Augmented brain 5-HT crosses the blood-brain barrier through the 5-HT transporter in rat

The present study re-evaluated an existing notion that serotonin (5-hydroxytryptamine; 5-HT) could not cross the brain to the circulating blood via the blood-brain barrier (BBB). To elevate brain 5-HT alone, 5-hydroxytryptophan (5-HTP; 30-75 mg/kg) was administrated intravenously to anaesthetized rats that had undergone gastrointestinal and kidney resections along with liver inactivation (organs contributing to increasing blood 5-HT after 5-HTP administration). A microdialysis method and HPLC system were used to determine the brain 5-HT levels in samples collected from the frontal cortex. Blood 5-HT levels were determined from whole blood, not platelet-poor plasma, collected from the central vein. We found that blood 5-HT levels showed a significant augmentation whenever brain 5-HT levels were significantly elevated after the administration of 5-HTP in those rats with the abdominal surgical procedures. This elevation was abolished after pretreatment with a selective serotonin reuptake inhibitor (fluoxetine; 10 mg/kg i.v.), although brain 5-HT levels remained augmented. These results indicate that augmented brain 5-HT can cross the BBB through the 5-HT transporter from the brain to the circulating blood.

Swim stress exaggerates the hyperactive mesocortical dopamine system in a rodent model of autism

Several clinical reports have suggested that there is a hyperactivation of the dopaminergic system in people with autism. Using rats exposed prenatally to valproic acid (VPA) as an animal model of autism, we measured dopamine (DA) levels in samples collected from the frontal cortex (FC) using in vivo microdialysis and HPLC. The basal DA level in FC was significantly higher in VPA-exposed rats relative to controls. Since the mesocortical DA system is known to be sensitive to physical and psychological stressors, we measured DA levels in FC before, during, and after a 60-min forced swim test (FST). There were further gradual increases in FC DA levels during the FST in the VPA-exposed rats, but not in the control rats. Behavioral analysis during the last 10 min of the FST revealed a significant decrease in active, escape-oriented behavior and an increase in immobility, which is thought to reflect the development of depressive behavior that disengages the animal from active forms of coping with stressful stimuli. These results suggest that this rodent model of autism exhibits a hyperactive mesocortical DA system, which is exaggerated by swim stress. This abnormality may be responsible for depressive and withdrawal behavior observed in autism.

Objective Assessment of Nerve Injury after Greater Saphenous Vein Stripping

AIM

The complication of nerve injury after greater saphenous vein stripping for varicosity is subjective, and a method for objective evaluation has never been established. The aim of this study was to evaluate postoperative sensory changes by quantitative assessment of current perception threshold (CPT), and to clarify the relation between CPT and symptoms.

PATIENTS AND METHODS

Between January 2003 and August 2005, 27 limbs in 18 patients were enrolled. Quantitative sensory function was determined through CPT using a Neurometer (Neurotron, Inc., USA), with which saphenous nerve neural fiber selective minimum sensing values against three electrical stimuli (2000, 250, 5 Hz) were measured. CPT measurements were scheduled on the day before the operation, and 2-7 days, 1, 3, and 6 months after the operation.

RESULTS

An increase in CPT value of more than 20% or decrease to below 50% compared to the preoperative value with at least two stimuli was defined as CPT abnormality. Subjective symptoms were observed in 13 limbs in the early postoperative period, and 10 limbs showed CPT abnormality. In 6 limbs with a CPT increase over 20% with all three stimuli, neurological symptoms continued for 6 months.

CONCLUSIONS

CPT evaluation provides an objective indication of neurological symptoms in the lower limb following varicose vein surgery.

Abnormality of circadian rhythm accompanied by an increase in frontal cortex serotonin in animal model of autism

Several clinical reports have indicated that autistic patients often show disturbance of the circadian rhythm, which may be related to dysfunction of the serotonergic system in the brain. Using rats exposed prenatally to valproic acid (VPA) as an animal model of autism, we examined locomotor activity and feeding under a reversed 12-h light/dark cycle, and found disturbance of the circadian rhythm characterized by frequent arousal during the light/sleep phase. In addition, measurement of brain serotonin (5-HT) level using in vivo microdialysis showed that the brain 5-HT level in VPA-exposed rats was significantly higher than that in control rats. These results suggest that a higher brain 5-HT level might be responsible for the irregular sleep/awake rhythm in autism.

