Guanfacine and HCN channels: bridging neuroinflammation and prefrontal cortex function in autism spectrum disorder.

Background: Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by social communication differences and restricted, repetitive behaviors. Convergent evidence implicates prefrontal cortex (PFC) circuit dysregulation and chronic neuroimmune activation in ASD. Despite increasing off-label use of guanfacine in children and adolescents with autism, its molecular and immunological rationale remains incompletely synthesized. Objective: To synthesize current evidence regarding the molecular, neurophysiological, and immunological mechanisms through which guanfacine may influence ASD-related neural and immune dysfunction. Methods: In this narrative review, we integrated evidence from pharmacology, systems neuroscience, immunology, and clinical studies to examine two converging mechanisms by which guanfacine may act in ASD and related conditions. Results: Guanfacine suppresses cAMP signaling through α2A-adrenoceptor activation, producing dual neuronal and immune effects. In PFC pyramidal neurons, reduced cAMP signaling promotes closure of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, strengthening network firing that supports working memory, attention, and emotion regulation. In parallel, activation of α2A-adrenoceptors on microglia and macrophages reduces production of pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, and interleukin-6, while promoting anti-inflammatory phenotypes through nuclear factor kappa B suppression and peroxisome proliferator-activated receptor gamma activation. Evidence from human studies and ASD models indicates that α2A-adrenoceptor signaling, HCN channel function, and microglial reactivity are altered in autism and converge on synaptic refinement, dendritic spine stability, and PFC-dependent behavior. We further review clinical evidence for guanfacine in individuals with autism and in related conditions, including attention-deficit/hyperactivity disorder, post-traumatic stress disorder, traumatic brain injury, post-COVID cognitive impairment, delirium, and age-related cognitive decline. Conclusion: Collectively, the available evidence supports a mechanistic framework linking guanfacine, HCN channel modulation, and neuroimmune regulation, thereby bridging neuroinflammation and PFC function in ASD. The broader α2A-HCN-microglia axis may represent a promising therapeutic target for PFC- and neuroimmune-related features of ASD; however, adequately powered autism-specific randomized trials and biomarker-informed stratification strategies are needed to establish clinical efficacy and validate this framework.