Affiliation: | Department of Physiology, Box 70,576, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614-70756, USA |
Abstract: | Hippocampal mineralocorticoid receptor mRNA expression was increased in male hamsters exposed to 18 days of short photoperiod relative to animals maintained under long day illumination (p<0.05). Short day hamsters were also characterized by increased weight gain, and heavier adrenal glands (p<0.05). The larger adrenals showed selective increases in the widths of the zonae reticularis and glomerulosa (p<0.001). Incidences of torpor and reduced body temperature were observed in the short day animals. No changes were found in reproductive organ weights, systolic blood pressure, open-field behavior, or stress levels of plasma corticosteroids. We conclude that the hamster brain–adrenal axis responds rapidly to changes in photoperiod, raising the possibility that this axis is a primary mediator of shortened photoperiod responses. |