Astrocytes in the spinal cord contributed to acute stress-induced gastric damage via the gap junction protein CX43.

Rat restraint water-immersion stress (RWIS) is a compound stress of high intensity and is widely used to study the pathological mechanisms of stress gastric ulcers. The spinal cord, as a part of the central nervous system, plays a dominant role in the gastrointestinal tract, but whether the spinal cord is involved in rat restraint water-immersion stress (RWIS)-induced gastric mucosal damage has not been reported. In this study, we examined the expression of spinal astrocytic glial fibrillary acidic protein (GFAP), neuronal c-Fos, connexin 43 (Cx43), and p-ERK1/2 during RWIS by immunohistochemistry and Western blotting. In addition, we intrathecally injected the astrocytic toxin L-a-aminoadipate (L-AA), gap junction blocker carbenoxolone (CBX), and ERK1/2 signaling pathway inhibitor PD98059 to explore the role of astrocytes in the spinal cord in RWIS-induced gastric mucosal damage and its possible mechanism in rats. The results showed that the expression of GFAP, c-Fos, Cx43, and p-ERK1/2 was significantly elevated in the spinal cord after RWIS. Intrathecal injection of both the astrocyte toxin L-AA and the gap junction blocker CBX significantly attenuated RWIS-induced gastric mucosal damage and decreased the activation of astrocytes and neurons induced in the spinal cord. Meanwhile, the ERK1/2 signaling pathway inhibitor PD98059 significantly inhibited gastric mucosal damage, gastric motility and RWIS-induced activation of spinal cord neurons and astrocytes. These results suggest that spinal astrocytes may regulate the RWIS-induced activation of neurons via CX43 gap junctions and play a critical role in RWIS-induced gastric mucosa damage through the ERK1/2 signaling pathway.

[Gastroprotective and antidepressant-like effect of plum pectin (Prunus domestica L.) under water-immobilization stress in laboratory mice].

Stress effects activate the processes of free radical oxidation in the organism, lead to hyper production of reactive radicals and oxidative stress, provoking the development of an inflammatory process in various parts of the gastrointestinal tract. Pectin polysaccharides together with the enzyme components of the endogenous antioxidant system contribute to the elimination of the imbalance between prooxidants and antioxidants in the tissues of stressed animals and have a gastroprotective and antidepressant-like effect. The aim of the research was to evaluate the gastroprotective, antioxidant and antidepressant-like effect of plum pectin orally administered to white laboratory mice before stressful exposure. Material and methods. In the experiment on white BALB/c mice weighing 20-25 g (90 males, 10 in each group), pectin isolated from fresh plum fruits in an artificial gastric environment was used. It was administered orally to mice 24 h before the onset of stress exposure or behavioral activity asessment. 50 animals were subjected to 5 h of water immersion stress. After this corticosterone concentration in blood plasma, and the activity of superoxide dismutase, catalase and glutathione peroxidase in the tissue supernatants of the gastrointestinal tract were determined, and the condition of the gastric mucosa was also assessed. Behavioral activity of experimental mice (n=30) was assessed in the open field and forced swimming tests. Results. The stress effect was accompanied by an increase in plasma corticosterone concentration (more than 3 fold), in the activity of superoxide dismutase, glutathione peroxidase in the tissues of the stomach wall and small intestine (17.9-28.6%) and destructive damage in the gastric mucosa compared with the indices of intact animals. Preliminary oral administration of plum pectin to animals at a dose of 80 mg per 1 kg of body weight helped to reduce the level of corticosterone and the number of stress-induced hemorrhages on the gastric mucosa, normalized the activity of antioxidant enzymes and also decreased the immobility time of mice in the forced swimming test. Preliminary oral administration of plum pectin to animals at a dose of 80 mg per 1 kg of body weight prevented an increase in the activity of antioxidant enzymes, corticosterone in the blood and the development of stress-induced hemorrhages on the gastric mucosa, and reduced the time of immobility of mice in the forced swimming test. Conclusion. Plum fruit pectin pre-administered into mice before stress prevents stress-induced damage in the tissues of the gastrointestinal tract, contributing to an increase in the body's resistance to the stress factor. Plum pectin has an antioxidant, gastroprotective and antidepressant-like effect and can be used as an ingredient in functional foods that reduce the risk of inflammatory diseases of the gastrointestinal tract under stress.

Stress-Relieving Effects of Sesame Oil Aroma and Identification of the Active Components.

