Neuroscience
-
Transcranial direct current stimulation (tDCS) in humans has been shown to affect the size of visual evoked potentials (VEPs) in a polarity-dependent way. VEPs have been widely employed in mice to study the visual system in physiological and pathological conditions and are extensively used as animal models of neurological and visual disorders. The present study was performed to evaluate whether mice VEPs could be modulated by tDCS in the same manner as in humans. ⋯ Compared with no stimulation condition, anodal tDCS increased P1 amplitude slightly more than 25%, while cathodal stimulation had opposite effects, with a decrease of P1 amplitude by about 30%. After-effects tended to reverse toward basal levels within 10 min after tDCS. These results, suggesting polarity-dependent modulation similar to what described in humans of tDCS effects on VEPs, encourage the use of mice models to study tDCS mechanisms of action and explore therapeutic applications on neurological models of disease.
-
Our recent data suggest that noradrenaline (NA) regulates expression of Per1 mRNA in rat C6 cells, as a model of brain astrocytes, by two distinct NA-mediating pathways. Although C6 cells possess potential astrocyte-type characteristics, we hypothesize that astrocytes located in a distinct tissue or organ play specific roles consistent with their own unique functions in response to the surrounding environment. We have herein found in primary rat spinal astrocytes using real-time RT-PCR that NA induced robust transient increases in Per1, Cry1, Cry2 and Bmal1 mRNA expression. ⋯ In addition, we found that NA induced phosphorylation of transcription-related proteins such as cAMP response element binding protein (CREB) and c-Jun. These phosphorylation processes were regulated through distinct pathways: CREB phosphorylation was dependent on the PKA and JNK pathways but c-Jun phosphorylation was mediated by the ERK and JNK pathways. These results suggest that Per1 plays a key role in noradrenergic regulation on clock gene expression in spinal astrocytes and activation of α1 and β2 adrenoceptors are of importance in regulation of Per1 mRNA expression via PKA/JNK-CREB and ERK/JNK-c-Jun cascades.
-
The purpose of the present study was to examine whether the rostroventral portion of the medulla oblongata (RVM) exerts descending modulation on the cardiosomatic motor reflex (CMR) in rats. Capsaicin (1 μg/ml, 0.2 ml) was injected into the pericardial sac as an algesic substance to induce the CMR, which was monitored via electromyogram (EMG) responses of dorsal spinotrapezius muscle to the noxious cardiac stimulus. Descending modulation of the CMR was observed by electrical or chemical stimulation of RVM. ⋯ In addition, glutamate receptor activation in RVM replicated the effects of electrical stimulation. Lidocaine interruption of the ventrolateral funiculus/ventral funiculus (VLF/VF) or transection of the dorsolateral funiculus (DLF) revealed that the descending facilitatory and inhibitory influences from RVM were conveyed via the VLF/VF and DLF, respectively. Furthermore, intrathecal administration of naloxone or yohimbine partly reversed the inhibitory effect of RVM electrical stimulation, suggesting that opioid and noradrenergic systems are involved in descending RVM modulation of the CMR.
-
Chronic widespread pain, such as observed in irritable bowel (IBS) and fibromyalgia (FMS) syndrome, are markedly affected by stress. While such forms of stress-induced hyperalgesia are generally considered manifestations of "central sensitization," recent studies in patients with IBS and FMS suggest an additional, peripheral contribution. ⋯ Stress also induced an increase in conduction velocity from 1.25 m/s to 2.09 m/s, and increased variability in neuronal activity. Given that these changes, each of at least moderate magnitude, would be expected to enhance nociceptor activity, it is likely that, taken together, they contribute to the enhanced nociception observed in this model of stress-induced chronic widespread pain.
-
The reconsolidation hypothesis proposes that a previously consolidated memory recalled by a reminder enters an unstable state (memory labilization) during which it is transiently sensitive to disruption. Although this process has been shown in very diverse species and types of memories, including human declarative memory, elucidating the role of this process is still an open challenge. The hypothesis that reconsolidation allows the incorporation of new information has recently been demonstrated in humans. ⋯ Conversely, robust memory performance was shown at testing when the CPS administration was concurrent with the retrieved-labile memory state. Results from the present study reveal that a naturalistic mild stressor can enhance reconsolidation, improving the long-term expression of this declarative memory. This finding might have significant implications for the comprehension of memory persistence and memory expression, and add new evidence in order to understand the adaptive meaning of the reconsolidation process.