Chronic stress interacts with chronic amphetamine on locomotion, object recognition and synaptophysin expression in female rats.

V. BISAGNO; C. GRILLO; G. PIROLI; P. GIRALDO; B. MCEWEN; V.N. LUINE

PHARMACOLOGY BIOCHEMISTRY AND BEHAVIOR

Elsevier

Lugar: New York; Año: 2004 vol. 78 p. 541 - 550

0091-3057

Previous studies show that stress cross-sensitizes or alters many behavioral and neural effects of amphetamine in male rats; however, few studies have included female rats.  We investigated the effects of combining daily restraint stress (21 days for 6h/day) with chronic AMPH injections (10 i.p. injections on every other day) on locomotor activity, exploratory activity on an open field and object recognition, a memory task, in female rats. A synaptic protein, synaptophysin, was also quantified by radioimmunocytochemistry (RICC) in brain areas in order to determine possible mechanisms for  behavioral changes.  Subjects were evaluated on days 1-5 following the last injection; post sacrifice, serum corticosterone and brain synaptophysin expression was measured. AMPH impaired object recognition, increased locomotion, modified exploration and increased corticosterone levels. Stress did not alter these parameters, but stress blocked AMPH effects on object recognition and exploration while it potentiated AMPH dependent locomotor effects and did not alter increased corticosterone levels.  AMPH groups showed decreased synatophysin expression in the hippocampus.  In the caudate nucleus, the AMPH group showed increased synaptophysin expression, an effect that was reversed by stress. Results suggest that chronic stress counteracts AMPH dependent cognitive impairments by blocking both the induction of AMPH anxiety-like effects and neuroplastic changes in the caudate nucleus of female rats.