(1) Sesame oil aroma has stress-relieving properties, but there is little information on its effective use and active ingredients. (2) Methods: ICR male mice were housed under water-immersion stress for 24 h. Then, the scent of sesame oil or a typical ingredient was inhaled to the stress groups for 30, 60, or 90 min. We investigated the effects of sesame oil aroma on mice behavior and the expression of the dual specificity phosphatase 1 (DUSP1) gene, a candidate stress marker gene in the brain. (3) Results: In an elevated plus-maze test, the rate of entering into the open arm of a maze and the staying time were increased to a maximum after 60 min of inhalation, but these effects decreased 90 min after inhalation. As for the single component, anxiolytic effects were observed in the 2,5-dimethylpyrazine and 2-methoxy phenol group, but the effect was weakened in the furfuryl mercaptan group. The expression levels of DUSP1 in the hippocampus and striatum were significantly decreased in 2,5-dimethylpyrazine and 2-methoxy phenol groups. (4) Conclusions: We clarified the active ingredients and optimal concentrations of sesame oil for its sedative effect. In particular, 2,5-dimethylpyrazine and 2-methoxy phenol significantly suppressed the stress-induced changes in the expression of DUSP1, which are strong anti-stress agents. Our results suggest that these molecules may be powerful anti-stress agents.

Water immersion tolerance by larval instars of stable fly, Stomoxys calcitrans, L1758 (Diptera: Muscidae) impairs the fitness performance of their subsequent stages.

BACKGROUND: In holometabolous insects, environmental factors experienced in pre-imaginal life stages affect the life-history traits within that stage and can also influence subsequent life stages. Here, I assessed tolerance to water immersion by the larval instars of the stable fly, Stomoxys calcitrans L. (Diptera: Muscidae) and its impact on the life-history traits of their subsequent life stages. RESULTS: After submerging the three larval instars of S. calcitrans in distilled water, I found that the first instar larvae remained active for longer as compared to the second and third instar larvae. Also, the first instar larvae took a longer period to recover from the stress-induced immobility when removed from the water and returned to ambient temperature. When I followed the development of individuals of each larval instar that survived from water immersion, I found that their developmental time, weight, pupation percentage, adult emergence percentage and adult weight were negatively affected by this stressor. However, the weight of S. calcitrans adults developed from immersed first larval instar individuals was not affected by water immersion whereas their counterparts developed from immersed second and third larval instars had lower body weight. This suggests that in S. calcitrans, water immersion stress at the earlier stage is less detrimental than that experienced at late stages. CONCLUSION: This study provides a comparative overview of the fitness consequences associated with water immersion stress during S. calcitrans larval ontogeny. The results prove that the fitness shift induced by water immersion in S. calcitrans is stage-specific. My results illustrate the importance of considering each larval instar when assessing the impact of environmental factors on holometabolous insect performance as these may be decoupled by metamorphosis.

Neurons and Astrocytes in Ventrolateral Periaqueductal Gray Contribute to Restraint Water Immersion Stress-Induced Gastric Mucosal Damage via the ERK1/2 Signaling Pathway.

BACKGROUND: The restraint water immersion stress (RWIS) model includes both psychological and physical stimulation, which may lead to gastrointestinal disorders and cause gastric mucosal damage. The ventrolateral periaqueductal gray (VLPAG) contributes to gastrointestinal function, but whether it is involved in RWIS-induced gastric mucosal damage has not yet been reported. METHODS: The expression of glial fibrillary acidic protein, neuronal c-Fos, and phosphorylated extracellular signal regulated kinase 1/2 in the VLPAG after RWIS was assessed using western blotting and immunocytochemical staining methods. Lateral ventricle injection of astrocytic toxin L-a-aminoadipate and treatment with extracellular signal-regulated kinase (ERK)1/2 signaling pathway inhibitor PD98059 were further used to study protein expression and distribution in the VLPAG after RWIS. RESULTS: The expression of c-Fos, glial fibrillary acidic protein, and phosphorylated extracellular signal regulated kinase 1/2 in the VLPAG significantly increased following RWIS and peaked at 1 hour after RWIS. Lateral ventricle injection of the astrocytic toxin L-a-aminoadipate significantly alleviated gastric mucosal injury and decreased the activation of neurons and astrocytes. Treatment with the ERK1/2 signaling pathway inhibitor PD98059 obviously suppressed gastric mucosal damage as well as the RWIS-induced activation of neurons and astrocytes in the VLPAG. CONCLUSIONS: These results suggested that activation of VLPAG neurons and astrocytes induced by RWIS through the ERK1/2 signaling pathway may play a critical role in RWIS-induced gastric mucosa damage.

