Biomedical subjects

Hiroyuki Ichikawa

Publications and source records attributed to Hiroyuki Ichikawa.

14 recordsLinked to original sources

PubMed2005

The origin of sensory nerve fibers that innervate the submandibular salivary gland in the rat.

The origin of sensory nerves that innervate the submandibular salivary gland was investigated in the rat. After application of wheat germ agglutinin-horseradish peroxidase to the cut endings of the sympathetic and parasympathetic nerve branches at the hilus of the gland, labeled cells were mainly found in the dorsal root ganglia and the trigeminal ganglion, respectively. The labeled neurons in these ganglia were of various sizes compared to unlabeled neurons, suggesting that the sensory nerves of the gland conduct various modalities of sensory information.

Animals↗

PubMed2005

Involvement of caspase cascade in capsaicin-induced apoptosis of dorsal root ganglion neurons.

Capsaicin induces apoptosis in some types of neurons, but the exact molecular mechanism remains unclear. In this study, capsaicin was systemically administrated in newborn rats and the dorsal root ganglion (DRG) neurons were examined for caspase-immunoreactivity. Capsaicin-induced neuronal apoptosis was revealed by TUNEL. TUNEL-positive neurons rapidly increased, reaching the peak at 24 h post-injection when 10.6% of DRG neurons were apoptotic. Neurons expressing immunoreactivity for activated caspases-9 and -3 concomitantly increased. At 24 h, 15.9% and 17.7% of DRG neurons exhibited immunoreactivity for caspase-9 and caspase-3, respectively. DNA fragmentation signal and caspase-immunoreactivity were detected in less than 0.5% of DRG neurons of vehicle control rats. The immunoreactivity and TUNEL-positivity returned to the vehicle control level by 120 h. Double label immunohistochemistry revealed co-expression of caspase-9 and DNA fragmentation or caspase-3 and DNA fragmentation. These results suggest that the caspase cascade is involved in the primary neuronal apoptosis induced by neurotoxin capsaicin.

Animals↗

PubMed2005

Brn-3a deficiency increases tyrosine hydroxylase-immunoreactive neurons in the dorsal root ganglion.

Immunohistochemistry for tyrosine hydroxylase (TH) was performed on the dorsal root ganglia (DRG) in wild-type, heterozygous and Brn-3a knockout mice at embryonic day 18.5. TH-immunoreactive (-IR) neurons were detected in the DRG of wild-type and heterozygous mice, but their proportion was greatly increased by the loss of Brn-3a function (wild-type and heterozygot, 8.4%; knockout, 20.9%). IR neurons were of various sizes in wild-type (mean+/-S.D.=118.1+/-55.4 microm2, range=26.6-306.3 microm2) and heterozygous mice. In the knockout mice, however, TH-IR neurons were mostly small (mean+/-S.D.=68.2+/-34.3 microm2, range=11.8-166.8 microm2). The present study suggests that Brn-3a may normally suppress TH expression in many small DRG neurons but activate TH expression in large DRG neurons.

Animals↗

PubMed2005

Dynamic guided-mode resonant grating filter with quadratic electro-optic effect.

We propose a novel and simple concept of dynamic switching of guided-mode resonant grating filters with quadratic electro-optic effect within a waveguide layer modulated by external fields due to comb-shaped electrodes that also behave as a grating. As the device has subwavelength structure, the performance must be analyzed electromagnetically. We describe numerical simulation with the finite-difference time-domain method specially modified so that it can treat inhomogeneous anisotropic media such as lead lanthanum zirconate titanate.

Journal Article↗

PubMed2005

Activation of the caspase cascade underlies the rat trigeminal primary neuronal apoptosis induced by neonatal capsaicin administration.

