Effects of heating coagulation of middle meningeal artery on plasma CGRP level and c-fos expression in migraine rat triggered by nitroglycerin

Current theory or hypothesis relevant to migraine indicates that trigeminovascular system plays a pivotal role in the pathophysiology of migraine. Particularly, release of neuropeptide and induction of c-fos like immunoreactivity (c-fos LI) within trigeminal nucleus caudalis neurons are regarded as activation markers of trigeminovascular system. In the present study, we set up a rat model for migraine triggered by nitroglycerin (NTG) and coagulated the middle meningeal artery by heating. Using this model, we determined the plasma calcitonin gene-related peptide (CGRP) level as well as the expression of c-fos in trigeminal nucleus caudalis of rats. We found that NTG led to markedly increase in plasma CGRP level and c-fos expression in trigeminal nucleus caudalis compared with the isotonic saline-treated group (P < 0.05). More importantly, heat coagulation of middle meningeal artery could decrease plasma CGRP level and c-fos expression in trigeminal nucleus caudalis (P < 0.05). Heat coagulation of middle meningeal artery may ameliorate sufferings of rat induced by NTG and play an important role in restraining the release of CGRP as well as the activation of neurons in trigeminal nucleus caudalis in rats following NTG infusion.     

Sensitization and pain

Migraine is often accompanied with signs of increased intracranial and extracranial mechanical sensitivities. The prevailing view today is that migraine headache is a neurovascular disorder with intracranial origin and involvement of meningeal blood vessels and their pain nerve fibers. Allodynia, defined as perception of pain following not painful stimulation, is a common clinical feature in various pain syndromes, and as part of migraine pain, it can be considered an indicator of trigeminal neural network sensitization. The cutaneous allodynia that accompanies the migraine headache in a large percentage of patients may be considered the clinical expression of central nervous system sensitization and is characterized by pain provoked by stimulation of the skin that would ordinarily not produce pain. An altered codification process of sensory impulses in the brainstem, in particular by the nucleus caudalis trigeminalis, may justify the temporal aspects and symptoms in the course of migraine attack.     

Expression of ASIC3 in the Trigeminal Nucleus Caudalis Plays a Role in a Rat Model of Recurrent Migraine

Acid-sensing ion channel 3 (ASIC3) is abundant in the trigeminal nervous system and is most sensitive to a slight pH decrease. Recent studies have indicated that ASIC3 in the peripheral trigeminal ganglia is likely involved in the pathogenesis of migraine pain. However, it is unclear whether this receptor plays a role in recurrent migraine, namely, migraine chronicity. Here, we aimed to investigate the role of ASIC3 in an animal model of recurrent migraine (RM). In this study, we established a rat model of RM through repeated administration of inflammatory soup (IS) onto the dura. Then, we tested the mechanical pain thresholds of the face and hindpaws by von Frey filaments. qRT-PCR, Western blot and immunofluorescence labelling were used to detect the expression and localization of ASIC3 in the trigeminal nucleus caudalis (TNC). The protein levels of calcitonin gene-related peptide (CGRP), its receptor component receptor activity modifying protein 1 (RAMP1) and c-Fos were analysed following treatment with the ASIC3 inhibitor APETx2 and activator 2-guanidine-4-methylquinazoline (GMQ). We found decreased pain thresholds after repeated dural inflammatory stimulation, which suggested the establishment of an RM model. Based on this model, we observed elevated expression of ASIC3 in the TNC group compared to that in the Sham group. ASIC3 was primarily expressed in neurons but not in astrocytes of the TNC. Moreover, APETx2 attenuated tactile allodynia and significantly decreased the expression of c-Fos, CGRP and RAMP1, while GMQ aggravated these effects compared to those observed in the IS + vehicle group. These findings indicate a critical role of ASIC3 channels in the pathophysiology of RM, and ASIC3 might represent a potential therapeutic target to prevent the progression of migraine.     

