Vigilant Attention, Cerebral Blood Flow and Grey Matter Volume Change after 36 h of Acute Sleep Deprivation in Healthy Male Adults: A Pilot Study.

It is commonly believed that alertness and attention decrease after sleep deprivation (SD). However, there are not enough studies on the changes in psychomotor vigilance testing (PVT) during SD and the corresponding changes in brain function and brain structure after SD. Therefore, we recruited 30 healthy adult men to perform a 36 h acute SD experiment, including the measurement of five indicators of PVT every 2 h, and analysis of cerebral blood flow (CBF) and grey matter volume (GMV) changes, before and after SD by magnetic resonance imaging (MRI). The PVT measurement found that the mean reaction time (RT), fastest 10% RT, minor lapses, and false starts all increased progressively within 20 h of SD, except for major lapses. Subsequently, all indexes showed a significant lengthening or increasing trend, and the peak value was in the range of 24 h-32 h and decreased at 36 h, in which the number of major lapses returned to normal. MRI showed that CBF decreased in the left orbital part of the superior frontal gyrus, the left of the rolandic operculum, the left triangular part, and the right opercular part of the inferior frontal gyrus, and CBF increased in the left lingual gyrus and the right superior gyrus after 36 h SD. The left lingual gyrus was negatively correlated with the major lapses, and both the inferior frontal gyrus and the superior frontal gyrus were positively correlated with the false starts. Still, there was no significant change in GMV. Therefore, we believe that 36 h of acute SD causes alterations in brain function and reduces alert attention, whereas short-term acute SD does not cause changes in brain structure.

Disrupted Small-world Networks are Associated with Decreased Vigilant Attention after Total Sleep Deprivation.

Sleep deprivation critically affects vigilant attention. Previous neuroimaging studies have revealed altered inter-regional functional connectivity after sleep deprivation, which may disrupt topological properties of brain functional networks. However, little is known about alterations in the topology of intrinsic connectivity and its involvement in attention performance after sleep deprivation. In the current study, we investigated the topological properties of brain networks derived from resting-state functional magnetic resonance imaging of 26 healthy men in rested wakefulness (RW) state and after 36 h of total sleep deprivation (TSD). In the predefined sparsity threshold range, both global and nodal network properties were evaluated based on graph theory analysis. Vigilant attention was assessed using the psychomotor vigilance test (PVT) before and after TSD. Furthermore, Pearson's correlation analyses were conducted to explore the association between altered network properties and changed PVT performance after TSD. At the global level, the brain functional networks in the TSD state showed a significantly lower small-world coefficient than RW, with decreased global efficiency. At the nodal level, the altered regions were selectively distributed in frontoparietal networks, sensorimotor networks, temporal regions, and salience networks. More specifically, the altered clustering coefficient in the posterior superior temporal sulcus (pSTS) and insula, and altered local efficiency in pSTS were further associated with PVT performance after TSD. Our results suggest that the topological properties of brain functional networks are disrupted, and aberrant topology of temporal networks and salience networks may act as neural signatures underlying the vigilant attention impairments after TSD.

Gabapentin regulates dopaminergic neuron firing and theta oscillation in the ventral tegmental area to reverse depression-like behavior in chronic neuropathic pain state.

PURPOSE: Ventral tegmental area (VTA) dopamine system plays an important role in depression and is also involved in pain experience. In this study, we investigated the VTA dopaminergic (DA) neuron firing and local field potential (LFP) in pain-related depression, and we try to explore the underlying relationship between pain and depression. MATERIALS AND METHODS: We used neuropathic pain model [spare nerve injury (SNI)] to induce pain-related depression. The Dixon up-down method was used to test mechanical hypersensitivity. Behavioral changes like open field test, sucrose preference test, and forced swim test were used to test depression-like behaviors. Gabapentin (GBP) was used to explore the chronic analgesic treatment that could reverse pain-related depression. To investigate the in vivo variations of VTA DA neuron firing and LFP, multichannel acquisition processor system was used. RESULTS: We used SNI to induce depression-like behaviors. Repeated GBP treatment reversed these behaviors after 14 days of injection. An in vivo electrophysiological analysis of the firing characteristics of VTA DA neurons and LFP revealed that SNI increased the firing rate of DA neurons, but not the burst firing activity. Surprisingly, chronic GBP reversed the firing rate of DA neurons and reduced the burst firing activity. Moreover, SNI increased the LFP power in delta and theta oscillation and decreased it in beta oscillation. Repeated administration of GBP significantly suppressed theta oscillation. Above all, chronic GBP altered these characteristics to reverse depression-like behaviors. CONCLUSION: The present study confirmed that the tonic firing activity of VTA DA neurons, but not the burst firing activity, was the key factor in peripheral neuropathy-induced depression. Chronic GBP regulated the firing pattern of DA neurons and decreased theta oscillation in VTA to treat pain-related depression. This variation tendency of electrophysiological characteristics of VTA DA neurons and theta oscillation in VTA might represent an attempt to cope with pain-related negative mood disorder.

