DAUN02-INDUCED VENTRAL HIPPOCAMPAL INACTIVATION DOES NOT AFFECT CARDIOVASCULAR OR AUTONOMIC RESPONSES TO ACUTE STRESS BUT MODULATES ADAPTATIONS TO CHRONIC RESTRAINT STRESS IN C-FOS–LACZ RATS

Stress induces autonomic and thermoregulatory alterations mediated by brain structures such as the ventral hippocampus (vHip). This study investigated the role of vHip in cardiovascular and thermal responses to acute (ARS; 1 day/2h) or chronic restraint stress (CRS; 21 days/2h). Using c-Fos–lacZ transgenic rats, previously activated neurons were selectively inactivated by microinjection of Daun02 (ARS n= 6; CRS n=5) into the vHip. The study was approved by the Ethics Committee on Animal Use (CEUA) of FCFAr–UNESP (#02/2021). Changes in mean arterial pressure (ΔMAP), heart rate (ΔHR), and tail skin temperature (ΔT°C) were analyzed. During ARS, inactivation of vHip neurons did not alter physiological responses; only a main effect of time was observed for ΔMAP, ΔHR, and ΔT°C, with no differences between groups. In contrast, during CRS, neuronal inactivation resulted in increased ΔMAP and reduced ΔT°C, indicating a specific modulatory role of these neurons following prolonged stress exposure. ΔHR did not differ significantly between groups. Area under the curve (AUC) analysis in vehicle-treated animals (ARS n= 5; CRS n=6) showed that ARS elicited greater ΔMAP and ΔHR responses and a more pronounced decrease in ΔT°C compared to CRS, indicating physiological adaptation to repeated stress exposure. These findings demonstrate that neurons activated in the vHip are essential for cardiovascular and thermoregulatory modulation during chronic, but not acute restraint stress, highlighting the functional plasticity of this region in response to stress chronicity.
Funding: The State of São Paulo Research Foundation (FAPESP #2018/04899-1; 2021/00148-4; 2021/04572-5; 2021/06709-8; 2023/00306-4; 2023/15852-4).