The impact of the nonpeptide corticotropin-releasing hormone antagonist antalarmin on behavioral and endocrine responses to stress.
The nonpeptide CRH antagonist antalarmin has been shown to block both behavioral and endocrine responses to CRH. However, it's potential activity in blunting behavioral and endocrine sequelae of stressor exposure has not been assessed. Because antagonism of central CRH by alpha-helical CRH attenuates conditioned fear responses, we sought to test antalarmin in this regard. In addition, it remains unclear as to whether this is a result of receptor blockade during conditioning or during testing. Thus, we explored whether CRH mediates the induction or expression of conditioned fear (freezing in a context previously associated with 2 footshocks; 1.0 mA, 5 sec each). Furthermore, because rats previously exposed to inescapable shock (IS; 100 shocks, 1.6 mA, 5 sec each), demonstrate enhanced fear conditioning, we investigated whether this effect would be blocked by antalarmin. Antalarmin (20 mg/kg x 2 ml i.p.) impaired both the induction and expression of conditioned fear. In addition, antalarmin blocked the enhancement of fear conditioning produced by prior exposure to IS. Despite the marked behavioral effects observed in antalarmin-treated rats, antalarmin had no effect on IS-induced rises in ACTH or corticosterone. However, antalarmin did block the ACTH response produced by exposure to 2 footshocks.
Deak
T
T
Department of Psychology, University of Colorado, Boulder 80309-0345, USA. tdeak@clipr.colorado.edu
Nguyen
K T
KT
Ehrlich
A L
AL
Watkins
L R
LR
Spencer
R L
RL
Maier
S F
SF
Licinio
J
J
Wong
M L
ML
Chrousos
G P
GP
Webster
E
E
Gold
P W
PW
D000305:Adrenal Cortex Hormones / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D003216:Conditioning, Operant / Q000187:drug effects; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D004597:Electroshock; D004924:Escape Reaction / Q000187:drug effects; D005239:Fear / Q000187:drug effects; D008297:Male; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000503:physiopathology; D011743:Pyrimidines / Q000494:pharmacology*; D011758:Pyrroles / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018019:Receptors, Corticotropin-Releasing Hormone / Q000037:antagonists & inhibitors*; D013312:Stress, Physiological / Q000503:physiopathology*
D000305:Adrenal Cortex Hormones; D011743:Pyrimidines; D011758:Pyrroles; D018019:Receptors, Corticotropin-Releasing Hormone; C103016:antalarmin; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone