title: Circannual fluctuations of the serum cortisol in the European ground squirrel, Citellus citellus L.
abstract: 1. Serum cortisol levels were measured throughout an annual cycle in male European ground squirrels, Citellus citellus L. 2. A circannual rhythm of these levels in euthermic animals was found: the highest being in late October, November and December, the lowest in May, early October and March. 3. The levels varied in the hibernating period as well: strongly reduced during the first part (October-December) and significantly elevated in the second one (January-March). 4. A significant elevation of the cortisol levels was marked 18-20 hr after full arousal from hibernation in October.
mesh_terms: D000818:Animals; D001143:Arousal / Q000502:physiology; D006605:Hibernation; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D011863:Radioimmunoassay; D012589:Sciuridae / Q000097:blood*; D012621:Seasons
chemical_list: D006854:Hydrocortisone