Effect of social isolation on the reinforcing properties of morphine in the conditioned place preference test

Isolation rearing enhances the locomotor stimulant properties of intra-perifornical sulpiride, but impairs the acquisition of a conditioned place preference

“…This result is consistent with previous reports of the e¤ects of isolation rearing upon drug-induced conditioned place preference. Thus, rearing in social isolation was shown to block the ability of cocaine (Schenk et al 1986), d-amphetamine (Wongwitdecha and Marsden 1995) and morphine (Wongwitdecha and Marsden 1996) and to impair the ability of heroin (Schenk et al 1983(Schenk et al , 1985 to induce a conditioned place preference. Given that the acquisition of a conditioned place preference is considered to be dependent upon a functionally intact mesoaccumbens dopamine projection (see above, and Introduction), the consistency of the current result with previous reports of the e¤ects of isolation rearing upon drug-induced conditioned place preference lends further support to the proposition that blockade of dopamine receptors of the D 2 family within the perifornical region engages neural circuitry relevant to activation of the mesoaccumbens dopamine projection.…”

Social and environmental influences on opioid sensitivity in rats: importance of an opioid’s relative efficacy at the mu-receptor

“…Rats in this group received supplemental enrichment from a variety of objects (e.g., PVC tubes, ladders, Ping-Pong balls, animal toys) that were changed daily. Consistent with previous studies (Schenk et al 1982;Bardo and Hammer 1991;Bowling et al 1993;Wongwitdecha and Marsden 1996;Smith et al 2003), rats were housed under these conditions for at least 6 weeks prior to behavioral testing. Rats in both groups were kept in a large colony room maintained on a 12-h light/dark cycle with food and drinking water available in the home cages.…”

“…These studies have shown that grouphoused rats (i.e., rats that are housed socially but not given novel objects to explore and manipulate) are more sensitive than isolated rats to the antinociceptive effects of morphine in the tail-shock and tail-compression tests (Czlonkowski and Kostowski 1977;Panksepp 1980) and are more sensitive to the rewarding effects of morphine and heroin in the place-conditioning procedure (Schenk et al 1983;Wongwitdecha and Marsden 1996;Coudereau et al 1997). The effects of other mu-opioids, particularly those possessing lower efficacy at the mu-receptor, have not been examined.…”

Behavioural and neurochemical effects of post-weaning social isolation in rodents—Relevance to developmental neuropsychiatric disorders

“…Isolation in Lister hooded rats prevents the development of a conditioned place preference to either amphetamine (Wongwitdecha and Marsden, 1995) or morphine (Wongwitdecha and Marsden, 1996a). In Long-Evans rats isolated immediately post-weaning (Schenk et al, 1985(Schenk et al, , 1983 heroin conditioning was impaired when a biased training procedure which initially paired drug treatment with the nonpreferred compartment was used (similar to that used by Wongwitdecha and Marsden (1996a)). Notably this impairment was only observed when rats were isolated immediately postweaning and not at 3 months of age, confirming the importance of 'early-life' intervention on this behaviour.…”