Discovery of a potent and efficacious peptide derivative for δ/μ opioid agonist/neurokinin 1 antagonist activity with a 2',6'-dimethyl-L-tyrosine: in vitro, in vivo, and NMR-based structural studies

Multivalent ligands with δ/μ opioid agonist and NK1 antagonist activities have shown promising analgesic potency without detectable sign of toxicities, including motor skill impairment and opioid-induced tolerance. To improve their biological activities and metabolic stability, structural optimization was performed on our peptide-derived lead compounds by introducing 2',6'-dimethyl-L-tyrosine (Dmt) instead of Tyr at the first position. The compound 7 (Dmt-D-Ala-Gly-Phe-Met-Pro-Leu-Trp-NH-[3',5'-(CF(3))(2)-Bzl]) showed improved multivalent bioactivities compared to those of the lead compounds, had more than 6 h half-life in rat plasma, and had significant antinociceptive efficacy in vivo. The NMR structural analysis suggested that Dmt(1) incorporation in compound 7 induces the structured conformation in the opioid pharmacophore (N-terminus) and simultaneously shifts the orientation of the NK1 pharmacophore (C-terminus), consistent with its affinities and activities at both opioid and NK1 receptors. These results indicate that compound 7 is a valuable research tool to seek a novel analgesic drug.

Spinal or systemic TY005, a peptidic opioid agonist/neurokinin 1 antagonist, attenuates pain with reduced tolerance

BACKGROUND AND PURPOSE

The use of opioids in treating pain is limited due to significant side effects including somnolence, constipation, analgesic tolerance, addiction and respiratory depression. Pre-clinical studies have shown that neurokinin 1 (NK(1) ) receptor antagonists block opioid-induced antinociceptive tolerance and may inhibit opioid-induced rewarding behaviours. Here, we have characterized a bifunctional peptide with both opioid agonist and NK(1) antagonist pharmacophores in a rodent model of neuropathic pain.

EXPERIMENTAL APPROACH

Rats were evaluated for behavioural responses to both tactile and thermal stimuli in either an uninjured, sham- or nerve-injured state. TY005 (Tyr-DAla-Gly-Phe-Met-Pro-Leu-Trp-O-3,5-Bn(CF(3) )(2) ) was delivered spinally or systemically to assess the antinociceptive effects after acute exposure. Motor skills were evaluated using the rotarod test to determine potential sedative effects. Spinal TY005 was given chronically to sham- or nerve-injured animals to determine the development of tolerance.

KEY RESULTS

Bolus injections of TY005 produced dose-dependent antinociception in non-injured animals and alleviated nerve injury-induced thermal and tactile hypersensitivities (i.e. antihyperalgesia) more effectively than morphine. Sedative effects were not evident from the rotarod test at doses that were antihyperalgesic, nor at doses threefold higher. Repeated administration of TY005 did not lead to the development of antihyperalgesic tolerance or alter sensory thresholds.

CONCLUSIONS AND IMPLICATIONS

Collectively, the data suggest that opioid agonist/NK(1) antagonist bifunctional peptides represent a promising novel approach to the management of chronic pain without the development of tolerance, reducing the need for escalation of doses and unwanted side effects associated with opiates alone.

Development of potent μ and δ opioid agonists with high lipophilicity

An SAR study on the Dmt-substituted enkephalin-like tetrapeptide with a N-phenyl-N-piperidin-4-ylpropionamide moiety at the C-terminal was performed and has resulted in highly potent ligands at μ and δ opioid receptors. In general, ligands with the substitution of D-Nle(2) and halogenation of the aromatic ring of Phe(4) showed highly increased opioid activities. Ligand 6 with good biological activities in vitro demonstrated potent in vivo antihyperalgesic and antiallodynic effects in the tail-flick assay.

