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Abstract

Social isolation is a stress factor increasing animal anxiety and impairing food-reinforced instrumental learning. Social isolation modulates sensitivity to psychoactive substances: it potentiated the depressive and analgesic effects of morphine, but attenuated the activating and anxiogenic effects of caffeine. These behavioral changes and changes in sensitivity to psychoactive agents can be explained by a well-known phenomenon of activation of the endogenous opioid system during stress.

Female rats consume and prefer oxycodone more than males in a chronic two-bottle oral voluntary choice paradigm

“…One caveat to the present study is that the 2-bottle paradigm used here necessitated that the rats be individually housed for ~10 months, and thus the results must in interpreted in the context of this social isolation. Social isolation augments many effects of opioids including oral self-administration and locomotor activity (Alexander et al, 1981;Coudereau et al, 1996;Deroche et al, 1994;Francès et al, 2000;Hadaway et al, 1979;Sudakov et al, 2003) , but reduces morphine-induced place preference and analgesia (Bozarth et al, 1989;Coudereau et al, 1997;Schenk et al, 1983;Wongwitdecha and Marsden, 1996) . If isolation indeed reduces the effects of opioids results in increased compensatory intake, the effects of isolation would be sex-dependent since the preference, intake, and blood levels were elevated in females compared to males.…”