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1.
Neurosci Lett ; 472(1): 1-4, 2010 Mar 12.
Article in English | MEDLINE | ID: mdl-20097266

ABSTRACT

Potentiation of inhibitory gamma-aminobutyric acid subtype A (GABA(A)) receptor function is involved in the mechanisms of anesthetic action. The present study examined the immobilizing action of the volatile anesthetic isoflurane in mice with double knockout (DKO) of phospholipase C-related inactive protein (PRIP)-1 and -2. Both of these proteins play important roles in the expression of GABA(A) receptors containing the gamma2 subunit on the neuronal cell surface. Immunohistochemistry for GABA(A) receptor subunits demonstrated reduced expression of gamma2 subunits in the spinal cord of the DKO mice. Immunohistochemistry also revealed up-regulation of the alpha1 and beta3 subunits even though there were no apparent differences in the immunoreactivities for the beta2 subunits between wild-type and DKO mice. The tail-clamp method was used to evaluate the anesthetic/immobilizing effect of isoflurane and the minimum alveolar concentration (MAC) was significantly lower in DKO mice compared with wild-type controls (1.07+/-0.01% versus 1.36+/-0.04% atm), indicating an increased sensitivity to isoflurane in DKO mice. These immunohistochemical and pharmacological findings suggest that reduced expression of the GABA(A) receptor gamma2 subunit affects the composition and function of spinal GABA(A) receptors and potentiates the immobilizing action of isoflurane.


Subject(s)
Anesthetics, Inhalation/pharmacology , Isoflurane/pharmacology , Receptors, GABA-A/biosynthesis , Adaptor Proteins, Signal Transducing/genetics , Animals , Immobilization , Intracellular Signaling Peptides and Proteins/genetics , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Receptors, GABA-A/genetics , Spinal Cord/drug effects , Spinal Cord/metabolism
2.
J Neurosci Methods ; 181(1): 67-72, 2009 Jun 30.
Article in English | MEDLINE | ID: mdl-19409417

ABSTRACT

Dental treatments sometimes cause sensory impairment, especially in the region innervated by the third division of the trigeminal nerve. The most frequent symptoms are loss of sensation and abnormal sensation. Although most studies have addressed the neuropathic symptom "allodynia" using experimental animal models of the infraorbital nerve, there is little information regarding the sensory impairment that frequently occurs clinically. Therefore, different experimental models are required to clarify the mechanisms of the clinical effects, and previous experimental models have been limited to rats. Here, we report a sensory impairment model in mice whose mechanical touch threshold increased after tight ligation of the mental nerve. Habituation before surgery by mechanical touching of the face enabled us to observe the long-term chronological changes in sensation. The mechanical touch thresholds within the mental nerve region were measured for 70 postoperative (PO) days. Changes in the distribution of substance P (SP) were evaluated by immunohistochemistry to clarify the involvement of axonal flow in the sensory impairment and its recovery. The mechanical touch thresholds transiently increased by PO days 2-3, but decreased to the preoperative levels at around PO day 14. Apparent SP immunoreactivity was recognizable on the medial side to the ligation at PO days 2-3 and disappeared at PO day 7. These behavioural and immunohistochemical changes appeared to exhibit similar time courses, suggesting a possible relationship between them. Therefore, we suggest that our experimental mouse model could represent a new model for clarifying the mechanism of the sensory impairment caused by peripheral nerve injury.


Subject(s)
Behavior, Animal/physiology , Sensation Disorders/etiology , Sensation Disorders/pathology , Trigeminal Neuralgia/complications , Analysis of Variance , Animals , Disease Models, Animal , Functional Laterality , Male , Mice , Mice, Inbred C57BL , Pain Measurement/methods , Pain Threshold/physiology , Physical Stimulation/methods , Substance P/metabolism , Time Factors , Touch
4.
Neurosci Res ; 52(3): 201-10, 2005 Jul.
Article in English | MEDLINE | ID: mdl-15927721