Mechanism based prevention and treatment of migraine]

Triptan therapy results in good relief of headache in 68% of the patients. For many of the patients with migraine, triptan provides complete pain relief in some attacks but not in others. A recent theory proposes that allodynia (pain sensitization) develops in the brain during migraine to increase the intensity of headache significantly. The presence of cutaneous allodynia, an exaggerated painful sensation resulting from a no noxious stimulus to normal skin, is reported in more than 70% of the patients. In our prospective study with 41 patients with migraine, 54.2% presented with skin allodynia. Triptan was effective in 77% of the patients without allodynia which was higher than the base line efficacy rate of 68% in all the patients. Our data support the hypothesis that the development and maintenance of cutaneous allodynia is propelled by sensitization of central trigeminal nucleus. It is suggested that the pain-free outcome increases drastically if triptan therapy is given before the phenomenon of allodynia develops during the attacks of migraine.     

瞬时感受电位香草酸亚家族蛋白1受体在慢性偏头痛大鼠模型中的作用研究

目的本研究通过炎性汤(IS)反复刺激SD大鼠上矢状窦区硬脑膜建立慢性偏头痛(CM)大鼠模型,探讨瞬时感受电位香草酸亚家族蛋白1(TRPV1)受体在CM发病过程中的作用,为研究CM发病机制和治疗药物提供理论依据。方法 72只SD大鼠随机数字表法分为空白对照组(A组)、假手术组(B组)、CM模型组(C组)及TRPV1受体拮抗剂Capsazepine组(D组),采用免疫组织化学染色、Western-Blot、Real-time PCR技术检测大鼠硬脑膜、三叉神经节(TG)、三叉神经脊束尾侧核(TNC)中的TRPV1受体、降钙素基因相关肽(CGRP)表达量变化。结果 TRPV1受体和CGRP在CM大鼠硬脑膜、TG及TNC上的表达量均增加(P0.05),通过侧脑室注射Capsazepine药物后明显缓解大鼠疼痛,且TRPV1受体、CGRP表达量均明显下降(P0.05)。结论 TRPV1受体通过影响CGRP释放参与CM神经源性炎症反应及痛觉传导,提示TRPV1可能通过TRPV1-CGRP信号通路参与CM病理生理过程。     

CGRP receptor antagonism and migraine

Calcitonin gene-related peptide (CGRP) is expressed throughout the central and peripheral nervous systems, consistent with control of vasodilatation, nociception, motor function, secretion, and olfaction. αCGRP is prominently localized in primary spinal afferent C and AA fibers of sensory ganglia, and βCGRP is the main isoform in the enteric nervous system. In the CNS there is a wide distribution of CGRP-containing neurons, with the highest levels occurring in striatum, amygdala, colliculi, and cerebellum. The peripheral projections are involved in neurogenic vasodilatation and inflammation, and central release induces hyperalgesia. CGRP is released from trigeminal nerves in migraine. Trigeminal nerve activation results in antidromic release of CGRP to cause non-endothelium-mediated vasodilatation. At the central synapses in the trigeminal nucleus caudalis, CGRP acts postjunctionally on second-order neurons to transmit pain signals centrally via the brainstem and midbrain to the thalamus and higher cortical pain regions. Recently developed CGRP receptor antagonists are effective at aborting acute migraine attacks. They may act both centrally and peripherally to attenuate signaling within the trigeminovascular pathway.     

Effect of systemic nitroglycerin on CGRP and 5-HT afferents to rat caudal spinal trigeminal nucleus and its modulation by estrogen