Effects of Sesame Oil Aroma on Mice after Exposure to Water Immersion Stress: Analysis of Behavior and Gene Expression in the Brain.

(1) Background: Sesame has been popular as a healthy food since ancient times, and effects of the aroma component of roasted sesame are also expected. However, little research has been reported on its scent; (2) Methods: Jcl:ICR male mice were housed under water immersion stress for 24 h. Then, the scent of saline or sesame oil was inhaled to stress groups for 90 min. We investigated the effects of sesame oil aroma on the behavior and brains of mice; (3) Results: In an elevated plus maze test, the rate of entering to open arm and the staying time were decreased by the stress. These decrements were significantly enhanced by sesame oil aroma. Stress had a tendency to increase the serum corticosterone concentration, which was slightly decreased by the aroma. Expression of Kruppel-like factor-4 (Klf-4) and Dual-specificity phosphatase-1 (Dusp-1) in the striatum were increased by water immersion stress, and the level of Klf-4 and Dusp-1 in the striatum and hippocampus were significantly attenuated by sesame oil aroma (4) Conclusions: The present results strongly suggest that the odor component of sesame oil may have stress suppressing effects. Moreover, Klf-4 and Dusp-1 may be sensitive stress-responsive biomarkers.

Nervous mechanisms of restraint water-immersion stress-induced gastric mucosal lesion.

Stress-induced gastric mucosal lesion (SGML) is one of the most common visceral complications after trauma. Exploring the nervous mechanisms of SGML has become a research hotspot. Restraint water-immersion stress (RWIS) can induce GML and has been widely used to elucidate the nervous mechanisms of SGML. It is believed that RWIS-induced GML is mainly caused by the enhanced activity of vagal parasympathetic nerves. Many central nuclei, such as the dorsal motor nucleus of the vagus, nucleus of the solitary tract, supraoptic nucleus and paraventricular nucleus of the hypothalamus, mediodorsal nucleus of the thalamus, central nucleus of the amygdala and medial prefrontal cortex, are involved in the formation of SGML in varying degrees. Neurotransmitters/neuromodulators, such as nitric oxide, hydrogen sulfide, vasoactive intestinal peptide, calcitonin gene-related peptide, substance P, enkephalin, 5-hydroxytryptamine, acetylcholine, catecholamine, glutamate, γ-aminobutyric acid, oxytocin and arginine vasopressin, can participate in the regulation of stress. However, inconsistent and even contradictory results have been obtained regarding the actual roles of each nucleus in the nervous mechanism of RWIS-induced GML, such as the involvement of different nuclei with the time of RWIS, the different levels of involvement of the sub-regions of the same nucleus, and the diverse signalling molecules, remain to be further elucidated.

Proteomics of the mediodorsal thalamic nucleus of rats with stress-induced gastric ulcer.

BACKGROUND: Stress-induced gastric ulcer (SGU) is one of the most common visceral complications after trauma. Restraint water-immersion stress (RWIS) can cause serious gastrointestinal dysfunction and has been widely used to study the pathogenesis of SGU to identify medications that can cure the disease. The mediodorsal thalamic nucleus (MD) is the centre integrating visceral and physical activity and contributes to SGU induced by RWIS. Hence, the role of the MD during RWIS needs to be studied. AIM: To screen for differentially expressed proteins in the MD of the RWIS rats to further elucidate molecular mechanisms of SGU. METHODS: Male Wistar rats were selected randomly and divided into two groups, namely, a control group and an RWIS group. Gastric mucosal lesions of the sacrificed rats were measured using the erosion index and the proteomic profiles of the MD were generated through isobaric tags for relative and absolute quantitation (iTRAQ) coupled with two-dimensional liquid chromatography and tandem mass spectrometry. Additionally, iTRAQ results were verified by Western blot analysis. RESULTS: A total of 2853 proteins were identified, and these included 65 dysregulated (31 upregulated and 34 downregulated) proteins (fold change ratio ≥ 1.2). Gene Ontology (GO) analysis showed that most of the upregulated proteins are primarily related to cell division, whereas most of the downregulated proteins are related to neuron morphogenesis and neurotransmitter regulation. Ingenuity Pathway Analysis revealed that the dysregulated proteins are mainly involved in the neurological disease signalling pathways. Furthermore, our results indicated that glycogen synthase kinase-3 beta might be related to the central mechanism through which RWIS gives rise to SGU. CONCLUSION: Quantitative proteomic analysis elucidated the molecular targets associated with the production of SGU and provides insights into the role of the MD. The underlying molecular mechanisms need to be further dissected.

