TDK conference 2018

Although the hypothalamus is responsible for the control of many neuroendocrine processes, it is a relatively small, anatomically "crowded" part of the central nervous system. Like many other areas of the brain, the core groups of the hypothalamus are symmetrically located in the right and left side of the brain and the hypothalamus is functionally considered as a parallel structure of identical parties.

According to our hypothesis, the hypothalamus, as the upper brain regions, is not redundantly identical in function, but it is formed by two hemispheres that share their tasks in yet mostly unknown hierarchies. Based on previous works of my research group, it has become apparent that control of female reproductive functions is disproportionately divided between the two hypothalamic hemispheres, supported by the above hypothesis. In the present study, we will find the answer to the question whether this type of functional asymmetry in male animals can be observed in the two most energy-intensive functions controlled by the concerned brain region, in terms of food intake and reproductive control.

To verify our hypothesis, we performed metabolic examinations through the analysis of mitochondrial respiratory activity. In order to obtain viable mitochondrial fractions from the isolated left and right hypothalamus of male rats for this purpose, we applied differential and Percoll-based gradient fractionation procedure developed by our research group. The experimental animals were examined in different reproductive (bilateral orchiectomy, testosterone treatment) and satiety states (food deprivation, scheduled feeding, etc.).

Our results on reproductive processes with male animals (compared to females) did not confirm our assumption of lateralized operation of the hypothalamus. On the other hand, with regard to satiety state, it has been proved that starvation and fasting increase the metabolic activity of the left hypothalamus by suppressing the characteristic right side dominance. It became clear that this metabolic change was gradually increased, throughout the starvation period. After refeeding, metabolic dominance of the right side was gradually reverted.

Based on these results, while hypothalamic functional asymmetry in females showed strong estrogen-dependence, in case of males, state of satiety played a predominant role. Our results can basically redefine the point of view how up to date the hypothalamus is regarded, and therefore offering new diagnostic and therapeutic options.