The systemic administration of capsaicin is known to cause a massive loss of sensory primary neurons in newborn rats. Here we examined the trigeminal ganglion neurons immunohistochemically for the possible induction of activated forms of caspases-9 and -3 following a subcutaneous injection of capsaicin in newborn rats. The DNA fragmentation signal was labeled by a TUNEL method. TUNEL-positive neurons were rare (< 0.5%) at 24 h after injection of the vehicle without capsaicin. After the capsaicin injection, TUNEL-positive neurons began to increase by 12 h, reached a peak at 24 h (11.4%), and returned to the control level by 120 h. Vehicle control levels of caspase- 9-immunoreactive (ir) and caspase-3-ir neurons were low (< 0.5%). Neonatal capsaicin administration induced caspase-9-immunoreactivity (ir) and -3-ir. The temporal distributions of caspase-9-ir and caspase-3-ir neurons were similar to those of TUNEL-positive neurons with peak expressions at 24 h of 13.2 and 11.1%, respectively. A double-stain analysis at 24 h post-injection indicated 72% of TUNEL-positive neurons were caspase-9-ir, and 70% caspase-3-ir. Conversely, 78 and 68% of caspase-9-ir and caspase-3-ir neurons, respectively, were TUNEL-positive. Comparison of two adjacent sections immunostained for the two different antigens revealed the co-expression of the two caspases. These results suggest that neonatal capsaicin triggers the caspase cascade and, thereby, induces trigeminal primary neuronal apoptosis.

Animals↗

PubMed2004

Induction of activated caspase-3-immunoreactivity and apoptosis in the trigeminal ganglion neurons by neonatal peripheral nerve injury.

Immunohistochemistry for activated caspase-3 and terminal deoxynucleotidyl transferease-mediated dUTP-biotin nick end labeling (TUNEL) was performed on the trigeminal ganglion after infraorbital nerve transection in newborn rats. The injury induced caspase-3-immunoreactivity and DNA fragmentation in neuronal cell bodies in the maxillary division of the ganglion ipsilateral to the injury. Starting at 16 h post-injury the immunoreactive and TUNEL-positive neurons increased and reached the peak at 24 h (7.9% and 8.9%, respectively). Thereafter they decreased and returned to the normal control level (<<1%) by 72 h. A double staining procedure revealed coexpression of caspase-3-immunoreactivity and DNA fragmentation. 75.5% (114/151) of TUNEL-positive neurons expressed the immunoreactivity, while 84.4% (114/135) of immunoreactive neurons exhibited DNA fragmentation signal. These results suggest that caspase-3 plays an important role in apoptotic elimination of neonatally axotomized rodent primary neurons.

Animals↗

PubMed2004

The co-expression of P2X3 receptor with VR1 and VRL-1 in the rat trigeminal ganglion.

The co-expression of P2X3 receptor with the vanilloid receptor subtype I (VR1) and vanilloid receptor 1-like receptor (VRL-1) was examined in the rat trigeminal ganglion (TG) by a double immunofluorescence method. P2X3 receptor-immunoreactive (ir) neurons were predominantly small to medium-sized (range=93.8-1844.4 microm(2), mean+/-S.D.=503.8+/-286.5 microm(2)); 35% and 9% of P2X3 receptor-ir TG neurons were immunoreactive for VR1 and VRL-1, respectively. Small and medium-sized P2X3 receptor-ir neurons contained VR1-immunoreactivity (ir), whereas medium-sized and large P2X3 receptor-ir neurons showed VRL-1-ir. The retrograde tracing and immunohistochemical methods revealed that 30% of the TG neurons retrogradely labeled from the facial skin and tooth pulp exhibited P2X3 receptor-ir. The co-expression of P2X3 receptor and VR1 was detected in 16% of cutaneous TG neurons and 6% of tooth pulp neurons. On the other hand, the co-expression of P2X3 receptor and VRL-1 was common in tooth pulp neurons (23%) and rare in cutaneous TG neurons (8%). In the tooth pulp, 95% of P2X3 receptor-ir TG neurons contained VRL-1-ir. The present study indicates that P2X3 receptor-ir TG neurons, which co-express VR-ir, are abundant in the facial skin. The tooth pulp is probably innervated by TG neurons, which contain both P2X3-and VRL-1-ir.

Animals↗

PubMed2004

The development of myelinated nociceptors is dependent upon trks in the trigeminal ganglion.

