A stress-induced anxious state in male rats: corticotropin-releasing hormone induces persistent changes in associative learning and startle reactivity.
BACKGROUND
Exposure to intense inescapable stressors induces a persistent anxious state in rats. The anxious state is evident as increased sensory reactivity and enhanced associative learning.


METHODS
We examine whether similar neurobehavioral changes are observed after intracerebroventricular (ICV) administration of corticotropin releasing hormone (CRH). Two behaviors were observed: acoustic startle responses (ASRs) and acquisition of the classically conditioned eyeblink response. Male Sprague-Dawley rats were administered ICV CRH either in a single dose (1.0 microg/rat) or in three doses each separated by 30 min.


RESULTS
Exaggerated ASRs were evident 2 hours after either CRH treatment; however, only the rats given three injections exhibited a persistently exaggerated ASR apparent 24 hours after CRH treatment. Rats administered three injections of CRH also exhibited faster acquisition of the eyeblink conditioned response beginning 24 hours after treatment. Yet, we did not find evidence for a persistent activation of the HPA-axis response; three CRH injections did not lead to elevated basal plasma corticosterone levels the following morning.


CONCLUSIONS
Repeated treatment with CRH over a 1.5-hour period models some of the behavioral changes observed after exposure to intense inescapable stressors.
Servatius
Richard J
RJ
Department of Veterans Affairs, New Jersey Health Care System, Neurobehavioral Research Laboratory, East Orange, New Jersey Medical School, Newark, New Jersey, USA. rjservatius@njneuromed.org
Beck
Kevin D
KD
Moldow
Roberta L
RL
Salameh
Gabriel
G
Tumminello
Tara P
TP
Short
Kenneth R
KR
D000161:Acoustic Stimulation; D000818:Animals; D001007:Anxiety / Q000523:psychology*; D001245:Association Learning / Q000187:drug effects* / Q000502:physiology*; D001767:Blinking / Q000187:drug effects / Q000502:physiology; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology; D003345:Corticosterone / Q000097:blood; D003346:Corticotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007276:Injections, Intraventricular; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013216:Reflex, Startle / Q000187:drug effects* / Q000502:physiology*; D013315:Stress, Psychological / Q000523:psychology*
D003346:Corticotropin-Releasing Hormone; D003345:Corticosterone