Fluidized landslides triggered by the liquefaction of subsurface volcanic deposits during the 2018 Iburi-Tobu earthquake, Hokkaido.

The 6.6 Mw Iburi-Tobu earthquake struck southern Hokkaido, Japan on 6 September 2018. The earthquake triggered widespread slope collapses in the hills near the epicenter, resulting in destructive landslides that killed 36 people. Volcanic deposits covering the region slid downhill in a flow-like manner suggestive of fluidized landslides. Here, we report a distinctive example of liquefaction in the field, which could be a prerequisite for the generation of fluidized landslides triggered by large earthquakes. In the scarp of a typical landslide, an altered halloysite-bearing volcanic layer is observed at a level almost coincident with the sliding surface. The layer is intensely undulating and can be divided into an upper clay-rich layer and a lower pumice-rich layer, suggesting that the altered layer had liquefied as a result of the strong coseismic ground motion. The layer had been soaked by heavy rainfall just one day before the earthquake and could have liquefied, producing a weak and slippery plane, resulting in the catastrophic landslides in this area.

Responses to noxious stimuli in mice lacking alpha(1d)-adrenergic receptors.

Nociceptive behaviors were examined in the mice lacking alpha1d-adrenergic receptor (alpha1d-AR) and wild type littermates using tail-flick, hot-plate (hindpaw-licking and jumping), tail-pinch and formalin tests. The distribution of alpha1d-AR was studied using in situ hybridization in the wild type mice. Mutant mice showed longer tail-flick and hindpaw-licking latencies while their jumping latency was shorter. Mechanical and chemical nociception was not altered in alpha1d-knockout mice. In situ hybridization study revealed dense alpha1d-AR mRNA expression in the reticular thalamic nucleus, the hippocampus, the cingulate cortex and the spinal cord. These results suggest that alpha1d-AR in the spinal cord contributes to thermal pronociception; and that the jump behavior seen when escaping from heat is inhibited via the supraspinal alpha1d-AR.

Characteristics of behavioral abnormalities in alpha1d-adrenoceptors deficient mice.

To investigate the functional role of alpha1d-adrenergic receptor (alpha1d-AR) in the CNS, we have generated mutant mice lacking the alpha1d-AR using a gene targeting approach and examined in detail the effects of alpha1d-AR knockout mice on motor function, sensory function, and learning and memory. alpha1d-AR knockout mice showed better motor coordination at the highest rotating speed of the rotarod performance and stronger muscle tone using the traction meter, but their locomotor activity and swimming ability in the water maze were not affected. In the water maze requiring reference memory, alpha1d-AR knockout mice showed normal spatial learning. In the Y-maze task requiring working memory or attention, alpha1d-AR knockout mice displayed an impaired spontaneous alternation performance. The alpha1d-AR knockout mice tended to display lower levels of acoustic startle responses than the wild-type group at lower pulse intensities, although the acoustic prepulse inhibition was not impaired in the alpha1d-AR knockout mice. Furthermore, the NMDA receptor antagonist, MK-801-induced deficits of acoustic prepulse inhibition were not observed in the alpha1d-AR knockout mice. These results clearly demonstrate that the alpha1d-AR receptor plays an important role in the process of auditory sensory function, attention or working memory rather than reference memory, and the sensorimotor gating deficits induced by the NMDA receptor antagonist.

Intrathecal clonidine inhibits mechanical allodynia via activation of the spinal muscarinic M1 receptor in streptozotocin-induced diabetic mice.

We examined the involvement of the spinal muscarinic receptors in the clonidine-induced antiallodynic effects. Mechanical sensitivity was assessed by stimulating the hind paw with von Frey filaments. In streptozotocin-treated (200 mg/kg, i.v.) diabetic mice, hypersensitivity to mechanical stimulation appeared 3 days after streptozotocin administration, and persisted for 11 days. This mechanical hypersensitivity (allodynia) was inhibited by the intrathecal (i.t.) injection of clonidine. The muscarinic receptor antagonist atropine (i.t.) and alpha2-adrenoreceptor antagonist yohimbine (i.t. or subcutaneous injection) abolished the antiallodynic effect of clonidine. The effect was mimicked by the muscarinic M1 receptor antagonist pirenzepine, but not by the muscarinic M2 receptor antagonist methoctoramine or the muscarinic M3 receptor antagonist 4-DAMP (4-diphenyl-acetoxy-N-methylpiperidine methiodide). In addition, the mechanical hypersensitivity in diabetic mice was reduced by the selective muscarinic M1 receptor agonist McN-A-343 (4-(m-chlorophenyl-carbamoyloxy)-2-butynyltrimethylammonium chloride) (i.t.). These results suggest that spinal muscarinic M1 receptors participate in the antiallodynic effect of clonidine in diabetic mice.

Intrathecal alpha2 adrenoceptor agonist clonidine inhibits mechanical transmission in mouse spinal cord via activation of muscarinic M1 receptors.