Reversal of pancreatitis-induced pain by an orally available, small molecule interleukin-6 receptor antagonist

Pancreatic pain resulting from chronic inflammation of the pancreas is often intractable and clinically difficult to manage with available analgesics reflecting the need for more effective therapies. The mechanisms underlying pancreatitis pain are not well understood. Here, the possibility that interleukin-6 (IL-6) may promote pancreatitis pain was investigated with TB-2-081 (3-O-formyl-20R,21-epoxyresibufogenin, EBRF), a small molecule IL-6 receptor antagonist that was semi-synthetically derived from natural sources. The potential activity and mechanism of TB-2-081 were investigated following the induction of persistent pancreatitis using dibutyltin dichloride (DBTC) in rats. TB-2-081 displaces the binding of IL-6 to the human recombinant soluble IL-6 receptor with apparent high affinity and inhibits IL-6 mediated cell growth. Systemic or oral, but not intrathecal, administration of TB-2-081 reversed DBTC-induced abdominal hypersensitivity in a dose- and time-dependent manner. IL-6 levels were significantly up-regulated in the dorsal root ganglia (DRG) of rats with pancreatitis on day 6 after DBTC injection. IL-6-enhanced capsaicin-evoked release of calcitonin gene-related peptide from cultured DRG neurons was blocked by TB-2-081. Our data demonstrate that TB-2-081 acts as a systemically available and orally active small molecule IL-6 receptor antagonist. TB-2-081 effectively reduces pancreatitis-induced pain through peripheral mechanisms that are likely due to (a) increased expression of IL-6 in the DRG and (b) IL-6-mediated sensitization of nociceptive neurons. The activity of TB-2-081 implicates an important role for IL-6 in sustaining pancreatitis pain. Strategies targeting IL-6 actions through small molecule antagonists may offer novel approaches to improve the therapy of chronic pancreatitis and other chronic pain states.

Synthesis and activity of endomorphin-2 and morphiceptin analogues with proline surrogates in position 2

The opioid agonists endomorphins (Tyr-Pro-Trp-Phe-NH(2); EM1 and Tyr-Pro-Phe-Phe-NH(2); EM2) and morphiceptin (Tyr-Pro-Phe-Pro-NH(2)) exhibit an extremely high selectivity for mu-opioid receptor. Here a series of novel EM2 and morphiceptin analogues containing in place of the proline at position 2 the S and R residues of beta-homologues of proline (HPro), of 2-pyrrolidinemethanesulphonic acid (HPrs) and of 3-pyrrolidinesulphonic acid (betaPrs) have been synthesized and their binding affinity and functional activity have been investigated. The highest micro-receptor affinity is shown by [(S)betaPrs(2)]EM2 analogue (6e) which represents the first example of a beta-sulphonamido analogue in the field of opioid peptides.

Biological and conformational evaluation of bifunctional compounds for opioid receptor agonists and neurokinin 1 receptor antagonists possessing two penicillamines

Neuropathic pain states and tolerance to opioids can result from system changes in the CNS, such as up-regulation of the NK1 receptor and substance P, lead to antiopioid effects in ascending or descending pain-signaling pathways. Bifunctional compounds, possessing both the NK1 antagonist pharmacophore and the opioid agonist pharmacophore with delta-selectivity, could counteract these system changes to have significant analgesic efficacy without undesirable side effects. As a result of the introduction of cyclic and topological constraints with penicillamines, 2 (Tyr-cyclo[d-Pen-Gly-Phe-Pen]-Pro-Leu-Trp-NH-[3',5'-(CF(3))(2)-Bzl]) was found as the best bifunctional compound with effective NK1 antagonist and potent opioid agonist activities, and 1400-fold delta-selectivity over the mu-receptor. The NMR structural analysis of 2 revealed that the relative positioning of the two connected pharmacophores as well as its cyclic and topological constraints might be responsible for its excellent bifunctional activities as well as its significant delta-opioid selectivity. Together with the observed high metabolic stability, 2 could be considered as a valuable research tool and possibly a promising candidate for a novel analgesic drug.

Triptan-induced enhancement of neuronal nitric oxide synthase in trigeminal ganglion dural afferents underlies increased responsiveness to potential migraine triggers