Systemic administration of nitroglycerin, a nitric oxide donor, triggers in migraine patients a delayed attack of unknown mechanism. After puberty migraine is more prevalent in women. Attacks can be triggered by abrupt falls in plasma estrogen levels, which accounts in part for sexual dimorphism, but lacks an established neurobiological explanation. We studied the effect of nitroglycerin on the innervated area of calcitonin gene-related peptide (CGRP) and serotonin-immunoreactive afferents to the superficial laminae of the spinal portion of trigeminal nucleus caudalis, and its modulation by estrogen. In male rats, nitroglycerin produced after 4 h a significant decrease of the area innervated by CGRP-immunoreactive afferents and an increase of that covered by serotonin-immunoreactive fibres. These effects were not observed in the superficial laminae of thoracic dorsal horns. The effect of nitroglycerin was similar in ovariectomized females. In estradiol-treated ovariectomized females the area in the spinal portion of trigeminal nucleus caudalis laminae I-II covered by CGRP-immunoreactive fibres was lower and that of serotonin-immunoreactive fibres was higher than in males and for both transmitters not significantly changed after nitroglycerin. The bouton size of CGRP profiles was smaller in estradiol-treated ovariectomized females, whereas after nitroglycerin it decreased significantly but only in males and ovariectomized females. Nitroglycerin, i.e. nitric oxide, is thus able to differentially influence afferent fibres in the superficial laminae of rat spinal trigeminal nucleus caudalis. Estradiol modulates the basal expression of these transmitters and blocks the nitroglycerin effect. These data may contribute to understanding the mechanisms by which estrogens influence migraine severity and the triggering of attacks by nitric oxide.     

Sensitization of the Trigeminovascular Pathway: Perspective and Implications to Migraine Pathophysiology

Migraine headache is commonly associated with signs of exaggerated intracranial and extracranial mechanical sensitivities. Patients exhibiting signs of intracranial hypersensitivity testify that their headache throbs and that mundane physical activities that increase intracranial pressure (such as bending over or coughing) intensify the pain. Patients exhibiting signs of extracranial hypersensitivity testify that during migraine their facial skin hurts in response to otherwise innocuous activities such as combing, shaving, letting water run over their face in the shower, or wearing glasses or earrings (termed here cephalic cutaneous allodynia). Such patients often testify that during migraine their bodily skin is hypersensitive and that wearing tight cloth, bracelets, rings, necklaces and socks or using a heavy blanket can be uncomfortable and/or painful (termed her extracephalic cutaneous allodynia). This review summarizes the evidence that support the view that activation of the trigeminovascular pathway contribute to the headache phase of a migraine attack, that the development of throbbing in the initial phase of migraine is mediated by sensitization of peripheral trigeminovascular neurons that innervate the meninges, that the development of cephalic allodynia is propelled by sensitization of second-order trigeminovascular neurons in the spinal trigeminal nucleus which receive converging sensory input from the meninges as well as from the scalp and facial skin, and that the development of extracephalic allodynia is mediated by sensitization of third-order trigeminovascular neurons in the posterior thalamic nuclei which receive converging sensory input from the meninges, facial and body skin.     

Distribution of calcitonin gene-related peptide immunoreactivity in relation to the rat central somatosensory projection

The distribution of the neuropeptide calcitonin gene-related peptide (CGRP) was studied in relation to the known subcortical somatosensory pathways and contiguous systems in the central nervous system (CNS) of rats by using peroxidase histochemical methods in order to relate zones of immunoreactivity (IR) to cytoarchitecture. CGRP is the most ubiquitous peptide found to date in sensory ganglion cells: principally small and medium-size neurons emitting thin axons inferred to be largely nociceptive in function on the basis of the peripheral distribution of their terminals. Its apparent absence in sympathetic axons provides an especially useful sensory marker. The distribution of CGRP-IR axons displays remarkable selectivity at each level of the CNS. The trigeminal root distributes axons primarily to the pericornual layers (laminae I and II) of spinal V nucleus caudalis and to subnucleus oralis, evading the subnucleus interpolaris and contributing only few axons to principal V. Although there are only a few CGRP-IR somata at each level, heavily labeled axon trajectories can be traced to the nuclei of the solitary tract, the parabrachial nuclei, several sectors of the caudal medial thalamus, and the central nucleus of the amygdala. A sector of labeled neuron somata lies contiguous to each of these axon terminal zones, the largest of which is a thalamic nucleus containing cells of distinctive dendritic architecture extending from the periaqueductal gray across the posterior group nuclei to the peripeduncular nucleus, forming a linear array at the mesodiencephalic junction. The relation of CGRP-IR axonal distribution to spinothalamic, visceral, and gustatory systems is discussed in the context of a specialized "chemosensory" component of the thin-fiber somatosensory system.     

