# Expression Profiles of Genes Related to Serotonergic Synaptic Function in Hypothalamus of Hypertensive and Normotensive Rats in Basal and Stressful Conditions

## TL;DR

This study compares gene expression in the hypothalamus of hypertensive and normotensive rats to understand how serotonergic systems differ under normal and stressful conditions.

## Contribution

The study identifies 14 differentially expressed genes linked to serotonergic synaptic function in the hypothalamus of hypertensive and normotensive rats under stress.

## Key findings

- 14 differentially expressed genes were found to contribute to inter-strain differences in serotonergic synaptic function in the hypothalamus.
- Downregulation of Slc18a1, Cacna1s, and Htr3a genes in hypertensive rats affects presynaptic and postsynaptic serotonergic function.
- Restraint stress induces strain-specific and shared changes in gene expression related to serotonergic and other neurotransmitter systems.

## Abstract

The hypothalamus belongs to the central brain structure designed for the neuroendocrine regulation of many organismal functions, including the stress response, cardiovascular system, and blood pressure, and it is well known that the serotonergic hypothalamic system plays a significant role in these processes. Unfortunately, the genetic determination of serotonergic hypothalamic mechanisms has been little studied. The aim of this article is to describe the expression profile of the genes in the hypothalamic serotonergic synapses in hypertensive ISIAH rats in comparison with normotensive WAG rats in control conditions and under the influence of a single short-term restraint stress. It was found that 14 differentially expressed genes (DEGs) may provide the inter-strain differences in the serotonergic synaptic function in the hypothalamus between the hyper- and normotensive rats studied. In hypertensive rats, downregulation of Slc18a1 gene in the presynaptic serotoninergic ends and decreased expression of Cacna1s and Htr3a genes determining the postsynaptic membrane conductance may be considered as a main factors causing differences in the function of hypothalamic serotoninergic synapses in hypertensive ISIAH and normotensive WAG rats at the basal conditions. Under basal conditions, glial cell genes were not involved in the formation of inter-strain differences in serotonergic synaptic function. The analysis of transcriptional responses to restraint stress revealed key genes whose expression is involved in the regulation of serotonergic signaling, and a cascade of interrelated changes in biological processes and metabolic pathways. Stress-dependent changes in the expression of some DEGs are similar in the hypothalamus of hypertensive and normotensive rats, but the expression of a number of genes changes in a strain-specific manner. The results suggest that in hypothalamic glial cells of both strains, restraint stress induces changes in the expression of DEGs associated with the synthesis of Ip3 and its receptors. Many of the identified serotonergic DEGs participate in the regulation of not only serotonergic synapses but may also be involved in the regulation of cholinergic, GABAergic, glutamatergic, and dopaminergic synapses. The results of the study provide new information on the genetic mechanisms of inter-strain differences in the functioning of the hypothalamic serotonergic system in hypertensive ISIAH and normotensive WAG rats at rest and under the influence of a single short-term restraint (emotional) stress.