Induction and habituation of c-fos and zif/268 by acute and repeated stressors.

Acute restraint and shaking stress each induced the mRNA for the immediate early gene (IEG), c-fos, within 1 h in locus coeruleus (LC), midbrain raphe nuclei and central gray. Both acute restraint stress and acute shaking stress activated c-fos and zif/268 mRNA in paraventricular nuclei within 1 h. Midbrain A9 and A10 dopaminergic neurons did not show any c-fos or zif/268 mRNA induction by either acute stressor. Repeated restraint stress (14d, 1h/d) produced habituation to acute restraint stress, but not to acute shaking stress, in PVN, raphe and central gray. In LC, repeated restraint stress caused some habituation to both acute stressors.