[Effects of HCN2 in the development of peripheral neuropathic pain in rats].

OBJECTIVE: To explore the effects of hyperpolarization-activated cyclic nucleotide-gated channels 2(HCN2) in the formation of peripheral neuropathic pain in rats. METHODS: Twenty-four healthy adult rats were divided into two groups randomly(n=12):the sham group rats were only isolated the left L4, L5 spinal nerve, the spinal nerve ligation(SNL) group was separated the spinal nerve and performed the corresponding ligation. The behavioral experiments were tested 7 days after operation; The model rats were randomly divided into 3 groups(n=6):① negative group(Saline), intra-plantar injection of saline in left hindpaws; ② positive group(gabapentin, GBPT), intraperitoneal injection of gabapentin; ③ experimental group(ZD7288), intra-plantar injection of ZD7288 in left hindpaws. The behavioral experiments were tested before injection and 1 h, 4 h, 24 h and 48 h after injection; Obtaining the dorsal root ganglion(DRG) of the control group (before operation), sham group and the SNL group(n=6), using qPCR and Western blot to analyze the mRNA and protein of HCN2 in rats' DRG. RESULTS: The rat model of neuropathic pain was successfully established. Compared with saline group, GBPT group and ZD7288 group could significantly reduce the symptoms of neuropathic pain in rats after injection 1 h (P<0.01), and there was no difference between GBPT group and ZD7288 group. Compared with control group and sham group, the expression of HCN2 mRNA in SNL group's DRG was significantly increased (P<0.01), and the expression of HCN2 channel protein was also increased significantly (P<0.05). CONCLUSIONS: HCN2 is involved in the development of peripheral neuropathic pain and is likely to be a potential new target for the treatment of neuropathic pain.

[The impact of electrophysiology of central dopaminergic neurons and the depression-state induced by chronic neuropathic pain].

OBJECTIVE: To explore the underlying electrophysiological mechanism of depression induced by chronic pain in dopaminergic neurons in midbrain ventral tegmental area (VTA) of rats. METHODS: Twenty-four healthy adult rats were divided into two groups randomly(n=12):12 rats formed the sham group by exposing the spared nerve, and another 12 rats were served as the spared nerve injury (SNI)group by branchedness sciatic nerve injury surgery. The mechanical allodynia test were detected on the day of 3, 7, 14, 28, 42 and 56 after surgery, and the depressive-like behaviors such as open-field test, sucrose preference and forcedswim test were detected at the same time. Then we used the Multichannel Acquisition Processor (MAP) system to record the firing activity of neurons in VTA in both Sham rats and SNI rats. RESULTS: ①Comparing to sham rats, the paw withdrawalmechanical threshold of SNI rats was decreased significantly (P< 0.01);② According to depression-related behavioral test, SNI rats showed significant difference in open field text, sucrose preference, focus swim text comparing with Sham rats (P< 0.01);③ The firing rate and burst activity of dopaminergic neuronsin midbrain VTA are increased in depression rats compare to sham rats(P<0.05). CONCLUSIONS: Chronic pain could induce depression, and the increase of spontaneous firing rate of dopaminergic neurons in midbrain VTA might be contribute to the depression induced by the chronic neuropathic pain.

[Role of HCN channels in the nervous system: membrane excitability and various modulations].

Hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels, distributing in a variety of tissues, especially in excitable cells such as heart cells and many kinds of neurons, have an important role in the modulation of heart rate and neuronal excitability. Different from typical voltage-gated sodium channels and potassium channels, HCN channels were evoked inward currents when the cell was hyperpolarized. More and more recent studies have disclosed that HCN channels play important roles in the nervous system, which were linked with its special electrophysiological features as well as its regulatory effect on the cellular membrane excitability. HCN channels could be modulated by many factors including both extracellular molecules and intracellular signaling cascades, which made its functions complicated in the different condition. Based on its role, HCN channels are presumed to be a promising target for chronic pain and brain disorders. In this paper, we will focus on the advancement of roles of HCN channels in the neural system as well as its complex modulator factors.

Underlying mechanism of ASIC1a involved in acidosis-induced cytotoxicity in rat C6 glioma cells.

AIM: To investigate the underlying mechanism of acid-sensing ion channel (ASIC) 1a involved in the acidosis-induced cytotoxicity of rat C6 glioma cells. METHODS: The stable ASIC1a-silenced C6 cells built with the RNA interference technology were confirmed by RT-PCR and Western blot analysis. Intracellular calcium ([Ca2+]i) in both the wild-type rat C6 glioma cells and the ASIC1a-silenced C6 cells were analyzed before and after acid application/exposure with the calcium imaging experiment. RESULTS: The rapid extracellular pH drop induced the increase of [Ca2+]i in the wild-type C6 cells, but not in the ASIC1a-silenced C6 cells. During the prolonged acid exposure, [Ca2+]i was lower in the ASIC1a-silenced C6 cells than that in the control cells. CONCLUSION: The resultant toxicity of [Ca2+]i might contribute to the acidosis-induced cytotoxicity.