Corticotropin-releasing factor neurons in the hypothalamic paraventricular nucleus are involved in arousal/yawning response of rats

Our previous studies have suggested that activation of the hypothalamic paraventricular (PVN) descending oxytocinergic projections is involved in the induction of yawning accompanied by an arousal response, but the possibility that neural systems other than the oxytocinergic system in the PVN also mediate the arousal/yawning response cannot be ruled out. We assessed the activity of corticotropin-releasing factor (CRF) neurons during yawning induced by the PVN stimulation in anesthetized, spontaneously breathing rats using double-staining for c-Fos and CRF. Yawning response was evaluated by monitoring an intercostals electromyogram as an index of inspiratory activity and a digastric electromyogram as an indicator of mouth opening. We also recorded the electrocorticogram (ECoG) to determine the arousal response during yawning. Microinjection of l-glutamate (2-5 nmol) into the PVN produced a frequent yawning accompanied by an arousal shift in the ECoG, and these behavioral effects were associated with a significant increase of c-Fos positive CRF neurons in the medial parvocellular subdivision of the PVN. In addition, a marked enhancement in the c-Fos expression was found in the both locus coeruleus (LC) and global area in the cortex when the frequency of yawning response was increased by the PVN stimulation, suggesting that the arousal response during yawning might be mediated by the activation of LC neurons. The present study suggests that an activation of CRF neurons in the PVN is responsible for the arousal response accompanied by yawning behavior.

Prolonged rhythmic gum chewing suppresses nociceptive response via serotonergic descending inhibitory pathway in humans

Serotonergic (5-HT) neurons are implicated in modulating nociceptive transmission. It is established that 5-HT neuronal activity is enhanced by rhythmic behaviors such as chewing and locomotion in animals. We thus hypothesized that 5-HT descending inhibitory pathways may be enhanced by rhythmic behavior of gum chewing in humans. To evaluate this idea, we examined nociceptive flexion reflex (NFR), while a subject chewed gum rhythmically for 20 min. NFR was elicited by electrical stimulation of the sural nerve, and the evoked potential was recorded from the biceps femoris muscle. Visual analogue scale (VAS) was also obtained. To assess 5-HT activity, we determined 5-HT levels quantitatively in platelet poor plasma (PPP) and whole blood (WB) using HPLC system. Both NFR area and VAS were significantly decreased at 5 min after the onset of chewing and these reductions persisted until cessation of chewing. There were no significant changes in NFR and VAS while resting without chewing. The PPP 5-HT level increased significantly just after cessation of chewing and had returned to the pre-chewing level by 30 min after cessation of chewing. The WB 5-HT level obtained 30 min after cessation of chewing was significantly greater than the pre-chewing level. Serotonin transporters have recently been discovered at the blood-brain barrier, suggesting that the rise in blood 5-HT may possibly reflect an increase in 5-HT level within the brain. The present results support our hypothesis that the rhythmic behavior of chewing suppresses nociceptive responses via the 5-HT descending inhibitory pathway.

Effects of practice on cardiorespiratory responses during postural control

The present study examined the effects of practice of a balance test on cardiorespiratory changes in response to a 1-min balance test performed by standing on one leg with eyes closed (SOLEC) in 30 females (n=15, 21+/-4 years, mean+/-SD, for the experimental group; n=15, 22+/-4 years for the control group). Blood pressure (BP), heart rate (HR), minute ventilation (VE), respiratory rate (RR), tidal volume (VT), expiratory duration (Te), inspiratory duration (Ti), and oxygen uptake (VO(2)) were measured during the balance test before and after 2 wk of daily practice. The experimental group was given a daily 15-min practice session for the balance test. In contrast, the control group was instructed not to do any special practice for the balance test. In both the experimental and control groups, SOLEC induced significant increases in BP, HR, VE, RR, and VO(2), and decreases in Te and Ti. Following the practice sessions, the balance time increased significantly in the experimental group (P<0.01). In addition, 2 wk of practice reduced the increases in BP (P<0.01), VE (P<0.05), and RR (P<0.01), and prolonged Te (P<0.01) during the SOLEC test. These results suggest that practice of a postural task affects cardiorespiratory responses to the balance test in addition to postural control.