ABSTRACT

The postnatal development of nociceptive afferent activity expansion and its modulation features were examined in mice using an optical imaging technique. Developing mice (1-2 weeks old (N1-2 w), 3-4 weeks old (N3-4 w), 5-6 weeks old (N5-6 w) and 7-8 weeks old (N7-8 w)) and neonatally capsaicin-treated mice were used. The propagation of neuronal excitation was measured by changes in fluorescent intensity in horizontal brain stem slices evoked by electrical stimulation to the trigeminal spinal tract. A single-pulse stimulation evoked excitation propagation in the trigeminal caudalis (Vc). The propagation area was larger in N1-2 w than in N7-8 w, and no differences were observed between capsaicin-treated and naive mice in the same age groups. Repetitive stimulation (100 Hz, 30 pulses) elicited long-lasting and widespread excitation propagation. The excitation propagation area was significantly larger in N7-8 w than in N1-2 w, N3-4 w and N5-6 w. This propagation was suppressed by 5 microM L-703.606, an NK1-receptor antagonist, suggesting that the repetitive stimulation-elicited excitation may require substance-P releases. Morphological observations demonstrated that the neural network in the Vc had grown by postnatal week 5. These results suggest that nociceptive afferent activity co-operatively matures with development of the network structure in the Vc, and that a mechanism for prolonged increase in central excitability is established during a later postnatal period.


Subject(s)
Afferent Pathways/radiation effects , Electric Stimulation , Trigeminal Caudal Nucleus/radiation effects , Afferent Pathways/drug effects , Afferent Pathways/growth & development , Age Factors , Analysis of Variance , Animals , Animals, Newborn , Capsaicin/pharmacology , Diagnostic Imaging/methods , Dizocilpine Maleate/pharmacology , Drug Interactions , Evoked Potentials/drug effects , Evoked Potentials/physiology , Evoked Potentials/radiation effects , Excitatory Amino Acid Antagonists/pharmacology , In Vitro Techniques , Male , Mice , Mice, Inbred C57BL , Neurokinin-1 Receptor Antagonists , Quinuclidines/pharmacology , Silver Staining/methods , Time Factors , Trigeminal Caudal Nucleus/anatomy & histology , Trigeminal Caudal Nucleus/drug effects , Trigeminal Caudal Nucleus/growth & development
5.
J Oral Maxillofac Surg ; 63(3): 298-303, 2005 Mar.
Article in English | MEDLINE | ID: mdl-15742277

ABSTRACT

PURPOSE: Paresthesia is a well known consequence of peripheral nerve injury. However, the neural mechanisms of the 2 recognized types, spontaneous and elicited, are currently unknown. This study aimed to investigate these 2 paresthesias and the possible mechanisms accompanying orthognathic surgery. PATIENTS AND METHODS: Mechanical-touch thresholds and current perception threshold were measured before and 7 days after surgery in 60 chin sites (mental nerve area) of 30 patients who underwent orthognathic surgery. Similar testing was conducted on healthy volunteers (controls). All sites were classified by the presence or absence of each paresthesia: spontaneous paresthesia or no spontaneous paresthesia, and elicited paresthesia or no elicited paresthesia. Presence or absence analyses were followed-up for 6 weeks after surgery. RESULTS: Gender differences and maxillary surgery did not change the incidence of paresthesia during postoperative week 1 (chi-square test, P > .05). A significantly higher mechanical-touch threshold was observed with spontaneous paresthesia compared with no spontaneous paresthesia (Mann-Whitney U-test; P < .05), but not between no elicited paresthesia and elicited paresthesia (Mann-Whitney U-test; P > .05). A significant increase in postsurgery current perception thresholds values compared with presurgery values was observed at 2,000 Hz in spontaneous paresthesia, and at 2,000 and 5 Hz in elicited paresthesia (paired t test, P < .05). The incidence of spontaneous paresthesia decreased more rapidly than elicited, while the latter tended to increase again during the 6-week postsurgical test period. CONCLUSION: The results suggested that both spontaneous and elicited paresthesias are associated with damage and dysfunction in myelinated primary afferent fibers, but additional neural mechanisms are implicated during elicited paresthesia.


