Detection of biomagnetic signals from induced pluripotent stem cell-derived cardiomyocytes using deep learning with simulation data.

The detection of spontaneous magnetic signals can be used for the non-invasive electrophysiological evaluation of induced pluripotent stem cell-derived cardiomyocytes (iPS-CMs). We report that deep learning with a dataset that combines magnetic signals estimated using numerical simulation and actual noise data is effective in the detection of weak biomagnetic signals. To verify the feasibility of this method, we measured artificially generated magnetic signals that mimic cellular magnetic fields using a superconducting quantum interference device and attempted peak detection using a long short-term memory network. We correctly detected 80.0% of the peaks and the method achieved superior detection performance compared with conventional methods. Next, we attempted peak detection for magnetic signals measured from mouse iPS-CMs. The number of detected peaks was consistent with the spontaneous beats counted using microscopic observation and the average peak waveform achieved good similarity with the prediction. We also observed the synchronization of peak positions between simultaneously measured field potentials and magnetic signals. Furthermore, the magnetic measurements of cell samples treated with isoproterenol showed potential for the detection of chronotropic effects. These results suggest that the proposed method is effective and has potential application in the safety assessment of regenerative medicine and drug screening.

Efficacy of a Deep Thermal Therapy System for Osteoarthritis of the Knee.

BACKGROUND: This study sought to assess the efficacy of a deep-tissue thermal therapy system with a resonant cavity applicator (DTT-RCA), which safely heats deep joint tissue for treating osteoarthritis (OA) of the knee. METHODS: Two groups of participants were recruited. The DTT-RCA group comprised 20 knees. Kellgren-Lawrence (K-L) grade was I and II in 8 knees (DTT-RCA I/II group) [mean age 73.3 years (standard deviation 11.4) ], III and VI in 12 knees (DTT-RCA III/IV group) [75.4 (8.6) years]. The control group comprised 13 knees [68.2 (10.8) years]. K-L grade was I in 7 knees and II in 6 knees. This group received exercise therapy. The DTT-RCA I/II group and the control group were imaged by MRI T2 mapping at baseline and 6 months to determine the area of cartilage degeneration. RESULTS: Visual Analogue Scale improved only in the DTT-RCA I/II post-intervention (p < 0.01). Japanese Orthopedic Association knee rating scores (DTT-RCA I/II: p < 0.01, control group: p < 0.01), the Japanese Knee Osteoarthritis Measure (DTT-RCA I/II: p < 0.05, control: p < 0.01), and the Knee injury and Osteoarthritis Outcome Score (DTT-RCA I/II: p < 0.01, DTT-RCA III/IV: p < 0.05, control: p < 0.01) post-intervention. The magnitude of change did not differ significantly between the three groups. The area of cartilage degeneration did not change significantly post-intervention in the DTT-RCA I/II group, not even relative to the control group. CONCLUSIONS: This was the first study to test a DTT-RCA system in patients with knee OA. The system reduced the clinical symptoms of knee OA and could potentially be effective for conservative therapy.

Deep heat therapy system with resonant cavity applicator for articular cartilage in knee osteoarthritis.

[Purpose] Heat can prevent cartilage degeneration when applied to articular cartilage, but the size of the human knee joint makes it difficult to target cartilage during heat treatment. In this study, we aimed to establish a heat therapy method capable of safely applying heat to deep intra-articular tissues utilizing a resonant cavity applicator and to confirm the extent of cartilage heating in the human knee when using this system. [Participants and Methods] Heating experiments were carried out on the knees of healthy three volunteers using a resonant cavity applicator and a microwave diathermy system. After heat application, temperature distributions inside the knee were measured noninvasively using our measurement method based on ultrasound imaging techniques. [Results] We observed an increase in the temperature around the cartilage tissue in the knees of the volunteers using an ultrasonic thermometer; there was no increase in temperature in the overlying layers. During heating with up to 20 W of power, none of the volunteers experienced adverse reactions. [Conclusion] This study indicates the potential safety and effectiveness of the resonant cavity heat therapy system for knee osteoarthritis in a clinical setting.

Validation of Noninvasive Ultrasound Temperature Measurement System Through Experiments Using Resonant Cavity Applicator.