Inhibition of acid-induced apoptosis by targeting ASIC1a mRNA with short hairpin RNA.

AIM: To study the role of acid-sensing ion channel (ASIC) 1a in the cell death and apoptosis induced by extracellular acid in C6 glioma cells. METHODS: The stable ASIC1a-silenced C6 cell line, built with RNA interference technology, were confirmed by RT-PCR and Western blot analysis. The cell viability following acid exposure was analyzed with lactate dehydrogenase (LDH) and 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. The apoptotic cells dyed with Annexin-V and propidium iodide were measured with a flow cytometer, while the changes of cell cycle were also assayed. RESULTS: The downregulation of ASIC1a proteins by stable transfection of short hairpin RNA decreased the cell death percentage and increased cell viability following acid exposure with LDH and the MTT assay. The rate of apoptosis was lower in the ASIC1a-silenced cell line than that in the wild-type C6 cell line. The percentage of sub-G0 cells was lower in the ASIC1a-silenced C6 cells than that in the wild-type cells. CONCLUSION: Extracellular acid induced cell death and apoptosis via ASIC1a mechanisms in the C6 glioma cells.

Two types of acid-sensing ion channel currents in rat hippocampal neurons.

Two types of acid-sensing ion channel (ASIC)-like currents in cultured rat hippocampal neurons were recorded and their characteristics were studied by using a whole-cell recording technique. The results revealed that the ASIC-like currents, induced by a quick drop of the extracellular pH, decayed with different time constants (tau) of 229 +/- 16 (Type I) and 1209 +/- 56 ms (Type II). The ASIC-like currents displayed different sensitivities to extracellular proton (pH0.5 was 6.17 +/- 0.04 for Type I and 5.70 +/- 0.07 for Type II) and amiloride, a specific ASIC channel blocker (IC50 was 1.19 +/- 0.37 microM for Type I and 0.14 +/- 0.02 microM for Type II). Among all the 360 recorded neurons, ASIC-like currents were induced in 314 neurons (87.2%). In the neurons expressing ASICs, Type I currents were evoked from 269 neurons (85.7%) and Type II currents were induced only from 45 neurons (14.3%). As these ASIC-like currents presented various electrophysiological and pharmacological properties, further experiments should be conducted to decipher the complex subunit composition of ASICs in the hippocampus.

Mechanism underlying blockade of voltage-gated calcium channels by agmatine in cultured rat hippocampal neurons.

AIM: To investigate whether agmatine could selectively block a given type of the voltage-gated calcium channels (VGCC) and whether related receptors are involved in the blocking effect of agmatine on VGCC. METHODS: The whole-cell patch recording technique was performed to record VGCC currents in the cultured neonatal rat hippocampal neurons. RESULTS: Verapamil (100 micromol/L), a selective blocker of L-type calcium channel, significantly inhibited VGCC current by 80 %+/- 7 %. Agmatine (100 micromol/L) could further depress the remained currents by 25 %+/-6 %. The alpha 2-adrenoceptor antagonist yohimbine (10 micromol/L) and the I2 imidazoline receptor antagonist idazoxon (10 and 40 micromol/L) had no significant effect on VGCC currents when used respectively. When the mixture of yohimbine and agmatine was applied, VGCC currents were still depressed remarkably. However, the blocking effect of agmatine was decreased by 29 %+/- 8 % in the presence of idazoxon (10 micromol/L). The effect of idazoxon did not increase at a higher concentration (40 micromol/L). CONCLUSION: Agmatine could block the L- and other types of VGCC currents in the cultured rat hippocampal neurons. Blocking effect of agmatine on VGCC was partially related to I2 imidazoline receptor and had no relationship with alpha 2-adrenoceptors.

Agmatine blocked voltage-gated calcium channel in cultured rat hippocampal neurons.

AIM: To investigate the mechanism of agmatine by observing the effect of agmatine on the voltage-gated channels in rat hippocampal neurons. METHODS: The whole-cell patch recording technique was performed to record the voltage-gated potassium, sodium, and calcium currents in cultured rat hippocampus. Agmatine was applied directly to the single neuron using a pressure injector with microtubules. RESULTS: Agmatine (500 micromol/L) had no significant effect on the voltage-gated potassium and sodium channels. Agmatine reversibly blocked the voltage-gated calcium channel and the blockade was enhanced with the increasing concentration of agmatine. The inhibitory rates were 21%+/-4%, 35%+/-6%, 49%+/-6%, 67%+/-4%, 69%+/-6%, 86%+/-8%, and 87%+/- 9%, at the concentration of 0.1, 0.5, 1.0, 5.0, 10.0, 50.0, and 100 micromol/L, respectively. IC50 was (1.2+/-0.4) micromol/L. Two-way ANOVA revealed that change of membrane potential displayed a significant interaction with the blockade by agmatine. CONCLUSION: Agmatine reversibly blocked the voltage-gated calcium channel in rat hippocampal neurons in a concentration- and voltage-dependent way. Agmatine might perform its physiological and pharmacological effects partially by blocking the calcium channel.