Adrenergic regulation of capsaicin-sensitive neurons in dental pulp

Effect of Back-Pressure Anesthesia on Postoperative Pain after the Endodontic Treatment in Patients with Symptomatic Irreversible Pulpitis: Randomized Double-Blind Clinical Trial

INTRODUCTION

The present study evaluated the effect of 2 different back pressure-based supplemental anesthesia on postoperative pain in patients receiving endodontic treatment for a mandibular molar with symptomatic irreversible pulpitis.

METHODS

One-hundred-thirty-five adult patients with symptomatic irreversible pulpits in a mandibular first or second molar, received an initial inferior alveolar nerve block (IANB) injection with 2% lidocaine with 1:80,000 epinephrine. Ten minutes following the injection, access to cavity preparation began. Lip numbness was a must for all patients. The Heft-Parker visual analogue scale (HP-VAS) was used to measure pain during endodontic therapy. Success of primary injections was defined as no or mild pain (less than 55 mm on HP-VAS) during access preparation. The patients with initial successful anesthesia served as control and received endodontic treatment. Ninety-five patients with unsuccessful primary anesthesia randomly received either intraligamentary injections of 2% lidocaine with 1:80,000 epinephrine or intrapulpal injections with similar anesthetic solution. Endodontic treatment was re-initiated and canals were instrumented till working length under copious irrigation. Intracanal medicament of calcium hydroxide was placed and teeth received a temporary restoration. Postoperative pain was measured at 2 hours, 4 hours, 6 hours, 24 hours, and 3 days. Data were analyzed using the Pearson chi-square test, one-way analysis of variance, and one-way repeated measures analysis of variance.

RESULTS

The initial initial inferior alveolar nerve block was successful in 40 cases (out of 135). The intraligamentary injections were successful in 33 out of 47 cases (70%), and intrapulpal injections were successful in all cases (45/45). The patients receiving intraligamentary injections reported significantly higher pain scores at all intervals till 24 hours. After 3 days, the pain significantly reduced in all the groups with no significant difference between them.

CONCLUSIONS

Patients receiving supplementary intraligamentary injections can experience increased postoperative pain till 24 hours after the endodontic treatment. The pain scores reduced to the level of the control group after 3 days.

Substance P/calcitonin gene-related peptide and their receptors expression in human periodontal ligament after root canal preparation with five different systems

AIM

The purpose of this study was to quantify the effect of five different root canal preparation instruments on Substance P (SP), Calcitonin gene-related peptide (CGRP) and their receptors expression in healthy human periodontal ligament.

METHODOLOGY

STROBE guidelines were used to design a study using 60 periodontal ligament samples obtained from healthy lower premolars where extraction was indicated for orthodontic reasons. Prior to extraction 40 of these premolars were equally divided into four groups and root canals were prepared using different systems: Mtwo, Reciproc Blue, HyFlex EDM and Plex-V. Ten premolars were prepared with hand files and served as a positive control group. The remaining 10 premolars where extracted without treatment and served as a negative control group. All periodontal ligament samples were processed to measure the expression of SP, CGRP and their receptors by radioimmunoassay. Kruskal-Wallis and Duncan tests were performed to determine statistically significant differences between the groups for each variable.

RESULTS

Greater expression of all the peptides measured were found in the hand-file preparation group, followed by the Reciproc Blue, Mtwo, HyFlex EDM and Plex-V groups. The lower SP, CGRP and their receptors values were for the intact teeth control group. Kruskal-Wallis test showed statistically significant differences amongst groups (p < .001). Dunn post-hoc tests showed statistically significant differences in SP, CGRP and their receptors expression between the intact teeth and the hand-file and Reciproc Blue groups. Hand-file group showed significant differences with the other groups, except with Reciproc Blue, where no differences were observed in any of the peptides measured. Finally, no differences were observed between Plex-V and HyFlex in any of the peptides measured.

CONCLUSIONS

Root canal preparation with hand files and Reciproc Blue generates the highest expression of SP, CGRP, NK1 and CGRP1R in human periodontal ligament, whilst Plex-V and HyFlex maintain the basal expression of neuropeptides and their receptors. Mtwo showed intermediate results between Reciproc Blue and HyFlex.