We developed a resonant cavity applicator for noninvasive deep hyperthermia treatment of osteoarthritis. In previous studies, we confirmed its viability by heating agar phantoms and conducting computer simulations. To evaluate the heating performance of this system on human subjects, it is necessary to develop a new noninvasive temperature measurement system. In this study, we developed a new temperature measurement system utilizing ultrasound imaging techniques. After heating an agar phantom with our resonant cavity applicator, temperature measurements from both our custom-made noninvasive ultrasonic thermometer and an optical fiber thermometer were collected and compared. Both temperature distributions showed a reliable trend, with heat energy concentrated at the center of the agar phantom. Average error rates were less than 13% for temperatures. The results of this study describe the viability of the temperature measurement system and the resonant cavity applicator for clinical applications.

Bromein, a Bromelain Inhibitor from Pineapple Stem: Structural and Functional Characteristics.

Bromelain inhibitor, "bromein", is a proteinase-inhibitor specific to the cysteine proteinase bromelain from pineapple stem. In the stem, eight bromein isoforms are known to exist, and each isoform has a short peptide (light chain) and a long one (heavy chain) with five disulfide bonds. The three-dimensional structure of the sixth isoform (bromein-6) is composed of inhibitory and stabilizing domains, and each domain contains a three-stranded antiparallel ß-sheet. The genomic sequence of a bromein precursor encodes three homologous bromein isoform domains, and each isoform domain has a signal peptide, three interchain peptides between the light chain and heavy chain, two interdomain peptides and a propeptide. Interestingly, at the protein level, bromein- 6 appears to share a similar folding and disulfide-bonding connectivity with Bowman-Birk serine proteinase inhibitors and shows weak inhibition toward chymotrypsin and trypsin. However, no significant similarity was found between them at the genomic level. This indicates that they have evolved convergently to possess such a structural similarity. To identify the essential reactive site(s) with bromelain, we investigated the inhibitory activity of 44 kinds of the single/double and insertion/ deletion mutants of bromein-6 towards stem bromelain. As a result, it was shown that both the appropriate positioning and the complete side-chain structure of Leu10 in the light chain are absolutely crucial for the inhibition, with an additional measure of importance for the preceding Pro9. Bromein and stem bromelain coexist in the acidic vacuoles of the stem tissue, and one of the key role of bromein appears to be the regulation of the bromelain activity.

Effectiveness of Radiofrequency Hyperthermia for Treating Cartilage in Guinea Pigs with Primary Osteoarthritis.

Objective Autophagy was reported to be essential for maintaining chondrocyte function, and reduced autophagy leads to osteoarthritis (OA). Previous studies showed involvement of heat shock stress in the control of autophagy in cells. This study sought to investigate the effect of hyperthermia on the expression of autophagy-related proteins in articular cartilage and the progression of naturally occurring OA in Hartley guinea pigs. Design Radiofrequency pulses of 13.56 MHz were applied to the animals' knees for 20 minutes to induce hyperthermia. The knee joints were resected at 8 hours, 24 hours, 72 hours, 7 days, and 6 months after hyperthermia. Serial sections of knees were examined for histopathological changes. The expression levels of Unc-51-like kinase 1 (ULK1) and Beclin1 were analyzed by immunohistochemistry. Results Analysis of the distribution of positive cells showed that, in cases of moderate OA, ULK1 and Beclin1 expression levels were significantly decreased in the superficial zone (SZ) and middle zone (MZ) ( P < 0.01) compared with normal cartilage. Seven days after exposure to radiofrequency waves, expression levels of ULK1 and Beclin1 were augmented in the SZ in animals with mild OA. The severity of cartilage degradation was significantly reduced ( P < 0.01) in the radiofrequency-treated knees versus the untreated knees. Conclusions This study showed that heat stimulation enhanced autophagy in healthy knee chondrocytes and chondrocytes in knees with mild OA. The study also showed that long-term periodic application of hyperthermia suppresses aging-related progression of OA. The activation of autophagy by radiofrequency hyperthermia may be an effective therapeutic approach for osteoarthritis.

[Changes in Electrolytic Concentration Resulting from Perioperative Amino Acid Fluid Administration].

