Effect of chronic social stress on delta-opioid receptor function in the rat

Citation
La. Pohorecky et al., Effect of chronic social stress on delta-opioid receptor function in the rat, J PHARM EXP, 290(1), 1999, pp. 196-206
Citations number
53
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Pharmacology & Toxicology
Journal title
JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS
ISSN journal
0022-3565 → ACNP
Volume
290
Issue
1
Year of publication
1999
Pages
196 - 206
Database
ISI
SICI code
0022-3565(199907)290:1<196:EOCSSO>2.0.ZU;2-Q
Abstract
Previous studies have shown that stressors modify endogenous opioid systems . However, the consequences of social stress on the function of endogenous opioid systems is not well documented. The present studies investigated the effect of rank and housing condition on response to SNC-80, a delta recept or agonist. Triad-housed rats were assessed for dominance status by their b ehavior and alteration in body weights. At 3 and 50 days, triad- and indivi dually housed rats were injected with SNC-80 (35 mg/kg i.p.) or saline, and evaluated using a test battery consisting of open field behaviors, rectal temperature, analgesia, and air-puff-induced ultrasonic vocalizations. Afte r 50 days of housing, plasma corticosterone, adrenal catecholamines, and th e density of cyclic[D-penicillamine(2)-D-penicillamine(2)]enkephalin-stimul ated guanylyl 5'-[gamma[S-35]thio]triphosphate binding in the prefrontal co rtex, the amygdala, nucleus accumbens, thalamus, arcuate, and median eminen ce were also determined. The first 24 h of triad housing resulted in loss o f body weight in subdominant (beta s and gamma s) but not dominant alpha ra ts. SCN-80-induced hypothermia was smaller, and there was no depression of headpoke and locomotor behavior in the periphery and the center of the fiel d of alpha rats, in contrast to subdominant and singly housed rats. Rank st atus did not influence SNC-80's analgesic effect or its inhibition of air-p uff-induced ultrasonic vocalizations. Plasma corticosterone levels of alpha s and ys were lower compared with ps and singly housed rats. Agonist stimu lation of delta receptor guanylyl 5'-[gamma[S-35]thio]triphosphate binding was lateralized in prefrontal cortex and amygdala, but not nucleus accumben s. Binding was highest in all brain areas of singly housed rats and lowest in the thalamus of beta and of gamma rats. Lateralized binding in amygdala, high locomotor activity, and sensory sensitivity correlated positively wit h greater sensitivity to SNC-80-induced depression in these measures. Highe r binding in the right amygdala correlated with higher plasma corticosteron e levels. These findings indicate that dominant rats displayed stimulant ra ther than depressant responses to delta-opioid activation. Therefore in rod ents rank-related stress can alter responsiveness of the endogenous opioid system, and dominance can increase the excitatory effects of delta agonists .