Sympathetic and Sensory-Motor Nerves in Peripheral Small Arteries

Small arteries, which play important roles in controlling blood flow, blood pressure, and capillary pressure, are under nervous influence. Their innervation is predominantly sympathetic and sensory motor in nature, and while some arteries are densely innervated, others are only sparsely so. Innervation of small arteries is a key mechanism in regulating vascular resistance. In the second half of the previous century, the physiology and pharmacology of this innervation were very actively investigated. In the past 10-20 yr, the activity in this field was more limited. With this review we highlight what has been learned during recent years with respect to development of small arteries and their innervation, some aspects of excitation-release coupling, interaction between sympathetic and sensory-motor nerves, cross talk between endothelium and vascular nerves, and some aspects of their role in vascular inflammation and hypertension. We also highlight what remains to be investigated to further increase our understanding of this fundamental aspect of vascular physiology.

Dental nerves: a neglected mediator of pulpitis

As one of the most densely innervated tissues, the dental pulp contains abundant nerve fibres, including sensory, sympathetic and parasympathetic nerve fibres. Studies in animal models and human patients with pulpitis have revealed distinct alterations in protein expression and histological appearance in all types of dental nerve fibres. Various molecules secreted by neurons, such as classical neurotransmitters, neuropeptides and amino acids, not only contribute to the induction, sensitization and maintenance of tooth pain, but also regulate non-neuronal cells, including fibroblasts, odontoblasts, immune cells and vascular endothelial cells. Dental nerves are particularly important for the microcirculatory and immune responses in pulpitis via their release of a variety of functional substances. Further, nerve fibres are found to be involved in dental soft and hard tissue repair. Thus, understanding how dental nerves participate in pulpitis could have important clinical ramifications for endodontic treatment. In this review, the roles of dental nerves in regulating pulpal inflammatory processes are highlighted and their implications for future research on this topic are discussed.

The CGRP receptor antagonist BIBN4096 inhibits prolonged meningeal afferent activation evoked by brief local K+ stimulation but not cortical spreading depression-induced afferent sensitization

Calcitonin gene-related peptide mediates K⁺-evoked delayed and prolonged activation of cranial meningeal afferents but does not contribute to their enhanced responsiveness following cortical spreading depression.

Introduction:

Cortical spreading depression (CSD) is believed to promote migraine headache by enhancing the activity and mechanosensitivity of trigeminal intracranial meningeal afferents. One putative mechanism underlying this afferent response involves an acute excitation of meningeal afferents by cortical efflux of K⁺ and the ensuing antidromic release of proinflammatory sensory neuropeptides, such as calcitonin gene-related peptide (CGRP).

Objectives:

We sought to investigate whether (1) a brief meningeal K⁺ stimulus leads to CGRP-dependent enhancement of meningeal afferent responses and (2) CSD-induced meningeal afferent activation and sensitization involve CGRP receptor signaling.

Methods:

Extracellular single-unit recording were used to record the activity of meningeal afferents in anesthetized male rats. Stimulations included a brief meningeal application of K⁺ or induction of CSD in the frontal cortex using pinprick. Cortical spreading depression was documented by recording changes in cerebral blood flow using laser Doppler flowmetery. Calcitonin gene-related peptide receptor activity was inhibited with BIBN4096 (333 μM, i.v.).

Results:

Meningeal K⁺ stimulation acutely activated 86% of the afferents tested and also promoted in ∼65% of the afferents a 3-fold increase in ongoing activity, which was delayed by 23.3 ± 4.1 minutes and lasted for 22.2 ± 5.6 minutes. K⁺ stimulation did not promote mechanical sensitization. Pretreatment with BIBN4096 suppressed the K⁺-induced delayed afferent activation, reduced CSD-evoked cortical hyperemia, but had no effect on the enhanced activation or mechanical sensitization of meningeal afferents following CSD.

Conclusion:

While CGRP-mediated activation of meningeal afferents evoked by cortical efflux of K⁺ could promote headache, acute activation of CGRP receptors may not play a key role in mediating CSD-evoked headache.

