Interactions of stress and CRF in ethanol-withdrawal induced anxiety in adolescent and adult rats.
BACKGROUND
Repeated stress or administration of corticotropin-releasing factor (CRF) prior to ethanol exposure sensitizes anxiety-like behavior in adult rats. Current experiments determined whether adolescent rats were more sensitive to these challenges in sensitizing ethanol withdrawal-induced anxiety and altering CRF levels in brain during withdrawal.


METHODS
Male adult and adolescent Sprague-Dawley rats were restraint stressed (1 hour) twice 1 week apart prior to a single 5-day cycle of ethanol diet (ED; stress/withdrawal paradigm). Other rats received control diet (CD) and three 1-hour restraint stress sessions. Rats were then tested 5, 24, or 48 hours after the final withdrawal for anxiety-like behavior in the social interaction (SI) test. In other experiments, adolescent rats were given two microinjections of CRF icv 1 week apart followed by 5 days of either CD or ED and tested in social interaction 5 hours into withdrawal. Finally, CRF immunoreactivity was measured in the central nucleus of the amygdala (CeA) and paraventricular nucleus (PVN) after rats experienced control diet, repeated ethanol withdrawals, or stress/withdrawal.


RESULTS
Rats of both ages had reduced SI following the stress/withdrawal paradigm, and this effect recovered within 24 hours. Higher CRF doses were required to reduce SI in adolescents than previously reported in adults. CRF immunohistochemical levels were higher in the PVN and CeA of CD-exposed adolescents. In adolescent rats, repeated ethanol withdrawals decreased CRF in the CeA but was not associated with decreased CRF cell number. There was no change in CRF from adult treatments.


CONCLUSIONS
In the production of anxiety-like behavior, adolescent rats have equal sensitivity with stress and lower sensitivity with CRF compared to adults. Further, adolescents had higher basal levels of CRF within the PVN and CeA and reduced CRF levels following repeated ethanol withdrawals. This reduced CRF within the CeA could indicate increased release of CRF, and future work will determine how this change relates to behavior.
Wills
Tiffany A
TA
Neurobiology Curriculum, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Knapp
Darin J
DJ
Overstreet
David H
DH
Breese
George R
GR
D000284:Administration, Oral; D000367:Age Factors; D000679:Amygdala / Q000378:metabolism; D000818:Animals; D001007:Anxiety / Q000139:chemically induced* / Q000150:complications; D003346:Corticotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D000431:Ethanol / Q000008:administration & dosage / Q000494:pharmacology*; D007276:Injections, Intraventricular; D008297:Male; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013315:Stress, Psychological / Q000523:psychology*; D013375:Substance Withdrawal Syndrome / Q000523:psychology*
D000431:Ethanol; D003346:Corticotropin-Releasing Hormone