Proteome changes in rat hippocampus and pre-frontal/frontal cortex in Flinders rats after Nortriptyline treatment.

Although most available antidepressants increase monoaminergic neurotransmitter concentration in synapses, their therapeutic efficacy is likely mediated by longer-term molecular adaptations. GENDEP is an Integrated Project combining large-scale pharmacogenomic studies on depressed patients with preclinical investigations on animal models of disease, focussing on treatment with proserotonergic and pronoradrenergic antidepressants. Within GENDEP, in order to gain a better understanding of the molecular changes induced by chronic antidepressant treatment we have analysed proteomic changes in rat brain regions after pronoradrenergic drug administration. A wide-scale analysis of protein expression was performed by 2D-electrophoresis on the Flinders Sensitive Line (FSL), a genetically selected rat model of depression that displays good face, predictive and construct validity. As controls, the Flinders Resistant Line (FRL) rats which do not show the depressive-like behaviour were analysed. Both FSL and FRL animals were split into groups receiving nortriptyline (NOR) admixed to food (25 mg/kg/day) or vehicle for 31 days. Proteins from pre-frontal/frontal cortex (PC) and hippocampus (HP) were separated by 2-D electrophoresis. Protein level comparisons were performed between groups sharing the same genetic background and receiving either vehicle or NOR in order to detect changes with both univariate (Student’s t test) and multivariate (Partial Least Squares) statistical analysis methods. Significantly different proteins were identified using peptide fingerprinting mass spectrometry. NOR treatment in HP regulated 34 and 33 protein spots in FSL and FRL groups, respectively. In PC samples, 72 and 101 protein spots were modulated in FSL and FRL groups respectively. The results showed that besides some overlaps, several proteins were differently modulated by NOR treatment in the different genetic backgrounds. Proteins modulated by NOR treatment in FRL rats exert their function in cytoskeleton assembly and remodelling, such as actin and tubulin, modified in both regions; dynamin and profilin, changed in HP. Additionally, proteins involved in metabolism and biosynthesis were modulated, such as glutamine synthase in both regions and fructose bisphosphate aldolase-A in PC and malate dehydogenase in HP. Proteins involved in transport and vesicle trafficking, such as alpha-synuclein and fatty-acid-binding protein in PC and synapsin-2 in HP were also changed after NOR treatment. Moreover, proteins playing a role in neurogenesis and neuronal differentiation were modified, e.g. prohibitin and alpha-internexin in HP, phosphatidylethanolamine binding protein-1 and microtubule-associated protein RP/EB family member-3 in PC. Proteins modulated by NOR treatment in FSL rats exert their function in neurogenesis/neuronal differentiation (e.g. drebrin in HP, phosphatidylethanolamine-binding protein-1 and gamma-enolase in PC); in cell survival (glyceraldehyde- 3-phosphate dehydrogenase in both regions, C-crk in HP and prohibitin in PC); in cytoskeleton assembly and remodelling, such as actin and tubulin, altered in both regions; dynamin and cofilin, modulated in HP. Moreover, proteins playing a role in cell division, such as septin and NSFL1-cofactor-p47 were altered by NOR exposure in HP and in PC, respectively. Other influenced cellular functions were transport and secretion (e.g. alphasynuclein, apolipoprotein-E in PC and vacuolar-ATP-synthase in PC); metabolism and biosynthesis, such as phosphoglycerate kinase in PC and transketolase in HP. These findings suggest new molecular correlates of vulnerability to depression and of response to antidepressant treatment.