Effects of L-carnitine supplementation on the quality of life in diabetic patients with muscle cramps

Diabetic patients often suffer from muscle cramps. This study aimed to compare the quality of life (QOL) of diabetic patients with and without muscle cramps and to investigate the effect of L-carnitine supplementation in diabetic patients with muscle cramps. A total of 91 patients with diabetes were enrolled in this study: 69 patients with muscle cramps and 22 patients without muscle cramps. Muscle cramps and QOL were evaluated using the muscle cramp questionnaire and the Short Form 36 health survey version 2 (SF-36), respectively. Clinical characteristics were compared between diabetic patients with and without muscle cramps. In the prospective portion of the study, 25 diabetic patients with muscle cramps received L-carnitine supplementation (600 mg/day orally) for 4 months. The questionnaires were administered before and after supplementation. The SF-36 scores in diabetic patients with muscle cramps were lower than those in patients without muscle cramps on the subscales of physical function, role physical, bodily pain, vitality, general health, and social function. In the 25 patients with muscle cramps who received L-carnitine supplementation, the monthly frequency of muscle cramps and Wong-Baker FACES^® Pain Rating Scale scores were significantly decreased. Scores on the following SF-36 subscales improved after L-carnitine supplementation: body pain, vitality, social function, and role emotional. This study demonstrated that muscle cramps decrease the QOL in patients with diabetes, and L-carnitine supplementation may improve the QOL by reducing the frequency and severity of muscle cramps in these patients.

Repeated forced swim stress prior to complete Freund's adjuvant injection enhances mechanical hyperalgesia and attenuates the expression of pCREB and ΔFosB and the acetylation of histone H3 in the insular cortex of rat

Exposure to stressors causes substantial effects on the perception and response to pain. In several animal models, chronic stress produces hyperalgesia. The insular (IC) and anterior cingulate cortices (ACC) are the regions exhibiting most reliable pain-related activity. And the IC and ACC play an important role in pain modulation via descending pain modulatory system. In the present study we examined the expression of phospho-cAMP response element-binding protein (pCREB) and ΔFosB and the acetylation of histone H3 in the IC and ACC after forced swim stress (FS) and complete Freund's adjuvant (CFA) injection to clarify changes in the cerebral cortices that affect the activity of the descending pain modulatory system in rats with stress-induced hyperalgesia. CFA injection into the hindpaw or FS (day 1, 10min; days 2-3, 20min) induced a significant increase in the expression of pCREB and ΔFosB and the acetylation of histone H3 in the IC. Quantitative image analysis showed that the numbers of ΔFosB-immunoreactivity (IR) cells in the bilateral anterior and posterior IC (AIC and PIC) were significantly higher in the CFA group (AIC R, 548.0±98.6; AIC L, 433.5±89.4; PIC R, 546.1±72.8; PIC L, 415.5±53.5) than those in the naive group (AIC R, 86.6±14.8; AIC L, 85.5±24.7; PIC R, 124.5±29.9; PIC L, 107.0±19.8, p<0.01). However the FS prior to the CFA injection enhanced the mechanical hyperalgesia and attenuated the expression of pCREB and ΔFosB and the acetylation of histone H3 in the IC. There was no significant difference in the numbers of ΔFosB-IR cells in the bilateral PIC between the FS+CFA and naive groups. These findings suggest neuroplasticity in the IC after the FS, which may be involved in the enhancement of CFA-induced mechanical hyperalgesia through dysfunction of the descending pain modulatory system.

Reversible hypopituitarism with pituitary tuberculoma

A 50-year-old woman presented with a headache and nausea. A sellar and suprasellar mass was detected on MRI; the tumor was heterogeneously enhanced with gadolinium, and the pituitary stalk was slightly thickened. Laboratory tests revealed severe growth hormone, luteinizing hormone, follicle-stimulating hormone and thyroid-stimulating hormone deficiencies. A pathological examination of the tumor showed scattered granulomas with central necrosis and Langhans giant cells. Tuberculin skin and QuantiFERON TB-Gold tests (QFT-2G) were positive. Accordingly, we diagnosed the patient with pituitary tuberculoma presenting with pituitary dysfunction. Following treatment with antituberculous drugs, the pituitary hormone function normalized and the pituitary tuberculoma disappeared.