Migraine is a common neurological disorder often treated with triptans. Triptan overuse can lead to increased frequency of headache in some patients, a phenomenon termed medication overuse headache. Previous preclinical studies have demonstrated that repeated or sustained triptan administration for several days can elicit persistent neural adaptations in trigeminal ganglion cells innervating the dura, prominently characterized by increased labelling of neuronal profiles for calcitonin gene related peptide. Additionally, triptan administration elicited a behavioural syndrome of enhanced sensitivity to surrogate triggers of migraine that was maintained for weeks following discontinuation of drug, a phenomenon termed 'triptan-induced latent sensitization'. Here, we demonstrate that triptan administration elicits a long-lasting increase in identified rat trigeminal dural afferents labelled for neuronal nitric oxide synthase in the trigeminal ganglion. Cutaneous allodynia observed during the period of triptan administration was reversed by NXN-323, a selective inhibitor of neuronal nitric oxide synthase. Additionally, neuronal nitric oxide synthase inhibition prevented environmental stress-induced hypersensitivity in the post-triptan administration period. Co-administration of NXN-323 with sumatriptan over several days prevented the expression of allodynia and enhanced sensitivity to stress observed following latent sensitization, but not the triptan-induced increased labelling of neuronal nitric oxide synthase in dural afferents. Triptan administration thus promotes increased expression of neuronal nitric oxide synthase in dural afferents, which is critical for enhanced sensitivity to environmental stress. These data provide a biological basis for increased frequency of headache following triptans and highlight the potential clinical utility of neuronal nitric oxide synthase inhibition in preventing or treating medication overuse headache.

Synthesis and evaluation of new endomorphin-2 analogues containing (Z)-alpha,beta-didehydrophenylalanine (Delta(Z)Phe) residues

New endomorphin-2 (EM-2) analogues incorporating (Z)-alpha,beta-didehydrophenylalanine (Delta(Z)Phe) in place of the native phenylalanine in EM-2 are reported. Tyr-Pro-Delta(Z)Phe-Phe-NH(2) {[Delta(Z)Phe(3)]EM-2} (1), Tyr-Pro-Phe-Delta(Z)Phe-NH(2) {[Delta(Z)Phe(4)]EM-2} (2), and Tyr-Pro-Delta(Z)Phe-Delta(Z)Phe-NH(2) {[Delta(Z)Phe(3,4)]EM-2}(3) have been synthesized, their opioid receptor binding affinities and tissue bioassay activities were determined, and their conformational properties were examined. Compound 2 shows high mu opioid receptor selectivity and mu agonist activity comparable to those of the native peptide. The conformation adopted in solution and in the crystal by N-Boc-Tyr-Pro-Delta(Z)Phe-Phe-NH(2) (8) is reported.

Improving metabolic stability by glycosylation: bifunctional peptide derivatives that are opioid receptor agonists and neurokinin 1 receptor antagonists

In order to obtain a metabolically more stable analgesic peptide derivative, O-beta-glycosylated serine (Ser(Glc)) was introduced into TY027 (Tyr-d-Ala-Gly-Phe-Met-Pro-Leu-Trp-NH-3',5'-Bzl(CF(3))(2)) which was a previously reported bifunctional compound with delta/micro opioid agonist and neurokinin-1 receptor antagonist activities and with a half-life of 4.8 h in rat plasma. Incorporation of Ser(Glc) into various positions of TY027 gave analogues with variable bioactivities. Analogue 6 (Tyr-d-Ala-Gly-Phe-Nle-Pro-Leu-Ser(Glc)-Trp-NH-3',5'-Bzl(CF(3))(2)) was found to have effective bifunctional activities with a well-defined conformation with two beta-turns based on the NMR conformational analysis in the presence of DPC micelles. In addition, 6 showed significant improvement in its metabolic stability (70 + or - 9% of 6 was intact after 24 h incubation in rat plasma). This improved metabolic stability, along with its effective and delta selective bifunctional activities, suggests that 6 could be an interesting research tool and possibly a promising candidate as a novel analgesic drug.

Triptan-induced latent sensitization: a possible basis for medication overuse headache

OBJECTIVE

Identification of the neural mechanisms underlying medication overuse headache resulting from triptans.

METHODS

Triptans were administered systemically to rats by repeated intermittent injections or by continuous infusion over 6 days. Periorbital and hind paw sensory thresholds were measured to detect cutaneous allodynia. Immunofluorescent histochemistry was employed to detect changes in peptidic neurotransmitter expression in identified dural afferents. Enzyme-linked immunoabsorbent assay was used to measure calcitonin gene-related peptide (CGRP) levels in blood.

RESULTS

Sustained or repeated administration of triptans to rats elicited time-dependent and reversible cutaneous tactile allodynia that was maintained throughout and transiently after drug delivery. Triptan administration increased labeling for CGRP in identified trigeminal dural afferents that persisted long after discontinuation of triptan exposure. Two weeks after triptan exposure, when sensory thresholds returned to baseline levels, rats showed enhanced cutaneous allodynia and increased CGRP in the blood following challenge with a nitric oxide donor. Triptan treatment thus induces a state of latent sensitization characterized by persistent pronociceptive neural adaptations in dural afferents and enhanced responses to an established trigger of migraine headache in humans.

