Ketamine holds promise for the treatment of post-traumatic stress disorder (PTSD), but challenges remain in delivery and sustained effects. This controlled study evaluates a novel intranasal formulation, employing AmyloLipid nanovesicles (ALN) to enhance ketamine's therapeutic efficacy in a predator-scent stress (PSS) rat model of PTSD. A total of 130 rats underwent PSS or sham-PSS exposure, followed by intranasal administration of ketamine-ALN (4.8, 2.4, 1.2 and 0.6 mg/kg), unloaded-ALN, saline, or standard ketamine three times weekly for two weeks, starting seven days post-trauma. Behavioral assessments, including the elevated plus maze, acoustic startle response, and contextual freezing tests, were complemented by immunohistochemical and Golgi-Cox analyses of hippocampal and paraventricular nucleus (PVN) tissues. Low-dose ketamine-ALN (0.6 mg/kg) significantly reduced anxiety-like behaviors, hyperarousal, and the prevalence of PTSD-like responses (extreme behavior responses) by 45% compared to unloaded-ALN controls. Unlike standard ketamine, ALN-mediated delivery bypassed the blood-brain barrier, enhancing bioavailability and sustaining therapeutic benefit. Mechanistically, ketamine-ALN normalized the expression of hyperpolarization-activated cyclic nucleotide-gated (HCN1) channels-which were upregulated in the CA1 stratum lacunosum-moleculare (SLM) post-PSS-thereby stabilizing neuronal excitability. This normalization of HCN1, critical for regulating neuronal excitability and membrane potential, was accompanied by increased levels of brain-derived neurotrophic factor (BDNF) and neuropeptide Y (NPY), enhancing neuroplasticity and dendritic complexity. These findings demonstrate that ALN-based intranasal delivery of ketamine is more effective than standard administration, particularly at low doses. The results suggest that low-dose ketamine-ALN modulates a hippocampal circuit involving HCN1, BDNF, and NPY to foster adaptive stress responses. Collectively, ketamine-ALN represents a promising targeted therapy for PTSD, with HCN1 channels as a key mediator of stress-induced neuronal dysfunction and ketamine's therapeutic action, thus advancing the prospects for precision treatment of stress-related disorders.
