Hepatic glucose balance in response to direct stimulation of sympathetic nerves in the intact liver of cats.

Changes in hepatic glucose balance in response to direct stimulation of the hepatic nerves were measured in cats. Simultaneous measurements were made of glucose concentrations entering and leaving the intact liver; this, combined with measured blood flows, allows calculation of hepatic glucose balance. Stimulation of the hepatic sympathetic nerves (8 Hz, 15 V, 1 ms) produced a rapid increase in hepatic glucose output that was statistically significant after 1 min and reached a peak 3--5 min after onset of stimulation, after which time the output declined somewhat. The half time for deactivation of the response was 1.8--2 min. Variability in the responses was largely accounted for by the variable control base lines measured immediately prior to stimulation. Those animals showing the highest basal output showed the least increase in output in response to the nerves. The response to stimulation of the mixed nerve trunk in the presence and absence of atropine (1 mg/kg, intraportal) was similar. Simultaneous activation of hepatic sympathetic and parasympathetic nerves therefore produces a purely sympathetic type of effect on net glucose balance across the liver. It was also shown that changes in net splanchnic output or simply in arterial--hepatic venous glucose differences are an adequate reflection of liver glucose balance under the currently tested responses.