Reactivation of hepatitis C virus caused by steroid monotherapy for sudden deafness

Hepatitis C virus (HCV) reactivation has been reported to be caused due to several anticancer drugs and immunosuppressive agents; however, HCV reactivation after steroid monotherapy has rarely been reported. Here, we report the case of a 65-year-old Japanese man with HCV infection who developed HCV reactivation after the administration of prednisolone (PSL) for 6 days for sudden deafness. In the patient history, the positivity for anti-HCV antibody was observed, but serum level of HCV RNA was not measured. Two months after PSL administration, the patient experienced an alanine aminotransferase (ALT) flare and the serum level of HCV RNA was observed to be 6.2 log IU/mL; then, the patient was admitted to our hospital for hepatitis treatment. Based on the clinical course and laboratory findings, the patient was diagnosed with HCV reactivation. Although the ALT levels decreased spontaneously during follow-up, they did not drop to normal range; subsequently, sofosbuvir and ledipasvir treatments were started. A sustained virological response 24 weeks after the end of treatment was achieved. This case study suggests that HCV reactivation with hepatitis flare can occur even after a steroid monotherapy, and doctors should pay attention to HCV reactivation when administering PSL for patients with HCV infection.

Inflammatory Hepatocellular Adenoma Mimicking Focal Nodular Hyperplasia That Grew during Pregnancy and Changed Its Appearance on Magnetic Resonance Imaging after Delivery

We reported a notable case of inflammatory hepatocellular adenoma that grew during pregnancy, consequently changing its appearance on magnetic resonance imaging remarkably. A 5-months-pregnant 35-year-old woman presented with a 37-mm liver nodule that had been diagnosed as focal nodular hyperplasia 3 years earlier. She had never used oral contraceptives. After 2 months, the nodule grew to 57 mm. The patient delivered a full-term infant without complications. Gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging performed after delivery revealed markedly different findings compared with the first images. A liver biopsy was performed, and the tumor was diagnosed as inflammatory hepatocellular adenoma.

[A case of invasive liver abscess syndrome caused by Klebsiella pneumoniae causing endophthalmitis-induced blindness]

An 82-year-old female patient was admitted to our hospital for visual acuity loss in both eyes. The patient was diagnosed with invasive liver abscess syndrome and bilateral endophthalmitis due to Klebsiella pneumoniae 4 days after the onset of ocular symptoms. The liver abscess improved by broad-spectrum antibiotics and intravitreal injection, but bilateral blindness occurred. Most literature reported fever as the first symptom of invasive abscess syndrome, but this case had no fever at the onset of ocular symptoms. Delayed invasive liver abscess syndrome diagnosis might cause poor visual acuity prognosis.

Liver abscess in advanced hepatocellular carcinoma after atezolizumab plus bevacizumab treatment: A case report

RATIONALE

Hepatocellular carcinoma (HCC) is the sixth most common type of cancer globally. Since 2020, combination treatment with atezolizumab and bevacizumab were approved in patients with unresectable HCC in Japan, and atezolizumab plus bevacizumab is the first-line treatment for unresectable HCC.

PATIENT CONCERNS

A 73-year-old Japanese man diagnosed with a large HCC was treated with atezolizumab plus bevacizumab. After 2 cycles, he had fever and fatigue and was admitted to the hospital.

DIAGNOSIS

Abdominal contrast-enhanced computed tomography revealed tumor necrosis in HCC with gas formation in the necrotic area. Laboratory examination revealed a white blood cell (WBC) count of 16,340/μL and C-reactive protein (CRP) level of 33.0 mg/dL. Based on the above findings, he was diagnosed with a liver abscess.

INTERVENTIONS

Percutaneous transhepatic liver abscess drainage and broad-spectrum antibiotics treatment were performed.

OUTCOMES

Despite liver abscess drainage, persistent fever and no improvement in the WBC count or CRP level was observed. The patient's respiratory condition and renal function gradually worsened; The patient's general condition did not improve despite the ventilator support and continuous hemodiafiltration, and he died on day 37.

LESSONS

We report the first case of liver abscess after atezolizumab plus bevacizumab treatment for unresectable HCC.

