Recent studies have suggested antidepressant involvement in synaptic plasticity, possibly mediated by neurotrophins and neuropeptides. Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide and neuromodulator. Since its discovery, PACAP has been extensively investigated with regard to its neurotrophic properties including regulation of brain-derived neurotrophic factor (BDNF) expression, a neurotrophin postulated to be involved in the mechanism of antidepressant action and etiology of affective disorders. Using real-time polymerase chain reaction (PCR) technique, we demonstrate in this paper a robust upregulation of BDNF messenger RNA (mRNA) expression in rat primary cortical neurons following a 6-hour incubation with PACAP, and subsequently elevated BDNF expression after prolonged treatment. Additional experiments were conducted to evaluate the effects of antidepressants on the expression of PACAP, its receptors and BDNF. In rat hippocampal neurons, prolonged (72-hour) treatment with selective serotonin reuptake inhibitors paroxetine and citalopram significantly up-regulated BDNF and PACAP expression and down-regulated PACAP receptor (PAC1 and VPAC2) expression; the tricyclic antidepressant imipramine had an opposite effect. These alterations in BDNF expression correlated negatively with PAC1 and VPAC2 expression, and positively with PACAP mRNA levels. Thus, our findings suggest the possible involvement of PACAP signaling in the neuronal plasticity induced by antidepressant treatment.

The serine/threonine kinase AKT/PKB plays a fundamental role in a wide variety of neuronal functions, including neuronal cell development, axonal growth, and synaptic plasticity. Multiple evidence link AKT signaling pathways to regulation of late phase long-term synaptic plasticity, synaptogenesis, and spinogenesis, as well as long-term memory formation. Nevertheless, the downstream effectors mediating the effects of AKT on early phase long-term potentiation (eLTP) are currently unknown. Here we report that using different regimes of pharmacological activation and inhibition of AKT activity in acute hippocampal slices, we found that AKT regulates the post-synaptic expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA) receptors affecting solely the expression of eLTP, with no effect on its induction and maintenance. We further show that both maintenance of basal synaptic activity and expression of eLTP require plasma membrane tethering by activated AKT and that basal synaptic activity may be regulated via the direct effects of AKT1 on the expression level of post-synaptic AMPA receptors bypassing the canonical AKT signaling. Finally, we establish that eLTP expression requires the involvement of both the canonical AKT signaling pathways and the direct effect of AKT1 on AMPA receptor activity/expression in the post-synaptic membrane. © 2016 Wiley Periodicals, Inc.

Spatial memory depends on the hippocampus, which is particularly vulnerable to aging. This vulnerability has implications for the impairment of navigation capacities in older people, who may show a marked drop in performance of spatial tasks with advancing age. Contemporary understanding of long-term memory formation relies on molecular mechanisms underlying long-term synaptic plasticity. With memory acquisition, activity-dependent changes occurring in synapses initiate multiple signal transduction pathways enhancing protein turnover. This enhancement facilitates de novo synthesis of plasticity related proteins, crucial factors for establishing persistent long-term synaptic plasticity and forming memory engrams. Extensive studies have been performed to elucidate molecular mechanisms of memory traces formation; however, the identity of plasticity related proteins is still evasive. In this study, we investigated protein turnover in mouse hippocampus during long-term spatial memory formation using the reference memory version of radial arm maze (RAM) paradigm. We identified 1592 proteins, which exhibited a complex picture of expression changes during spatial memory formation. Variable linear decomposition reduced significantly data dimensionality and enriched three principal factors responsible for variance of memory-related protein levels at (1) the initial phase of memory acquisition (165 proteins), (2) during the steep learning improvement (148 proteins), and (3) the final phase of the learning curve (123 proteins). Gene ontology and signaling pathways analysis revealed a clear correlation between memory improvement and learning phasecurbed expression profiles of proteins belonging to specific functional categories. We found differential enrichment of (1) Long-term synaptic plasticity is considered a cellular correlate of long-term memory (LTM) 1 . Contemporary understanding of memory formation is based on the initiation and maintenance of long-term synaptic plasticity (1-4), for which de novo protein synthesis is a vital requirement. De novo protein synthesis itself is secondary to activity-dependent changes in synapses that occur during learning processes. These activity changes trigger post-translational modifications of proteins initiating and sustaining multiple signal transduction pathways. In turn, these signaling pathways regulate changes in synaptic strength and connectivity by governing gene expression and protein translation (5-13). Depending on time elapsed since triggering of long-term synaptic plasticity, protein synthesis may be limited to the dendrites directly involved in the plasticity processes (14 -18). Multiple synaptic From the ‡Department

Recently, a consanguineous family was identified in Israel with three children affected by Infantile Nystagmus and Foveal Hypoplasia, following an autosomal recessive mode of inheritance. A homozygous stop mutation c.1861C > T; p.Q621 * in the aryl hydrocarbon receptor (AHR) gene (AHR; MIM 600253) was identified that cosegregated with the disease in the larger family. AHR is the first gene to be identified causing an autosomal recessive Infantile Nystagmus-related disease in humans. The goal of this study is to delineate the molecular basis of this newly discovered human genetic disorder associated with a rare AHR gene mutation. The gene and protein expression levels of AHR and selected AHR targets from leukocyte cultures of healthy subjects and the patients were analyzed. We observed significant variation between mRNA and protein expression of CYP1A1, CYP1B1, and TiPARP under rest and AHRinduced conditions. The CYP1A1 enzymatic activity in induced leukocytes also differs significantly between the patients and healthy volunteers. Intriguingly, the heterozygous subjects demonstrate CYP1A1 and TiPARP gene and protein expression similar to homozygous patients. In contrast, CYP1B1 inducibility and expression vary between hetero-and homozygous subjects. Similarity and differences in gene and protein expression between heterozygotes and homozygous patients can give us a hint as to which metabolic pathway/s might be involved in the Nystagmus etiology. Thus, we have a unique human model for AHR deficiency that will allow us the opportunity to study the biochemical basis of this rare human mutation, as well as the involvement of AHR in other physiological processes.