Interactions between acetylcholine and substance P effects on lung mechanics in the rabbit

The phenotype of migraine with unilateral cranial autonomic symptoms documents increased peripheral and central trigeminal sensitization. A case series of 757 patients

BACKGROUND

Migraine with unilateral cranial autonomic symptoms (UAS) is a putative migraine endophenotype with convincing response to trigeminal-targeted treatments that still needs a thorough characterization.

OBJECTIVE

The objective of this article is to carefully investigate the clinical phenotype of migraine with UAS in a large group of patients for more accurate migraine diagnoses, improved clinical management, and better outcome prediction.

METHODS

We studied 757 consecutive episodic and chronic migraineurs in a tertiary headache clinic with face-to-face interviews, detailing in depth their lifestyle, sociodemographic and headache characteristics.

RESULTS

Migraineurs with UAS (37.4%) differed from the general migraine population with respect to longer attack duration (OR = 2.47, p < 0.02, having >72-hour long attacks), more strictly unilateral (OR = 3.18, p < 0.001) and severe headache (OR = 1.72, p = 0.011), more frequent allodynia (OR = 3.03, p < 0.001) and photophobia (OR = 1.87, p = 0.019).

CONCLUSIONS

Migraine patients with UAS are characterized not only by symptoms due to intense peripheral trigeminal activation but also to central sensitization. Our study broadens the knowledge on the clinical and phenotypic characteristics of migraine with UAS, suggests pathophysiological implications, and supports the need for future prospective clinical studies.

2003 Wolff Award: Possible parasympathetic contributions to peripheral and central sensitization during migraine

BACKGROUND

Neurologic signs of increased parasympathetic outflow to the head often accompany migraine attacks. Because increased parasympathetic outflow to the cranial cavity induces vasodilation of cerebral and meningeal blood vessels, it can enhance plasma protein extravasation and the release of proinflammatory mediators that activate perivascular nociceptors. We recently showed that activation of intracranial perivascular nociceptors induces peripheral and central sensitization along the trigeminovascular pathway and proposed that these sensitizations mediate the intracranial hypersensitivity and the cutaneous allodynia of migraine.

METHODS

The present study investigates possible parasympathetic contributions to the generation of peripheral and central sensitization during migraine by applying intranasal lidocaine to reduce cranial parasympathetic outflow through the sphenopalatine ganglion.

RESULTS

In the absence of migraine, patients were pain-free, and their skin sensitivity was normal. Their mean baseline pain thresholds were less than 15 degrees C for cold, more than 45 degrees C for heat, and more than 100 g for mechanical pressure. Their mean pain score was 7.5 of 10 (standard deviation, 1.4) during untreated migraine and 3.5 of 10 (standard deviation, 2.4) after the nasal lidocaine-induced sphenopalatine ganglion block (P <.0001). Most patients developed cutaneous allodynia during migraine, and their mean pain thresholds changed to more than 25 degrees C for cold, less than 40 degrees C for heat, and less than 10 g for mechanical pressure. Following the nasal lidocaine administration (sphenopalatine ganglion block), this allodynia remained unchanged in spite of the pain relief.

CONCLUSION

These findings suggest that cranial parasympathetic outflow contributes to migraine pain by activating or sensitizing (or both) intracranial nociceptors, and that these events induce parasympathetically independent allodynia by sensitizing the central nociceptive neurons in the spinal trigeminal nucleus.

Modulatory effect of imetit, a histamine H3 receptor agonist, on C-fibers, cholinergic fibers and mast cells in rabbit lungs in vitro

The pharmacological mechanisms involved in the interactions between C-fibers, cholinergic fibers and mast cells were investigated in tracheally perfused rabbit lungs by measuring the simultaneous release of substance P and histamine in lung effluents. The amounts of substance P and histamine released in lung superfusates were measured by radioimmunoassay (RIA) after administration of capsaicin and carbachol. Capsaicin (10(-4) M) induced a simultaneous increase in substance P (273 +/- 56% of baseline) and histamine (460 +/- 138%) release. Similarly, carbachol (10(-4) M) caused an increase in the release of both substance P (367 +/- 111%) and histamine (1379 +/- 351%). The effect of capsaicin was prevented by pretreating the lungs with the tachykinin NK1 receptor antagonist SR 140333 (10(-7) M), and atropine (10(-6) M). SR 140333 prevented the carbachol-induced release of substance P but not of histamine. Exogenous substance P induced an increase in histamine release (136 +/- 7%) which was significantly greater in lungs perfused with the neutral endopeptidase inhibitor, thiorphan (10(-5) M) (272 +/- 35%). This effect was prevented by atropine (10(-6) M). Pretreatment of lungs with imetit (5 x 10(-8) M), a selective H3 receptor agonist, prevented the capsaicin-induced release of both mediators. Imetit also blocked the carbachol-induced release of substance P but not of histamine. Exogenous substance P-evoked histamine release was inhibited by imetit. Therefore, it can be concluded that substance P released through the action of capsaicin can activate cholinergic fibers, leading to cholinoceptor stimulation with subsequent activation of C-fibers and mast cells. While the presence of presynaptic H3 receptors modulating substance P-induced acetylcholine release was only surmised, the existence of modulating histamine H3 receptors on C-fibers was confirmed.