Efficacy and safety of glecaprevir and pibrentasvir in Japanese patients with hepatitis C virus infection aged 75 years or older

Background

It is estimated that approximately 50% of patients with hepatitis C virus (HCV) infection in Japan are currently over 75 years old. However, patients aged ≥ 75 years are typically underrepresented in clinical trials of direct-acting antivirals. This study aimed to evaluate the efficacy and safety of glecaprevir and pibrentasvir (G/P) treatment in Japanese patients with HCV infection aged ≥ 75 years.

Methods

This multicenter, retrospective study included 271 Japanese patients with HCV infection from 12 centers in Miyazaki Prefecture, Japan. Demographic, clinical, virological, and adverse events (AEs) data obtained during and after G/P treatment were collected from medical records. The patients were divided into two groups: younger (n = 199, aged < 75 years) and older (n = 72, aged ≥ 75 years). Virological data and AEs were analyzed according to the age group.

Results

In intention-to-treat (ITT) and per-protocol analyses, the overall sustained virological response 12 (SVR12) rates were 93% and 98.8%, respectively. Two patients in the older group and 14 patients in the younger group dropped out before SVR12 assessment. Although patients in the older group tended to have liver cirrhosis, 95.8% in the older group and 92% in the younger group achieved SVR12 in the ITT analysis (P = 0.404). In total, 48 (17.7%) patients experienced treatment-related AEs. Common AEs during treatment included pruritus, headache, and fatigue. The AEs were not significantly different between the two groups.

Conclusions

Compared with younger patients, older patients showed similar virological response and tolerance to G/P treatment.

Frailty Status Predicts New Long-term Care Insurance Certification in Hepatitis C Patients Receiving Antiviral Therapy

BACKGROUND/AIM

Direct-acting antiviral (DAA) therapies for patients with hepatitis C virus (HCV) infection deliver higher cure rates and lower frequencies of adverse events than existing therapies, though DAA treatment costs $45,000-64,000 in Japan. The prognosis of patients who require new long-term care insurance (LTCI) certification is inferior to that of patients who do not. Here, we clarify the factors associated with new LTCI certification in elderly patients with HCV infection who undergo DAA therapy.

PATIENTS AND METHODS

We retrospectively surveyed 53 patients aged ≥70 years who were treated with DAAs, and evaluated the factors associated with new LTCI certification.

RESULTS

Of 53 patients, 10 required new LTCI certification. Age ≥85 years and a modified Japanese Cardiovascular Health Study index ≥2 were independently associated with new LTCI certification.

CONCLUSION

In elderly HCV patients, poor frailty status strongly predicted new LTCI certification after DAA therapy.

Acute Liver Failure Due to Severe Hepatic Metastasis of Small-cell Lung Cancer Producing Adrenocorticotropic Hormone Complicating Ectopic Cushing Syndrome

A 72-year-old man was admitted to a general hospital with progressive liver dysfunction, hypokalemia, hyperglycemia, and nodules in the lung and liver and then transferred to our institution on the seventh hospital day. Plasma levels of adrenocorticotropic hormone (ACTH), cortisol, and neuron-specific enolase concentrations were extremely high. He developed acute liver failure, his consciousness and general condition deteriorated rapidly, and he died on Day 11. At the postmortem examination, he was found to have extensive metastases from small-cell lung cancer, including advanced hepatic metastases. This is the first reported case of acute liver failure caused by metastases derived from an ACTH-producing pulmonary small-cell carcinoma.

Monocyte-derived fibrocytes elimination had little contribution on liver fibrosis

BACKGROUND

Monocyte-derived fibrocytes play an important role in the progression of fibrosis in the skin, lungs, heart and kidney. However, the contribution of fibrocytes to liver fibrosis is unclear. The aim of this study was to investigate whether fibrocytes contributed to fibrosis progression in the livers of carbon tetrachloride (CCl₄)-treated mice.

