Effect of induced Dalton's lymphoma on circadian locomotor activity rhythm of adult male mice

Dalton's lymphoma (DL) is a spontaneous and highly invasive T-cell lymphoma that develops as an ascitic tumor in murines. DL was induced by serial implantation of live ascite cells in laboratory-acclimated age-matched male AKR mice. The effects of DL on the locomotor activity rhythm were studied under 12: 12 h light: dark (LD) cycle. A significant decrease in the total and peak wheel-running activity was seen after the induction of DL, in comparison with the vehicle-injected control group. Durations of activity and rest were altered in DL mice, with a sharp daily increase in the duration of rest in the DL group. Circadian time period and acrophase of the rhythm remained similar in both control and DL mice. The mean estimate of statistic of rhythmicity (MESOR) and the amplitude of the locomotor activity rhythm were significantly lesser in post-DL-induced mice. A reduction in the span of the M1 and M2 motor cortex regions in DL mice and anatomical changes in the dentate gyrus were also seen. Thus, the effects of DL on the circadian clock seem restricted and mouse can still synchronize to an LD cycle. Impact of DL extends to motor cortices and may be the cause of the dampening of the amplitude of the rest-activity rhythm.