[Changes in blood sugar after administration of xylazine and adrenergic blockers in the rat]

Xylazine (rompun) has sedative, analgetic and myorelaxative effects; in addition to this, it also influences the homeostasis of glucose in the organism. The changes in glucose tolerance were studied in young rats after the administration of xylazine in combination with the blockers of adrenergic receptors. Xylazine caused hyperglycaemia and glucose intolerance in young rats and the administration of the beta-adrenergic blocker (propranolol) prolonged this diabetogenic effect. On the other hand, glucose tolerance after the administration of xylazine with alpha-adrenergic blocker (phentolamine) is close to the normal level. It is supposed on the basis of our results that xylazine-induced glucose intolerance and hyperglycaemia are mediated by the stimulation of the alpha-adrenergic system. Besides inhibition of insulin secretion, hepatic glycogenolysis probably also increases.

[Food intake in suckling rats after glycerol administration]

The influence of administered glycerol on the food intake was followed in suckling rats in five age periods (on the 5th, 9th, 13th, 17th and 23rd day of life). Glycerol significantly reduced the food intake (P less than 0.01) in the last three age categories. This finding indicates that from the 13th day of life glycerol becomes one of the limiting factors of food intake for suckling rats in connection with a gradual functional maturing of their control mechanism, regulating the food intake.

Nucleic acids and protein content of some fetal and neonatal rat organs after insulin treatment

In 17 1/2--21 1/2 day-old fetuses and 1--4 day-old rats the DNA, RNA and protein content of the liver, heart and brain was daily investigated 6 hours after injecting approximately 40 mU . g-1 insulin. The DNA content in the mentioned organs was not affected by the insulin. The RNA content in the fetal and neonatal brain and neonatal heart was significantly elevated, while the liver RNA was not altered. Only in the 4 day-old brain did the protein content increase. The experimental dates indicate that the cell RNA content of some perinatal tissues can be elevated by insulin depending on the type of tissue and its developmental stage.

[The development of the regulation of food intake during ontogenesis--the effect of hyperalimentation on body weight gain in suckling rats]

In an experiment, the number of young rats per nest was reduced to two in time intervals from the 1st to the 6th, from the 6th to the 11th, from the 11th to the 16th, and from the 16th to the 21st day after birth (groups P1, P2, P3 and P4 respectively). The plenty of milk available to the young for a period of five days positively influenced the body weight of the rats in group P2, whereas in the remaining groups the total weight showed no significant change in comparison with normally fed animals. The subsequent normalization of nutrition in the test young (the number of the young in nests was increased to eight) induced a decrease in weight gains in the older test animals (groups P3, P4), whereas in the 6- to 11-day-old rats (P2) the higher weight gains were retained in the next growth stages. The results give evidence that an external interference in the nutrition of rats (hyperalimentation) in the period from the 6th to the 11th day of life can influence, for a longer time, feeding behaviour and weight gains. The relative stability of the body weight of the young after the 11th day of life suggests to the functional involvement of the regulatory mechanisms controlling feed intake in this period of life.