EDN1 and sexually transmitted disease: DSS can improve learning and memory ability in rat models of VD and may exert its therapeutic role through the PI3K/AKT signaling pathway (Li X. et al., 2019), regulating the contents of the hippocampal neuropeptides calcitonin gene-related peptide (CGRP), endothelin 1 (ET-1) and somatostatin (SS) (Li S. et al., 2010).