Differential alterations in brain sensitivity to amphetamine and pentylenetetrazol in socially deprived mice

Mice deprived of social interactions for different periods of time (56, 69, 79, 89 or 97 days) were studied. Social isolation increased both general activity observed in an open-field and amphetamine-induced hyperactivity; CNS responsiveness to pentylenetetrazol-induced convulsions, however, decreased. The differences in general activity were detected after 69 and 79 days of social deprivation; the hyperactivity induced by amphetamine was greater after 79 days of isolation and the pentylenetetrazol CD50's were higher after 56, 69 and 79 days of solitude. These data, obtained with mice, show first that isolation time is an important variable to display drug effects and secondly that long-term deprivation of social stimuli does not increase CNS susceptibility to all stimulant drugs. A combination of a higher release of catecholamines onto previously supersensitive receptors was considered to be involved with the differences observed.