Changes in food intake after hepatic vagotomy at a stage of development in rats

The role of the autonomic nervous system in liver regeneration and apoptosis--recent developments

Hepatocytes have a great replicative capacity and are capable of repopulating the liver. Previous studies have suggested that the autonomic nervous system regulates liver regeneration and apoptosis. Moreover, the central nervous system modulates them through the autonomic nervous system. The lateral hypothalamus (LH) area and the ventromedial hypothalamus (VMH) nucleus have been studied for their role in the integration of neurohumoral information. The LH is part of the parasympathetic system, while the VMH belongs to the sympathetic system. Lesions of the LH reportedly induced an increase in sympathetic nerve activity, while those in the VMH produced facilitation of vagus nerve activity. Moreover, VMH or LH lesions facilitate hepatic regeneration after partial hepatectomy. Furthermore, the hypothalamus mediates hepatic apoptosis through the autonomic nervous system. Although further studies are needed to define the role clearly, the autonomic nervous system is one of the important factors that regulate liver regeneration and apoptosis.

Hepatic branch vagotomy can block liver regeneration enhanced by ursodesoxycholic acid in 66% hepatectomized rats

The effect of hepatic branch vagotomy on liver regeneration induced by ursodesoxycholic acid was examined in 66% hepatectomized rats. A standard feeding was obtained from animals with hepatic branch vagotomy, and all rats examined received pair food intake. Liver regeneration was evaluated by the hepatocyte mitotic index. When ursodesoxycholic acid 12.5 mg kg(-1) day(-1) was administered orally, a significant increase in the mitotic index was observed 2 and 3 days after hepatectomy, and the mitotic index response 2 days after hepatectomy was dose-dependent in the range of 0-25 mg kg(-1) day(-1). Hepatic branch vagotomy suppressed the mitotic index 2 days after hepatectomy, and the mitotic index increase due to ursodesoxycholic acid was blocked by hepatic branch vagotomy, but not by gastric branch vagotomy. It was also noted that hepatic branch vagotomy or ursodesoxycholic acid or both did not affect serum parameters indicating liver and kidney function. Because ursodesoxycholic acid exists in the bile juice, these results suggest that the hepatic vagus nerve is specifically active with endogenous bile acids in the control of liver regeneration.

Control of motor and secretory functions of the stomach by a portal glucose signal

D-glucose solution injected into the portal vein influences efferent tonic activities of the vagal nerve innervating the stomach. This suggested the existence of a neural connection between hepatic vagal branch afferents and gastric vagal efferents in the brain. Considering this observation together with findings indicating that electrical stimulation of the proximal cut end of the hepatic vagal branch changes acidity in the gastric perfusing fluid or pressure within the stomach, it has been presumed that hepatic afferent signals related to glucose may regulate the motor or secretory function of the stomach through a change in central nervous activity. Recently active interaction between the portal and medullary glucose signals in gastric function was discovered, and analysis of the characteristic features of the system is in progress.

The body weight loss of young rats caused by hepatic branch vagotomy is influenced by environmental temperature

Changes in body weight after hepatic branch vagotomy or sham vagotomy were examined in rats of three different body weights (about 100, 200 and 280 g), and it was noted that the weight loss was evident only in 100 g rats. In a second experiment, 100 g animals were hepatic branch vagotomized or sham operated and housed at three different room temperatures (12-17, 17-22, 22-27 degrees C). Subsequently, the reduction in weight of the vagotomized animal was correlated with the lowest room temperature in the vagotomized animal, and food intake was also decreased in direct relation to the temperature. The results suggest that there might be a hepatic vagal mechanism modulating food intake in young animals, and such a mechanism may be modulated by the environmental temperature.

Alterations in gastric acid secretion following hepatic vagotomy at a stage of development in rats

The relation of gastric acid secretion to the hepatic vagal section was examined in consideration of developmental stages of a rat. Acid outputs in rats deprived of food for 22 hr before the experiment were estimated with or without insulin. The animals were classified into five groups according to their body weights at the experiments (50, 100, 200, 300 and 400 g). Hepatic vagotomy was effective in decreasing acid output in all of the groups treated with food deprivation and insulin, and it was found that there was a close relationship between the output and glucose concentration in the portal blood. In rats treated only with food deprivation, hepatic vagotomy produced different effects for the five groups; the vagotomy failed to cause acid response when the rats weighed about 300 and 400 g, while in the animals weighing about 50, 100 and 200 g acid outputs were reduced following the vagotomy. It was noted that the sensitivity to hypoglycemia in the acid output was greater in the young rats than the older ones. Results suggest that function of the hepatic vagal nerve may be prominent in modulating acid secretion in an earlier stage of development when the animals are most sensitive to hypoglycemia.