Participation of Various Nuclei of the Hypothalamus in the Implementation of the Drinking Skill Developed

The hypothalamus is a small area in the diencephalon that
includes a large number of cell groups (more than 30 nuclei) that
regulate the neuroendocrine activity of the brain and homeostasis of
the body...


Introduction
The hypothalamus is a small area in the diencephalon that includes a large number of cell groups (more than 30 nuclei) that regulate the neuroendocrine activity of the brain and homeostasis of the body [1][2][3][4]. The hypothalamus is connected by nerve pathways with almost all parts of the central nervous system, including the cortex, hippocampus, amygdala, cerebellum, brain stem, and spinal cord [5]. Together with the pituitary gland, the hypothalamus forms the hypothalamic-pituitary system, in which the hypothalamus controls the synthesis and secretion of many pituitary hormones, is the central link between the nervous and endocrine systems. It secretes hormones and neuropeptides and regulates functions such as hunger and thirst. body thermoregulation, sexual behavior, sleep and wakefulness (circadian rhythms) [1,2,6].
Recent studies show that the hypothalamus plays an important role in higher functions, such as memory and emotional state, and thus participates in the formation of various aspects of behavior [2,7,8]. The hypothalamus controls the activity of the human endocrine system, due to the fact that its neurons are able to secrete neuroendocrine transmitters (liberins and statins) that stimulate or inhibit the production of hormones from the adenohypophysis [3,5]. Suppression of the functional activity of the hypothalamus leads to a violation of drinking and eating behavior [9]. Considering all of the above, the task of this study was to study the role of various nuclei of the hypothalamus in the implementation of the drinking skill developed.

Methods
Experiments were performed using 20 rabbits breeds of "Chinchilla" in weight 2-3kg trained to perform a conditioned operant drinking behavior reflex. The animals were subjected to water deprivation for 24 and 48 hours, after which they were trained in the instrumental drinking skill. In response to the sound signal, the rabbit pressed the pedal, as a result of which the door opened, jumped over the barrier from the starting compartment of the chamber to its target section to receive water in a strictly defined dose (5-10 ml) and then returned back to the starting section cameras. The conditioned stimulus was applied at regular intervals

Results and Discussions
Observations of conditioned reflex activity before the start of   [11], irritation of the preoptic region [12], as well as destruction of the VMH of the hypothalamic nucleus in rats [13].
In our experiments, various effects of novocaine blockade of the studied nuclei of the hypothalamus were revealed. So, if the blockade of VMH and MM did not cause an effect on the developed drinking habit, then even one-sided switching off of the SO of the nucleus caused an increase in all time parameters. The amount of water consumed has significantly decreased. Bilateral application of novocaine to this nucleus led to a complete inhibition of the performance of the developed drinking habit and refusal of water, despite the fact that before coagulation the animals had a pronounced drinking motivation. Complete adipsia and a sharp decrease in water consumption after the destruction of the anterior nuclei of the hypothalamus were observed by a number of authors [10], in the opposite of the data of other researchers who caused adipsia when the lateral hypothalamus was damaged [14], with the joint destruction of the lateral hypothalamus and the lateral preoptic region [15], as well as with damage to the medial hypothalamus.
The appearance of thirst upon electrical stimulation of the SO of the anterior hypothalamus and its disappearance with bilateral novocaine blockade of this area, apparently, can be explained by the presence of osmosensitive neurons in the SO, which were found in this nucleus [16] and to which some researchers assign a primary role in the regulation of water consumption [17].
Thus, the results of the studies carried out on electrical stimulation and temporary switching off the SO suggest that the osmoreceptors of the SO of the anterior hypothalamus play a certain role in the processes of the formation of thirst.