Repeated forced swim stress enhances CFA-evoked thermal hyperalgesia and affects the expressions of pCREB and c-Fos in the insular cortex

Stress affects brain activity and promotes long-term changes in multiple neural systems. Exposure to stressors causes substantial effects on the perception and response to pain. In several animal models, chronic stress produces lasting hyperalgesia. The insular (IC) and anterior cingulate cortices (ACC) are the regions exhibiting most reliable pain-related activity. And the IC and ACC play an important role in pain modulation via the descending pain modulatory system. In the present study we examined the expression of phospho-cAMP response element-binding protein (pCREB) and c-Fos in the IC and ACC after forced swim stress (FS) and complete Freund's adjuvant (CFA) injection to clarify changes in the cerebral cortices that affect the activity of the descending pain modulatory system in the rats with stress-induced hyperalgesia. FS (day 1, 10min; days 2-3, 20min) induced an increase in the expression of pCREB and c-Fos in the anterior IC (AIC). CFA injection into the hindpaw after the FS shows significantly enhanced thermal hyperalgesia and induced a decrease in the expression of c-Fos in the AIC and the posterior IC (PIC). Quantitative image analysis showed that the numbers of c-Fos-immunoreactive neurons in the left AIC and PIC were significantly lower in the FS+CFA group (L AIC, 95.9±6.8; L PIC, 181.9±23.1) than those in the naive group (L AIC, 151.1±19.3, p<0.05; L PIC, 274.2±37.3, p<0.05). These findings suggest a neuroplastic change in the IC after FS, which may be involved in the enhancement of CFA-induced thermal hyperalgesia through dysfunction of the descending pain modulatory system.

Distinctions in burst spiking between thalamic reticular nucleus cells projecting to the dorsal lateral geniculate and lateral posterior nuclei in the anesthetized rat

Thalamic cell activity is under a significant influence of inhibition from the thalamic reticular nucleus (TRN) that is composed of domains connected with first and higher order thalamic nuclei, which are thought to subserve transmission of sensory inputs to the cortex and cortico-thalamo-cortical transmission of cortical outputs, respectively. Provided that TRN cells have distinct activities along with their projections to first and higher order thalamic nuclei, TRN cells could shape cell activities of the two thalamic nuclei in different manners for the distinct functions. In anesthetized rats, visual response and spontaneous activity were recorded from TRN cells projecting to the dorsal lateral geniculate (first order) and lateral posterior (higher order) nuclei (TRN-DLG and TRN-LP cells), using juxta-cellular recording and labeling techniques. TRN-DLG cells had a higher propensity for burst spiking and exhibited bursts of larger numbers of spikes with shorter inter-spike intervals as compared to TRN-LP cells in both visual response and spontaneous activity. Sustained effects of visual input on burst spiking were recognized in recurrent activation of TRN-DLG but not of TRN-LP cells. Further, the features of burst spiking were related with the locations of topographically connected cell bodies and terminal fields. The difference in burst spiking contrasts with the difference between thalamic cells in the DLG and LP, which show low and high levels of burst spiking, respectively. The synergy between thalamic and TRN cell activities with their contrasting features of burst spiking may compose distinctive sensory processing and attentional gating functions of geniculate and extra-geniculate systems.

Chronic restraint stress decreases glial fibrillary acidic protein and glutamate transporter in the periaqueductal gray matter

Stress affects brain activity and promotes long-term changes in multiple neural systems. Exposure to stressors causes substantial effects on the perception and response to pain. In several animal models, chronic stress produces lasting hyperalgesia. Postmortem studies of stress-related psychiatric disorders have demonstrated a decrease in the number of astrocytes and the level of glial fibrillary acidic protein (GFAP), a marker for astrocyte, in the cerebral cortex. Since astrocytes play vital roles in maintaining neuroplasticity via synapse maintenance and secretion of neurotrophins, impairment of astrocytes is thought to be involved in the neuropathology. In the present study we examined GFAP and excitatory amino acid transporter 2 (EAAT2) protein levels in the periaqueductal gray matter (PAG) after subacute and chronic restraint stresses to clarify changes in descending pain modulatory system in the rat with stress-induced hyperalgesia. Chronic restraint stress (6h/day for 3 weeks), but not subacute restraint stress (6h/day for 3 days), caused a marked mechanical hypersensitivity and aggressive behavior. The chronic restraint stress induced a significant decrease of GFAP protein level in the PAG (32.0 ± 8.9% vs. control group, p<0.05). In immunohistochemical analysis the remarkable decrease of GFAP was observed in the ventrolateral PAG. The EAAT2 protein level in the 3 weeks stress group (79.6 ± 6.8%) was significantly lower compared to that in the control group (100.0 ± 6.1%, p<0.05). In contrast there was no significant difference in the GFAP and EAAT2 protein levels between the control and 3 days stress groups These findings suggest a dysfunction of the PAG that plays pivotal roles in the organization of strategies for coping with stressors and in pain modulation after chronic restraint stress.

