TY - JOUR
T1 - Short-term fasting affects locomotor activity, corticosterone, and corticosterone binding globulin in a migratory songbird
AU - Lynn, Sharon E.
AU - Breuner, Creagh W.
AU - Wingfield, John C.
N1 - Funding Information:
We thank Morgan Benowitz-Fredericks, Shallin Busch, Lisa Hayward, Meta Landys, Ignacio Moore, Noah Owen-Ashley, Nicole Perfito, Matt Richardson, Marilyn Ramenofsky, Samrrah Raouf, and Todd Sperry for assistance with collecting blood samples. Work described in this paper was supported by NSF Grant OPP-9530826 (to J.C.W.) and NSF Grant DBI-9804183 (to C.W.B.). S.E.L. was supported by an NSF predoctoral fellowship.
PY - 2003/1
Y1 - 2003/1
N2 - Unpredictable events such as severe storms lead to an increase in circulating corticosterone (CORT) in breeding birds. This increase is often accompanied by elevations in foraging and irruptive behavior. We were interested in determining if acute food restriction (such as might occur during inclement weather) is a sufficient cue to elicit an increase in locomotor activity, increase CORT secretion, and/or decrease circulating levels of corticosterone binding globulin (CBG) in white-crowned sparrows (Zonotrichia leucophrys gambelii). Male Z.l. gambelii were housed individually in environmental chambers on long days (LD 20:4) to simulate breeding season daylength. Birds were fed ad libitum, and on select days, food was removed 2 h after lights on (fasted treatment), or was removed and replaced (control). We analyzed CORT and CBG levels after 1, 2, 6, 22 (lights on), and 23 h under fasted and control conditions. We also measured activity during the 23-h experiment. Activity levels were increased under fasted conditions during the daytime relative to control conditions, but activity levels did not differ between treatments during the night. Fasting as little as 1, 2, and 6 h significantly increased total CORT levels above baseline (control), although after 22 h, total CORT levels under fasted conditions matched those under control conditions. Plasma CBG decreased after the 22-h fast, and remained low after the 23-h fast. This change was sufficient to significantly elevate free CORT levels in fasted birds relative to ad libitum food conditions, despite the lack of difference in total CORT levels.
AB - Unpredictable events such as severe storms lead to an increase in circulating corticosterone (CORT) in breeding birds. This increase is often accompanied by elevations in foraging and irruptive behavior. We were interested in determining if acute food restriction (such as might occur during inclement weather) is a sufficient cue to elicit an increase in locomotor activity, increase CORT secretion, and/or decrease circulating levels of corticosterone binding globulin (CBG) in white-crowned sparrows (Zonotrichia leucophrys gambelii). Male Z.l. gambelii were housed individually in environmental chambers on long days (LD 20:4) to simulate breeding season daylength. Birds were fed ad libitum, and on select days, food was removed 2 h after lights on (fasted treatment), or was removed and replaced (control). We analyzed CORT and CBG levels after 1, 2, 6, 22 (lights on), and 23 h under fasted and control conditions. We also measured activity during the 23-h experiment. Activity levels were increased under fasted conditions during the daytime relative to control conditions, but activity levels did not differ between treatments during the night. Fasting as little as 1, 2, and 6 h significantly increased total CORT levels above baseline (control), although after 22 h, total CORT levels under fasted conditions matched those under control conditions. Plasma CBG decreased after the 22-h fast, and remained low after the 23-h fast. This change was sufficient to significantly elevate free CORT levels in fasted birds relative to ad libitum food conditions, despite the lack of difference in total CORT levels.
KW - Activity
KW - Corticosterone
KW - Corticosterone binding globulin
KW - Food restriction
KW - Free corticosterone
KW - Sparrows
UR - http://www.scopus.com/inward/record.url?scp=0345269844&partnerID=8YFLogxK
U2 - 10.1016/S0018-506X(02)00023-5
DO - 10.1016/S0018-506X(02)00023-5
M3 - Article
C2 - 12614645
AN - SCOPUS:0345269844
SN - 0018-506X
VL - 43
SP - 150
EP - 157
JO - Hormones and Behavior
JF - Hormones and Behavior
IS - 1
ER -