METHODS

C57BL/6J mice were divided into 4 groups: normal control group, CCl₄-treated group, CCl₄ + control liposome-treated group, and CCl₄ + clodronate liposome-treated group. For the elimination of systemic monocyte and monocyte-derived fibrocyte, one group was treated with clodronate liposome, and another group with control liposome as a control. After 4 weeks of treatment, hepatic mononuclear cells were subjected to immunofluorescent (IF) staining and fluorescence-activated cell sorter (FACS) analysis to detect fibrocytes. Measurement of collagen-positive Sirius red stained area and collagen-I mRNA expression in the liver were performed to evaluate the degree of liver fibrosis quantitatively.

RESULTS

In the liver of the CCl₄-treated and CCl₄ + control liposome-treated groups, the number of fibrocytes, the area positive for Sirius red staining and collagen-I mRNA expression significantly increased compared with those in the normal control group. In the liver of the CCl₄ + clodronate liposome-treated group, few fibrocytes was observed as in the normal control group, but Sirius red staining positive area and collagen-I mRNA expression were increased and equivalent to the CCl₄-treated and CCl₄ + control liposome-treated groups.

CONCLUSION

Monocyte-derived fibrocytes play a minimal role in CCl₄-induced liver fibrosis. Cells other than fibrocytes such as hepatic stellate cells play a central role in liver fibrosis.

Efficacy and safety of sofosbuvir and ledipasvir in Japanese patients aged 75 years or over with hepatitis C genotype 1

AIM

To evaluate the efficacy and safety of a regimen containing sofosbuvir (SOF) and ledipasvir (LDV) in Japanese patients aged ≥ 75 years with hepatitis C genotype 1.

METHODS

This multicenter, retrospective study consisted of 246 Japanese patients with HCV genotype 1 at nine centers in Miyazaki prefecture in Japan. Demographic, clinical, virological, and adverse effects (AE)-related data obtained during and after SOF/LDV therapy were collected from medical records. These patients were divided into two groups, younger (aged < 75 years) and elderly (aged ≥ 75 years). Virological data and AEs were analyzed by age group.

RESULTS

The sustained virological response (SVR) rates at 12 wk after treatment were 99.2%, 99.4%, and 98.7% in the overall population and in patients aged < 75 and ≥ 75 years, respectively. Common AEs during therapy were headache, pruritus, constipation, and insomnia. These occurred in fewer than 10% of patients, and their incidence was not significantly different between the younger and elderly groups. Two patients discontinued treatment, one due to a skin eruption and the other due to cerebral bleeding.

CONCLUSION

Compared with younger patients, elderly patients had a similar virological response and tolerance to SOF/LDV therapy.

Loss of Tyrosine Kinase 2 Does Not Affect the Severity of Jak2V617F-induced Murine Myeloproliferative Neoplasm

BACKGROUND/AIM

In myeloproliferative neoplasms (MPN), Janus kinase 2 (JAK2) is activated by mutations including JAK2V617F (JAK2VF). It is unclear whether JAK kinases [i.e. JAK1, JAK2, JAK3, or tyrosine kinase 2 (TYK2)] other than JAK2 have cooperative actions such as enhancement or suppression of JAK2. If other kinases enhance activation, therapies that co-target them could have a therapeutic efficacy. We examined the role of TYK2 in Jak2VF-induced murine MPN.

MATERIALS AND METHODS

We crossed Jak2VF transgenic mice and Tyk2-knockout (Tyk2KO) mice to generate Jak2VF/Tyk2KO mice. The disease severity and treatment effect with a JAK2 inhibitor was compared between Jak2VF and Jak2VF/Tyk2KO mice.

RESULTS

Both types of mice developed MPN, and there were no differences in peripheral blood counts, spleen weight, or survival period. Upon JAK2 inhibitor therapy, both types of mice had equally improved leukocytosis and splenomegaly.

CONCLUSION

TYK2 does not have cooperative effects with JAK2VF upon MPN onset nor in the presence of a JAK2 inhibitor.

TET2 mutation in diffuse large B-cell lymphoma

Ten-eleven translocation-2 (TET2) mutation is frequently observed in myeloid malignancies, and loss-of-function of TET2 is essential for the initiation of malignant hematopoiesis. TET2 mutation presents across disease entities and was reported in lymphoid malignancies. We investigated TET2 mutations in 27 diffuse large B-cell lymphoma (DLBCL) patients and found a frameshift mutation in 1 case (3.7%). TET2 mutation occurred in some populations of DLBCL patients and was likely involved in the pathogenesis of their malignancies.