Cell size of primary sensory neurons and distribution patterns of neurons that are immunopositive (ip) for VRL-1, a newly cloned capsaicin-receptor homologue, were examined in trigeminal ganglia (TGs) of knockout mice for trkA, trkB or trkC to determine the developmental dependency of myelinated nociceptors on expression of the genes. The number of TG neurons was strongly decreased in the knockout mice as compared to wildtype and heterozygous mice (82%, 39%, and 48% reduction for trkA, trkB and trkC, respectively). The absence of trkA and trkC reduced the number of TG neurons in all cell-size ranges. The number of medium-sized and large TG neurons was decreased in trkB-knockout mice, whereas that of small TG neurons was barely affected by trkB deficiency. TG contained abundant VRL-1-ip neurons in wildtype and heterozygous mice; 9% of TG neurons exhibited immunopositivity. In trkA-knockout mice, VRL-1-ip neurons almost disappeared (1% of TG neurons were VRL-1-ip). However, 13% and 9% of TG neurons in trkB- and trkC-knockout mice, respectively, were immunostained for the ion channel protein. In trkC-knockout mice, the proportion of large VRL-1-ip neurons decreased whereas that of small and medium-sized VRL-1-ip neurons increased. In addition, immunohistochemistry of the protein gene product 9.5 (PGP 9.5) demonstrated that trkA deficiency caused a marked reduction of varicose endings in the epithelium of the palatal mucosa. Loss of trkC diminished the number of PGP 9.5-ip varicose fibers in the deep layer of mucosal connective tissue of the palate. In tooth pulp, PGP 9.5-ip nerve fibers were absent in trkA-knockout mice but abundant in trkB- and trkC-knockout mice. The present study suggests that the development of myelinated nociceptors is dependent on trkA and trkC but not on trkB.

Animals↗

PubMed2003

Kv1.2-immunoreactive primary sensory neurons in the rat trigeminal ganglion.

Immunohistochemistry for Kv1.2, a subunit of voltage-gated K(+) channels, was performed on the trigeminal ganglion (TG). Immunoreactivity (ir) was detected in half (48%) the TG neurons. These neurons were mostly medium-sized to large (range 137.6-2664.8 microm(2), mean+/-S.D. 892.6+/-413.3 microm(2)). A double immunofluorescence method also revealed co-expression of Kv1.2 and parvalbumin. Half (54%) the Kv1.2-immunoreactive (ir) neurons exhibited parvalbumin-ir, and parvalbumin-ir neurons mostly showed Kv1.2-ir (95%). Kv1.2-ir neurons which co-expressed CGRP-ir were rare in this ganglion. Some 40% of TG neurons retrogradely labeled from the facial skin exhibited Kv1.2-ir, whereas ir was detected in 16% of those labeled from the tooth pulp. The present study indicates that Kv1.2-ir TG neurons include low-threshold mechanoreceptors and nociceptors which innervate the facial skin and tooth pulp, respectively.

Animals↗

PubMed2002

The difference of osteocalcin-immunoreactive neurons in the rat dorsal root and trigeminal ganglia: co-expression with nociceptive transducers and central projection.

The co-expression of osteocalcin (OC) with the capsaicin receptor (VR1) and vanilloid receptor 1-like receptor (VRL-1) was examined in the dorsal root (DRG) and trigeminal ganglia (TG). Virtually all OC-immunoreactive (ir) DRG neurons were devoid of VR1- and VRL-1-immunoreactivity (ir). In the TG, 14.1% of OC-ir neurons were also immunoreactive for VR1. Only 1.7% of OC-ir TG neurons co-expressed VRL-1-ir. The distribution of OC-ir was also examined in the spinal cord and trigeminal sensory nuclei. In the spinal cord, the superficial laminae of the dorsal horn were devoid of OC-ir. The neuropil was weakly stained in other regions of the spinal horns. The medullary dorsal horn (MDH) contained numerous OC-ir varicose fibers in laminae I and II. These fibers were occasionally observed originating from the spinal trigeminal tract. The neuropil was weakly stained in deeper laminae of the MDH, and the rostral parts of the trigeminal sensory nuclei. The present study suggests that OC-ir TG nociceptors send their unmyelinated axons to the superficial laminae of the MDH.

Animals↗

PubMed2002

Innervation of the carotid body: Immunohistochemical, denervation, and retrograde tracing studies.

