Disruption of circadian locomotor activity in rats after portacaval anastomosis is not gender dependent.

A recent study suggested that female rats are less affected by a portacaval anastomosis (PCA) than their male counterparts, as measured by body weight and changes in locomotor activity. In this study, we evaluated the entrainment of locomotor activity to the light/dark (LD) cycle, a consistent abnormality in the portacaval shunted rat. The degree of entrainment was measured in male and female rats before and after PCA or sham operation. All four groups of animals showed strong entrainment to an LD cycle before surgery. After portacaval anastomosis, male and female rats exhibited a highly significant decrease in overall motor activity as compared with the preoperative period and as compared with sham-operated animals of the same gender. The percentage of total activity during daytime was significantly increased after portacaval anastomosis. The reduction in parameters of entrainment indicates a disruption of circadian function in both portacaval-shunted groups. Portal pressure measurements confirmed the patency of the shunts. Cortical brain glutamine levels were similarly increased in male and female shunted rats. The loss of body weight was slightly, but not significantly, more pronounced in male animals after shunt surgery. In conclusion, our results do not support a role for gender in the disruption of circadian function in rats after PCA.