selectively bred ethanol-preferring and nonpreferring rats, which are the most widely accepted animal models of genetic predisposition to alcoholism. The present experiments were designed to characterize free-running circadian activity (wheel-running) rhythms under both constant darkness and constant light in selectively bred ethanol-preferring (P, HAD2) and nonpreferring (NP, LAD2) rats. Differences in circadian organization between ethanol-preferring and nonpreferring animals were seen for both pairs of selected lines (P vs. NP; HAD2 vs. LAD2), but these differences were not identical in the two line pairs. For example, although P rats showed shorter free-running periods than NP rats only in constant light, HAD2 rats showed shorter free-running periods than LAD2 rats only in constant darkness. In addition, ethanol-preferring HAD2 rats showed a high rate of rhythm “splitting” that was not seen in any of the other three lines. Taken together, these results suggest that the circadian pacemakers of P and NP rats differ mainly in light sensitivity, whereas those of HAD2 and LAD2 rats differ in their intrinsic period.

Keywords: Ethanol, Preference, Rat, Circadian activity rhythm, Sleep