Severe insulin allergy successfully treated with continuous subcutaneous insulin infusion

Insulin allergy is a rare complication of insulin therapy. Proper management, though difficult, is critical. Here, we report the case of a patient with type 2 diabetes and insulin allergy, successfully treated with continuous subcutaneous insulin infusion (CSII).

[Neuromyelitis optica in a patient with Sjögren syndrome with distal renal tubular acidosis: case report]

We report the case of a 31-year-old woman who presented with neuromyelitis optica (NMO) associated with Sjögren syndrome and distal renal tubular acidosis. She was hospitalized because of cervical transverse myelopathy and right optic neuritis. She had been clinically diagnosed with Sj6gren syndrome, with a high titer of anti-SS-A antibody (1:500) and anti-SS-B antibody (1:498). She also showed hypokalemia, metabolic acidosis, and nephrocalcinosis caused by distal renal tubular acidosis associated with Sjögren syndrome. T2-weighted magnetic resonance imaging (MRI) revealed long lesions extending from the medulla oblongata to the lower thoracic cord. In addition, gadolinium-enhanced MRI revealed a right optic nerve lesion in the optic canal. High titer of anti-aquaporin-4 (AQP4) antibody was detected in the patient's serum (1:131,072). A combination therapy comprising steroid pulse therapy and plasmapheresis improved her clinical symptoms, and the administration of oral prednisolone (20 mg/ day) was effective in preventing the recurrence of NMO. In patients with myelitis/transverse myelopathy associated with autoimmune disorders such as Sjögren syndrome, examining the titer values of anti-AQP4 antibody is indispensable in determining the appropriate therapy.

Activation of central 5HT2A receptors reduces the craniofacial nociception of rats

We assessed the contribution of central 5HT2A receptors to the craniofacial tissue nociception in naïve male rats. First, we tested whether activation of central 5HT2A receptors affected nociceptive neural activities recorded from superficial laminae of the trigeminal subnucleus caudalis (Vc)/upper cervical spinal cord junction (Vc/C2) region. Two types of units, such as deep-nociceptive or skin-wide dynamic range (WDR) units were identified from extracellular recordings. Topical administration of 5HT2A receptor agonist, (+/-)-2,5-dimethoxy-4-iodoamphetamine (DOI) onto the Vc/C2 region significantly reduced deep-nociceptive unit discharges evoked by formalin injection into the masseter muscle. Noxious pinch stimulation to the facial skin-evoked skin-WDR unit discharges was significantly reduced by topical administration of 0.1 mg/rat DOI onto the Vc/C2 region. Second, we tested whether i.c.v. administration of DOI affected Fos-like immunoreactivity (-LI) evoked by formalin injection into the masseter muscle. Fos-LI was significantly induced mainly at the ventrolateral (vl) area of trigeminal subnucleus interpolaris (Vi)/Vc junction (vl-Vi/Vc) region and Vc/C2 region in vehicle-treated rats. Formalin-evoked Fos-LI was significantly reduced in laminae I-II of the Vc/C2, but not vl-Vi/Vc region after i.c.v. administration of DOI. Finally, orofacial nocifensive behavioral activities evoked by formalin injection into the masseter muscle were significantly reduced by intracisternal administration of DOI. These results suggest that 5HT2A receptors in the Vc/C2 region mediate antinociceptive effects in the craniofacial nociception.