Appearance of high-frequency alpha band with disappearance of low-frequency alpha band in EEG is produced during voluntary abdominal breathing in an eyes-closed condition

This study examined the effects of voluntary abdominal breathing (VAB) on the electroencephalogram (EEG) in 22 healthy subjects. VAB was characterized by prolonged rhythmic contraction of abdominal muscles for 20 min in an eyes-closed condition. The breathing rate was instructed to be very slow, i.e., 3-4 breaths/min (inspiratory time for 6-8s and expiratory time for 9-12s). A low-frequency alpha band appeared immediately after eye closing, but it later disappeared and was replaced by a new development of a high-frequency alpha band 4-5 min after the onset of VAB. The subjects had a feeling of vigor-activity with a tendency of reduced anxiety during and/or after VAB, as assessed by POMS and STAI questionnaire scores. On the other hand, during resting in the eye-closed condition, the disappearance of the low-frequency alpha band was replaced by the occurrence of a theta/delta band. The subjects became drowsy in this condition. We therefore conclude that the increase in high-frequency alpha activity is linked to the state of vigor-activity with a tendency of reduced anxiety. Since the urinary serotonergic level significantly increased after the VAB, we suggest that the serotonergic neurons within the brain may produce the changes in the EEG patterns.

Hiccup reflex is mediated by pharyngeal branch of glossopharyngeal nerve in cats

Hiccup reflex is a coordinated motor activity that causes a brief strong inspiratory movement accompanied by glottic adduction. Our previous study has demonstrated that mechanical stimulation of the dorsal epipharynx elicits hiccup-like response. To identify the afferent pathway of the hiccup-like response, the pharyngeal branch of the glossopharyngeal nerve (PB-GPN) which distributed to the dorsal epipharyngeal area was electrically stimulated in anesthetized, spontaneously breathing cats. To access the epipharynx and to directly observe a glottic movement, we made a submental opening at the region rostral to the epiglottis. An activity from the lateral cricoarytenoid (LCA) muscle of the larynx was recorded as an index of glottic adduction, and intrapleural pressure (Ppl) as an index of an inspiratory movement. Electrical stimulation of PB-GPN evoked a fixed motor pattern of hiccup-like response representing a spiky strong negative change in Ppl accompanied by an initial brief burst of LCA electromyogram (EMG). LCA excitation occurred prior to the spiky inspiratory movement. An initial and transient glottic adduction during the response was confirmed by direct observation. Electrical stimulation of the main trunk of the glossopharyngeal nerve evoked expiratory reflex, but not inspiratory (hiccup-like) response. These results indicated that PB-GPN is responsible for hiccup reflex.

Light induces cortical activation and yawning in rats

We examined the effects of light stimulation on cortical activation and yawning response in anesthetized, spontaneously breathing rats. Cortical activation was assessed by means of an electrocorticogram (ECoG) and yawning response was evaluated by monitoring an intercostal electromyogram as an index of inspiratory activity and a digastric electromyogram as an indicator of mouth opening. Light stimulation elicited an arousal shift in the ECoG to faster rhythms. This arousal response was followed by a single large inspiration with mouth opening, i.e. a yawning response. Higher light intensity significantly reduced the onset latency of the arousal/yawning response. Pretreatment with pyrilamine, an H1-histamine receptor antagonist, injected into the lateral ventricle blocked both the cortical activation and the yawning response induced by light stimulation, suggesting a role of brain histaminergic neurotransmission in modulating the light-induced arousal/yawning responses.