Comparison of pulpal anesthesia and cardiovascular parameters with lidocaine with epinephrine and lidocaine with clonidine after maxillary infiltration in type 2 diabetic volunteers

OBJECTIVES

The pulpal anesthetic and cardiovascular parameters obtained by 2 % lidocaine with epinephrine (LE; 1:80,000) or clonidine (LC; 15 mcg/ml) were studied in diabetes mellitus (DM) type 2 and healthy volunteers (72), after maxillary infiltration anesthesia.

MATERIALS AND METHODS

Onset and duration of pulpal anesthesia were measured by electric pulp tester; vasoconstrictive effect of used local anesthetic mixtures by laser Doppler flowmetry (LDF) through pulpal blood flow (PBF); systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were registered by electrocardiogram monitoring.

RESULTS

Onset of pulpal anesthesia was shorter for LC than for LE in healthy, while it was not different in diabetic participants; duration of pulpal anesthesia was significantly longer in type 2 diabetic participants, regardless of used anesthetic mixture. Significant reduction of PBF with LE was observed during 45 min in healthy and 60 min in diabetic participants, while with LC such reduction was observed during 45 min in both groups. LE caused a significant increase of SBP in the 5th and 15th minutes in diabetic versus healthy participants, while LC decreased SBP from the 10th to 60th minutes in healthy versus diabetic participants.

CONCLUSIONS

DM type 2 influences duration of maxillary infiltration anesthesia obtained with LE and LC, and systolic blood pressure during LE anesthesia.

CLINICAL RELEVANCE

The obtained results provide elements for future protocols concerning intraoral local anesthesia in DM type 2 patients.

Lipopolysaccharide from Porphyromonas gingivalis sensitizes capsaicin-sensitive nociceptors

Although odontogenic infections are often accompanied by pain, little is known about the potential mechanisms mediating this effect. In this study we tested the hypothesis that trigeminal nociceptive neurons are directly sensitized by lipopolysaccharide (LPS) isolated from an endodontic pathogen, Porphyromonas gingivalis. In vitro studies conducted with cultures of rat trigeminal neurons demonstrated that pretreatment with LPS produced a significant increase in the capsaicin-evoked release of calcitonin gene-related peptide (CGRP) when compared with vehicle pretreatment, thus showing sensitization of the capsaicin receptor, TRPV1, by LPS. Furthermore, confocal microscopic examination of human tooth pulp samples showed the colocalization of the LPS receptor (toll-like receptor 4, TLR4) with CGRP-containing nerve fibers. Collectively, these results suggest the direct sensitization of nociceptors by LPS at concentrations found in infected canal systems as one mechanism responsible for the pain associated with bacterial infections.

The effect of three different rotary instrumentation systems on substance P and calcitonin gene-related peptide expression in human periodontal ligament

INTRODUCTION

The purpose of this study was to quantify the effect of three different rotary root canal preparation systems on substance P and calcitonin gene-related peptide expression in healthy human periodontal ligament.

METHODS

Fifty periodontal ligament samples were obtained from healthy premolars in which extraction was indicated for orthodontic reasons. Before extraction, 40 of these premolars were equally divided into four groups, and root canals were prepared using four different systems: the ProTaper Universal rotary system, the RaCe rotary system, the Mtwo rotary system, and the hand instrumentation technique. The remaining 10 healthy premolars that were extracted without treatment served as a negative control group. All periodontal ligament samples were processed, and SP and CGRP were measured by radioimmunoassay.

RESULTS

Greater SP and CGRP expression were found in the ProTaper Universal group followed by the hand instrumentation group, the RaCe, and the Mtwo groups. The lower SP and CGRP values were for the negative control group. The Kruskal-Wallis test showed statistically significant differences between groups (p < 0.0001). Post hoc Least Significant Difference (LSD) tests showed statistically significant differences in SP and CGRP expression between the negative control group and all the other groups except the Mtwo group. Hand instrumentation also showed statistically significant differences with all the other groups, except the ProTaper Universal group. Differences between the three rotary systems were also statistically significant.