Efferent connections of the ventral auditory area in the rat cortex: implications for auditory processing related to emotion

In the rat auditory cortex, ventral (VA) and posterodorsal (PD) areas are the two major auditory fields that receive thalamic afferents from the dorsal division of the medial geniculate body (MGD). VA and PD are presumed to serve distinct functions in tandem as the pair of major cortical recipients of extralemniscal thalamic inputs. To deduce the functional significance of VA, efferent connections of VA were examined with the anterograde tracer biocytin. VA lies primarily in the ventral margin of area Te1 and represents frequencies primarily < 15 kHz [Donishi, T., Kimura, A., Okamoto, K. & Tamai, Y. (2006) Neuroscience, 141, 1553-1567.] Biocytin was iontophoretically injected into cortical regions which were defined as VA based on histological location, auditory response and thalamocortical connectivity. Anterograde labelling revealed two important aspects of cortical projections. First, VA sent a projection to a well-confined region in the caudal end of the insular cortex (Ins) pivotal for fear memory formation during aversive conditioning. Second, VA sent parallel projections to cortical regions that probably comprise the other nonprimary auditory fields, including PD. The results suggest that VA relays auditory input from the MGD to the Ins for affective memory formation and at the same time dispatches the auditory signal, which may represent emotional content, to the remaining nonprimary auditory fields. PD is assumed to play a pivotal role in auditory spatial processing for directed attention (Kimura et al., 2004). As the counterpart of PD, VA is assumed to give rise to another major stream of cortical information processing, most probably related to emotion.

Contribution of peripheral 5-HT2A or 5-HT3 receptors to Fos expression in the trigeminal spinal nucleus produced by acute injury to the masseter muscle during persistent temporomandibular joint inflammation in rats

We investigated the contribution of peripheral 5-HT2A or 5-HT3 receptors to Fos expression in the trigeminal spinal nucleus (VSP) following acute masseter muscle injury in male rats with or without temporomandibular joint (TMJ) inflammation persisting for 7 days. TMJ inflammation was evoked by an injection of complete Freund's adjuvant (CFA). Two hours after formalin injection into the masseter muscle produced Fos-like immunoreactivity (Fos-LI) in several regions of the VSP and upper cervical spinal cord (C2), such as ventrolateral (vl) area of the trigeminal subnucleus caudalis (Vc)/subnucleus interpolaris (Vi) transition (vl-Vi/Vc), paratrigeminal nucleus (dPa5), middle portion of the Vc (mid-Vc) and Vc/C2 transition (Vc/C2) regions in both groups. Significant increases in the number of Fos-LI were observed in these areas in CFA group compared with non-CFA group. TMJ inflammation alone did not induce a significant level of Fos-LI in the VSP. In order to assess the effect of antagonizing 5-HT2A or 5-HT3 receptors on formalin-induced Fos-LI, rats were pre-treated with local (masseter muscle) administration of ketanserin or tropisetron (0.01, 0.1 mg/rat) 20 min prior to formalin injection. In CFA group, these antagonists given locally reduced the Fos-LI response in the laminae I-II at the mid-Vc and Vc/C2 regions. These antagonists reduced the Fos-LI response in the dPa5, but not in the vl-Vi/Vc region. The Fos-LI response was not affected by i.v. administration of ketanserin (0.01, 0.1 mg/rat) or tropisetron (0.01 mg/rat). In non-CFA group, these antagonists given locally did not reduce the Fos-LI response. These results suggest that peripheral 5-HT2A and 5-HT3 receptors contribute to nociceptive processing in the masseter muscle in TMJ inflammatory conditions.

Central serotonin 3 receptors play an important role in the modulation of nociceptive neural activity of trigeminal subnucleus caudalis and nocifensive orofacial behavior in rats with persistent temporomandibular joint inflammation