Association of HLA-A*3303-B*4403-DRB1*1302 haplotype, but not of TNFA promoter and NKp30 polymorphism, with postherpetic neuralgia (PHN) in the Japanese population

Herpes zoster is a common disease caused by reactivation of the varicella zoster virus (VZV). In a small number of herpes zoster patients, pain persists beyond 4 weeks or more after healing of vesicular eruptions; this condition is termed postherpetic neuralgia (PHN). Positive associations of human histocompatibility leukocyte antigens (HLA) class I antigens, A33 and B44, with PHN in the Japanese population have been reported. Our hypothesis is that susceptibility genes to PHN might exist in the HLA region and the study objective is to further examine possible associations of genes in HLA class I, II and III regions, HLA-A, -B, -DRB1, tumor necrosis factor alpha (TNFA) promoter, and a natural killer cell activating receptor, NKp30 polymorphisms with PHN. Although TNFA or NKp30 in the class III region had been considered as a candidate locus, we found no associations of TNFA promoter or NKp30 polymorphisms with PHN in this study. We demonstrated that HLA-A*3303, -B*4403 and -DRB1*1302 alleles were significantly associated with PHN (P = 0.0007 for A*3303, P = 0.001 for B*4403 and P = 0.001 for DRB1*1302). The frequency of the HLA-A*3303-B*4403-DRB1*1302 haplotype was also significantly higher in the PHN patients than in the healthy controls (P = 0.0039). Our results suggest that this haplotype might be related to the pathogenesis of PHN.

Yawning/cortical activation induced by microinjection of histamine into the paraventricular nucleus of the rat

The effects of microinjection of histamine into the paraventricular nucleus (PVN) of the hypothalamus on yawning responses were investigated in anesthetized, spontaneously breathing rats. Yawning responses were evaluated by monitoring the intercostal electromyogram (EMG) as an index of inspiratory activity and digastric EMG as an indicator of mouth opening. We also recorded the electrocorticogram (ECoG) to determine the arousal response during yawning. Autonomic function was evaluated by measuring blood pressure and heart rate. Microinjection of histamine into the medial parvocellular subdivision (mp) of the PVN elicited a yawning response, i.e. a single large inspiration with mouth opening, and an arousal shift in ECoG to lower voltage and faster rhythms. Microinjection of HTMT dimaleate, an H1 receptor agonist, into the PVN also caused the yawning/arousal response. Pretreatment with pyrilamine, an H1 receptor antagonist, inhibited the histamine induced yawning behavior. These data demonstrate that a histamine receptive site for triggering yawning/arousal responses exists in the PVN, and suggest that these responses are mediated by activation of H1 receptor within the PVN.

Cortical arousal induced by microinjection of orexins into the paraventricular nucleus of the rat

Orexin-A is a neuropeptide which has been suggested to be involved in sleep and arousal mechanisms. Orexin-A, for example, stimulates arousal when administrated intracerebroventricularly to rats. We attempted to identify specific neural sites of orexin-A and orexin-B action. Orexin-A and orexin-B were microinjected into the medial parvocellular subdivision of the paraventricular nucleus (PVN) in anesthetized, spontaneously breathing rats, and cortical arousal and yawning responses were assessed. Cortical arousal responses were monitored with the electrocorticogram (ECoG), and yawning responses were evaluated by monitoring intercostal electromyograms as an index of inspiratory activity and digastric electromyograms as an indicator of mouth opening. We also measured blood pressure and heart rate during yawning responses, since yawning is accompanied by changes in autonomic activity. Microinjection of orexin-A into the PVN elicited an arousal shift in the ECoG to lower voltage and faster rhythms. This cortical arousal response was followed by a single large inspiration with mouth opening, i.e. a yawning response. On the other hand, microinjection of orexin-B into the PVN elicited an arousal shift in the ECoG without yawning responses. These results demonstrate that an orexin receptive site for triggering arousal/yawning responses exists in the PVN, and suggest that the PVN is involved in arousal mechanisms.