CONCLUSION

SP and CGRP expression in periodontal ligament increases when teeth are prepared with ProTaper Universal and RaCe rotary instrumentation systems as well as with hand instrumentation. Mtwo maintains SP and CGRP levels.

Animal models of orofacial pain

Pain is one of the most common reasons for which patients seek dental and medical care. Orofacial pain conditions consist of a wide range of disorders including odontalgia (toothache), temporomandibular disorders, trigeminal neuralgia and others. Most of these conditions are either inflammatory or neuropathic in nature. This chapter provides an overview of the commonly used models to study inflammatory and neuropathic orofacial pain.

The effect of different vasoconstrictors and local anesthetic solutions on substance P expression in human dental pulp

The purpose of this study was to quantify the effect of the infiltration injection of different vasoconstrictor and anesthetic solutions on substance P (SP) expression in healthy human dental pulp. Thirty pulp samples were obtained from healthy upper premolars in which extraction was indicated for orthodontic reasons and were randomly assigned into three groups of 10 samples each: 2% lidocaine with 1:80,000 epinephrine (Lido group), 3% Prilocaine with 1:200000 felypressin (Prilo group); and 4% Prilocaine without vasoconstrictor (Prilo-no-VC group). All teeth were extracted 10 minutes after anesthetic application. Pulp samples were processed and SP was measured by radioimmunoassay. SP expression for the Lido, Prilo, and Prilo-no-VC groups were 616.49, 663.76, and 760.79 pmol/mg pulp tissue, respectively. Analysis of variance showed statistically significant differences between groups (p = 0.001). Tukey Honestly Significant Difference (HSD) post hoc tests showed significant statistical differences between the Prilo-no-VC group and the Lido group (p < 0.01) and between the Prilo-no-VC group and the Prilo group (p < 0.05). It can be concluded that infiltration injection of local anesthetics with vasoconstrictor attenuate SP expression in human dental pulp.

Capsaicin-evoked iCGRP release from human dental pulp: a model system for the study of peripheral neuropeptide secretion in normal healthy tissue

The mechanisms underlying trigeminal pain conditions are incompletely understood. In vitro animal studies have elucidated various targets for pharmacological intervention; however, a lack of clinical models that allow evaluation of viable innervated human tissue has impeded successful translation of many preclinical findings into clinical therapeutics. Therefore, we developed and characterized an in vitro method that evaluates the responsiveness of isolated human nociceptors by measuring basal and stimulated release of neuropeptides from collected dental pulp biopsies. Informed consent was obtained from patients presenting for extraction of normal wisdom teeth. Patients were anesthetized using nerve block injection, teeth were extracted and bisected, and pulp was removed and superfused in vitro. Basal and capsaicin-evoked peripheral release of immunoreactive calcitonin gene-related peptide (iCGRP) was analyzed by enzyme immunoassay. The presence of nociceptive markers within neurons of the dental pulp was characterized using confocal microscopy. Capsaicin increased the release of iCGRP from dental pulp biopsies in a concentration-dependent manner. Stimulated release was dependent on extracellular calcium, reversed by a TRPV1 receptor antagonist, and desensitized acutely (tachyphylaxis) and pharmacologically by pretreatment with capsaicin. Superfusion with phorbol 12-myristate 13-acetate (PMA) increased basal and stimulated release, whereas PGE2 augmented only basal release. Compared with vehicle treatment, pretreatment with PGE2 induced competence for DAMGO to inhibit capsaicin-stimulated iCGRP release, similar to observations in animal models where inflammatory mediators induce competence for opioid inhibition. These results indicate that the release of iCGRP from human dental pulp provides a novel tool to determine the effects of pharmacological compounds on human nociceptor sensitivity.

