Long-term behavioral and neurochemical effects of chronic stress exposure in rats.
Rats exposed to acute unavoidable stress develop a deficit in escaping avoidable aversive stimuli that lasts as long as unavoidable stress exposure is repeated. A 3-week exposure to unavoidable stress also reduces dopamine (DA) output in the nucleus accumbens shell (NAcS). This study showed that a 7-day exposure to unavoidable stress induced in rats an escape deficit and a decrease in extraneuronal DA basal concentration in the NAcS. Moreover, animals had reduced DA and serotonin (5-HT) accumulation after cocaine administration in the medial pre-frontal cortex (mPFC) and NAcS, compared with control animals. After a 3-week exposure to unavoidable stress, escape deficit and reduced DA output in the NAcS were still significant at day 14 after the last stress administration. In the mPFC we observed: (i) a short-term reduction in DA basal levels that was back to control values at day 14; (ii) a decrease in DA accumulation at day 3 followed by a significant increase beyond control values at day 14; (iii) a significant reduction in 5-HT extraneuronal basal levels at day 3, but not at day 14. Finally, a significant decrease in 5-HT accumulation following cocaine administration was present in the NAcS and mPFC at day 3, but not at day 14. In conclusion, a long-term stress exposure induced long-lasting behavioral sequelae associated with reproducible neurochemical modifications.
Mangiavacchi
S
S
Department of Neuroscience, Università di Siena, Siena, Italy.
Masi
F
F
Scheggi
S
S
Leggio
B
B
De Montis
M G
MG
Gambarana
C
C
D000818:Animals; D002908:Chronic Disease; D003042:Cocaine / Q000494:pharmacology; D004298:Dopamine / Q000172:deficiency* / Q000378:metabolism; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D004924:Escape Reaction; D006380:Helplessness, Learned; D008297:Male; D017551:Microdialysis; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009714:Nucleus Accumbens / Q000378:metabolism*; D017397:Prefrontal Cortex / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012149:Restraint, Physical / Q000009:adverse effects* / Q000523:psychology; D012601:Scopolamine / Q000494:pharmacology; D012701:Serotonin / Q000172:deficiency* / Q000378:metabolism; D013312:Stress, Physiological / Q000503:physiopathology* / Q000523:psychology; D013997:Time Factors
D018765:Dopamine Uptake Inhibitors; D018727:Muscarinic Antagonists; D012701:Serotonin; D012601:Scopolamine; D003042:Cocaine; D004298:Dopamine