Effects of eletriptan on the peptidergic innervation of the cerebral dura mater and trigeminal ganglion, and on the expression of c-fos and c-jun in the trigeminal complex of the rat in an experimental migraine model

Nociceptive axons and terminals in the supratentorial cerebral dura mater display an intense calcitonin gene-related peptide (CGRP) immunoreactivity. In an experimental migraine model, it has been shown that electrical stimulation of the rat trigeminal ganglion induced an increase in the lengths of CGRP-immunoreactive axons, increased size and number of pleomorphic axonal varicosities in the dura mater, and an increased number of c-jun and c-fos protein-expressing nerve cells in the trigeminal complex. We demonstrate the effect of the highly specific and moderately lipophilic serotonin agonist eletriptan (Pfizer) which prevents the effects of electrical stimulation in the dura mater. Eletriptan also affected the caudal trigeminal complex; it markedly reduced the numbers of the oncoprotein-expressing cells, mainly after stimulation and to some extent also in nonstimulated animals. Eletriptan also affected expression of CGRP in perikarya of trigeminal ganglion cells, insofar as the number of small nerve cells exhibiting a compact CGRP immunoreaction was decreased to one quarter of the original value. In all these respects, eletriptan acted in a similar way to sumatriptan, with the notable exception that eletriptan also blocked the stimulation-induced effects in the nucleus caudalis trigemini and the upper cervical spinal cord (trigeminal complex), whereas sumatriptan did not. It is concluded that eletriptan, acting on perikarya and both the peripheral and the central axon terminals of primary sensory neurons, exerts its antimigraine effect by an agonist action on 5-HT1B/1D receptors throughout the entire trigeminal system, probably by passing the blood-brain-barrier because of its lipophilic character.     

Mild closed head traumatic brain injury-induced changes in monoamine neurotransmitters in the trigeminal subnuclei of a rat model: mechanisms underlying orofacial allodynias and headache

Our recent findings have demonstrated that rodent models of closed head traumatic brain injury exhibit comprehensive evidence of progressive and enduring orofacial allodynias, a hypersensitive pain response induced by non-painful stimulation. These allodynias, tested using thermal hyperalgesia, correlated with changes in several known pain signaling receptors and molecules along the trigeminal pain pathway, espe-cially in the trigeminal nucleus caudalis. This study focused to extend our previous work to investigate the changes in monoamine neurotransmitter immunoreactivity changes in spinal trigeminal nucleus oralis, pars interpolaris and nucleus tractus solitaries following mild to moderate closed head traumatic brain injury, which are related to tactile allodynia, touch-pressure sensitivity, and visceral pain. Our results exhib-ited significant alterations in the excitatory monoamine, serotonin, in spinal trigeminal nucleus oralis and pars interpolaris which usually modulate tactile and mechanical sensitivity in addition to the thermal sensi-tivity. Moreover, we also detected a robust alteration in the expression of serotonin, and inhibitory molecule norepinephrine in the nucleus tractus solitaries, which might indicate the possibility of an alteration in visceral pain, and existence of other morbidities related to solitary nucleus dysfunction in this rodent model of mild to moderate closed head traumatic brain injury. Collectively, widespread changes in monoamine neurotransmitter may be related to orofacial allodynhias and headache after traumatic brain injury.     