BACKGROUND: Amino acid infusion is frequently selected to avoid hypothermia during surgery. However, changes in electrolytic concentration resulting from its use are unclear. The aim of this study was to identify the effect of amino acid on body temperature and changes in electrolytic concentrations. METHODS: Thirty women undergoing breast cancer surgery under general anesthesia were divided into the following three groups: no amino acid administration, low-dose administration (2 ml x kg(-1) x hr(-1)), and high-dose administration (4 ml x kg(-1) x hr(-1)). Esophageal temperature was recorded every ten minutes and arterial blood samples were obtained before and after surgery. Body temperatures at each time point and arterial blood gas data, including blood gases, electrodes, serum glucose, and hematocrit were compared between the three groups. RESULTS: Body temperature started to increase significantly 40 minutes after starting general anesthesia in the high-dose group, 90 minutes after starting general anesthesia in the low-dose group compared with the no amino acid group. Body temperature was maintained until surgery was completed. The concentration of sodium ion decreased significantly (2.4 mmol x l(-1)) in the high-dose group compared with the other two groups. The concentration of other electrolytes, including potassium, chloride, and calcium, did not change significantly. CONCLUSIONS: Perioperative amino acid administration was effective in maintaining a stable body temperature during surgery under general anesthesia. However, sodium ion concentration might decrease after amino acid administration of 4 ml x kg(-1) x hr(-1) or greater.

The effects of radiofrequency hyperthermia on pain and function in patients with knee osteoarthritis: a preliminary report.

BACKGROUND: The clinical evidence of the efficacy of hyperthermia on osteoarthritis (OA) has not yet been clearly established. In addition, the application of a modality that can control the temperature inside the joints has not been reported. The purpose of this study was to investigate the effect of percutaneous radiofrequency hyperthermia, which could safely raise the temperature of the body core, in patients with OA knees. METHODS: Temperature changes inside the knee joint without OA were measured during exposure to radiofrequency. Radiofrequency hyperthermia was performed on 12 OA knees by exposure to 8 MHz and 200 W for 20 min, 3 times, at 1-week intervals. The clinical outcome was evaluated by use of the Lequesne index (LI) and the Japan Orthopaedic Association (JOA) scale. The osteoarthritis research society international (OARSI) responder criteria were also analyzed. RESULTS: Radiofrequency hyperthermia of 8 MHz and 200 W for 20 min increased the temperature inside the joint from 34.4 to 39.4°C. The LI decreased by 3.55 points from baseline during the 3 weeks. The JOA scale improved significantly during the period, reaching 86.25 points at the final examination from baseline of 67.5 points. 67% of patients had a response to the therapy according to OARSI criteria. No side effects were observed. CONCLUSIONS: Radiofrequency hyperthermia can safely increase the temperature inside the knee joint. Radiofrequency hyperthermia on OA knees provides a remarkable pain relief effect and can improve the patients' daily life. In the future, clinical studies should be performed with a protocol containing more cases, with appropriate control groups.

Structure-activity relationships and the cytotoxic effects of novel diterpenoid alkaloid derivatives against A549 human lung carcinoma cells.

The cytotoxicity of three alkaloids from the roots of Aconitum yesoense var. macroyesoense as well as 36 semi-synthetic C(20)-diterpenoid atisine-type alkaloid derivatives against A549 human lung carcinoma cells was examined. Ten acylated alkaloid derivatives, pseudokobusine 11-veratroate (9), 11-anisoate (12), 6,11-dianisoate (14), 11-p-nitrobenzoate (18), 11,15-di-p-nitrobenzoate (22), 11-cinnamate (25) and 11-m-trifluoromethylbenzoate (27), and kobusine 11-p-trifluoromethylbenzoate (35), 11-m-trifluoromethylbenzoate (36) and 11,15-di-p-nitrobenzoate (39), exhibited cytotoxic activity, and 11,15-dianisoylpseudokobusine (16) was found to be the most potent cytotoxic agent. Their IC(50) values against A549 cells ranged from 1.72 to 5.44 µM. In the occurrence of cytotoxic effects of atisine-type alkaloids, replacement by an acyl group at both C-11 and C-15 resulted in the enhancement of activity of the parent alkaloids compared to that from having hydroxy groups at this position, and the presence of a hydroxy group at the C-6 position was required for the cytotoxic effects. These acylated alkaloid derivatives inhibit cell growth through G1 arrest.

Structure-activity relationships between the Aconitum C20-diterpenoid alkaloid derivatives and the growth suppressive activities of Non-Hodgkin's lymphoma Raji cells and human hematopoietic stem/progenitor cells.