The role of central serotonin 3 receptors on neural activities recorded from superficial laminae of trigeminal subnucleus caudalis/upper cervical spinal cord junction region was investigated using rats with (Complete Freund's Adjuvant day 7 group) or without (non-Complete Freund's Adjuvant group) persistent temporomandibular joint inflammation evoked by Complete Freund's Adjuvant for 7 days. We identified two types of units, Deep-wide dynamic range units and Skin-wide dynamic range units from extracellular recordings. Deep-wide dynamic range units have mechanoreceptive fields in the deep craniofacial tissues including masseter muscle but do not have cutaneous mechanoreceptive fields. Deep-wide dynamic range unit discharges evoked by the formalin injection into masseter muscle were significantly enhanced in the late phase in Complete Freund's Adjuvant day 7 group. Discharges of Skin-wide dynamic range units evoked by the noxious pinch stimulation to facial skin in Complete Freund's Adjuvant day 7 group were significantly enhanced compared with those in non-Complete Freund's Adjuvant group. Topical administration of central serotonin 3 receptor antagonist, tropisetron, onto trigeminal subnucleus caudalis/upper cervical spinal cord junction region significantly reduced both formalin-evoked Deep-wide dynamic range unit and pinch-evoked Skin-wide dynamic range unit discharges in non-Complete Freund's Adjuvant and Complete Freund's Adjuvant day 7 groups significantly. The inhibitory effects of tropisetron on pinch-evoked Skin-wide dynamic range unit discharges were prolonged in Complete Freund's Adjuvant day 7 group compared with those in non-Complete Freund's Adjuvant group. The role of central serotonin 3 receptors in trigeminal subnucleus caudalis/upper cervical spinal cord junction region was also tested by orofacial formalin test in Complete Freund's Adjuvant day 7 group. Intracisternal administration of tropisetron decreased the orofacial nocifensive behavior in the late phase evoked by the injection of formalin into the masseter muscle. These results suggest that central serotonin 3 receptors in trigeminal subnucleus caudalis/upper cervical spinal cord junction region are involved in mediating pronociceptive effects in both superficial and deep craniofacial tissues nociception during persistent temporomandibular joint inflammation.

The role of peripheral 5HT2A and 5HT1A receptors on the orofacial formalin test in rats with persistent temporomandibular joint inflammation

The role of peripheral serotonin (5HT) 2A and 5HT1A receptors on the orofacial nocifensive behavioral activities evoked by the injection of formalin into the masseter muscle was evaluated in the rats with persistent temporomandibular joint (TMJ) inflammation evoked by Complete Freund's Adjuvant (CFA). The orofacial nocifensive behavioral activities evoked by the injection of formalin into masseter muscle were significantly enhanced at 1 day (CFA day 1 group) or 7 days (CFA day 7 group) during TMJ inflammation. Pretreatment with local administration of 5HT2A receptor antagonist, ketanserin (0.01, 0.1 mg/rat) into the masseter muscle or systemic administration of ketanserin via i.p. injection (1 mg/kg) reduced the orofacial nocifensive behavioral activities of the late phase evoked by formalin injection into masseter muscle on the side of TMJ inflammation (CFA day 7 group). However, local (0.001-0.1 mg/rat) or systemic (1 mg/kg) administration of 5HT1A receptor antagonist, propranolol, into masseter muscle did not produce the antinociceptive effect in CFA day 7 group. Moreover, local administration of ketanserin (0.1 mg) or propranolol (0.1 mg) into masseter muscle did not inhibit nocifensive orofacial behavior in rats without TMJ inflammation. These data suggest that persistent TMJ inflammation causes the elevation of the orofacial nocifensive behavior, and peripheral 5HT2A receptors play an important role in mediating the deep craniofacial tissue nociception in rats with TMJ inflammation.

Orofacial deep and cutaneous tissue inflammation and trigeminal neuronal activation. Implications for persistent temporomandibular pain

A rat model has been developed to characterize the responses of brainstem trigeminal neurons to orofacial deep and cutaneous tissue inflammation and hyperalgesia. Complete Freund's adjuvant (CFA) was injected unilaterally into the rat temporomandibular joint (TMJ) or perioral (PO) skin to produce inflammation in deep or cutaneous tissues, respectively. The TMJ and PO inflammation resulted in orofacial behavioral hyperalgesia and allodynia that peaked within 4-24 h and persisted for at least 2 weeks. Compared to cutaneous CFA injection, the injection of CFA into the TMJ produced a significantly stronger inflammation associated with a selective upregulation of preprodynorphin mRNA in the trigeminal spinal complex, an enhanced medullary dorsal horn hyperexcitability, and a greater trigeminal Fos protein expression, a marker of neuronal activation. The Fos-LI induced by TMJ inflammation persisted longer, was more intense, particularly in the superficial laminae, and more widespread rostrocaudally. Thus, the inflammatory irritant produces a stronger effect in deep than in cutaneous orofacial tissue. As there is heavy innervation of the TMJ by unmyelinated nerve endings, a strong nociceptive primary afferent barrage is expected following inflammation. An increase in TMJ C-fiber input after inflammation and strong central neuronal activation may initiate central hyperexcitability and contribute to persistent pain associated with temporomandibular disorders. Since deep inputs may be more effective in inducing central neuronal excitation than cutaneous inputs, greater sensory disturbances may occur in pain conditions involving deep tissues than in those involving cutaneous tissues.