Effects of Restraint Water-Immersion Stress-Induced Gastric Mucosal Damage on Astrocytes and Neurons in the Nucleus Raphe Magnus of Rats via the ERK1/2 Signaling Pathway.

Restraint water-immersion stress (RWIS) consists of psychological and physical stimulation, and it has been utilized in the research of gastric mucosal damage. It has been shown by previous studies that the nucleus raphe magnus (NRM) is closely involved in the gastrointestinal function, but its functions on the stress-induced gastric mucosal injury (SGMI) have not been thoroughly elucidated to date. Consequently, in this research, we aim to measure the expression of astrocytic glial fibrillary acidic protein (GFAP), neuronal c-Fos, and phosphorylation extracellular signal regulated kinase 1/2 (p-ERK1/2) in the process of RWIS with immunohistochemistry and western blot methods. What is more, we detect the relation between astrocytes and neurons throughout the stress procedure and explore the regulation of the ERK1/2 signaling pathway on the activity of astrocytes and neurons after RWIS. The results indicated that all three proteins expression multiplied following peaked 3 h substantially. The SMGI, astrocyte and neuron activity were affected after the astrocytotoxin L-A-aminohexanedioic acid (L-AA) and c-fos antisense oligonucleotide (ASO) injections. After the injection of PD98059, the gastric mucosal injury, astrocyte and neuron activity significantly fell off. These results suggested that RWIS-induced activity of astrocytes and neurons in the NRM may play a significant part in gastric mucosa damage via the ERK1/2 signaling pathway.

Nervous Mechanism of Gastric Mucosal Lesion Induced by Restraint Water-immersion Stress in Rats / 胃肠病学

Stress-induced gastric mucosal lesion (SGML) is one of the most common visceral complications after trauma. Restraint water-immersion stress (RWIS) can induce gastric mucosal lesion within a few hours. It has been confirmed that hyperfunction of parasympathetic nervous system contributes to the gastric dysfunction induced by RWIS. The dorsal motor nucleus of vagus, nucleus of solitary tract, hypothalamic supraoptic nucleus, paraventricular nucleus, mediodorsal thalamic nucleus, central amygdaloid nucleus and medial prefrontal cortex are all involved in the formation of SGML. Neurotransmitter/neuromodulation such as substance P, acetylcholine, oxytocin may be involved in the physiological process. This article reviewed the nervous mechanism of gastric mucosal lesion induced by RWIS in rats.

Altered Neuronal Activity in the Central Nucleus of the Amygdala Induced by Restraint Water-Immersion Stress in Rats.

Restraint water-immersion stress (RWIS), a compound stress model, has been widely used to induce acute gastric ulceration in rats. A wealth of evidence suggests that the central nucleus of the amygdala (CEA) is a focal region for mediating the biological response to stress. Different stressors induce distinct alterations of neuronal activity in the CEA; however, few studies have reported the characteristics of CEA neuronal activity induced by RWIS. Therefore, we explored this issue using immunohistochemistry and in vivo extracellular single-unit recording. Our results showed that RWIS and restraint stress (RS) differentially changed the c-Fos expression and firing properties of neurons in the medial CEA. In addition, RWIS, but not RS, induced the activation of corticotropin-releasing hormone neurons in the CEA. These findings suggested that specific neuronal activation in the CEA is involved in the formation of RWIS-induced gastric ulcers. This study also provides a possible theoretical explanation for the different gastric dysfunctions induced by different stressors.

Astrocytes and neurons in locus coeruleus mediate restraint water immersion stress-induced gastric mucosal damage through the ERK1/2 signaling pathway.

