Neuroscience
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Perineuronal net (PNN) is a specialized aggregate of the extracellular matrix, which is considered to be involved in regulation of structural plasticity of neuronal circuits. Here we examined the spatial and temporal differences in Wisteria floribunda agglutinin-labeled PNN intensity in single cells in the mouse hippocampus, where the neuronal circuits engaged in cognition and emotion are embedded in the dorsal and ventral parts, respectively. In young mice, the intensity of PNN was very low, and there were no significant dorsoventral differences in all hippocampal regions. ⋯ Contrary to expectations, developmental and aging-related changes in PV intensity were not comparable to those seen in PNN intensity. The correlation coefficients between PNN and PV intensities in single cells showed gradual decline during development and aging in the CA1 and CA3 regions, while there were little correlations in the dentate gyrus regardless of age. In summary, PNNs are differentially expressed in the dorsal and ventral hippocampal circuits during development and aging, indicating their possible role for cognition and emotion control.
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Reconsolidation refers to the destabilization/re-stabilization process upon memory reactivation. However, the parameters needed to induce reconsolidation remain unclear. Here we evaluated the capacity of memory retrieval to induce reconsolidation of object recognition memory in rats. ⋯ We observed that ani impaired reconsolidation in the absence of retrieval. Therefore, stored memory underwent reconsolidation even though it was not recalled. These results indicate that retrieval and reconsolidation of object recognition memory are independent processes.
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The neurobiological mechanisms of spinal cord stimulation (SCS) when applied for neuropathic pain are still incompletely known. Previous research indicates that brainstem circuitry is pivotal for the SCS effect. The present study aims at exploring the possible contribution to the SCS effects of the pain controlling system emanating from the locus coeruleus (LC) in the brain stem. ⋯ No differences were found between these groups. In awake animals, lidocaine silencing of the ipsilateral LC or blocking of spinal noradrenergic system by intrathecal administration of α1,2 adrenoceptor antagonists failed to influence the antihypersensitivity effect of SCS. The present results indicate that the SCS-induced control of hypersensitivity in an experimental animal model of peripheral neuropathic pain may not be explained by the activation of direct spinal projections of noradrenergic LC neurons, while supraspinal projections of LC neurons still may play a role in the SCS effect.
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In rodents as well as in many other mammalian and non-mammalian species, the arginine-vasopressin (AVP) system includes a parvocellular sexually dimorphic portion located within the bed nucleus of the stria terminalis (BST), the medial amygdaloid nucleus (MeA) and the lateral septum. In this system, males have more cells and denser projections than females, neurons show androgen and estrogen receptors, and gonadal hormones are required for the activation. However, the role of these hormones for the differentiation of the system is not clear. ⋯ To elucidate the role of androgens on differentiation and functioning of AVP parvocellular system, we compared male and female rats with a non-functional mutation of androgen receptor (Tfm, testicular feminization mutation) to their control littermates. Our data show that the lack of a functional androgen receptor significantly decreases the expression of AVP immunoreactivity within the BST and MeA of male Tfm. Thus supporting the hypothesis that androgens, through the action of their receptor, should have a relevant role in the organization and modulation of the AVP parvocellular sexually dimorphic system.
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Strychnine-sensitive glycine receptors are activated by glycine and facilitate chloride influx into neurons. Glycinergic transmission might be either mediated by synaptic or extrasynaptic glycine receptors. While phasic neurotransmission is provided by a synaptic pathway, activation of extrasynaptic glycine receptors induces tonic inhibition. The glycine transporter 2 (GlyT2) regulates the uptake of glycine into presynaptic boutons. It is not determined yet, whether inhibition of GlyT2 by ALX 1393 can produce inhibition of spinal motoric networks and, whether phasic or tonic glycinergic inhibition is mostly enhanced. ⋯ GlyT2 inhibition induced glycinergic tonic currents, which might be the underlying mechanism for the observed suppression of spontaneous action potential activity by ALX 1393 in the spinal ventral horn. Silencing neuronal action potential activity by blocking GlyT2 might be a novel principle to inhibit locomotor circuits in the ventral horn area and to induce muscle relaxation.