Chronic stress sensitizes frontal cortex dopamine release in response to a subsequent novel stressor: reversal by naloxone.
The present study examined the influence of an early chronic variable stress procedure with or without concurrent naloxone administration at different doses (1, 2 or 3 mg/kg, i.p.) on stress (restraint)-induced dopamine release in the frontal cortex in vivo. A higher increase in cortical dopamine release in response to a subsequent restraint event was observed in chronically stressed rats as compared with those without chronic stress exposure. Naloxone pretreatment normalized this sensitized response only at the higher dose (3 mg/kg, i.p.). The present results indicate that cortical dopamine response to a novel and uncontrollable stressor sensitizes after exposure to a chronic variable stress procedure and that an endogenous opiate mechanism, presumably activated during chronic stress, may be involved in the development of such a sensitization process.
Cuadra
G
G
Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Argentina.
Zurita
A
A
Lacerra
C
C
Molina
V
V
D000818:Animals; D002908:Chronic Disease; D004298:Dopamine / Q000378:metabolism*; D005625:Frontal Lobe / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D017551:Microdialysis; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D018847:Opioid Peptides / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012149:Restraint, Physical; D013312:Stress, Physiological / Q000503:physiopathology*
D009292:Narcotic Antagonists; D018847:Opioid Peptides; D009270:Naloxone; D004298:Dopamine