CNS--endocrine pancreas system. III. Further studies on the vagal responsiveness to insulin deficiency.

Distribution and activity of acetylcholinesterase (AChE) in the neurons of the central vagal nuclei at the level of the medulla oblongata were studied in intact and alloxan-diabetic adult male rats by Gomori's histochemical method. Peculiarities of intracellular distribution of the enzyme in the Nucl. dorsalis n. vagi (ND) and Nucl. ambiguus n. vagi (NA) of intact animals were demonstrated. Changes in the ratio of cholinergic neurons with moderate and strongly-positive AChE staining reactions were revealed in the ND of alloxan-diabetic rats. The dynamics of the changes attested to increased AChE activity of these neurons in response to insulin deficiency. The data obtained are additional evidence for the responsiveness of ND neurons to insulin deficiency, which was demonstrated earlier in alloxan-diabetic rats by karyometry (Akmayev and Rabkina, 1976 b). It is suggested that changes in the plasma glucose or insulin levels may be the stimulus that influences the activity of the ND cholinergic neurons. By means of this mechanism the central vagal nucleus at the medulla oblongata level may be implicated in the feedback control of insulin secretion.

[Sensitivity of the central nuclei of the vagus to insulin deficiency in rats (histoenzymologic study)]. / Chuvstvitel'nost' tsentral'nykh iader vagusa u krys k defitsitu insulina (gistoénzimologicheskoe issledovanie).

Distribution and activity of acetylcholine esterase (AChE) in the central vagal nuclei (Nucl. dorsalis and Nucl. ambiguus) in male intact rats and in rats with experimental alloxan diabetes were investigated. In alloxan-diabetic rats there was noted an increase of the number of cells with a high AChE activity in the Nucl. dorsalis by 6%. These data suggest the participation of the vagal dorsal nucleus in the control of the endocrine function of the pancreas.

[Experimental aspects of the central nervous system - the insular system. 2. Reaction of the dorsal nucleus of the vagus nerve to insulin deficiency]. / Eksperimental'nye aspekty TsNS - insuliarnoi sistemy. II. Reaktsiia dorsal'nogo iadra vagusa na defitsit insulina.

The kariometric method was used to study the response of the nerve cells of the Nucl. dorsalis nervi vagi to insulin deficiency in rats with alloxan diabetes. Response to experimentally-induced diabetes of the nerve cells of the Nucl. tractus solitarii, adjacent nucleus in the medulla oblongata, served as control. In both cases the size of the cell nuclei of the areas under study was compared with the size of the cell nuclei in the same regions of the medulla oblongata of intact rats. Distinct and statistically significant shifts in the size of the cell nuclei of the Nucl. dorsalis nervi vagi in rats with alloxan diabetes were revealed in comparison with control measurements. Thus, sensitivity of the central nucleus of the vagus to insulin deficiency was revealed. Possible ways of participation of the vagus in the control of the insular apparatus are discussed.

[Experimental aspects of the CNS-insular system]. / Eksperimental'nye aspekty TsNS-insuliarnoi sistemy

The work was aimed at detection and precise localization of the hypothalamic nuclei sensitive to insulin deficiency. For this purpose nuclei of the whole hypothalamic area of the brain were examined in rats with experimentally-induced alloxan diabetes. Only individual nuclei, particularly the supraoptic nucleus of the anterior hypothalamus and the ventro-medial and the arcuate nuclei of the medial hypothalamus proved to react to insulin deficiency. The nuclei of the posterior hypothalamus failed to react to insulin deficiency. Possible ways and methods of participation of the insulin-dependent areas of the hypothalamus in the regulation of the endocrine function of the pancreas are discussed.

CNS-endocrine pancreas system. I. The hypothalamus response to insulin deficiency.

The anterior, medial and posterior hypothalamic nuclei in alloxan-diabetic male rats were studied by karyometry. Selective responsiveness of separate nuclei of the medial basal hypothalamus (MBH) and the anterior hypothalamus was revealed. In the MBH cell nuclear-size changes were most prominent in the ventromedial nucleus and less pronounced, but significant, in the arcuate nucleus. In the anterior hypothalamus a significant response was produced by the supraoptic nucleus. The authors do not exclude the possibility that the reaction of the neurosecretory cells of the supraotic nucleus is indirect and reflects disturbed vasopressin balance in alloxan-diabetic rats in response to impairment of water-salt metabolism. The responsiveness of the MBH nuclei is considered as evidence for their involvement, the bentromedial nucleus in particular, in hypothalamic control of the endocrine pancreas. Various means by which insulin-sensitive hypothalamic areas may be implicated in this control are discussed.

CNS-endocrine pancreas system. II. Response of dorsal nucleus of the vagus nerves to insulin deficiency.

Sensitivity of the vagal dorsal nucleus nerve cells to insulin deficiency was revealed in alloxan-diabetic rats by karyometry. Control measurements showed absence of similar changes in cell nuclear sizes of the adjoining area, the Nucltractus solitarii. The results provide evidence in favour of a selective response of the dorsal nucleus of the vagus nerves to insulin deficiency and allow assumption that not only the peripheral vagus but the central component of this cholinergic system contribute to endocrine pancreas control. It is suggested that the medial basal hypothalamus and the system of the vagus are links of a single control mechanism regulating endocrine pancreas and represented at different levels of the central and peripheral nervous system.

[Method for the intavital of the isolated pancreatic islands of Langerhans in rats]. / Metod prizhiznennogo vyiavleniia izolirovannykh ostrovkov Langergansa v podzheludochnoi zheleze u krys

The authors describe a method of vital detection and isolation of individual islands of Langerhans in rats. This method is based on the capacity of the beta-cells of the islands to accumulate the stain during life. Since the stain (0.05% neutral red solution) is harmless and it is rapidly eliminated by the cells this method permits vital marking on the surface of the pancreas of individual islands and their distinguishment under steroscopic microscope; these islands can be isolated from the surrounding parenchyma of the pancreas with the aid of a microknife. Thus obtained islands of the pancreas could be used as material for experiments with implantation and for other experimental studies.