Subject(s)
Mandible/surgery , Paresthesia/classification , Postoperative Complications , Adolescent , Adult , Chin/innervation , Electric Stimulation , Female , Follow-Up Studies , Humans , Male , Mandibular Nerve/physiopathology , Maxilla/surgery , Nerve Fibers, Myelinated/physiology , Neurons, Afferent/physiology , Osteotomy/adverse effects , Osteotomy/methods , Paresthesia/etiology , Sensory Thresholds/physiology , Sex Factors , Time Factors , Touch/physiology
6.
J Oral Maxillofac Surg ; 62(10): 1193-7, 2004 Oct.
Article in English | MEDLINE | ID: mdl-15452804

ABSTRACT

PURPOSE: Steroid hormones are therapeutic for motor and/or sensory dysfunctions caused by nerve injury. However, the timing for giving such medicine is unclear. This study aimed to estimate the efficacy of steroid treatment and determine an appropriate start time after sensory impairment. PATIENTS AND METHODS: Twenty-seven patients with sensory impairment who received orthognathic surgery were classified into groups called 1W (n = 6), 3W (n = 6), or 6W (n = 8) group on the basis of start time for steroid treatment, being 1 week, 3 weeks, or 6 weeks after surgery, respectively, and a no steroid treatment (NST) group (a control group) (n = 6) that did not receive treatment for 10 to 12 weeks after surgery. Sensory impairment was diagnosed if postoperative first week mechanical-touch threshold was over 4.0 as measured by Semmes aesthesiometer. Prednisolone treatment was administered orally to patients at 30 mg for 7 days, 15 mg for 4 days, and 5 mg for 3 days. Mechanical-touch threshold and thermal perceptions were compared before and after treatment. RESULTS: At 1 week postoperatively, there were no significant differences in mechanical-touch threshold among the 4 groups (analysis of variance, P >.05). Changes in mechanical-touch threshold in the 1W group showed no significant improvement (analysis of variance, P >.05), but in the 3W and 6W groups, there were significant differences compared with the NST group (Dunns methods, P <.05). CONCLUSIONS: Steroid treatment for sensory impairment after orthognathic surgery has the potential to accelerate recovery and it appears desirable to start treatment later than 1 week postoperatively.


Subject(s)
Cranial Nerve Injuries/drug therapy , Glucocorticoids/administration & dosage , Mandible/surgery , Osteotomy/adverse effects , Prednisolone/administration & dosage , Sensation Disorders/drug therapy , Administration, Oral , Adolescent , Adult , Analysis of Variance , Cold Temperature , Cranial Nerve Injuries/etiology , Drug Administration Schedule , Female , Hot Temperature , Humans , Male , Oral Surgical Procedures/adverse effects , Recovery of Function/drug effects , Sensation Disorders/etiology , Sensory Thresholds/drug effects , Touch , Treatment Outcome
7.
Neuroreport ; 14(10): 1321-5, 2003 Jul 18.
Article in English | MEDLINE | ID: mdl-12876465

ABSTRACT

A high-speed optical imaging technique was employed for visualizing neuronal excitation propagation elicited by afferent stimulation in the mouse trigeminal caudalis (Vc) to clarify the central nociceptive modulation mechanism. Membrane depolarization evoked by a single-pulse stimulation to the spinal trigeminal tract (Tr) was propagated rostrally to the Vc, which was suppressed by CNQX. This is consistent with our morphological observation that axons expand from the Tr into the Vc. A trained-pulse (tetanus) stimulation to the Tr evoked a broad, persistent excitation in the Vc, while MK-801 suppressed it. Neonatally capsaicin-treated mice maintained a single-pulse response but a lacked tetanus-evoked one. These indicated that prolonged depolarization elicited by repetitive stimulation is a prerequisite to C-fiber excitation for activating the NMDA receptors.


