Impairment of environmental effects on brain weight by adrenergic drugs in rats

Injection of clonidine or methyldopa in rats immediately after daily two-hour exposure to a complex environment (EC) reduced the increase in occipital cortical weight normally associated with such exposure in comparison with animals kept in isolation. Drug injection four hours after EC exposure had no effect. Drug induced suppression of REM sleep during the first four hours after EC exposure was suggested to be the critical variable.