Light-enhanced and fear-potentiated startle: temporal characteristics and effects of alpha-helical corticotropin-releasing hormone.
BACKGROUND
It has been suggested that the light-enhanced startle paradigm (LES) is an animal model for anxiety, because of the unconditioned and nonspecific cue and the long-term effect. In contrast, the fear-potentiated startle (FPS) is suggested to model fear. In the present study, we assessed in detail the time course of LES and FPS and investigated whether corticotropin-releasing hormone (CRH) is differentially involved in these two models.


METHODS
In experiment 1, the amplitude of the startle response was tracked in the presence of the light and after light offset, in both models. In experiment 2, the effects of intracerebroventricular administration of the CRH-receptor antagonist alpha-helical CRH (0, 1, 5, and 25 microg) on LES and FPS were studied.


RESULTS
In LES, light onset resulted in a long-lasting potentiation of the startle response and a slow return to baseline after light offset. In FPS, the potentiation of the startle response returned to baseline almost immediately after light offset. Alpha-helical CRH reduced the potentiation in LES at the 5-microg dose but not at 25 microg. In FPS, alpha-helical CRH had no effect.


CONCLUSIONS
The results show that the time course of LES is markedly different from that of FPS, which together with the differences in eliciting stimuli suggest that they model anxiety and fear, respectively. Moreover, the results suggest that CRH is involved in LES and not in FPS.
de Jongh
Reinoud
R
Department of Psychopharmacology, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands.
Groenink
Lucianne
L
van der Gugten
Jan
J
Olivier
Berend
B
D000161:Acoustic Stimulation; D000818:Animals; D001007:Anxiety / Q000378:metabolism*; D001522:Behavior, Animal; D003214:Conditioning, Classical; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology*; D003624:Darkness; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005239:Fear; D005260:Female; D006727:Hormone Antagonists / Q000494:pharmacology*; D007276:Injections, Intraventricular / Q000379:methods; D008027:Light; D008297:Male; D010775:Photic Stimulation; D051381:Rats; D017208:Rats, Wistar; D013216:Reflex, Startle / Q000187:drug effects* / Q000502:physiology
D006727:Hormone Antagonists; C069206:alpha helical corticotropin-releasing hormone; D003346:Corticotropin-Releasing Hormone