Effects of amphetamine on NK-related cytotoxicity in rats differing in locomotor reactivity and social position

The effect of i.p. administration of 1 mg/kg of amphetamine (AMPH) on natural killer cells cytotoxicity (NKCC) and number of large granular lymphocytes (LGL-NK) together with plasma corticosterone (CORT) level and WBC was evaluated in male Wistar rats differing in two behavioral features: locomotor reactivity to novelty (high, HR and low, LR responders) and social position (dominants, D and subordinates, S). In the majority of animals AMPH evoked (30 min after administration) an increase in NKCC and LGL (NK) number accompanied by lymphopenia, neutrocytosis, monocytosis, and an increase in CORT level. Changes in NKCC (LU20) showed substantial individual variability: in HR group ∼513Δ%, p<.001 (relative to the control); LR group ∼56Δ%, p>.05; D group ∼441Δ%, p<.001; S group ∼216Δ%, p>.05; HR/D group ∼643Δ%, p<.001; HR/S group ∼414Δ%, p<.001; LR/D group ∼191Δ%, p>.05; and LR/S group ∼−19Δ%, p>.05. The increase in CORT level, lymphopenia, and neutrocytosis indicated a stress-like reaction to AMPH. No significant correlation between NKCC and CORT level was found. The results obtained indicate that AMPH can evoke an increase in NK-related cytotoxic activity quantitatively related to high behavioral reactivity to novelty and social dominance, however NKCC is not related to the AMPH-induced CORT changes.