Progress in brain research
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Converging evidence from both human and animal studies has highlighted the pervasive role of two neuropeptides, oxytocin (OXT) and arginine vasopressin (AVP), in mammalian social behaviours. Recent molecular genetic studies of the human arginine vasopressin 1a (AVPR1a) and oxytocin (OXTR) receptors have strengthened the evidence regarding the role of these two neuropeptides in a range of normal and pathological behaviours. Significant association between both AVPR1a repeat regions and OXTR single nucleotide polymorphisms (SNPs) with risk for autism has been provisionally shown which was mediated by socialization skills in our study. ⋯ Future studies should profitably focus on pharmacogenomic and genomic imaging strategies facilitated by the ease and efficacy of manipulating AVP-OXT neurotransmission by intranasal administration. Importantly, physiological measures, behavioural paradigms and brain activation can be informed by considering between-group and also within-group individual differences defined by common polymorphisms. Ultimately, investigators should strive to develop a cohesive model explaining how genomic variations are translated into individual and group differences in higher-order social behaviours.
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Based on electrophysiological, neurochemical and neuropharmacological approaches, it is currently accepted that serotonin (5-HT) and dopamine (DA) function to promote waking (W) and to inhibit slow wave sleep (SWS) and/or rapid-eye-movement sleep (REMS). Serotonergic neurons of the dorsal raphe nucleus (DRN) fire at a steady rate during W, decrease their firing during SWS and virtually cease activity during REMS. On the other hand, DA cells in the ventral tegmental area (VTA) and the substantia nigra pars compacta (SNc) do not change their mean firing rate across the sleep-wake cycle. ⋯ Thus, depending on the receptor subtype involved, 5-HT either facilitates or inhibits the functioning of DA cells. On the other hand, activation of DA D(2)-like receptors in the DRN increases the activity of 5-HT neurons. Thus, it can be speculated that local microinjection of DA and 5-HT ligands into the DRN and the VTA/SNc, respectively, would affect the actions of the corresponding neurons on sleep and W.
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Synaptic plasticity has often been argued to play an important role in learning and memory. The discovery of long-term potentiation (LTP) and long-term depression (LTD), the two most widely cited cellular models of synaptic plasticity, significantly spurred research in this field. ⋯ In this review, we discuss a number of recent advancements in the understanding of the mechanisms that mediate LTP and LTD in the rodent hippocampus and focus on the use of subunit-specific N-methyl-d-aspartate receptor antagonists and interference peptides as potential tools to study the role of synaptic plasticity in learning and memory. By using the modulation of synaptic plasticity and hippocampal-dependent learning and memory by acute stress as an example, we review a large body of convincing evidence indicating that alterations in synaptic plasticity underlie the changes in learning and memory produced by acute stress.
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Post-traumatic stress disorder (PTSD) is a well-recognized complication of severe illness. PTSD has been described in patients after multiple trauma, burns, or myocardial infarction with a particularly high incidence in survivors of acute pulmonary failure (Acute Respiratory Distress Syndrome) or septic shock. Many patients with evidence of PTSD after critical illness have been treated in intensive care units (ICUs). ⋯ This can possibly be explained by a cortisol-induced temporary impairment in traumatic memory retrieval that has previously been demonstrated in both rats and humans. ICU therapy of critically ill patients can serve as a stress model that allows the delineation of stress hormone effects on traumatic memory and PTSD development. This could also result in new approaches for prophylaxis and treatment of stress-related disorders.
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The neuropeptides arginine vasopressin (AVP) and oxytocin (OXT) are acknowledged as important modulators of diverse social behaviours. Here we discuss recent studies using intracerebral microdialysis to investigate the dynamics of AVP and OXT release patterns within distinct brain regions during the display of social behaviours in rats. Manipulation of local receptor-mediated actions of AVP and OXT via retrodialysis of either agonists or antagonists revealed the behavioural significance of changes in local neuropeptide release. ⋯ Interestingly, OXT released within the PVN during sexual activity in male rats was found to be associated with a robust decrease in anxiety-related behaviour up to 4h after mating. These data illustrate distinct modes of behavioural actions of AVP and OXT, reaching from acute regulation of the respective social behaviour to the long-term modulation of related behaviours including anxiety and social cognition. In conclusion, measuring the in vivo release patterns of AVP and OXT within distinct brain regions during the display of diverse social behaviours and manipulation of local AVP and OXT activity has yielded new insights into the specific roles of these neuropeptides in the regulation of complex social behaviours.