TET2 Mutation in Adult T-Cell Leukemia/Lymphoma

Loss-of-function of ten-eleven translocation-2 (TET2) is a common event in myeloid malignancies, and plays pleiotropic roles, including augmenting stem cell self-renewal and skewing hematopoietic cells to the myeloid lineage. TET2 mutation has also been reported in lymphoid malignancies; 5.7～12% of diffuse large B-cell lymphomas and 18～83% of angioimmunoblastic T-cell lymphomas had TET2 mutations. We investigated TET2 mutations in 22 adult T-cell leukemia/lymphoma (ATLL) patients and identified a missense mutation in 3 cases (14%). TET2 mutation occurred in a number of ATLL patients and was likely involved in their leukemogenesis.

Gene expression profiling of loss of TET2 and/or JAK2V617F mutant hematopoietic stem cells from mouse models of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are clinically characterized by the chronic overproduction of differentiated peripheral blood cells and the gradual expansion of malignant intramedullary/extramedullary hematopoiesis. In MPNs mutations in JAK2 MPL or CALR are detected mutually exclusive in more than 90% of cases [1], [2]. Mutations in them lead to the abnormal activation of JAK/STAT signaling and the autonomous growth of differentiated cells therefore they are considered as “driver” gene mutations. In addition to the above driver gene mutations mutations in epigenetic regulators such as TET2 DNMT3A ASXL1 EZH2 or IDH1/2 are detected in about 5%–30% of cases respectively [3]. Mutations in TET2 DNMT3A EZH2 or IDH1/2 commonly confer the increased self-renewal capacity on normal hematopoietic stem cells (HSCs) but they do not lead to the autonomous growth of differentiated cells and only exhibit subtle clinical phenotypes [[4], [6], [7], [8],5]. It was unclear how mutations in such epigenetic regulators influenced abnormal HSCs with driver gene mutations how they influenced the disease phenotype or whether a single driver gene mutation was sufficient for the initiation of human MPNs. Therefore we focused on JAK2V617F and loss of TET2—the former as a representative of driver gene mutations and the latter as a representative of mutations in epigenetic regulators—and examined the influence of single or double mutations on HSCs (Lineage⁻Sca-1⁺c-Kit⁺ cells (LSKs)) by functional analyses and microarray whole-genome expression analyses [9]. Gene expression profiling showed that the HSC fingerprint genes [10] was statistically equally enriched in TET2-knockdown-LSKs but negatively enriched in JAK2V617F–LSKs compared to that in wild-type-LSKs. Double-mutant-LSKs showed the same tendency as JAK2V617F–LSKs in terms of their HSC fingerprint genes but the expression of individual genes differed between the two groups. Among 245 HSC fingerprint genes 100 were more highly expressed in double-mutant-LSKs than in JAK2V617F–LSKs. These altered gene expressions might partly explain the mechanisms of initiation and progression of MPNs which was observed in the functional analyses [9]. Here we describe gene expression profiles deposited at the Gene Expression Omnibus (GEO) under the accession number GSE62302 including experimental methods and quality control analyses.

Portal vein thrombosis during eltrombopag treatment for immune thrombocytopenic purpura in a patient with liver cirrhosis due to hepatitis C viral infection

