Rodent doxapram model of panic: behavioral effects and c-Fos immunoreactivity in the amygdala.
BACKGROUND
Panic attacks, the hallmark of panic disorder, are often characterized by hyperventilation. Existing animal models of anxiety have not addressed the effects of the hyperventilation on anxiety-related behaviors. Doxapram is a respiratory stimulant that reliably evokes panic attacks in patients with panic disorder. We examined doxapram in four rodent models of anxiety and sought to identify brain regions involved in its behavioral effects.


METHODS
The effects of doxapram were determined for cue and contextual fear conditioning, the open field test, and the social interaction test. The effect of doxapram on c-Fos-like immunoreactivity was examined in three brain regions.


RESULTS
Doxapram at 4 mg/kg increased anxiety-related behaviors in all four anxiety models. An inverted U-shaped dose-response curve was identified for fear conditioning to cue. Doxapram induced c-Fos-like immunoreactivity in the central nucleus of the amygdala but not the lateral nucleus or the nucleus tractus solitarius.


CONCLUSIONS
Doxapram enhanced anxiety-related behaviors in four animal models of anxiety that involve conditioning or spontaneous avoidance. The effect of doxapram may result from activation of neurons in the amygdala. Doxapram, by inducing hyperventilation, may be a useful adjunct to existing animal anxiety models for improving validity for panic anxiety.
Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
Gregory M
GM
Sullivan
John
J
Apergis
Jack M
JM
Gorman
Joseph E
JE
LeDoux
D000679:Amygdala / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D001007:Anxiety; D001522:Behavior, Animal / Q000187:drug effects*; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003213:Conditioning, Psychological / Q000187:drug effects; D003463:Cues; D004195:Disease Models, Animal; D004315:Doxapram / Q000494:pharmacology*; D005239:Fear / Q000187:drug effects; D007150:Immunohistochemistry; D008297:Male; D010200:Panic; D016760:Proto-Oncogene Proteins c-fos / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019141:Respiratory System Agents / Q000494:pharmacology*; D017552:Solitary Nucleus / Q000187:drug effects / Q000378:metabolism
D000697:Central Nervous System Stimulants; D016760:Proto-Oncogene Proteins c-fos; D019141:Respiratory System Agents; D004315:Doxapram