The anti-tumor properties of novel derivatives prepared from Aconitum C(20)-diterpenoid alkaloid, which show the least toxicity among the Aconitum alkaloids, were investigated in the Non-Hodgkin's lymphoma cell line Raji cells. Two novel Aconitum C(20)-diterpenoid alkaloid derivatives, 11-m-Trifluorometylbenzoyl (Mb)-pseudokobuisne and 11-Anisoyl (As)-pseudokobusine, showed significant suppressive effects and their 50% inhibitory concentrations were 2.2 µg/ml and 2.4 µg/ml against Raji cells, respectively. Both compounds have the same structure except for a functional group in the C-11 position. One of the active compounds, 11-Mb-pseudokobusine, clearly inhibited the phosphorylation of extracellular signal-regulated kinase, induced enhanced phosphoinositide 3 kinase phosphorylation and led to the subsequent accumulation of G1 and/or sub G1 phase in Raji cells. In addition, no significant suppressive effects on the growth of human CD34(+) hematopoietic stem/progenitor cells (HSPC) were observed by 11-Mb-pseudokobusine which showed a strong suppressive activity on the growth of Raji cells, whereas 11-As-pseudokobusine also a showed significantly suppressive effect on the growth of HSPC. Therefore, the atisine type structure characteristic of C(20)-diterpenoid alkaloids plays a very important role in the pharmacological properties. In particular, the C-11 residues are an important component for the anti-tumor properties and for the lower toxicity to hematopoiesis.

Vitamin E prevents steroid-induced osteonecrosis in rabbits.

BACKGROUND AND PURPOSE: Prevention of osteonecrosis after corticosteroid administration would be important. We examined the potential of vitamin E (alpha-tocopherol) to reduce the incidence of corticosteroid-induced osteonecrosis in an animal model. METHODS: Japanese white rabbits were divided into 2 groups; the control group was fed a normal diet and the experimental group was fed alpha-tocopherol-supplemented diet in which alpha-tocopherol (600 mg/kg diet) was added to the normal diet. To induce osteonecrosis, high-dose methylprednisolone acetate (MPSL) (20 mg/kg body weight) was injected once into the right gluteus medius muscle of all rabbits. 4 weeks after the injection of MPSL, the presence or absence of osteonecrosis of bilateral femurs was examined histopathologically. The tocopherol/cholesterol ratios were calculated. The plasma levels of thiobarbituric acid-reactive substances (TBARS) were measured. RESULTS: Alpha-tocopherol-supplemented diet reduced the incidence of osteonecrosis, which developed in 14 of 20 rabbits in the control group and 5 of 21 rabbits in the experimental group (p = 0.004). The tocopherol/cholesterol ratio was higher in the experimental group than in the control group after the alpha-tocopherol administration. The plasma TBARS level was lower in the experimental group than in the control group at 4 weeks after the MPSL administration. INTERPRETATION: Our findings may offer a new approach for the prevention of corticosteroid-induced osteonecrosis.

MDR1a/1b gene silencing enhances drug sensitivity in rat fibroblast-like synoviocytes.

BACKGROUND: Drug resistance mediated by P-glycoprotein (P-gp) is one of the major reasons for the failure of rheumatoid arthritis (RA) therapy with disease modifying anti-rheumatic drugs and glucocorticoids. In the present study, we aimed to investigate the in vitro effectiveness of small interfering RNA (siRNA) to render rat fibroblast-like synoviocytes (FLS) susceptible to drugs. We also attempted the electroporation-mediated transfer of siRNA against multidrug resistance (MDR) genes into rat knee joints. METHODS: FLS were transfected with siRNAs corresponding to MDR1a and MDR1b genes. FLS were treated with dexamethasone (DEX) and lipopolysaccharide. The mRNA and protein levels of tumor necrosis factor-alpha, interleukin (IL)-6 and IL-1beta were measured. Both siRNAs were co-transduced into rat knee joints by an electroporation method and evaluated the target gene expressions in the synovium. RESULTS: Each siRNA could sequence-specifically reduce the target gene expression by over 70% and effectively suppressed P-gp expression and function in the FLS. Both gene expression and protein production of the inflammatory cytokines in the cells transfected with siRNA were reduced by a greater amount compared to in control cells. The in vivo electroporation-mediated transduction of siRNA could significantly inhibit the target gene expressions. CONCLUSIONS: MDR1a/1b gene silencing by siRNA could effectively inhibit P-gp in rat FLS, resulting in a significant enhancement of the anti-inflammatory effects of DEX. The in vivo siRNA transduction could successfully silence MDR gene expression in the rat synovium. These findings indicate that the siRNA targeting MDR gene could be a useful tool for treating refractory arthritis in RA.