This review presents information about multiple neurochemical substances in the carotid body. Nerve fibers around blood vessels and glomus cells within the chemoreceptive organ contain immunoreactivities (IR) for tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP), substance P (SP), galanin (GAL), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), calretinin (CR), calbindin D-28k (CB), parvalbumin (PV), and nitric oxide synthase (NOS). Parasympathetic neurons scattered around the carotid body contain VIP, choline acetyltransferase, and vanilloid receptor 1-like receptor. In the mammalian carotid body, transection of the carotid sinus nerve (CSN) causes the absence or decrease of CGRP-, SP-, and NOS-immunoreactive (IR) nerve fibers, whereas all NPY-IR nerve fibers disappear after removal of the superior cervical ganglion. Most VIP-IR nerve fibers disappear but a few persist after sympathetic ganglionectomy. In addition, the CSN transection appears to cause the acquisition of GAL-IR in originally immunonegative glomus cells and nerve fibers within the rat carotid body. On the other hand, 4%, 25%, 17%, and less than 1% of petrosal neurons retrogradely labeled from the rat CSN contain TH-, CGRP-, SP-, and VIP-IR, respectively. In the chicken carotid body, many CGRP- and SP-IR nerve fibers disappear after vagus nerve transection or nodose ganglionectomy. GAL-, NPY-, and VIP-IR nerve fibers mostly disappear after removal of the 14th cervical ganglion of the sympathetic trunk. The origin and functional significance of the various neurochemical substances present in the carotid body is discussed.

Animals↗

PubMed2002

Effect of Brn-3a deficiency on CGRP-immunoreactivity in the dorsal root ganglion.

Immunohistochemistry for calcitonin gene-related peptide (CGRP) was performed on the dorsal root ganglion (DRG) and spinal cord in wildtype and knockout mice for Brn-3a. CGRP-immunoreactive (-IR) neurons were abundant in the DRG of wildtype, heterozygous and knockout mice. Cell size analysis revealed that CGRP-IR neurons were of various sizes in wildtype and heterozygous mice. In the knockout mice, however, most of CGRP-IR neurons were small. In the spinal cord of knockout mice, the number of CGRP-IR fibers increased in the dorsal column but decreased in the deep part of the dorsal horn. The loss of Brn-3a may have different effects on CGRP-IR expression in small and large DRG neurons.

Animals↗

PubMed2002

Ruffini endings are absent from the periodontal ligament of trkB knockout mice.

To clarify the role of neurotrophin receptors in the development of Ruffini endings, periodontal ligaments and trigeminal ganglia of trkA, trkB, and trkC knockout mice were immunostained for protein gene product 9.5 (PGP 9.5), calcitonin gene-related peptide (CGRP), parvalbumin (PV), and calretinin (CR). Innervation patterns of PGP 9.5- and CGRP-immunoreactive fibers were examined in the periodontal ligament of the knockout mice. PGP 9.5-positive fibers in the incisal periodontal ligaments of trkA and trkC knockout mice form Ruffini endings distinguished by dendritic ramifications and branches. However, Ruffini endings were not present in the periodontal ligament of trkB knockout mice. Only free nerve endings were observed in tissue of trkB knockout mice. Compared with trkA and trkC knockouts, the proportion of CR-positive neurons in mandibular and maxillary regions of the trigeminal ganglion of trkB knockout mice is decreased. These findings indicate that the development of periodontal Ruffini endings is regulated by trkB-dependent and CR-coexpressing neurons.

Animals↗

PubMed1995

Disruption and restoration of dorsal horn sensory map after peripheral nerve crush and regeneration.

Formalin injection into the hindpaw of rats produces many neurons with c-fos protein-like immunoreactivity (fos-neurons) in the medial 3/4 of the ipsilateral dorsal horn laminae I and II at the junction of 4th and 5th lumbar segments (the sciatic territory). The tibial nerve transection 2 or 3 days earlier resulted in almost complete elimination of stimulation-induced fos-neurons in the tibial territory (medial 1/2 of the sciatic territory). When the animals had been conditioned by crushing the tibial nerve 2 weeks before stimulation (11 or 12 days before transection), the number of fos-neurons significantly increased compared to simple transection alone. The increase (2.5-fold) was greatest in the tibial territory. Therefore, the dorsal horn neurons in the deafferented tibial territory exhibited hypersensitivity to intact peroneal primary input, and the somatotopy map was disrupted. When the nerve had been crushed 3 weeks (18 or 19 days earlier than transection) rather than 2 weeks before stimulation, however, the number and distribution of fos-neurons were not different from those without conditioning (transection alone). Regenerated tibial nerve fibers were capable of transganglionic transport of WGA-HRP from the hindpaw receptive field to the tibial territory of the dorsal horn by 3 weeks but not by 2 weeks following the nerve crush. When transection was omitted, noxious signal transmitted through the tibial nerve fibers regenerated by 3 weeks after crush was capable of inducing c-fos in the tibial territory. The injury-induced hypersensitivity of dorsal horn neurons and resulting disruption of somatotopy map were reversed by re-establishment of peripheral tissue-nerve interaction.

Analysis of Variance↗