Comparison of ozone-induced effects on lung mechanics and hemodynamics in the rabbit

The effects of rabbit exposure to ozone (O3)(0.4 ppm for 4 h) on pulmonary mechanical properties and hemodynamics have been investigated on the isolated perfused lung model. Tracheal pressure, airflow, and tidal volume were measured in order to calculate lung resistance (RL) and dynamic compliance (Cdyn). Using the arterial/venous/double occlusion method, the total pressure gradient (deltaPT) was partitioned into four components (arterial, pre-, postcapillary and venous). Dose-response curves to acetylcholine (ACh), substance P (SP), and histamine were constructed in lungs isolated from rabbits immediately or 48 h after air or O3 exposure O3 induced a significant increase in the baseline value of deltaPt, more markedly 48 h after the exposure. Immediately after the exposure, O3 partly inhibited the ACh-, SP-, and histamine-induced decreases in Cdyn and increases in RL. This inhibitory effect was still in part present 48 h after O3 treatment. In the groups studied immediately after exposure, O3 did not significantly modify the ACh-, SP-, and histamine-induced vasoconstriction. Forty-eight hours after exposure, O3 induced a contractile response to ACh and SP in the arterial segment but decreased the response to histamine. We conclude that O3 can induce direct vascular constriction. Directly, but also 48 h after exposure, O3 can inhibit the ACh-, SP-, and histamine-induced changes in lung mechanical properties. Ozone can also induce some changes in the intensity and in the location of the vascular responses to ACh, SP, and histamine.

Effect of different ozone concentrations on the neurogenic contraction and relaxation of guinea pig airways

Prejunctional and postjunctional effects of several ozone (O3) concentrations, including those found in highly polluted cities, were evaluated in guinea pig airways. Animals bred in O3-free conditions were exposed to air or O3 (0.3, 0.6 or 1.2 ppm) during 4 h, and studied 16-18 h later. Tracheal and bronchial rings were studied in organ baths. Electrical field stimulation (EFS) (100 V, 2 ms, 10 s) was given at increasing frequencies (0.25-16 Hz). Some tissues received atropine (2 microM) and/or propranolol (10 microM). Concentration-response curves to carbachol, isoproterenol, nitroprusside, and substance P were constructed. In tracheas, almost all O3 concentrations decreased the relaxation at low EFS frequencies, but had no effect on the propranolol-resistant (i-NANC) relaxation, suggesting that only adrenergic relaxation was affected. This was a prejunctional effect, since O3 did not modify the responses to isoproterenol. Relaxation induced by a nitric oxide (NO) donor, nitroprusside, was not affected by O3, which agrees with the lack of O3-effect on i-NANC system. O3 did not modify the EFS-induced e-NANC contraction in atropine-treated bronchi, nor the contraction caused by exogenous substance P. By contrast, in bronchi without atropine, 1.2 ppm O3 increased the e-NANC contraction induced by the highest EFS (16 Hz). O3 increased the maximum responses to carbachol in tracheas (1.2 ppm) and bronchi (0.6 and 1.2 ppm). In conclusion, we found that: a) O3 decreased adrenergic relaxation in guinea pig tracheas at low EFS frequencies through a prejunctional alteration; b) O3 did not modify the i-NANC relaxation in tracheas, at least the NO-mediated; c) O3 added a cholinergic component to the bronchial slow-phase (e-NANC) contraction evoked by EFS; and d) O3 enhanced the cholinergic responses in trachea and bronchi by a postjunctional mechanism.

Plasma protein extravasation induced in the rat dura mater by stimulation of the parasympathetic sphenopalatine ganglion

It has been proposed that migraine could result from a neurogenic inflammation of the dura mater. According to this theory, inflammation could be initiated by an axon reflex of nociceptive nerve fibers, but the trigger of this axon reflex remains poorly understood. Previous works have shown that parasympathetic agonists can activate mast cells and/or sensory C-fibers, inducing pain and inflammation. The aim of the present work was to determine whether the activation of intracranial parasympathetic nerve fibers could trigger an inflammatory mechanism within the rat dura mater. Activation of the intracranial parasympathetic system was achieved by electrical stimulation of the sphenopalatine ganglion (SPG). The development of a neurogenic inflammation was estimated either by microscopic examination or by quantitative measurement of plasma protein extravasation (PPE) in the dura. To determine the respective roles of the parasympathetic and sensory innervations, two groups of rats were pretreated either with atropine or with capsaicin. Stimulation of the SPG induced a PPE increase of about 200% in the stimulated side on the dura mater. Extravasated material was mainly concentrated around small blood vessels. This extravasation was significantly reduced by capsaicin pretreatment and completely abolished by atropine. Infusion of carbachol in the common carotid artery induced PPE in the ipsilateral dura comparable to that induced by electrical stimulation of the SPG. This extravasation was also blocked by atropine infusion. These data indicate for the first time that the parasympathetic nervous system can trigger a neurogenic inflammation in the dura via muscarinic cholinergic receptors. Sensory C-fibers seem to play a role in this phenomenon. With respect to the potential autonomic imbalance described in the etiology of various types of vascular headaches, such a mechanism could be important in inducing attacks.