INTERPRETATION

Triptans represent the treatment of choice for moderate and severe migraine headaches. However, triptan overuse can lead to an increased frequency of migraine headache. Overuse of these medications could induce neural adaptations that result in a state of latent sensitization, which might increase sensitivity to migraine triggers. The latent sensitization could provide a mechanistic basis for the transformation of migraine to medication overuse headache.

Design and synthesis of trivalent ligands targeting opioid, cholecystokinin, and melanocortin receptors for the treatment of pain

It has been known that co-administration of morphine with either cholecystokinin (CCK) receptor or melanocortin (MC) receptor antagonists enhance morphine's analgesic efficacy by reducing serious side effects such as tolerance and addiction. Considering these synergistic effects, we have designed trivalent ligands in which all three different pharmacophores for opioid, CCK, and MC receptors are combined in such a way as to conserve their own topographical pharmacophore structures. These ligands, excluding the cyclic compound, were synthesized by solid phase synthesis using Rink-amide resin under microwave assistance in very high yields. These trivalent ligands bind to their respective receptors well demonstrating that the topographical pharmacophore structures for the three receptors were retained for receptor binding. Ligand 10 was a lead compound to show the best biological activities at all three receptors.

CCR2 regulates monocyte recruitment as well as CD4 T1 allorecognition after lung transplantation

Graft rejection remains a formidable problem contributing to poor outcomes after lung transplantation. Blocking chemokine pathways have yielded promising results in some organ transplant systems. Previous clinical studies have demonstrated upregulation of CCR2 ligands following lung transplantation. Moreover, lung injury is attenuated in CCR2-deficient mice in several inflammatory models. In this study, we examined the role of CCR2 in monocyte recruitment and alloimmune responses in a mouse model of vascularized orthotopic lung transplantation. The CCR2 ligand MCP-1 is upregulated in serum and allografts following lung transplantation. CCR2 is critical for the mobilization of monocytes from the bone marrow into the bloodstream and for the accumulation of CD11c(+) cells within lung allografts. A portion of graft-infiltrating recipient CD11c(+) cells expresses both recipient and donor MHC molecules. Two-photon imaging demonstrates that recipient CD11c(+) cells are associated with recipient T cells within the graft. While recipient CCR2 deficiency does not prevent acute lung rejection and is associated with increased graft infiltration by T cells, it significantly reduces CD4(+) T(h)1 indirect and direct allorecognition. Thus, CCR2 may be a potential target to attenuate alloimmune responses after lung transplantation.

Case-control study of a HLA-G 14-bp insertion-deletion polymorphism in women with recurrent miscarriages

Human leucocyte antigen (HLA)-G is an important molecule for maintaining an immunotolerant foetal-maternal relationship. A 14-bp insertion (+14-bp)/deletion (-14-bp) polymorphism in exon 8 of the 3' untranslated region of the HLA-G gene has been proposed to be associated with HLA-G mRNA stability and the expression of HLA-G. This might play an immunomodulatory role in human pregnancy. In this study, a total of 526 Chinese women were genotyped for the +14-bp/-14-bp polymorphism, including 137 who had recurrent miscarriages (three miscarriages: 86, four or more miscarriages: 51), 138 women who had experienced two abortions and 251 women with normal fertility as controls. The +14-bp homozygote sequence was more prominent among those with recurrent miscarriages (three or more recurrent miscarriages) in contrast to fertile control women. Significant difference was observed in the distribution of +14-bp/+14-bp genotype between controls and the recurrent abortions group with four or more abortions. A 14-bp insertion/deletion polymorphism in exon 8 has a possible role in HLA-G expression in certain cases of recurrent miscarriage. However, additional studies are needed in this regard.

Comparison of magnetic resonance imaging–fluorodeoxy- glucose positron emission tomography fusion with pathological staging in rectal cancer

Background

This study represents an initial experience with combined magnetic resonance imaging (MRI) and [18F]fluorodeoxyglucose positron emission tomography (FDG PET) (MRI–PET fusion) in the primary staging of rectal carcinoma.