We examined the role of the spinal muscarinic receptor subtype in the anti-nociceptive effect of intrathecal (i.t.) alpha2 adrenoceptor agonist clonidine in mice. I.t. injection of the muscarinic receptor antagonist atropine completely inhibited i.t. clonidine-induced increase in the mechanical threshold, but did not affect the increase in tail-flick latency induced by i.t. clonidine. The clonidine-induced increase in mechanical threshold was inhibited by i.t. injection of the M1 receptor antagonist pirenzepine in a dose-dependent manner, and by the M3 receptor antagonist 4-DAMP, but not by the M2 receptor antagonist methoctramine. The potency of pirenzepine was greater than that of 4-DAMP. These results suggest that the clonidine-induced increase in mechanical threshold is mediated via the activation of M1 receptors in the spinal cord.

Roles of the central prostaglandin EP3 receptors in cardiovascular regulation in rats.

In this study, we examined the effects of an intracerebroventricular (i.c.v.) administration of prostaglandin E2 (PGE2) and of selective agonists for PGE2 receptor subtypes, EP1, EP2, EP3 and EP4, on central cardiovascular regulation and renal sympathetic nerve activity (RSNA) in urethane-anesthetized rats. The central administration of PGE2 (0.01-1.0 nmol) resulted in increases in blood pressure, heart rate (HR) and RSNA in a dose-dependent manner. Cardiovascular responses to PGE2 (0.5 nmol, i.c.v.) were attenuated by pretreatment with ganglionic and adrenoceptor blocking agents, but not with SC-19220 (20 nmol, i.c.v.), an EP1 receptor antagonist. An i.c.v. administration of the EP3 agonist ONO-AE-248 (50.0 nmol) resulted in an increase in RSNA with pressor and tachycardia responses, while administration of the EP2 agonist ONO-AE1-259 and the EP4 agonist ONO-AE1-329 caused transient hypotension and slight increases in HR and RSNA. The administration of the selective EP1 agonist ONO-DI-004 showed no effect. These results suggest that the central PGE2-induced activation of the sympathetic nerve activity with hypertension and tachycardia may depend on stimulation of the EP3 receptors in the central nervous system.

Measurement of dorsal root ganglion P2X mRNA by SYBR Green fluorescence.

The P2X receptor is a receptor-gated cationic channel that responds to ATP. The quantification of P2X mRNA expression in dorsal root ganglion (DRG) provides important information for neuropathic pain studies. We developed a rapid and sensitive external-standard-based real-time quantitative PCR assay for the quantification of mRNA of P2X receptors in mouse tissue samples. The assay uses a double-stranded DNA fluorescent dye, SYBR Green I, to continuously monitor product formation with a GeneAmp 5700 Sequence Detection System (PE Applied Biosystems). To establish the quantitative PCR amplification in a wide range of target transcripts, optimum parameters of primer sequences, concentrations of primers and/or templates, and PCR thermal protocols were experimentally determined. We also tested the reliability of this method in established experimental murine models, which were made by ligation or cutting down of the sciatic nerve. The parameters defined in this assay should be applicable to the quantification of other types of pain models and other tissue samples of mouse.

Roles of substance P and NK(1) receptor in the brainstem in the development of emesis.

The emetic response is primarily a protective reflex occurring in a wide variety of vertebrates in response to the ingestion of toxic compounds. The role of the nuclei in the brainstem, including the area postrema, nucleus tractus solitarius, the dorsal motor nucleus of the vagus, and the central pattern generator for vomiting, as well as the involvement of the abdominal visceral innervation relevant to the emetic reflex, have all been discussed by many researchers. The introduction of serotonin 5-HT(3)-receptor antagonists into clinical practice allowed for a dramatic improvement in the management of vomiting. However, vomiting still remains a significant problem. The mechanism of the emetic response is even more complicated than was first thought. This review attempts to bring together some of the evidence suggesting the roles of substance P and its receptor, neurokinin NK(1) receptor, in the brainstem nuclei in the development of emesis. Accordingly, NK(1)-receptor antagonists might represent novel drugs for the management of major types of emesis.

The role of spinal muscarinic acetylcholine receptors in clonidine-induced anti-nociceptive effects in rats.

We have examined the effects of intrathecal (i.t.) injection of the muscarinic acetylcholine receptor antagonist atropine on the clonidine-induced nociceptive effect in formalin-induced nociception in rats. The injection of 5% formalin into the hind paw caused biphasic nociceptive responses, and i.t. injection of clonidine inhibited both phases of the nociceptive response in a dose-dependent manner. Pretreatment with atropine (i.t.) only partially inhibited the nociceptive effect of clonidine. These results suggest that the nociceptive effect of clonidine in the rat formalin model may be at least partly mediated by muscarinic acetylcholine receptors in the spinal cord.