D2 dopamine receptor-mediated mechanisms of dopaminergic system modulation in in vivo and in vitro experimental models of migraine

The dopaminergic system is implicated in the pathophysiology of migraine. However, the underlying mechanisms remain unclear. We explored the effects and mechanisms of dopaminergic system modulation in the in vivo and in vitro rat models of migraine. Dopaminergic agonist apomorphine, D2 receptor antagonists metoclopramide and haloperidol and 5-HT3 receptor antagonist ondansetron alone and together were tested in nitroglycerin-induced migraine model, in vivo. Likewise, the combinations of drugs were also tested on basal calcitonin gene-related peptide (CGRP) release in vitro hemiskull preparations. Mechanical allodynia was tested by von Frey filaments. CGRP concentrations in trigeminovascular structures and in vitro superfusates and c-Fos levels in the brainstem were determined by enzyme-linked immunosorbent assay. Meningeal mast cells were evaluated with toluidine blue staining. Apomorphine further enhanced nitroglycerin-induced mechanical allodynia, brainstem c-fos expression, trigeminal ganglion and brainstem CGRP concentrations and meningeal mast cell degranulation, in vivo. Haloperidol completely antagonised all apomorphine-induced effects and also alleviated changes induced by nitroglycerin without apomorphine. Metoclopramide and ondansetron partially attenuated apomorphine- or nitroglycerin-induced effects. A combination of haloperidol and ondansetron decreased basal CGRP release, in vitro, whereas the other administrations were ineffective. Apomorphine-mediated dopaminergic activation exacerbated nitroglycerin-stimulated nociceptive reactions by further enhancing c-fos expression, CGRP release and mast cell degranulation in strategical structures associated with migraine pain. Metoclopramide partially attenuated the effects of apomorphine, most likely because it is also a 5-HT3 receptor antagonist. Haloperidol with pure D2 receptor antagonism feature appears to be more effective than metoclopramide in reducing migraine-related parameters in dopaminergic activation- and/or NTG-induced migraine-like conditions.     

Trigeminal projections to the nucleus submedius of the thalamus in the rat.

Methods involving the anterograde and retrograde transport of wheat-germ agglutinin conjugated horseradish peroxidase and the retrograde transport of Fluoro-Gold were used in rats to examine the distribution within the spinal trigeminal nucleus of trigeminal neurons projecting to the nucleus submedius (Sm) of the thalamus, as well as the distribution of axon terminals within the Sm. Following injections into the trigeminal nucleus, axon terminals were seen in the dorsal part of the anterior Sm; the terminals occurred bilaterally but had an obvious contralateral dominance. To help determine the precise location of the Sm-petal neurons, the border between trigeminal subnuclei interpolaris and caudalis was examined by the use of immunohistochemical procedures for calcitonin gene-related peptide (CGRP). The Sm-petal neurons that were labeled retrogradely occurred only at the caudal interpolaris and rostral caudalis levels; the number of labeled neurons on the contralateral side was approximately six times that on the ipsilateral side. Most of these neurons were located in the ventral part of the caudal interpolaris and rostral caudalis and spinal trigeminal tract; in caudalis, the neurons were almost exclusively localized to its superficial layers. There were approximately three times more labeled neurons in interpolaris than in caudalis. In the experiments combined with immunohistochemistry for CGRP, many neurons (34%) were seen in proximity to CGRP-like immunopositive fibers. These results suggest that the Sm of the rat receives its orofacial afferent inputs from brainstem neurons that are localized to the caudal interpolaris and rostral caudalis. In view of previous studies that have implicated these three structures in somatosensory function, and in particular nociception, our data point to a role for this direct projection from interpolaris and caudalis to Sm in the central processing of pain.     

Paroxetine engenders analgesic effects through inhibition of p38 phosphorylation in a rat migraine model

In this study,a model of migraine was established by electrical stimulation of the superior sagittal sinus in rats.These rats were then treated orally with paroxetine at doses of 2.5,5,or 10 mg/kg per day for 14 days.Following treatment,mechanical withdrawal thresholds were significantly higher,extracellular concentrations of 5-hydroxytryptamine in the periaqueductal grey matter and nucleus reticularis gigantocellularis were higher,and the expression of phosphorylated p38 in the trigeminal nucleus caudalis was lower.Our experimental findings suggest that paroxetine has analgesic effects in a rat migraine model,which are mediated by inhibition of p38 phosphorylation.     

Visceral targets specify calcitonin gene-related peptide and substance P enrichment in trigeminal afferent projections.