Methods

A retrospective analysis of data recorded on patients with rectal cancer was undertaken. Patients requiring long-course radiotherapy were excluded. Chest radiography, abdominal computed tomography and endorectal ultrasonography were performed. In addition, MRI of the pelvis, whole-body FDG PET and MRI–PET fusion were carried out. All patients subsequently underwent anterior resection.

Results

Twenty-three patients with rectal carcinoma (15 men), of median age 60 (range 46–75) years, were enrolled. In tumour (T) assessment, MRI correctly staged 14 of 22 T2/T3 tumours. In lymph node assessment, MRI–PET fusion had a sensitivity of 44 per cent, with a specificity and positive predictive value of 100 per cent. No additional information was acquired from MRI–PET fusion over MRI plus abdominal computed tomography and chest radiography.

Conclusion

MRI–PET fusion adds little to conventional investigations for staging rectal carcinoma.

The biological activity and metabolic stability of peptidic bifunctional compounds that are opioid receptor agonists and neurokinin-1 receptor antagonists with a cystine moiety

In order to improve metabolic stability, a ring structure with a cystine moiety was introduced into TY027 (Tyr-D-Ala-Gly-Phe-Met-Pro-Leu-Trp-NH-[3',5'-(CF(3))(2)Bzl]), which is a lead compound of our developing bifunctional peptide possessing opioid agonist and NK1 antagonist activities. TY038 (Tyr-cyclo[D-Cys-Gly-Phe-Met-Pro-D-Cys]-Trp-NH-[3',5'-(CF(3))(2)Bzl]) was found as a highly selective delta opioid agonist over mu receptor in conventional tissue-based assays, together with an effective NK1 antagonist activity and good metabolic stability with more than 24h half life in rat plasma.

Synthesis and evaluation of new endomorphin analogues modified at the Pro(2) residue

Six new endomorphin analogues, incorporating constrained amino acids in place of native proline have been synthesized. Residues of (S)-azetidine-2-carboxylic acid (Aze), 3,4-dehydro-(S)-proline (Delta(3)Pro), azetidine-3-carboxylic acid (3Aze) and dehydro-alanine (DeltaAla) have been used to prepare [Delta(3)Pro(2)]EM-2 (1), [Aze(2)]EM-1 (2), [Aze(2)]EM-2 (3), [3Aze(2)]EM-1 (4), [3Aze(2)]EM-2 (5) and [DeltaAla(2)]EM-2 (6). Binding assays and functional bioactivities for mu- and delta-receptors are reported. The highest affinity, bioactivity and selectivity are shown by peptides 2 and 3 containing the Aze residue.

Synthesis and investigations of double-pharmacophore ligands for treatment of chronic and neuropathic pain

Acids 9a-f as possible bivalent ligands designed as a structural combination of opioid mu-agonist (Fentanyl) and NSAID (Indomethacin) activities and produced compounds which were tested as analgesics. The obtained series of compounds exhibits low affinity and activity both at opioid receptors and as cyclooxygenase (COX) inhibitors. One explanation of the weak opioid activity could be stereochemical peculiarities of these bivalent compounds which differ significantly from the fentanyl skeleton. The absence of significant COX inhibitory properties could be explained by the required substitution of an acyl fragment in the indomethacin structure for 4-piperidyl.

Costimulatory blockade-mediated lung allograft acceptance is abrogated by overexpression of Bcl-2 in the recipient