Clearance of group X secretory phospholipase A(2) via mouse phospholipase A(2) receptor

Given the potent hydrolyzing activity toward phosphatidylcholine, group X secretory phospholipase A(2) (sPLA(2)-X) elicits a marked release of arachidonic acid linked to the potent production of lipid mediators in various cell types. We have recently shown that sPLA(2)-X can also act as a ligand for mouse phospholipase A(2) receptor (PLA(2)R). Here, we found that sPLA(2)-X was internalized and degraded via binding to PLA(2)R associated with the diminished prostaglandin E(2) (PGE(2)) formation in PLA(2)R-expressing Chinese hamster ovary (CHO) cells compared to CHO cells. Indirect immunocytochemical analysis revealed that internalized sPLA(2)-X was co-localized with PLA(2)R in the punctate structures in PLA(2)R-expressing CHO cells. Moreover, in mouse osteoblastic MC3T3-E(1) cells that endogenously express the PLA(2)R, the internalized sPLA(2)-X was localized in lysosomes. These findings demonstrate that PLA(2)R acts as a clearance receptor for sPLA(2)-X to suppress its strong enzymatic activity.

[Acute myocardial infarction in the postoperative period in an elderly man with low coronary risk factor before the operation]

An 86-year-old man complicated by severe asthma developed myocardial infarction after the operation of abdominal aortic aneurysm. Emergency coronary angiography (CAG) revealed 99% stenosis of main trunks of left coronary artery (LMT). Because the patient had been without major coronary risk factors, it was difficult to predict coronary lesions preoperatively. Elderly patients have frequently latent complications not detected by usual consultation. Therefore, in elderly patients, we have to evaluate each individual risk factor more rigidly, and perform more thorough preoperative tests, including CAG.

Prevention of allergic inflammation by a novel prostaglandin receptor antagonist, S-5751

Prostaglandin (PG) D2, the major cyclooxygenase metabolite generated from immunologically stimulated mast cells, is thought to contribute to the pathogenesis of allergic diseases due to its various inflammatory effects. However, since no DP receptor antagonist has been developed as an antiallergic drug, the role of PGD2 in the pathogenesis of allergic diseases remains uncertain. Here, we report the in vivo efficacy of our newly established DP receptor antagonist, S-5751 [((Z)-7-[(1R,2R,3S,5S)-2-(5-hydroxy benzo[b]thiophen-3-ylcarbonylamino)-10-norpinan-3-yl]hept-5- enoic acid)], using various allergic inflammation guinea pig models. In allergic rhinitis models, oral administration of S-5751 dramatically inhibited not only early nasal responses, as assessed by sneezing, mucosal plasma exudation, and nasal blockage, but also late responses such as mucosal plasma exudation and eosinophil infiltration. Even when S-5751 was administered after recovery from the early responses, these late phase responses were almost completely suppressed. In addition, S-5751 alleviated allergen-induced plasma exudation in the conjunctiva in an allergic conjunctivitis model and antigen-induced eosinophil infiltration into the lung in an asthma model. These findings provide evidence for the crucial role of PGD2 as a mediator of allergic inflammation in guinea pigs and suggest that DP receptor antagonists may be useful in the treatment of allergic diseases triggered by mast cell activation.

[Preliminary report: the efficacy of clonidine hydrochloride ointment for postherpetic neuralgia]

The combination of clonidine hydrochloride, alpha 2-agonist, and opioid is useful for relieving the pain due to surgical procedures or cancer. The routes of administrations used are intravenous, intramuscular as well as intrathecal, epidural and transmucosal. However, transdermal clonidine has not been reported. We, therefore, investigated the analgesic effect of local administration of clonidine ointment. Ten patients with postherpetic neuralgia (PHN) were selected randomly. They were requested to fill out a questionnaire after applying clonidine ointment (150 micrograms/ointment 1 g) to the painful area. Items included in the questionnaire were: effectiveness, visual analog scale (VAS) before and after the administration of clonidine ointment, onset time, with or without allodynia and effectiveness to allodynia in the former case, side effects, and patients' background. Analysis of the answers indicates that clonidine ointment produced a satisfactory effect in nine patients. Onset time was within a few minutes in most patients. No patients suffered any side effects. Specific mechanism of effectiveness or the site affected has not been confirmed in this study, but considering the quick onset, it is presumed that the site where the ointment was applied was the very site that was affected. Clonidine hydrochloride ointment was effective in relieving the symptoms of PHN.