Rat trigeminal ganglion projections to a visceral target (intracranial blood vessels) are enriched in calcitonin gene-related peptide (CGRP) and substance P (Sub P) compared to trigeminal ganglion projections to a cutaneous target (the forehead skin). We asked if transplants of a novel visceral target (fetal stomach antrum tissue) into the path of the neonatal rat trigeminal frontal nerve projection to forehead skin would induce neuronal CGRP and Sub P enrichment. By postnatal day (P) 25, the percentage of nerves containing CGRP increased from 14-15% in the control trigeminal projection to forehead skin to 20-31% (in different experiments) in the trigeminal projection to transplanted stomach antrum. The percentage of Sub P-containing neurons increased from 10% in the control forehead skin projection to 22% in the trigeminal projection to stomach transplants over the same time period. The number of neurons in the trigeminal frontal nerve projection to stomach antrum transplants was not significantly different from the number of frontal neurons projecting to control forehead skin. We suggest that respecification of trigeminal neurons to the CGRP and Sub P phenotype, not selective survival of CGRP- and Sub P-positive afferents, is the mechanism by which stomach antrum induces enrichment of CGRP and Sub P. A subpopulation of rat trigeminal neurons with cutaneous forehead skin projections also sends a transient axon collateral projection to a visceral target (the cerebral arteries) during early postnatal development. Postnatal maintenance of an axonal projection to a cutaneous target (forehead skin) may be incompatible with a neuron also maintaining a visceral collateral to the cerebral arteries.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glial cell line-derived neurotrophic factor-like immunoreactivity in human trigeminal ganglion and nucleus

Glial cell line-derived neurotrophic factor (GDNF) is shown by immunohistochemistry in human trigeminal sensory system from 22 weeks of gestation to adulthood. In the trigeminal ganglion, a distinct subpopulation of GDNF-positive neurones is observed, which amounts to about 15% at early pre-term and adult ages and peaks to around 30% at perinatal ages. Labelled neurones are mostly small- and medium-sized. Occasionally, Schwann and satellite cells are stained. GDNF/substance P (SP) and GDNF/calcitonin gene-related peptide (CGRP) double stained neurones occur at all ages examined, whereas GDNF/trkA coexistence can be observed in pre- and full-term newborns only. Centrally, GDNF-immunostained fibers and terminal-like structures are mainly restricted to the spinal trigeminal nucleus, where they are codistributed with SP and CGRP. In the subnucleus caudalis, positive neurones can also be observed both in the superficial laminae and in the magnocellular part, with higher frequency in adults. These results suggest that GDNF may play a functional role in human trigeminal primary sensory neurones throughout life and provide indication for its possible involvement in the regulation of pain-related neuronal circuits in human trigeminal sensory system.     

Enrichment of a vasoactive neuropeptide (calcitonin gene related peptide) in the trigeminal sensory projection to the intracranial arteries

Trigeminal sensory innervation of cerebral vessels and the surrounding dura is responsible for most intracranial head pain. Small-diameter fibers containing substance P (Sub P) have been observed in the periadventitia around feline cerebral blood vessels, and it has been suggested that these fibers are the trigeminal substrate for vascular pain associated with cluster and migraine headaches. Calcitonin gene related peptide (CGRP) coexists with Sub P in some of these fibers and with some Sub P containing neurons in the trigeminal ganglion. In addition, a population of trigeminal neurons containing CGRP but not Sub P has been observed. We now report that the population of trigeminal ganglion cells projecting to the cerebral vasculature is enriched in CGRP-containing neurons, and especially in the population of neurons containing CGRP and not Sub P. Using retrograde tracing of fluorescent tracers combined with immunocytochemistry after explant culture, we found approximately 32% of trigeminal ganglion cells projecting to the cerebral vasculature contained CGRP. Approximately 18 and 17% of these cells contained Sub P and cholecystokinin (CCK), respectively. The 32% of ganglion cells projecting to the cerebral vasculature that contain CGRP stands in contrast to the 12% CGRP positive seen in the population of ganglion cells projecting out to another target (the forehead), and the 21 and 23% CGRP positive observed in the mandibular branch and entire ganglion, respectively. Sub P and CCK are not enriched in the trigeminal innervation of the vasculature compared with their presence in cells throughout the ganglia.(ABSTRACT TRUNCATED AT 250 WORDS)     

