Social behavior, dominance, and social deprivation of rats determine drug choice.

Relationships between social deprivation, dominance, and voluntary intake of ethanol (ETOH) and diazepam (D) were studied in male adult Wistar rats. Social behavior was registered by tetradic encounters in the open field prior to the rats' drug experiences. Social deprivation was induced by individual housing (LI) and contact caging (C). Nondeprived rats were housed in groups of four individuals (G) each. Social deprivation facilitated ETOH intake: LI rats consumed 30% more ETOH than G. Increase of deprivation by change of housing condition additionally raised ETOH consumption. ETOH experiences did not affect subsequent D choice. However, rats with a high ETOH consumption also preferred D. Individual drug disposition correlated with social dominance (in G: to social activity). Even in individual isolation dominant rats took less drugs than subordinate ones, but these rats raised their ETOH consumption when the housing conditions were changed. After nine months of voluntary ETOH intake and subsequently nine months without access to ETOH the rats showed signs of "behavioral dependence." Compared to naive animals they took twice as much ETOH and even after adulterating ETOH by quinine a high preference was perpetuated. During this state modifying social factors were no longer effective.