Subject(s)
Afferent Pathways/physiology , Neurons/physiology , Trigeminal Caudal Nucleus/physiology , 6-Cyano-7-nitroquinoxaline-2,3-dione/pharmacology , Analysis of Variance , Animals , Capsaicin/pharmacology , Dizocilpine Maleate/pharmacology , Electric Stimulation/methods , Evoked Potentials/drug effects , Evoked Potentials/physiology , Excitatory Amino Acid Antagonists/pharmacology , Immunohistochemistry/methods , In Vitro Techniques , Male , Membrane Potentials/drug effects , Membrane Potentials/physiology , Mice , Mice, Inbred C57BL , Microscopy, Fluorescence , Neurons/drug effects , Time Factors , Trigeminal Caudal Nucleus/drug effects
8.
Neurosci Lett ; 335(2): 107-10, 2002 Dec 25.
Article in English | MEDLINE | ID: mdl-12459510

ABSTRACT

The influence of testosterone on the postnatal development of reflex electromyographic (EMG) jaw muscle activity evoked by injection of mustard oil (MO) into the temporomandibular joint region and the later recurrence of this EMG activity after intravenous injection of naloxone, was studied in male rats. MO-evoked EMG activity in the contralateral digastric muscle and naloxone-induced recurrence of this EMG activity were fully developed in intact, 8-week-old rats. Castration at 4 weeks of age inhibited the development of the contralateral MO-evoked EMG activity, but did not influence the naloxone-induced recurrence. Contralateral MO-evoked responses were observed in 8-week-old castrated rats if they received testosterone replacement therapy beginning at 4 weeks of age. These data suggest that testosterone is required for the development of a contralateral nociceptive reflex in the digastric muscle of male rats.


Subject(s)
Muscle, Skeletal/physiology , Temporomandibular Joint/drug effects , Testosterone/physiology , Aging/physiology , Analysis of Variance , Animals , Area Under Curve , Castration , Electromyography , Functional Laterality , Jaw , Male , Masseter Muscle/drug effects , Masseter Muscle/physiology , Muscle, Skeletal/drug effects , Mustard Plant , Naloxone/pharmacology , Narcotic Antagonists/pharmacology , Pain , Plant Extracts/pharmacology , Plant Oils , Rats , Reflex , Temporomandibular Joint/physiology , Time Factors
9.
Brain Res ; 934(2): 157-61, 2002 May 03.
Article in English | MEDLINE | ID: mdl-11955479

ABSTRACT

The effect of intrathecal administration of the 5-HT(3) receptor agonist 2-methyl-5-hydroxytryptamine (2m-5HT) on jaw muscle activity evoked by mustard oil (MO) injection into the temporomandibular joint of anesthetized rats was examined. One microgram or 100 microg of 2m-5HT significantly enhanced or suppressed jaw muscle responses, respectively. Pre-administration of tropisetron, a 5-HT(3) receptor antagonist, attenuated the effect of 2m-5HT. These results indicate that activation of 5-HT(3) receptors can modulate trigeminal nociceptive responses.


Subject(s)
Afferent Pathways/metabolism , Efferent Pathways/metabolism , Masticatory Muscles/physiology , Nociceptors/metabolism , Serotonin Receptor Agonists/pharmacology , Serotonin/analogs & derivatives , Temporomandibular Joint/innervation , Trigeminal Caudal Nucleus/metabolism , Afferent Pathways/cytology , Afferent Pathways/drug effects , Animals , Dose-Response Relationship, Drug , Drug Interactions/physiology , Efferent Pathways/cytology , Efferent Pathways/drug effects , Electromyography , Indoles/pharmacology , Male , Masticatory Muscles/innervation , Muscle Contraction/drug effects , Muscle Contraction/physiology , Mustard Plant , Neurons, Afferent/cytology , Neurons, Afferent/drug effects , Neurons, Afferent/metabolism , Nociceptors/cytology , Nociceptors/drug effects , Plant Extracts/pharmacology , Plant Oils , Rats , Rats, Sprague-Dawley , Serotonin/pharmacology , Serotonin Antagonists/pharmacology , Synaptic Transmission/drug effects , Synaptic Transmission/physiology , Temporomandibular Joint/drug effects , Temporomandibular Joint/physiopathology , Trigeminal Caudal Nucleus/cytology , Trigeminal Caudal Nucleus/drug effects , Tropisetron
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