[A case of pathological complete response of metachronous multiple liver metastases from colorectal cancer after mFOLFOX+bevacizumab chemotherapy].

A 25-year-old man with RS rectal cancer received a radical resection of the original tumor and lymph node dissection. Oral tegafur/uracil (UFT)/Leucovorin (LV) therapy has been used for adjuvant chemotherapy, as the pathological Stage was T3N1M0, Stage IIIa. After 10 months from operation, multiple liver metastases were recognized and not resectable. So a systemic chemotherapy by mFOLFOX6+bevacizumab was begun via CV port. After 5 courses of mFOLFOX6+bevacizumab, abdominal CT revealed liver metastases showed remarkable reduction in size. Hepatic resection of S6 segment was enforced, and the patient uneventfully discharged. Pathological findings of S6 segment revealed no residual cancer cells, indicating the histological effect of mFOLFOX6+bevacizumab was Grade 3. And no liver damage was recognized.

Hyperthermia for the treatment of articular cartilage with osteoarthritis.

Osteoarthritis (OA) is one of the most frequent musculoskeletal disorders in the elderly population. OA is characterised by a gradual loss of extracellular matrix in the articular cartilage of joints. OA can only be managed by artificial joint replacement when joint destruction becomes severe. Therefore, it is preferable to administer conservative therapy that is easy, simple and effective in inhibiting OA progression at the early stage. Heat shock protein 70 (Hsp70) has a protective effect on the cartilage and inhibits the apoptosis of chondrocytes. Heat stimulation by microwave to the joints can increase Hsp70 expression in chondrocytes, and at the same time, Hsp70 expression partially enhances matrix metabolism of the cartilage. These findings suggest that hyperthermia can be positively applied to the treatment of OA. Hyperthermia is therefore expected to be an inexpensive and less-invasive conservative therapy for OA.

[A case of resection of synchronous multiple liver metastases from colorectal cancer after FOLFOX chemotherapy].

A 41-year-old man with multiple liver metastases from sigmoid colon cancer received a radical resection of the original tumor and 16 courses of weekly high-dose 5-FU(WHF)chemotherapy via hepatic arterial reservoir. The metastatic lesions showed stable disease(SD), and systemic chemotherapy by mFOLFOX6 was begun via CV port. After 14 courses of mFOLFOX4, abdominal CT revealed liver metastases were remarkably reduced in size. Hepatic resection of lateral segment and radio frequency ablation(RFA)for S6 were enforced, and the patient was uneventfully discharged. Pathological findings of lateral segment revealed no residual cancer cells, indicating that the histological effect of mFOLFOX6 was Grade 3.

Suppressive effects of novel derivatives prepared from Aconitum alkaloids on tumor growth.

Little information has so far been reported regarding the antiproliferative properties of Aconitum alkaloids against human tumor cells despite of their intense toxicities. In the present study, the antitumor properties and radiation sensitizing effects were investigated by various types of novel derivatives prepared from Aconitum alkaloids. The antitumor properties were investigated against human tumor cell lines, A172, A549, HeLa and Raji, respectively, by a cell growth, a clonogenic assay, cell cycle distribution, cell cycle related molecules and gammaH2AX expression. The novel compounds derived from C(20)-diterupenoid alkaloids showed a significantly suppressive effect in all cell lines. In contrast, natural C(19)-norditerpenoid alkaloids and their derivatives showed either no effect or only a slight effect. One of the compounds also showed radiosensitizing properties on A549 cells. These effects are not related to either the cell cycle distribution, the enhancement of apoptosis or the gammaH2AX expression. Novel derivatives prepared from Aconitum alkaloids, not but natural alkaloids, clearly showed anti-proliferative activity in human tumor cell lines.

Inhibitory effects of isoliquiritigenin and licorice extract on voltage-dependent K(+) currents in H9c2 cells.

The effect of isoliquiritigenin (ISL), a component of licorice, on the voltage-dependent, ultra-rapidly activating delayed-rectifier K(+) current (IKur) was examined in H9c2 cells, a cell-line derived from rat cardiac myoblasts. IKur was recorded using the whole-cell patch clamp method with a pipette solution containing 140 mM K(+). Depolarizing voltage pulses of 200-ms duration were given with 10-mV steps every 10 s from -40 mV holding potential. ISL inhibited IKur in a concentration-dependent manner. The median inhibitory concentration (IC(50)) of ISL was approximately 0.11 microM and the Hill coefficient was 0.71. Using CHO cells expressing Kv1.5 IKur channels, ISL also inhibited Kv1.5 IKur, but less potently than the IKur current in H9c2 cells. Furthermore, in H9c2 cells, the licorice extract itself inhibited IKur in a manner similar to ISL. We conclude that ISL, one component of licorice, is a potent inhibitor of K(+) channels, which specifically in H9c2 cells could be Kv2.1, and that this inhibition may be involved in various pharmacological effects of licorice.