Lung allografts are considered to be more immunogenic than other solid organs. Little is known about the effectiveness of immunosuppressive regimens after lung transplantation. Herein, we describe a novel model of murine vascularized orthotopic lung transplantation we used to study the effects of costimulatory blockade on lung rejection. Transplants were performed in the Balb --> B6 strain combination. Recipients were either not immunosuppressed or received perioperative CD40/CD40L and CD28/B7 costimulatory blockade. Nonimmunosupressed Balb/c --> B6 lung transplants had severe acute rejection 7 days after transplantation and CD8(+) T cells outnumbered CD4(+) T cells within the allografts. Alternatively, B6 recipients that received perioperative costimulatory blockade had minimal inflammation and there were nearly equal numbers of CD8(+) and CD4(+) T cells in these grafts. Approximately one third of graft-infiltrating CD4(+) T cells expressed Foxp3. CD4(+) T cells isolated from these grafts induced apoptosis of alloreactive CD8(+) T cells that were stimulated with donor splenocytes in vitro. In contrast with wild-type B6 recipient mice, we observed severe rejection of Balb/c lungs 7 days after transplantation into Bcl-2 transgenic B6 recipients that had received costimulatory blockade. CD8(+) T cells outnumbered CD4(+) T cells in these immunosuppressed Bcl-2 transgenic recipients and, compared with immunosuppressed wild-type B6 recipients, a lower percentage of graft-infiltrating CD4(+) T cells expressed Foxp3, and a higher percentage of graft-infiltrating CD8(+) T cells expressed intereferon-gamma. Thus, our results show that perioperative blockade of the CD40/CD40L and CD28/B7 costimulatory pathways markedly ameliorates acute rejection of lung allografts in wild type but not Bcl-2 transgenic recipients.

Monocyte differentiation is controlled by MyD88 after mouse orthotopic lung transplantation

In lung grafts, ischemia-reperfusion signals rapidly induce the recruitment and differentiation of host monocytes into macrophages and dendritic cells. The nature of ischemia-reperfusion signals are antigen independent, but have been hypothesized to initiate Toll-like receptor (TLR) and interleukin (IL)-1R-mediated signaling pathways that are thought to potentiate alloimmune responses. We wondered whether MyD88, an adaptor molecule critical for both TLR and IL-1R-mediated inflammatory responses, regulated monocyte differentiation in a mouse model of vascularized orthotopic lung transplantation. Orthotopic left lung transplants were performed in the following syngeneic combinations: CD45.1(+) B6 --> CD45.2(+) MyD88(-/-) and CD45.1(+) B6 --> CD45.2(+) B6. One day later, recipient-derived dendritic cells and macrophage numbers were assessed in the bronchiolar lavage by FACS analysis. Compared with the bronchiolar lavage of wildtype recipients, MyD88(-/-) recipients had lower numbers of dendritic cells in lung graft airways that were of recipient origin. Lower numbers of newly differentiated lung graft dendritic cells was coincident with the appearance of higher numbers of undifferentiated monocytes in the lung airways of MyD88(-/-) recipients as compared with wild-type recipients. Moreover, adoptive transfer experiments demonstrated that MyD88(-/-) monocytes were poorer at differentiating into lung dendritic cells as compared with wild-type monocytes. Taken together, these data show that MyD88 regulates graft-infiltrating monocyte differentiation and suggests a mechanism by which TLR/IL-1R-signaling pathways control adaptive responses in lung allografts through controlling monocyte fate.

Medullary pain facilitating neurons mediate allodynia in headache-related pain

OBJECTIVE

To develop and validate a model of cutaneous allodynia triggered by dural inflammation for pain associated with headaches. To explore neural mechanisms underlying cephalic and extracephalic allodynia.

METHODS

Inflammatory mediators (IM) were applied to the dura of unanesthetized rats via previously implanted cannulas, and sensory thresholds of the face and hind-paws were characterized.

RESULTS

IM elicited robust facial and hind-paw allodynia, which peaked within 3 hours. These effects were reminiscent of cutaneous allodynia seen in patients with migraine or other primary headache conditions, and were reversed by agents used clinically in the treatment of migraine, including sumatriptan, naproxen, and a calcitonin gene-related peptide antagonist. Consistent with clinical observations, the allodynia was unaffected by a neurokinin-1 antagonist. Having established facial and hind-paw allodynia as a useful animal surrogate of headache-associated allodynia, we next showed that blocking pain-facilitating processes in the rostral ventromedial medulla (RVM) interfered with its expression. Bupivacaine, destruction of putative pain-facilitating neurons, or block of cholecystokinin receptors prevented or significantly attenuated IM-induced allodynia. Electrophysiological studies confirmed activation of pain-facilitating RVM "on" cells and transient suppression of RVM "off" cells after IM.

INTERPRETATION

Facial and hind-paw allodynia associated with dural stimulation is a useful surrogate of pain associated with primary headache including migraine and may be exploited mechanistically for development of novel therapeutic strategies for headache pain. The data also demonstrate the requirement for activation of descending facilitation from the RVM for the expression of cranial and extracranial cutaneous allodynia, and are consistent with a brainstem generator of allodynia associated with headache disorders.