The effect of tooth bleaching on substance P expression in human dental pulp

The purpose of this study was to quantify the effect of tooth bleaching on substance P (SP) expression in healthy human dental pulp. Forty pulp samples were obtained from healthy premolars in which extraction was indicated for orthodontic reasons. Thirty of these premolars were assigned into three different tooth-bleaching protocols: group 1 (n = 10): Opalescence Xtra Boost (Ultradent Products, South Jordan, UT) (38% H(2)O(2)) for 15 minutes; group 2 (n = 10): Lase Peroxide (DMC, Brazil) (35% H(2)O(2)) activated with infrared laser diode (Biolux; BioArt, Brazil) for 3 minutes, and group 3 (n = 10): Zoom! Whitening System (Discuss Dental, Culver City, CA) (25% H(2)O(2)) light activated for 20 minutes. The remaining 10 healthy premolars serve as a control group. Teeth were anesthetized immediately after bleaching and were extracted 10 minutes later. All pulp samples were processed and SP was measured by radioimmunoassay. Greater SP expression was found in the Zoom! Whitening System, followed by the Lase Peroxide group, Opalescence Xtra Boost, and the lower SP values were for the control group. Analysis of variance showed statistically significant differences between groups (p = 0.0001). Tukey HSD post hoc tests showed significant differences in the light (p < 0.01) and laser (p < 0.05) activated bleaching systems when compared with control values. It can be concluded that light- and laser-activated tooth-bleaching systems increase SP expression in human dental pulp significantly higher than normal values.

Substance P receptor expression in healthy and inflamed human pulp tissue

AIM

To use radioreceptor analysis for comparing substance P (SP) receptor expression in human pulp tissue samples collected from teeth having a clinical diagnosis of acute irreversible pulpitis, healthy pulps and teeth with induced inflammation.

METHODOLOGY

Five pulp samples were obtained from teeth having a clinical diagnosis of acute irreversible pulpitis. Another 10 pulp samples were obtained from healthy premolars where extraction was indicated for orthodontic purposes. In five of these premolars inflammation was induced prior to pulp collection. All of the samples were processed and labelled with 125I-SP. Binding sites were identified by 125I-SP and standard SP competition assays. Kruskal-Wallis and Mann-Whitney (post-hoc) tests were used to establish statistically significant differences between the groups.

RESULTS

Substance P receptor expression was found in all human pulp tissue samples. Most receptors were found in the group of pulps from teeth having a clinical diagnosis of acute irreversible pulpitis, followed by the group of pulps having induced inflammation. The least number of receptors was expressed in the group of healthy pulps. Statistical analysis revealed significant differences between the group of healthy pulp and both inflamed pulp groups (P < 0.01).

CONCLUSION

Substance P receptor expression in human pulp tissue is significantly increased during inflammatory phenomena such as acute irreversible pulpitis.

Peripheral mechanisms of odontogenic pain

In this article, we review the key basic mechanisms associated with this phenomena and more recently identified mechanisms that are current areas of interest. Although many of these pain mechanisms apply throughout the body, we attempt to describe these mechanisms in the context of trigeminal pain.

The Contribution of Alpha-1 and Alpha-2 Adrenoceptors in Peripheral Imidazoline and Adrenoceptor Agonist-Induced Nociception

We evaluated the effects of activation of peripheral adrenoceptors (AR) and imidazoline receptors on nociception and the contribution of alpha-1 and alpha-2 AR receptors in agonist-induced nociception by using the tail-flick test in mice. Clonidine (alpha-2 AR agonist), agmatine (imidazoline receptor and alpha-2 AR agonist), noradrenaline (mixed alpha-1 and alpha-2 AR agonist), phenylephrine (alpha-1 AR agonist), or 0.9% saline was given by intradermal injection (10 microL) into the tail. The intradermal injection of clonidine (1, 3, and 10 microg) and agmatine (3, 30, and 50 microg) produced dose-dependent antinociception, whereas noradrenaline (1, 10, and 30 microg) and phenylephrine (1, 10 and 30 microg) produced dose-dependent thermal hyperalgesia. Clonidine (10 microg) and agmatine (50 microg)-induced peripheral antinociception were antagonized by pretreatment with yohimbine (2.5 mg/kg IP), a selective alpha-2 AR antagonist, but not by prazosin (1 mg/kg IP), a selective alpha-1 AR antagonist. Noradrenaline (30 microg) and phenylephrine (30 mug)-induced thermal hyperalgesia were antagonized by prazosin (1 mg/kg IP) but not by yohimbine (2.5 mg/kg IP). Our results suggest that local thermal hyperalgesic effects of noradrenaline and phenylephrine are linked to alpha-1 AR and the peripheral antinociceptive action of clonidine and agmatine are linked to alpha-2 AR.

