Objective To explore the effects of chronic sleep deprivation (CSD) on the ultrastructure and downstream signaling pathway of dopamine D₁ receptor of the hippocampus in rats. Methods Thirty-five male SD rats were selected in this experiment, of which 11 with the lightest weight, shortest weight-bearing swimming time or no finding the platform within 90 s in Morris water maze experiment were excluded. The other 24 rats were randomly divided into tank control (TC) group, CSD group and CSD+dopamine D₁ receptor agonist SKF38393 (SKF) group. The CSD rat model was established by modified multi-platform water environment, and then the rats in the SKF group were intraperitoneally injected with SKF38393 (1 mg/kg) at 15-21 d of CSD. At 21 d after CSD, the ultrastructure of hippocampus was observed by transmission electron microscopy, and the expression of key factors in dopamine D₁ receptor-related signal pathway in the hippocampus was detected by Western blotting and qPCR. Results The mitochondrial swelling, degeneration and destruction of membrane structure of the hippocampus neurons induced by CSD were improved by SKF38393. Compared with the TC group, the mRNA expression levels of adenylate cyclase 5 (Adcy5), protein kinase cAMP-dependent catalytic α (Prkacα), dopamine and cAMP-regulated phosphoprotein (Darpp32), Ras-related protein (Rap) 1a, extracellular signal regulated kinase 1 and 2 (ERK1/2), phospholipase C β1 (PLCβ1), calcium/calmodulin-dependent protein kinase Ⅱa and Ⅳ (CaMKⅡa, CaMKⅣ) in the CSD group were significantly decreased (P<0.05), and the protein levels of total and phosphorylatied protein kinase A catalyzes subunit α (PKAcα), phosphorylated ERK1/2, phosphorylated PLCβ1, and phosphorylated CaMKⅣ were significantly decreased (P<0.05). Compared with the CSD group, the mRNA expressions of Prkacα, Darpp32, Rap1a, Rap1b, ERK1 and CaMKⅣ in the SKF group were significantly increased (P<0.05), and the protein levels of total and phosphorylated PKAcα and phosphorylated CaMKⅣ were significantly increased (P<0.05), while the expression of PLCβ1 and total CaMKⅣ was similar in the two groups. Conclusion CSD damages the ultrastructure of the hippocampus neurons in rats, which can be effectively improved by dopamine D₁ receptor agonist SKF38393, and the protective mechanism may be related to the PKA pathway and phosphoinositol pathway.