Restraint water-immersion stress (RWIS) is considered to be a compound stress model that includes psychological and physical stimulation and may cause gastric mucosal damage. Studies have shown that locus coeruleus (LC) is involved in the gastrointestinal function, but whether it is involved in RWIS-induced gastric mucosal damage has not yet been reported. Here, we investigated the expression of glial fibrillary acidic protein (GFAP), c-Fos, and phosphorylation extracellular signal regulated kinase 1/2 (p-ERK1/2) in the LC after RWIS using immunocytochemical staining and western blotting in order to explore whether the ERK1/2 signaling pathway interacts with the neuron-astrocyte network in the LC during RWIS and whether it is involved in causing RWIS-induced gastric mucosal damage. Expression of c-Fos, GFAP, and p-ERK1/2 increased significantly following RWIS and peaked at 3 h after RWIS. After intracerebroventricular injection of c-Fos antisense oligodeoxynucleotides (ASO) and astrocytic toxin L-a-aminoadipate (L-AA), the gastric mucosal damage and the activation of neurons and astrocytes in the LC significantly decreased. Intracerebroventricular injection of ERK1/2 signaling pathway inhibitor PD98059 suppressed gastric mucosal damage as well as the RWIS-induced activation of neurons and astrocytes in the LC. Activation of LC neurons and astrocytes induced by RWIS through the ERK1/2 signaling pathway may play a critical role in RWIS-induced gastric mucosa damage.

Altered Neuronal Activity in the Central Nucleus of the Amygdala Induced by Restraint Water-Immersion Stress in Rats / 神经科学通报·英文版

Restraint water-immersion stress (RWIS), a compound stress model, has been widely used to induce acute gastric ulceration in rats. A wealth of evidence suggests that the central nucleus of the amygdala (CEA) is a focal region for mediating the biological response to stress. Different stressors induce distinct alterations of neuronal activity in the CEA; however, few studies have reported the characteristics of CEA neuronal activity induced by RWIS. Therefore, we explored this issue using immunohistochemistry and in vivo extracellular single-unit recording. Our results showed that RWIS and restraint stress (RS) differentially changed the c-Fos expression and firing properties of neurons in the medial CEA. In addition, RWIS, but not RS, induced the activation of corticotropin-releasing hormone neurons in the CEA. These findings suggested that specific neuronal activation in the CEA is involved in the formation of RWIS-induced gastric ulcers. This study also provides a possible theoretical explanation for the different gastric dysfunctions induced by different stressors.

Effect of Manual Acupuncture Stimulation at "Bai-Hui" (GV 20) or "Yintáng" (Ex-HN3) on Depressed Rats.

A previous study on rats showed that simultaneous acupuncture stimulation at the "Bai-Hui" (GV 20) and the "Yintáng" (Ex-HN3) acupoints alleviated the state of depression to an extent similar to that achieved by pharmacotherapy. This study investigated whether the alleviation of the depressed state required simultaneous acupuncture at these two acupuncture points. For the purposes of testing the effect of acupuncture on depressive symptoms, we treated a depression model rat, where depression had been induced by using a mild water-immersion stress technique, with either acupuncture stimulation at only one acupuncture point (GV 20 or Ex-HN3) or an antidepressant, and we measured the immobile time for evaluating the state of depression. Anxiety, as a symptom commonly associated with depression, was also evaluated by measuring the number of head dips. Neither the immobile time nor the number of head dips decreased upon acupuncture stimulation. From this study, single acupuncture stimulation at either "GV 20" or "Ex-HN3" alleviated neither the state of depression nor the anxiety. The water-immersion stress used to make the depression model rats was shown not to induce anxiety; however, the stress induced by immobilizing the rats for acupuncture stimulation did lead to anxiety.

Hydrogen sulfide attenuates gastric mucosal injury induced by restraint water-immersion stress via activation of KATP channel and NF-κB dependent pathway.

AIM: To explore the effect of hydrogen sulfide (H2S) on restraint water-immersion stress (RWIS)-induced gastric lesions in rats and the influence of adenosine triphosphate (ATP)-sensitive potassium (KATP) channels and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway on such an effect. METHODS: Male Wistar rats were randomly divided into a control group, a physiological saline (PS) group, a sodium hydrosulfide (NaHS) group, a glibenclamide (Gl) group, Gl plus NaHS group, a pyrrolidine dithiocarbamate (PDTC) group, and a PDTC plus NaHS group. Gastric mucosal injury was induced by RWIS for 3 h in rats, and gastric mucosal damage was analyzed after that. The PS, NaHS (100 µmol/kg body weight), Gl (100 µmol/kg body weight), Gl (100 µmol/kg or 150 µmol/kg body weight) plus NaHS (100 µmol/kg body weight), PDTC (100 µmol/kg body weight), and PDTC (100 µmol/kg body weight) plus NaHS (100 µmol/kg body weight) were respectively injected intravenously before RWIS. RESULTS: RWIS induced serious gastric lesions in the rats in the PS pretreatment group. The pretreatment of NaHS (a H2S donor) significantly reduced the damage induced by RWIS. The gastric protective effect of the NaHS during RWIS was attenuated by PDTC, an NF-κB inhibitor, and also by glibenclamide, an ATP-sensitive potassium channel blocker, in a dose-dependent manner. CONCLUSION: These results suggest that exogenous H2S plays a protective role against RWIS injury in rats, possibly through modulation of KATP channel opening and the NF-κB dependent pathway.