The role of glutamate and its receptors in migraine

Glutamate (Glu) is the principal excitatory neurotransmitter in the central nervous system. Its receptors are classified into ionotropic receptors, which are ion channels and include NMDA, AMPA and kainate receptors, named after the agonists that selectively bind to them, and metabotropic receptors, which are G-protein coupled receptors. The trigeminal system is considered to play a key role in migraine pathophysiology, trafficking pain signals from the head and face to the trigeminal nucleus caudalis. The role of glutamate in the pathophysiology of migraine is implicated by data from animal and human studies. Animal studies include experiments of cortical spreading depression, studies of c-fos protein expression in trigeminal nucleus caudalis, studies of plasma protein extravasation and electrophysiological studies. Human studies investigating the role of Glu in migraine pathogenesis measured the levels of Glu in plasma, platelets and cerebrospinal fluid, studied its effect on migraine symptoms and examined the effect of Glu in modulating sensitization. Findings from both the animal and the human studies suggest a link between glutamate and migraine and further suggest that glutamate plays a key role in migraine mechanisms. In the future, efforts should be made to further investigate the role of glutamate in migraine pathogenesis and, subsequently, in migraine treatment.     

Efferent fiber connections of the marmoset (Oedipomidas oedipus) trigeminal nucleus caudalis

A study was made of the efferent fiber connections of the trigeminal nucleus caudalis in the marmoset monkey (Oedipomidas oedipus). Degeneration resulting from nucleus caudalis lesions in twelve animals was studied by the Nauta technique. Following lesions of the trigeminal nucleus caudalis, degeneration was present bilaterally in the medial reticular formation, medial and spinal lemnisci, ventral horn and nucleus cuneatus. Ipsilateral preterminal degeneration was observed in the intermediate, hypoglossal, supraspinal and retroambigualis nuclei, the trigeminal interpolaris, oralis and main sensory nuclei, and motor nuclei of V and VII cranial nerves. An ipsilateral intranuclear trigeminal path is described. Nucleus caudalis efferent connections with the thalamus are discussed.     

Defeating migraine pain with triptans: a race against the development of cutaneous allodynia

For many migraine patients, triptan therapy provides complete pain relief in some attacks but not in others. Here, we tested whether the success of triptan therapy is hindered in the presence of cutaneous allodynia (pain resulting from a nonnoxious stimulus to normal skin), a phenomenon we previously described develop gradually during the course of the migraine attack in more than 70% of patients. We studied migraine patients repeatedly on three visits to the clinic: in the absence of migraine (baseline), within the first hour of one attack, or at 4 hours from onset of another attack. Presence or absence of allodynia was determined based on differences between migraine and baseline pain thresholds to mechanical and thermal stimulation of periorbital skin. In 31 patients, we studied 34 migraine attacks that were associated with allodynia at the time of triptan treatment and 27 attacks that were not. Within 2 hours of triptan treatment, patients were rendered pain-free in 5 of 34 (15%) of allodynic attacks versus 25 of 27 (93%) of nonallodynic attacks. Treating migraine attacks 1 hour (early) or 4 hours (late) after the onset of pain was equally ineffective in inducing a pain-free state in the presence of allodynia, and equally effective in the absence of allodynia. For patients susceptible to allodynia during the attack, triptan therapy was by far more likely to provide complete pain relief if administered before rather than after the establishment of cutaneous allodynia. Patients who never developed allodynia were highly likely to be rendered pain-free by triptan therapy anytime after the onset of pain. We conclude that the probability of consistent pain-free outcome increases drastically if triptan therapy is vigilantly timed to precede any signs of cutaneous allodynia.