Diurnal rhythm returns to normal after elimination of portacaval shunting

Abstract

Previous studies showed that portacaval shunting causes metabolic and behavioral changes in rats. Most metabolic changes reversed within 1–2 wk after restoration of normal circulation. However, the rate of cerebral glucose metabolism (CMRGlc) remained depressed in some areas. The question arose whether complete recovery was possible. Therefore, a long-term behavioral study was undertaken to determine the time course of recovery. Diurnal activity was monitored for 48 h each week over a period of 14 wk: 2 wk before shunting, 6 wk after shunting, and 6 wk after restoration of normal hepatic circulation. Nighttime activity was depressed within 1 wk of shunting and did not change. Normal circulation to the liver was reestablished after 6 wk. The diurnal cycle was normal 3 wk later. Thus, although recovery of the diurnal rhythm is possible, the relatively long period necessary suggests the correction of a significant structural or chemical abnormality. A study of CMRGlcwas made using the behavioral study as an index of the time necessary for recovery. CMRGlcreturned to normal throughout the brain 6 wk after cessation of shunting except in the hippocampus and amygdala (7–8% decrease).