Enhanced ultrasonic vocalization and Fos protein expression following ethanol withdrawal: effects of flumazenil.
BACKGROUND
Administration of flumazenil, a benzodiazepine (BZD) antagonist, has therapeutic efficacy against some anxiogenic effects of ethanol withdrawal. This observation has led to the suggestion that anxiety associated with ethanol withdrawal is related to release in brain of an endogenous BZD inverse agonist.


OBJECTIVE
The present studies further tested this hypothesis by assessing the effect of flumazenil on withdrawal-induced changes in a behavioral task and on the expression of the neuronal protein, Fos.


METHODS
Male Sprague-Dawley rats were withdrawn from a chronic ethanol regimen and tested, with or without flumazenil pretreatment, for either ultrasonic vocalization in response to air puff or for the induction of Fos protein-like immunoreactivity (Fos-LI) in brain. In addition, flumazenil effects on Fos-LI were measured in a group of animals treated with the BZD inverse agonist DMCM (0.75 and 1.0 mg/kg).


RESULTS
Flumazenil (5.0 mg/kg) significantly reduced the number of ultrasonic vocalizations observed following withdrawal from chronic ethanol. In contrast, flumazenil (5.0 mg/kg), given either 14 h before withdrawal from chronic ethanol, or during hours 3 and 5 following withdrawal, did not attenuate the effects of withdrawal on Fos-LI. Subsequent testing with DMCM confirmed that a benzodiazepine inverse agonist can induce Fos-LI in most of the same brain regions as observed following ethanol withdrawal, and that this change in Fos protein can be attenuated by pretreatment with flumazenil (5.0 mg/kg).


CONCLUSIONS
Overall, these results demonstrate that specific behavioral indices of anxiety, but not measures of Fos-LI, support the contribution of an endogenous BZD inverse agonist in the ethanol withdrawal syndrome.
Moy
S S
SS
Skipper Bowles Center for Alcohol Studies, Department of Psychiatry and UNC Neuroscience Center, UNC School of Medicine, Chapel Hill, NC 27599, USA. sheryl.moy@css.unc.edu
Knapp
D J
DJ
Duncan
G E
GE
Breese
G R
GR
D000818:Animals; D002243:Carbolines / Q000494:pharmacology; D000431:Ethanol / Q000009:adverse effects*; D005442:Flumazenil / Q000494:pharmacology*; D008297:Male; D016760:Proto-Oncogene Proteins c-fos / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000502:physiology*; D013375:Substance Withdrawal Syndrome / Q000209:etiology / Q000378:metabolism / Q000523:psychology*; D014828:Vocalization, Animal / Q000187:drug effects*
D002243:Carbolines; D016760:Proto-Oncogene Proteins c-fos; D011963:Receptors, GABA-A; C034818:methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate; D000431:Ethanol; D005442:Flumazenil