Group X secretory phospholipase A(2) induces potent productions of various lipid mediators in mouse peritoneal macrophages

We have previously shown the expression of group X secretory phospholipase A(2) (sPLA(2)-X) in mouse splenic macrophages and its powerful potency for releasing fatty acids from various intact cell membranes. Here, we examined the potency of sPLA(2)-X in the production of lipid mediators in murine peritoneal macrophages. Mouse sPLA(2)-X was found to induce a marked release of fatty acids including arachidonic acid and linoleic acid, which contrasted with little, if any, release by the action of group IB and IIA sPLA(2)s. In resting macrophages, sPLA(2)-X elicited a modest production of prostaglandin E(2) and thromboxane A(2). After the induction of cyclooxygenase-2 (COX-2) by pretreatment with lipopolysaccharide, a dramatic increase in the production of these eicosanoids was observed in sPLA(2)-X-treated macrophages, which was completely blocked by the addition of either the specific sPLA(2) inhibitor indoxam or the COX inhibitor indomethacin. In accordance with its higher hydrolyzing activity toward phosphatidylcholine, mouse sPLA(2)-X induced a potent production of lysophosphatidylcholine. These findings strongly suggest that sPLA(2)-X plays a critical role in the production of various lipid mediators from macrophages. These events might be relevant to the progression of various pathological states, including chronic inflammation and atherosclerosis.

Potential role of group X secretory phospholipase A(2) in cyclooxygenase-2-dependent PGE(2) formation during colon tumorigenesis

Although the cyclooxygenase-2 (COX-2) pathway of the arachidonic acid cascade has been suggested to play an important role in colon carcinogenesis, there is little information concerning the identity of phospholipase A(2) (PLA(2)) involved in the arachidonic acid release in colon tumors. Here, we compared the potencies of three types of secretory PLA(2)s (group IB, IIA and X sPLA(2)s) for the arachidonic acid release from cultured human colon adenocarcinoma cells, and found that group X sPLA(2) has the most powerful potency in the release of arachidonic acid leading to COX-2-dependent prostaglandin E(2) (PGE(2)) formation. Furthermore, immunohistological analysis revealed the elevated expression of group X sPLA(2) in human colon adenocarcinoma neoplastic cells in concert with augmented expression of COX-2. These findings suggest a critical role of group X sPLA(2) in the PGE(2) biosynthesis during colon tumorigenesis.

Yawning responses induced by local hypoxia in the paraventricular nucleus of the rat

Yawing was induced by microinjections of L-glutamate, cyanide and a nitric oxide-releasing compound (NOC12) into the paraventricular nucleus of the hypothalamus (PVN) in anesthetized, spontaneously breathing rats. To evaluate physiological aspects of yawning, we monitored intercostal electromyogram (EMG) as an index of inspiratory activity, digastric EMG, blood pressure and electrocorticogram (ECoG). Microinjection of L-glutamate in the medial parvocellular subdivision (mp) elicited a stereotyped yawning response, i.e. an initial depressor response and an arousal shift in ECoG followed by a single large inspiration with mouth opening. The same sequential events were observed during spontaneous yawning, indicating that the mp is responsible for triggering yawning. Microinjection of cyanide into the mp caused the same yawning responses as the ones elicited by microinjection of L-glutamate, suggesting that the mp is sensitive to chemical hypoxia or ischemia within the PVN. Microinjection of NOC12 into the mp elicited a single large inspiration with a variable onset delay, suggesting that diffusible nitric oxide (NO) within the mp may act as a paracrine agent to cause a yawning response. We hypothesize that the mp of the PVN contains an oxygen sensor that causes a yawning response.