Effect of sympathetic and parasympathetic mediators on the release of calcitonin gene-related peptide and prostaglandin E from rat dura mater, in vitro

Although not without controversy, an influence of the autonomic nervous system in headache is a matter for current debate. A possible contact site of autonomic and sensory nerves is the dura mater, where they form a dense network accompanying blood vessels. We investigated interactions between autonomic and nociceptive fibres by measuring release of calcitonin gene-related peptide (CGRP) and prostaglandin E2 (PGE2) from the dura mater, in vitro. The parasympathomimetic agent carbachol did not change basal release of CGRP or PGE2, whereas it diminished release induced by a mixture of inflammatory mediators. Norepinephrine did not change induced release of CGRP or PGE2, nor basal release of CGRP. However, basal release of PGE2 was enhanced by norepinephrine, and this enhancement was reduced by serotonin through 5-HT(1D) receptors. We conclude that sympathetic transmitters may control nociceptor sensitivity via increased basal PGE2 levels, a possible mechanism to facilitate headache generation. Parasympathetic transmitters may reduce enhanced nociceptor activity.

Quantification of neuropeptides (calcitonin gene-related peptide, substance P, neurokinin A, neuropeptide Y and vasoactive intestinal polypeptide) expressed in healthy and inflamed human dental pulp

AIM

To quantify the expression of calcitonin gene-related peptide (CGRP), substance P (SP), neurokinin A (NKA), neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) in healthy and inflamed human dental pulp tissue.

METHODOLOGY

Six pulp samples were obtained from teeth having a clinical diagnosis of acute irreversible pulpitis. Another 12 pulp samples were obtained from premolars where extraction was indicated for orthodontic purposes. In six of these premolar teeth inflammation was induced by mechanical pulp exposure prior to sample collection. All samples were processed and 125I-labelled; neuropeptides were quantified by competition assays. ANOVA and Mann-Whitney's (post hoc) tests were used to establish statistically significant differences between the groups.

RESULTS

Expression of five neuropeptides was found in all human pulp samples. Statistical analysis revealed a significantly higher (P < 0.05) expression of CGRP, SP, NKA and NPY in both inflammatory conditions compared with healthy pulp control values. VIP expression remained stable during the inflammatory conditions.

CONCLUSION

Expression of CGRP, SP and NKA released from C-fibres and NPY released from sympathetic fibres is significantly higher in the inflamed human pulp compared with healthy pulp. Expression of VIP released from parasympathetic fibres is not increased during the inflammatory conditions of human dental pulp.

The effect of cavity preparation on substance P expression in human dental pulp

Substance P (SP) plays an important role during neurogenic inflammation of dental pulp. The purpose of this study was to use a radioimmunoassay for determining the effect of cavity preparation on SP expression in healthy human dental pulp. Ten pulp samples were obtained from healthy premolars where extraction was indicated for orthodontic reasons. Deep cavity preparation (<1 mm remaining dentine thickness) was performed before extraction in five of these bicuspids. All samples were processed and I-SP labeled; SP was quantified by competition assay. The results revealed SP expression in all human pulp samples. Mann-Whitney's U test revealed statistically significant higher expression in pulp from teeth where cavity preparation had been performed compared to control values (p < 0.05). These findings suggest that SP is released during common dental procedures (such as cavity preparation) and its expression may have an important clinical significance in terms of experiencing inflammation and pain.