Selective upregulation of the flip-flop splice variants of AMPA receptor subunits in the rat spinal cord after hindpaw inflammation

Glutamate receptors are involved in spinal nociceptive transmission and the development of persistent inflammatory hyperalgesia. It is unclear, however, whether there are changes in glutamate receptor gene expression associated with tissue injury. In the present study, we used reverse transcription-polymerase chain reaction (RT-PCR) to examine the modulation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor gene expression in the rat spinal cord by inflammation. Inflammation was introduced into the hindpaw by intraplantar injection of 0.2 ml of complete Freund's adjuvant (CFA). At 2 h-14 d after inflammation, total RNAs from L4,5 spinal cord were used for RT-PCR with primers targeted at eight flip-flop splice variants of the AMPA receptor subunits. It was found that the GluR1-flop mRNA was up-regulated at 2 h-5 h (P<0.05), down-regulated at 3 d (P=0.05), and returned to control levels at 7 d following inflammation. The GluR2-flip and GluR3-flop mRNAs were up-regulated at 5 h-1 d (P<0.05) and returned to control levels at 3 d after inflammation. The GluR1-flip mRNA was not detected in the samples and the mRNAs for other splice variants did not exhibit significant changes. Immunocytochemical analysis of GluR1 and GluR2 subunits indicate that the protein translation products of these subunits were also increased in the spinal cord. These results demonstrate an increased expression of AMPA receptor subunits that correlates with the acute phase of CFA-induced inflammation and hyperalgesia. Selective changes in the expression of the flip-flop splice variants of the AMPA receptor suggest a reorganization of the composition of the AMPA receptor complex and its involvement in the development of inflammatory hyperalgesia.

The up-regulation of preprodynorphin mRNA in trigeminoparabrachial neurons after inflammation

Inflammation of the temporomandibular joint (TMJ) produces an increase in preprodynorphin (PPD) mRNA expression in the spinal trigeminal nucleus (Vsp) and paratrigeminal nucleus (Pa5) of the rat. In this study, we further demonstrated that a portion of the TMJ inflammation-induced PPD mRNA positive neurons in the Vsp and Pa5 projected to the parabrachial nucleus (PB). In inflamed rats, the percentage of trigemino- and paratrigeminoparabrachial neurons with up-regulation of PPD mRNA was significantly increased in the ipsilateral Vsp (5.7+/-1.8%) and Pa5 (22.8+/-7.4%, n = 3) when compared with the contralateral side and with saline-treated controls (p < 0.05). These results suggest that the selective up-regulation of PPD mRNA in the Vsp and Pa5 following TMJ inflammation involves ascending trigeminal nociceptive pathways.

Masseteric inflammation-induced Fos protein expression in the trigeminal interpolaris/caudalis transition zone: contribution of somatosensory-vagal-adrenal integration

The effects of vagotomy and adrenalectomy on the expression of Fos protein in brainstem neurons following the inflammation of masseter muscle were examined in order to differentiate the Fos activation related to nociceptive processing in contrast to that due to somatoautonomic processing. The inflammation was induced by a unilateral injection of complete Freund's adjuvant (CFA) into the masseter muscle under methohexital anesthesia after a small skin-cut (S-cut). After the CFA injection, Fos positive neurons were identified in bilateral spinal trigeminal nucleus (VSP), nucleus tractus solitarius (NTS), ventrolateral medulla (VLM) and inferior medial olivary nucleus (IOM). At the level of the trigeminal subnucleus interpolaris/caudalis (Vi/Vc) transition zone, there was a selective induction of Fos-like immunoreactivity (LI) in the VSP and NTS, when compared to control rats (anesthesia with or without S-cut). A major portion of the Fos-LI in the VSP at the level of the caudal Vc was apparently activated by S-cut. Bilateral adrenalectomy or a unilateral vagotomy resulted in a selective reduction of inflammation-induced Fos-LI in the VSP at the Vi/Vc transition zone (P<0.05) and NTS (P<0.05), but had less effect on Fos-LI in the caudal Vc. These results suggest that the inflammation of the masseter muscle, an injury of orofacial deep tissue, results in a widespread change in neuronal activity in the VSP and NTS that depends in part on the integrity of the adrenal cortex and vagus. Thus, in addition to somatotopically organized nociceptive responses, orofacial deep tissue injury also is coupled to somatovisceral and somatoautonomic processing that contribute to central neural activation.