Portal vein thrombosis is a rare, aggressive and life-threatening complication of liver cirrhosis (LC). Eltrombopag is effective for the treatment of chronic hepatitis with thrombocytopenia, and portal vein thrombosis at this time has rarely been reported. We describe the case of a 78-year-old woman who suffered from LC due to hepatitis C viral infection. The patient developed immune thrombocytopenic purpura (ITP) that was diagnosed on the basis of nasal bleeding, progressive severe thrombocytopenia, elevation of platelet-associated IgG (PAIgG), no response to the transfusion of platelets and no abnormal findings on bone marrow biopsy. Although we first administered prednisolone (0.5 mg/kg/day), there was no recovery of platelet function and the nasal bleeding persisted. Subsequently, we administered eltrombopag for refractory ITP at a dose of 12.5 mg/day, and the thrombocytopenia gradually improved. Fifty-four days after the start of eltrombopag therapy, she developed portal vein thrombosis. Eltrombopag was stopped immediately, and antithrombin III was administered for prophylaxis against further portal vein thrombosis. Despite these treatments, there were subsequent deep vein and pulmonary artery thromboses. We then administered heparin for recanalization of the thrombi. One month after the initiation of heparin, there was recanalization as well as improvements of the portal vein, deep vein and pulmonary artery thromboses. There was no further thrombosis progression after switching from heparin to warfarin therapy. Our case suggests that eltrombopag may increase the risk of portal vein thrombosis ; therefore, this drug must be used carefully in the treatment of ITP in patients with LC due to hepatitis C viral infection.

TET2 is essential for survival and hematopoietic stem cell homeostasis

Ten-Eleven-Translocation 2 (TET2) is an enzyme that catalyzes the conversion of 5-methylcytosine into 5-hydroxymethylcytosine (5-hmC) and thereby alters the epigenetic state of DNA; somatic loss-of-function mutations of TET2 are frequently observed in patients with diverse myeloid malignancies. To study the function of TET2 in vivo, we analyzed Ayu17-449 (TET2(trap)) mice, in which a gene trap insertion in intron 2 of TET2 reduces TET2 mRNA levels to about 20% of that found in wild-type (WT) mice. TET2(trap/trap) mice were born at Mendelian frequency but died at a high rate by postnatal day 3, indicating the essential role of TET2 for survival. Loss of TET2 results in an increase in the number of hematopoietic stem cells (HSCs)/progenitors in the fetal liver, and TET2(trap/trap) HSCs exhibit an increased self-renewal ability in vivo. In competitive transplantation assays, TET2(trap/trap) HSCs possess a competitive growth advantage over WT HSCs. These data indicate that TET2 has a critical role in survival and HSC homeostasis.

[Utility of convex echo probe in laparoscopic radio frequency ablation therapy for hepatocellular carcinoma]

We have examined the utility of the convex echo probe, which has the fine gutter of a puncture needle in laparoscopic radio frequency ablation therapy. When we use a flexible linear echo probe in RFA treatment, we have to puncture tumor with the hand piece in free hand. But it is difficult to treat in the case of HCC which is located in S1 and the lower area of S5 and S6 because we have a narrow space where colon, duodenum and netz are close for safe and exact puncturing of the tumor. We used a convex echo probe in RFA to the above mentioned area of the liver. We punctured with the hand piece exactly and easily without preliminary puncturing of the tumor. So we can perform RFA treatment successfully and safely by a choice of an appropriate echo probe.

Risk factors for the local recurrence of hepatocellular carcinoma after a single session of percutaneous radiofrequency ablation

BACKGROUND

Radiofrequency ablation (RFA) is a new, minimally invasive treatment for hepatocellular carcinoma (HCC). However, there is little available information regarding local recurrence after a single session of RFA with a single electron insertion.

METHODS

From February 1999 to September 2001, we treated 104 HCC tumors with an expandable needle with four hooks. Ninety-nine of the 104 tumors were successfully treated by single-session RFA with a single electrode insertion. We investigated the relationships between pretreatment factors (tumor size, tumor staining, tumor capsule, and tumor location) and local recurrence in these 99 tumors.

RESULTS

The mean size of the 99 tumors was 21.5 mm in diameter (range, 10 to 33 mm). The overall local recurrence rates were 9.7%, 15.4%, and 20.4%, at 1, 2, and 3 years, respectively. For small tumors (smaller than 25 mm), the local recurrence rates at 1, 2, and 3 years were 4.0%, 8.0%, and 14.6%, respectively. The local recurrence rates were 21.1% and 32.3% at 1 and 2 years, respectively, for large tumors (25 mm or larger), and at 3 years the rate was over 50% for tumors located close to the liver surface. Tumor size and tumor location relative to the liver surface were significantly associated with a higher local recurrence rate. However, other variables tested showed no significant relationship to the local recurrence rate.

