Study of Histomorphometric Parameters of the Microcirculatory Bed of the Rats Myocardium Under Conditions of Long-Term Experimental Exposure to Canabidiol Oil

Introduction. Cannabidiol (CBD), a non-psychoactive phytocannabinoid of Cannabis Sativa, demonstrates significant potential as a therapeutic agent for the treatment of cardiovascular pathology. Objective. To determine the histological and histomorphometric changes in the myocardial microcirculatory bed of white rats after 8- and 10-weeks oral administration of 10% CBD oil and to characterize the endothelial component of remodeling using the immunohistochemical marker CD31 (PECAM-1). Materials and Methods. The study was conducted on 52 sexually mature male non-linebred white rats, aged 5–7 months and weighing 180–230 g at the start of the experiment. The animals were divided into two series of 26 rats each, depending on the duration of CBD oil administration. Each series consisted of 3 groups: Group 1 (experimental) - 14 rats each, which received a 10% CBD oil solution (dose: 10 mg/kg/day) orally via dropper once daily for 8 and 10 weeks; Group 2 (control) – 6 rats each, which received a CBD carrier solvent (hemp seed oil) orally via drip once daily for 8 and 10 weeks; the dose was 0.1 ml/kg/day (low dose); Group 3 (intact) – 6 sexually mature male white rats. The study focused on the microvasculature of the myocardium. Morphometry of the rats’ cardiac microvessels, specifically their diameters and wall thicknesses, was performed using Aperio ImageScope v12.3.3 software (Leica Biosystems, Wetzlar, Germany). In all comparisons, a difference was considered statistically significant at a minimum significance level of p < 0.05. Results. It has been established that 8- and 10-week experimental oral administration of 10% CBD oil (10 mg/kg/day) leads to structural and morphometric remodeling of the myocardial microcirculatory bed, manifested by changes in the resistive and metabolic components. The results of the morphometric study of arterioles (increased internal diameter and decreased wall thickness) indicate a predominance of the vasodilatory-adaptive type of remodeling and represent a compensatory pattern of changes. The capillary bed is characterized by increased density and an enlarged capillary diameter, along with histological signs of hyperemia and perivascular edema, reflecting micro-hemodynamic remodeling. Immunohistochemical analysis using CD31 to visualize the vascular bed confirms the endothelial component and allows for a qualitative assessment of capillary network density and the intensity of endothelial positivity as markers of microvascular adaptation and reactivity. Conclusions. The results of the study showed that 8- and 10-week administration of CBD oil causes dilation of myocardial arterioles and a reduction in vascular wall thickness. A moderate increase in capillary density was observed. The morphological changes are predominantly adaptive in nature, with initial signs of an endothelial response.