Persistent Fos protein expression after orofacial deep or cutaneous tissue inflammation in rats: implications for persistent orofacial pain

This study was designed to systematically examine the effects of persistent orofacial tissue injury on prolonged neuronal activation in the trigeminal nociceptive pathways by directly comparing the effects of orofacial deep vs. cutaneous tissue inflammation on brainstem Fos protein expression, a marker of neuronal activation. Complete Freund's adjuvant (CFA) was injected unilaterally into the rat temporomandibular joint (TMJ) or perioral (PO) skin to produce inflammation in deep or cutaneous tissues, respectively. Rats were perfused 2 hours, 24 hours, 3 days, or 10 days following CFA injection. The TMJ and PO inflammation-induced Fos expression paralleled the intensity and course of inflammation over the 10-day observation period, suggesting that the increase in intensities and persistence of Fos protein expression may be associated with a maintained increase in peripheral input. Compared to PO CFA injection, the injection of CFA into the TMJ produced a significantly stronger inflammation associated with a greater Fos expression. In TMJ- but not in PO-inflamed rats, Fos-like immunoreactivity (LI) spread from superficial to deep upper cervical dorsal horn as the inflammation persisted and there was a dominant ipsilateral Fos-labeling in the paratrigeminal nucleus. Common to TMJ and PO inflammation, Fos-LI was induced in the trigeminal subnuclei interpolaris and caudalis, C1-2 dorsal horn, and other medullary nuclei. Substantial bilateral Fos-LI was found in the interpolaris-caudalis trigeminal transition zone. Further analysis revealed that Fos-LI in the ventral transition zone was equivalent bilaterally, whereas Fos-LI in the dorsal transition zone was predominantly ipsilateral to the inflammation. The differential induction of Fos expression suggests that an increase in TMJ C-fiber input after inflammation and robust central neuronal hyperexcitability contribute to persistent pain associated with temporomandibular disorders.

Orofacial deep and cutaneous tissue inflammation differentially upregulates preprodynorphin mRNA in the trigeminal and paratrigeminal nuclei of the rat

Preprodynorphin (PPD) and preproenkephalin (PPE) gene expression in a rat model of orofacial inflammation were examined in order to further characterize the neurochemical mechanisms underlying orofacial inflammation and hyperalgesia. Deep and cutaneous orofacial inflammation was produced by a unilateral injection of complete Freund's adjuvant (CFA) into the rat temporomandibular joint (TMJ) or perioral skin (PO), respectively. RNA blot analysis of the tissues including the spinal trigeminal complex revealed that the PPD mRNA level ipsilateral to TMJ inflammation was increased by 56.5+/-14.7% (n=4) when compared to the Naive group, and was significantly greater than the contralateral PPD mRNA level (p<0.05). The distribution of neurons that exhibited PPD mRNA after inflammation was localized by in situ hybridization (naive approximately 0). In TMJ-inflamed rats (n=6) PPD mRNA-positive neurons were found ipsilaterally in the medial portion of laminae I-II of the upper cervical dorsal horn (4.5+/-0.3), the dorsal portion of the subnucleus caudalis and caudal subnucleus interpolaris (5.2+/-0.3), and the paratrigeminal nucleus (6.4+/-1.2). A very localized induction of PPD mRNA was also identified in a group of neurons in the intermediate portion of the subnucleus caudalis (2.4+/-0.4) in PO-inflamed rats (n=6). The distribution of these PPD mRNA-positive neurons was somatotopically relevant to the site of injury. There were no significant changes in PPE mRNA expression in both TMJ- and PO-inflamed rats. These results indicate that TMJ inflammation resulted in a more intense and widespread increase in PPD mRNA expression when compared to PO inflammation. These changes may contribute to persistent central hyperexcitability and pain associated with temporomandibular disorders.