CONCLUSIONS

This study demonstrated that both tumor size and location relative to the liver surface influence the local efficacy of single-session RFA with a single electrode insertion.Radiofrequency ablation (RFA) is a new, minimally invasive treatment for hepatocellular carcinoma (HCC). However, there is little available information regarding local recurrence after a single session of RFA with a single electrode insertion.

[A case of a traumatic anterior cerebral artery aneurysm following the penetration of the skull base by an iron rod]

A 61-year-old male fell from a position 1 m high when building a house. An iron rod, which protruded upward from a solid base in cement, penetrated this patient's neck 15 cm to the head and was successfully extracted by himself. On admission, he complained of headache and vomiting. General examination disclosed nasal bleeding, intraoral bleeding, and L figured skin laceration in the left side of his neck at the level of the thyroid cartilage. Mild disorientation (JCS2) was noted. Otolaryngological examination disclosed hyperemia on the left side of the vocal cord as well as at the dome of the superior pharynx. Plain skull film disclosed pneumocephalus and that a piece of bone fragment of the planum sphenoidale had penetrated the brain. CT demonstrated air in the subarachnoid space, ventricular hemorrhage, intracerebral hematoma in the right frontal lobe, and subarachnoid hemorrhage in the anterior interhemispheric fissure. CAG detected neither cerebral vascular abnormalities nor cerebral aneurysm. While staying in our department, he developed mild fever and CSF rhinorrhea. The diagnosis of bacterial meningitis was made from the CSF finding and was well controlled with conservative therapy. CSF rhinorrhea stopped spontaneously with conservative treatment. Sagittal MRI continuously demonstrated contusional hematoma in the base of the right frontal lobe just above the fractured planum sphenoidale and genu of the corpus callosum following the course of the intracranially invading iron rod. The right CAG on Day 10 demonstrated vasospasm on the A1 and a 1 cm sized saccular cerebral aneurysm at the proximal right fronto-polar artery. CAG on Day 17 again showed the persistent presence of the aneurysm. For the purpose of preventing delayed rupture of the aneurysm, radical surgical treatment was planned. Microsurgical dissection disclosed that the aneurysm was located just behind the elevated fracture of the planum sphenoidale. Severe arachnoid adhesion was noted around the aneurysm. The aneurysm was successfully clipped with preservation of the parent artery without inducing new neurological deficits. From the general, otolaryngological, neuroradiological, and operative findings, this aneurysm was diagnosed as a traumatic cerebral artery aneurysm following the penetration of the skull base by the iron rod. The CAG performed at 8 months postoperatively demonstrated the patency of the parent artery and that there was no recurrence of the aneurysm. An unusual case of a traumatic cerebral artery aneurysm following the penetration of the skull base by an iron rod was thus reported.

Stimulus effects of the medial pontine reticular formation and the mesencephalic locomotor region upon medullary reticulospinal neurons in acute decerebrate cats

In acute decerebrate cats, medial pontine reticular formation (mPRF) and the mesencephalic locomotor region (MLR) were stimulated and their stimulus effects upon 250 medullary reticulospinal neurons (RSNs) were studied. One hundred and twenty-six RSNs were mono- and disynaptically activated. From the response patterns of the RSNs, they were divided into the mPRF-activated RSNs (n = 67) and the MLR-activated RSNs (n = 59). The former group of RSNs was located in the nucleus reticularis gigantocellularis (NRGc), while the latter group of RSNs was distributed in both the NRGc and the nucleus reticularis magnocellularis (NRMc). The activity of MLR-excited 12 RSNs was suppressed with the preceding mPRF stimulation. These RSNs were mainly located in the NRMc. Most mPRF-excited RSNs increased their discharge rates during mPRF-evoked suppression of postural muscle tone, and most MLR-excited RSNs increased their discharge rates during MLR-evoked locomotion. With mPRF stimulation, MLR-evoked locomotion was suppressed with cessation of MLR-excited RSNs activity. These results suggest that mPRF stimulation suppresses the activity of the locomotor rhythm generating system at the levels of not only the spinal cord but also the medullary output cells.