Electromagnetic fields: a novel prophylaxis for steroid-induced osteonecrosis.

Establishing a means to prevent osteonecrosis after corticosteroid administration is an important theme. We asked whether pulsed electromagnetic field stimulation, a noninvasive treatment, could prevent osteonecrosis. Ninety rabbits were divided into four treatment groups: (1) exposure of 10 hours per day to electromagnetic stimulation for 1 week, followed by injection of methylprednisolone (20 mg/kg), and exposure of 10 hours per day to electromagnetism for a further 4 weeks (n = 40); (2) methylprednisolone injection only (n = 40); (3) no treatment (n = 5); and (4) exposure of 10 hours per day to electromagnetism for 5 weeks (n = 5). After 5 weeks, we harvested and histologically examined femurs bilaterally. The frequency of osteonecrosis was lower in the steroid-electromagnetism group (15/40) than in the steroid-only group (26/40). No necrotic lesions were found in the two control groups. We observed no clear effects of electromagnetism on the number, location, extent, and repair of necrotic lesions and intramedullary fat cell size in affected rabbits. Pulsed electromagnetic field stimulation reportedly augments angiogenesis factors and dilates blood vessels; these effects may lower the frequency of osteonecrosis. Exposure to pulsed electromagnetic field stimulation before corticosteroid administration could be an effective means to reduce the risk of osteonecrosis.

Inhibitory effects of diterpenoid alkaloids on the growth of A172 human malignant cells.

The cytotoxicity against A172 human malignant glioma cells was examined for 14 alkaloids from the roots of Aconitum yesoense var. macroyesoense and of Aconitum japonicum and from the seeds of Delphinium elatum as well as for 25 semisynthetic derivatives. The major alkaloid constituents of A. yesoense var. macroyesoense, kobusine (2) and pseudokobusine (3), a minor alkaloid constituent of A. japonicum, aljesaconitine A (5), and six alkaloid derivatives, N-deethyldelcosine (10), N-deethyldelsoline (11), 12-benzoylluciculine (18), 12-anisoylluciculine (19), 6,11-dibenzoylpseudokobusine (28), and 6-veratroylpseudokobusine (29), had only very weak activity. Four acylated alkaloid derivatives, 12-acetylluciculine (23), 11-veratroylpseudokobusine (30), 11-(m-trifluoromethylbenzoyl)pseudokobusine (32), and 11-(m-trifluoromethylbenzoyl)kobusine (39), exhibited more potent activity, while pseudokobusine 11-cinnamoate (31), 11-anisoate (33), and 11-p-nitrobenzoate (34) were found to be the most potent cytotoxic agents.

Neural circuits containing pallidotegmental GABAergic neurons are involved in the prepulse inhibition of the startle reflex in mice.

BACKGROUND: Prepulse inhibition (PPI) of the startle response is a measure of the inhibitory function and time-linked information processing by which a weak sensory stimulus (the prepulse) inhibits the startle response caused by a sudden intense stimulus. We attempted to clarify the neuronal circuits underlying the control of PPI of the startle reflex in mice. METHODS: c-Fos immunohistochemistry was used to detect neurons activated by startle pulse and/or prepulse trials. Behavioural pharmacology and tracing studies were also conducted. RESULTS: The lateral globus pallidus (LGP) was activated by prepulses. Activation of the caudal pontine reticular nucleus (PnC) evoked by the startle pulses was inhibited under PPI conditions. Double-immunostaining revealed that c-Fos-positive cells in the LGP following prepulse trials were GABAergic neurons. Bilateral microinjections of lidocaine into the LGP resulted in an impairment of PPI. Fluoro-gold infusion into the PnC and the pedunculopontine tegmental nucleus (PPTg) retrogradely labeled neurons in the PPTg and LGP, respectively. Microinjections of phaclofen into the PPTg significantly impaired PPI. CONCLUSIONS: These results suggest that GABAergic neurons in the LGP which project to the PPTg play a crucial role through the activation of GABAB receptors in the regulation of PPI of the startle reflex in mice.