Efeitos do anti-hipertensivo de ação central rilmenidina nas alterações funcionais e moleculares resultantes do ave hemorrágico experimental no córtex insular de roedores

Abstract

Hemorrhagic stroke (AVEh) involving the insular cortex (IC) is associated with cardiovascular dysfunctions and increased morbidity and mortality. However, the central neurobiological mechanisms linking AVEh in the IC to these complications remain incompletely understood. The present study aimed to investigate, in an integrated manner, the functional and molecular effects of AVEh in the IC of rodents and to evaluate the therapeutic potential of rilmenidine, a centrally acting antihypertensive agent. To this end, cardiovascular, autonomic, neurochemical, and molecular parameters were evaluated following insular AVEh. Additionally, an insular AVEh model was developed in C57BL/6J mice, as this strain is widely used in research and serves as the basis for the generation of multiple knockout and transgenic models. Results in rats demonstrated that AVEh in the IC induced sustained tachycardia and increased arterial pressure, without significant changes in morphometric or neurological parameters or survival. Circadian rhythmicity of body temperature was identified in all groups, and AVEh in the IC altered both mesor and acrophase. At the molecular level, AVEh in the IC induced upregulation of the genes GAD1, GAD2, and Slc32a1. In the RVLM, insular AVEh promoted downregulation of NMDA, AMPA, vGLUT, GABA-A, and GABA-B expression. Neurotransmitter quantification showed that AVEh reduced glutamate concentration without significantly altering GABA concentration in the IC. In the RVLM, insular AVEh increased GABA concentration, without significant changes in glutamate levels. In the heart, norepinephrine concentration was significantly higher in the insular AVEh group compared with controls, characterizing cardiac sympathetic hyperactivity, while the expression of β1 and β2 receptors did not differ between groups. Treatment with rilmenidine restored cardiovascular function and the mesor of circadian body temperature rhythmicity, reversed molecular alterations in the IC, and, in the RVLM, negatively modulated only GAD1 protein and positively modulated GABRA4. In the IC, the treated group showed increased glutamate concentration, although it remained different from controls, while GABA concentration was unchanged. In the RVLM, treatment normalized GABA concentrations to levels similar to controls, whereas glutamate concentrations remained unchanged. In addition, rilmenidine normalized cardiac norepinephrine concentrations. In C57BL/6J mice, AVEh in the IC induced tachycardia, increased cardiac norepinephrine, triggered a mild cardiac inflammatory process, and caused possible damage to the left kidney. Rilmenidine treatment prevented tachycardia and norepinephrine elevation, cardiac inflammation, morphometric alterations in the left kidney, and increased animal survival. Taken together, this study demonstrates that AVEh in the IC of rodents triggers a centrally mediated sympathetic autonomic dysfunction, with functional and molecular consequences. The standardization and characterization of an experimental AVEh model in the insular cortex of C57BL/6J mice were successfully and originally established, demonstrating that injury to this region is capable of inducing intense sympathetic hyperactivation. These findings reinforce rilmenidine as a cardioprotective agent capable of reversing this autonomic imbalance through modulation of central circuits. Moreover, the results consolidate the critical role of the IC in cardiovascular control and indicate that the experimental model used herein represents an important and promising tool for pathophysiological and pharmacological investigation of the mechanisms underlying AVEh-related cardiomyopathies.