Effect of amitriptyline treatment on neurofilament-H protein in an experimental model of depression

It has been proposed that depression is associated with dysfunction of hippocampal plasticity. Novel hypotheses suggest that antidepressants induce neuronal structural plasticity, although the underly- ing mechanisms still remain unclear. Therefore, the aim of this study was to investigate the effects of amitriptyline on levels of phosphorylated heavy neurofilament subunit (NF-H) in the hippocampus of mice exposed to acute and chronic behavioral despair paradigms. Immunoblotting experiments showed that animals exposed to the tail suspension test (TST) displayed diminished levels of pNF-H 24 h after testing. Repeated administration of amitriptyline (10 mg/kg i.p.) prevented this decreased hippocampal phosphorylation of NF-H. Conversely, administration of citalopram (10 mg/kg i.p.) left unchanged pNF-H levels. The expression of pNF-H was also analyzed by immunofluorescence in mice exposed to the unpre- dictable chronic mild stress paradigm (UCMS), an experimental model of depression. Mice that developed a depressive-like behavior showed a decreased pNF-H immunostaining selectively in the hippocampal CA3 region. Chronic administration of amitriptyline reversed the despaired behavior induced by expo- sure to UCMS paradigm and, fully recovered pNF-H labeling to control values. Our results indicate that the cytoskeletal remodeling induced by amitriptyline in the hippocampal CA3 region might underpin its behavioral efficacy. Hippocampal alterations of the NF appeared associated with the mechanism of this antidepressant drug and may contribute to its psychotherapeutic actions.