Trigeminal nociceptors express TLR-4 and CD14: a mechanism for pain due to infection

Although certain bacterial species appear to be risk factors for pain due to odontogenic infections, comparatively little is known about the potential mechanisms mediating this effect. In this study, we tested the hypothesis that trigeminal nociceptive neurons express the TLR4 or CD14 receptors, thus enabling sensory neurons to detect and respond to tissue levels of bacterial substances such as lipopolysaccharide (LPS). Immunohistochemical analyses of human and rat trigeminal neurons demonstrated that a capsaicin-sensitive subclass of nociceptors (defined by expression of TRPV1, a capsaicin receptor) expresses both TLR4 and CD14. Moreover, human dental pulp collected from patients with caries lesions demonstrated co-localization of TLR4 and CD14, with markers of peripheral sensory neurons. Collectively, these studies indicate that the capsaicin-sensitive subclass of trigeminal nociceptors expresses TLR4 and CD14. These results indicate that pain due to bacterial infections may result, in part, from direct activation of nociceptors by bacterial products such as LPS.

Calcitonin gene-related peptide receptor expression in healthy and inflamed human pulp tissue

AIM

To use radioreceptor analysis for comparing calcitonin gene-related peptide (CGRP) receptor expression in human pulp tissue samples collected from teeth having a clinical diagnosis of acute irreversible pulpitis, healthy pulps and teeth with induced inflammation.

METHODOLOGY

Six pulp samples were obtained from teeth having a clinical diagnosis of acute irreversible pulpitis. Another eight pulp samples were obtained from healthy premolars where extraction was indicated for orthodontic purposes. In four of these premolars, inflammation was induced prior to pulp collection. All the samples were processed and labelled with 125I-CGRP. Binding sites were identified by 125I-CGRP and standard CGRP competition assays.

RESULTS

CGRP receptor expression was found in all human pulp tissue samples. Most receptors were found in the group of pulps from teeth having a clinical diagnosis of acute irreversible pulpitis, followed by the group of pulps having induced inflammation. The least number of receptors was expressed in the group of healthy pulps. The Kruskal-Wallis and Mann-Whitney (post-hoc) tests showed statistically significant differences between the groups (P < 0.05).

CONCLUSION

CGRP receptor expression in human pulp tissue is significantly increased during inflammatory phenomena such as acute irreversible pulpitis.

Expression and Characterization of Vanilloid Receptor Subtype 1 in Human Dental Pulp Cell Cultures

The expression of the vanilloid receptor subtype 1 (VR1, TRPV1) was detected in human dental pulp fibroblasts (PF-10) using RT-PCR, Western blotting, and immunocytochemical analysis. As revealed by ELISA, capsaicin induced IL-6 expression in PF-10 cells, and the VR1 antagonist capsazepine dose-dependently inhibited capsaicin-induced IL-6 production, indicating that capsaicin-induced IL-6 expression is related to VR1 activation. The interaction between capsaicin and mitogen-activated protein kinases (MAPKs) was investigated. The phosphorylation of p38 MAPK and c-Jun NH2-terminal kinase (JNK) were detected after capsaicin stimulation. p38 MAPK is involved in capsaicin-induced IL-6 production, as shown by the use of specific inhibitors of this kinase. The result of EMSA showed that capsaicin inhibited tumor necrosis factor-alpha (TNF-alpha)-induced nuclear factor-kappa B (NF-kappaB) activation in PF-10 cell cultures. These results suggest that the activation of VR1 plays an important role in dental pulp inflammation.

Calcitonin gene-related peptide and its role in migraine pathophysiology

Migraine is a common neurological disorder that is associated with an increase in plasma calcitonin gene-related peptide (CGRP) levels. CGRP, a neuropeptide released from activated trigeminal sensory nerves, dilates intracranial blood vessels and transmits vascular nociception. Therefore, it is propounded that: (i) CGRP may have an important role in migraine pathophysiology, and (ii) inhibition of trigeminal CGRP release or CGRP-induced cranial vasodilatation may abort migraine. In this regard, triptans ameliorate migraine headache primarily by constricting the dilated cranial blood vessels and by inhibiting the trigeminal CGRP release. In order to explore the potential role of CGRP in migraine pathophysiology, the advent of a selective CGRP receptor antagonist was obligatory. The introduction of di-peptide CGRP receptor antagonists, namely BIBN4096BS (1-piperidinecarboxamide, N-[2-[[5-amino-1-[[4-(4-pyridinyl)-1-piperazinyl]carbonyl] pentyl] amino]-1-[(3,5-dibromo-4-hydroxyphenyl) methyl]-2-oxoethyl]-4-(1,4-dihydro-2-oxo-3(2H)-quinazolinyl)-, [R-(R*,S*)]-), is a breakthrough in CGRP receptor pharmacology and can be used as a tool to investigate the role of CGRP in migraine headaches. Preclinical investigations in established migraine models that are predictive of antimigraine activity have shown that BIBN4096BS is a potent CGRP receptor antagonist and that it has antimigraine potential. Indeed, a recently published clinical study has reported that BIBN409BS is effective in treating acute migraine attacks without significant side effects. The present review will discuss mainly the potential role of CGRP in the pathophysiology of migraine and the various treatment modalities that are currently available to target this neuropeptide.