Multi-segmental and generalized suppression of postural muscle tone evoked by stimulating the dorsal tegmental field and the medial pontine reticular formation in acute decerebrate cats

In acute decerebrate cat, stimulation of the dorsal tegmental field (DTF) of the caudal pons along its midline and the medial pontine reticular formation (mPRF) evokes generalized suppression of postural muscle tone. In this study, the effects of stimulation of the DTF area were compared with those evoked by stimulating the mPRF unilaterally or bilaterally. By stimulating the mPRF bilaterally, simultaneous suppression of tonic activities in the neck, lumbar back, forelimb and hindlimb muscles, bilaterally, was evoked as that evoked by stimulating the DTF area alone.

Extracellular levels of serotonin in the medial pontine reticular formation in acute decerebrate cats with a microdialysis technique

Extracellular levels of serotonin (5-HT) and 5-hydroxyindolacetic acid (5-HIAA) were measured in the medial pontine reticular formation of acute decerebrate cats. The mean basal levels of 5-HT and 5-HIAA were 26 fmol/20 microliters and 15 pmol/20 microliters. Perfusion of the dialysis probe with high K+ and Ca(2+)-free Ringer solution for 60 min resulted in 4.8-8.5 x increase and 25-48% decrease in the extracellular levels of 5-HT, respectively, in comparison to the basal 5-HT levels. Perfusion with TTX-added Ringer solution for 60 min resulted in a consistent decrease in the extracellular levels of 5-HT.

Extracellular levels of serotonin in the medial pontine reticular formation in relation to sleep-wake cycle in cats: a microdialysis study

Extracellular levels of endogenous serotonin (5-hydroxytryptamine; 5-HT) and its major metabolite, 5-hydroxyindoleacetic acid (5-HIAA) were measured in the medial pontine reticular formation (medial PRF) of intact cats. A microdialysis probe was inserted through a guide cannula into the medial PRF. At least 12 h after the probe insertion, in vivo brain microdialysis was initiated. The perfusion rate was 1 microliters/min, and perfusate fractions at regular intervals of 20 min were collected. Changes in extracellular 5-HT levels were compared across sleep-wake states of the animals, such as waking (W), slow wave sleep (SWS) and rapid eye movement (REM) sleep. To assess sleep-wake states, EEG, EMG, EOG and PGO waves were simultaneously recorded in parallel with microdialysis of the medial PRF. Extracellular 5-HT levels were highest (20-28 fmol/20 microliters) during W. As the animals entered SWS, 5-HT levels decreased to about 90% of those during W. The state of REM sleep usually interrupted SWS for 3-8 min. During the longer periods of REM sleep, during the 20 min periods in which the perfusates were collected, we observed the lowest 5-HT levels (60-50%).

Pontine-induced generalized suppression of postural muscle tone in a reflexively standing acute decerebrate cat

In a reflexively standing acute decerebrate cat, the pontine tegmentum was electrically stimulated and the effects on postural muscle tone and locomotor movements evoked by stimulation of the mesencephalic locomotor region (MLR) were studied. A stimulating microelectrode was placed systematically at 1-mm increments throughout the pons (H - 2 to H - 10) at levels ranging from P0.0 to P6.5 dorsoventrally and mediolaterally from LR0 to L4 or R4. Another stimulating microelectrode was placed in the physiologically identified MLR. Stimuli delivered to the dorsomedial regions of the pontine tegmentum (P3 to P4, LR1.5 to 2.5, H - 4 to H - 6) resulted in simultaneous and bilateral suppression of tonic activities in the neck, lumbar back, forelimb and hindlimb muscles. The pontine inhibitory sites corresponded to the medial area of the central tegmental field (FTC) and the central area of the gigantocellular tegmental field (FTG), bilaterally. Effects of pontine induced suppression on those muscles were stimulus frequency and stimulus intensity-dependent and the effects persisted even after termination of the stimulation. With concomitant pontine stimulation, MLR-evoked locomotor movements were suppressed along with prolongation of the forelimb and hindlimb step cycles.