The timing of weaning alters the vulnerability to stress-induced gastric erosion in adult rats.

BACKGROUND AND PURPOSE: Weaning is an important period of life and its timing may influence the resilence for later stress. One of the most important stress-related disorder is gastric ulceration. METHODS: Therefore we aimed to investigate the sensitivity of gastric mucosa to cold (at 16°C) water immersion stress (WIS for 3h) in adult (75-day-old) female and male rats after weaning them at different timepoints (at 17, 21, 30, 36 or 42 postnatal days). The connection with stress was studied by comparing control groups to those underwent WIS at the time of weaning and measuring corticosterone levels at the time of collecting the stomach samples. RESULTS: The timing of weaning has strong impact on all studied parameters. Stress-induced erosion development was the smallest in rats weaned at 36-day independently from preconditioning with WIS at weaning, or sex, despite a clear sex-effect on blood corticosterone levels and body weight. WIS at weaning influenced only the body weight in adult rats weaned at 30-day, being higher in stressed than in control groups. There was no clear overall correlation between erosion area and blood corticosterone measures. CONCLUSION: Taken together our results confirm that the timing of weaning has long-lasting impact on the resiliance of gastric mucosa to ulcerogenic stressful events. In rats the postnatal day 30-36 seems to be optimal for weaning in both sexes as both earlier and later weaning increased vulnerability. Females seems to be more vulnerable to the effect of weaning than males.

Effect of acupuncture stimulation on rats with depression induced by water-immersion stress.

Depression is a kind of mood disorder. The incidence of depressed patients has demonstrated an upward trend in recent years. Symptoms may improve with treatments such as pharmacotherapy and cognitive-behavioral therapy, but such approaches may exert strong side effects, and therapeutic effects can be slow. We studied how acupuncture stimulation would affect depression as a method to reduce side effects. Mild depression was induced in rats by 1-week water-immersion stress. We treated these mildly depressed rats with either acupuncture stimulation at the "Bai-Hui" (GV 20) and "Yintáng" (Ex-HN3) points, or antidepressants. We then measured the immobile time and serum corticosterone level in rats. Immobile time and serum corticosterone level decreased on stimulation with acupuncture or antidepressants. These findings suggest that mild depression in rats was improved by stimulation with acupuncture The mechanisms underlying such improvement may effect HPA system activated by this stress, and inhibit the response to lead to the disorder of the hippocampal nerve cell.

The influence of restraint water-immersion stress on firing activities of pyramidal neurons in the medial prefrontal cortex in rats / 中华行为医学与脑科学杂志

Objective To explore the effects of restraint water-immersion stress (RWIS) on the firing activities of pyramidal neurons in the medial prefrontal cortex (MPFC) of rats.Methods Multi-channel in vivo recording techniques were used to record firing activities of pyramidal neurons before and during 4-h RWIS in rats.Firing rates,inter-spike intervals and burst firing rates were taken as indices to study the influence of RWIS on neuronal firing activities.Results Twenty-five pyramidal neurons of 12 rats were recorded.The opposite patterns of firing activities were observed in two different classes of neurons,type A and type B neurons which account for 72％ and 28％,respectively.In type A neurons,inhibited firing activities were in direct proportion to the stress-exposure.Mean firing rates and mean burst firing rates were significantly reduced to (0.81 ± 0.11) Hz and (1.012 ± 0.50) counts/min after 4h constant RWIS compared with those before RWIS,(3.57 ± 0.63) Hz and (10.29 ± 3.04) counts/min.However,in type B neurons,firing activities were enhanced.After 2h constant RWIS,mean firing rates and mean burst firing rates were increased from (1.77±0.45) Hz and (2.01±0.73) counts/min to (2.67±0.74)Hz and (9.04±2.42) counts/min,respectively.Moreover,the percentage of spikes in bursts was significantly increased and mean inter-spike intervals were remarkably shortened.Interestingly,the effect of RWIS on type B neurons lasted for shorter time compared with its effect on type A neurons.Conclusion RWIS differentially affects the firing activity of pyramidal neuron in the MPFC,i.e.,inhibiting the firing activity of type A neurons,but enhancing the firing activity of type B neurons.