The effect of capsaicin on substance P expression in pulp tissue inflammation

AIM

To evaluate the effect of capsaicin on substance P (SP) expression during induced inflammation in rat pulp tissue.

METHODOLOGY

Radioimmunoanalysis was used to measure SP levels in 36 mandibular molar pulps taken from six Wistar rats. Twelve samples were obtained from healthy pulps and used as negative control group. Another 12 samples were obtained after inducing inflammation with mechanical pulp exposure; these were used as the positive control group. Capsaicin was infiltrated into the inferior dental nerve in the experimental group and 12 samples were obtained after mechanical pulp exposure.

RESULTS

The lowest SP expression was found in mechanically exposed pulps where capsaicin pretreatment had been carried out (0.028 ng mL(-1)), followed by healthy pulps (0.302 ng mL(-1)). The highest SP expression was found in mechanically exposed pulps with no capsaicin pretreatment (124 ng mL(-1)). The Kruskal-Wallis test showed statistically significant differences between the groups (P < 0.001).

CONCLUSION

Inferior dental nerve infiltration with capsaicin reduces SP expression in dental pulp tissue in rats.

Cardiovascular Effects and Efficacy of a Hemostatic Agent in Periradicular Surgery

The purpose of this study was to evaluate the hemostatic efficacy and systemic cardiovascular effects of CollaCote collagen sponges saturated with 2.25% racemic epinephrine during endodontic surgery. A total of 48 patients participated in the study. Patients received CollaCote-saline or CollaCote-epinephrine placed in the bony crypt, after which hemostatic efficacy was evaluated. Blood pressure and pulse rate was recorded before and after administration of the local anesthetic, after the application of the test solutions, and before the patient's dismissal. Results showed no significant difference in blood pressure or pulse rate between the experimental and control groups. In the CollaCote-saline group, five of six cases failed to achieve hemorrhage control. In the CollaCote-epinephrine group, 1 of 42 cases had no hemorrhage control. Two patients had slight but apparent intermittent bleeding. Complete hemostasis was achieved in 39 of 42 cases. In conclusion, the results suggest that CollaCote collagen sponges saturated with 2.25% racemic epinephrine provide excellent hemostasis with no evident changes in blood pressure or pulse rate.

Expression of Calcitonin Gene-Related Peptide (CGRP) in Irreversible Acute Pulpitis

The main goal of this study was to evaluate tissue levels of calcitonin gene-related peptide (CGRP) in human pulpal samples collected from teeth with a clinical diagnosis of acute irreversible pulpitis, normal pulps, and teeth with induced pulpal inflammation. All the pulp tissue was mechanically separated, collagenase digested to release individual cells, and labeled with FITC detection of an anti-CGRP polyclonal antibody. Detection of CGRP was possible in these cells due to a binding of the antibody to CGRP that was itself bound to its cell surface receptor. Flow cytometry analysis indicated that the labeled pulp cells were located in a region of low size and complexity according to their forward (FSC) and side scatter (SSC) properties. Significant statistical differences were found between the percentages of CGRP expression in healthy pulps and pulps with induced inflammation and between healthy pulps and pulps with acute irreversible pulpitis. No significant statistical differences were found between pulps with induced inflammation and pulps with acute irreversible pulpitis. These findings support the hypothesis that the CGRP system is active in human pulpal inflammation and may modulate the inflammatory response.