Circadian performance of suprachiasmatic nuclei (SCN)-lesioned antelope ground squirrels in a desert enclosure

Author(s): Krulas, J. R., Mele, G., Holley, D. C.

Journal/Book: Physiol Behav. 1997; 62: The Boulevard, Langford Lane, Kidlington, Oxford, England OX5 1GB. Pergamon-Elsevier Science Ltd. 1099-1108.

Abstract: Circadian activity parameters of 53 white-tailed antelope ground squirrels, Ammospermophilus leucurus, were measured to determine the role of the suprachiasmatic nuclei (SCN) pacemaker in their health and survival. Wheel-running activity was monitored in the laboratory with 44 individuals to document the presence of free-running circadian rhythms and ability to entrain to light-dark cycles. Twenty-two individuals were returned to the desert site of origin, including 12 intact control animals and 10 animals whose circadian timing had been disrupted by SCN-lesioning. Time of activity was recorded continuously for 15 days in a large outdoor enclosure by a motion detector, a microchip transponder detector, and video surveillance. An unplanned nighttime attack by a feral cat resulted in the death of 60% of the SCN-lesioned animals and 29% of the control animals in the enclosure. Surface activity of SCN-lesioned animals at the food cache occurred both in daytime and at night, ranging from 16.0% nighttime activity for one partially lesioned individual to 52.1% for one completely lesioned animal. Controls were strongly day active, with nighttime surface trips constituting only 0-1.3% of all excursions to the cache. Nine wild free-ranging individuals, including one with a radiotransmitter collar, were exclusively day-active. One of the functions of the SCN in mammals may be to reduce activity of animals during times that are unfavorable for activity.

Note: Article DeCoursey PJ, Univ S Carolina, Dept Biol Sci, Columbia,SC 29208 USA

Keyword(s): circadian activity; SCN pacemaker; SCN lesion; antelope ground squirrel; ammospermophilus leucurus; predation; RHYTHMS; DROSOPHILA; LEUCURUS

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