<p>Objective(s): This study aimed to investigate the potential effects of different doses of Lavenderangustifolia essential oil (Lavender EO) administered by inhalation on sleep latency andneuromodulators regulating the sleep/wake cycle in rats with total sleep deprivation (TSD).Materials and Methods: Forty-eight male Sprague-Dawley rats were divided into five groups: Control,Alprazolam (ALP, 0.25 mg/kg given intraperitoneally), L1 (Lavender EO, 0.3 ml given by inhalation),L2 (Lavender EO, 0.5 ml given by inhalation), and L3 (Lavender EO, 1 ml given by inhalation); TSDwas applied to all groups. Rats in SD groups were kept on a platform surrounded by water for 18 hrfor 20 days, and for the remaining time, the animals were exposed to Lavender EO for 1 hr (11:00–12:00) and then were kept in their home cage for 5 hr (12:00-17:00). Their brain and brainstem wereremoved for histopathological and immunohistochemical analyses (c-Fos, ChAT, GAD, and ADRB2expression) in the locus coeruleus (LC), basal forebrain (BF), and preoptic area (PO).Results: The groups ranked by the severity of edema, hyperemia, and neurodegeneration in LC, BF,and PO areas were control, L3, L1, L2, and ALP. c-Fos expression significantly decreased in all brainregions in all groups except the L1 group. ChAT and GAD expressions increased dramatically in allbrain regions. ADRB2 significantly increased in LC in ALP and L2 groups; in the PO area in ALP, L1,and L2 groups; and in BF in all groups.Conclusion: Lavender EO treatment ameliorated c-Fos, ChAT, GAD, and ADRB2 expression, similarto the effect of ALP.</p>