Antimigraine Drug,Zolmitriptan,Inhibits High-Voltage Activated Calcium Currents in a Population of Acutely Dissociated Rat Trigeminal Sensory Neurons

Abstract

Background

Triptans, 5-HT_1B/ID agonists, act on peripheral and/or central terminals of trigeminal ganglion neurons (TGNs) and inhibit the release of neurotransmitters to second-order neurons, which is considered as one of key mechanisms for pain relief by triptans as antimigraine drugs. Although high-voltage activated (HVA) Ca²⁺ channels contribute to the release of neurotransmitters from TGNs, electrical actions of triptans on the HVA Ca²⁺ channels are not yet documented.

Results

In the present study, actions of zolmitriptan, one of triptans, were examined on the HVA Ca²⁺ channels in acutely dissociated rat TGNs, by using whole-cell patch recording of Ba²⁺ currents (I_Ba) passing through Ca²⁺ channels. Zolmitriptan (0.1–100 μM) reduced the size of I_Ba in a concentration-dependent manner. This zolmitriptan-induced inhibitory action was blocked by GR127935, a 5-HT_1B/1D antagonist, and by overnight pretreatment with pertussis toxin (PTX). P/Q-type Ca²⁺ channel blockers inhibited the inhibitory action of zolmitriptan on I_Ba, compared to N-and L-type blockers, and R-type blocker did, compared to L-type blocker, respectively (p < 0.05). All of the present results indicated that zolmitriptan inhibited HVA P/Q- and possibly R-type channels by activating the 5-HT_1B/1D receptor linked to G_i/o pathway.

Conclusion

It is concluded that this zolmitriptan inhibition of HVA Ca²⁺ channels may explain the reduction in the release of neurotransmitters including CGRP, possibly leading to antimigraine effects of zolmitriptan.

Background

It is known that the pain associated with migraine is relieved by triptans, 5HT_1B/1D agonists, including sumatriptan, zolmitriptan, naratriptan and so on. Indeed, they are in clinical use for treatment of migraine. It is shown that trigeminal ganglion stimulation leads to the release of CGRP in humans and cats, which is antagonized by sumatriptan administration [1]. Subsequently, several lines of histochemical and electrophysiological studies demonstrate the involvement of 5HT_1B/1D agonist in neurotransmitter release from trigeminal ganglion neurons (TGNs). First, 5HT_1B and/or _1D receptors are localized in trigeminal vascular systems [2]. 5HT_1B receptors are demonstrated on dural arteries [2] and 5HT_1D receptors on trigeminal sensory neurons including peripheral and central projections [2 –4]. Second, small and medium- sized TGNs possess 5HT_1B/1D receptors, colocalized with CGRP and Substance P [5]. Third, naratriptan inhibits neuronal activity in TGNs [6]. Fourth, synaptic transmission from TGNs to central trigeminovascular neurons is blocked by activation of presynaptic 5HT_1B/1D receptors on central terminals of meningeal nociceptors [7]. All of these studies suggest that triptans might act on 5HT_1B/1D receptors of TGNs and inhibit the release of neurotransmitters such as CGRP, reducing central and/or peripheral neuronal excitability.

An activation of high-voltage activated (HVA) Ca²⁺ channels is known to trigger the release of neurotransmitters and to control numerous neuronal functions such as neuronal excitability. HVA Ca²⁺ channels are divided into four subtypes; that is N-, P/Q-, L-, and R-type channels. All of four subtypes of HVA Ca²⁺ channels are demonstrated to be expressed in TGNs [8]. Recent findings indicate that the blockade of HVA Ca²⁺ channels prevents CGRP release and prevents dural vessel dilation, and so HVA Ca²⁺ blockade might minimize neurological inflammation [9]. Although it is shown that N- and P/Q-currents are inhibited via G protein-coupled mechanisms by agonists for 5HT_1A and _1D receptors in the primary spinal neurons of Xenopus larvae [10,11], effects of 5HT_1B/!D agonists on HVA Ca²⁺ channels in mammalian TGNs have not yet been evaluated.

As mentioned above, involvement of triptans in modulation of CGRP release as well as neuronal activity in the trigeminal ganglion is highly plausible. This prompted us to examine whether or not triptans could act on HVA Ca²⁺ channels of TGNs, leading to inhibition of the release of CGRP and neurotransmission, possibly involved in generation of migraine. In the present study, electrophysiological experiments were undertaken to analyze actions of zolmitriptan, one of triptans, on HVA Ca²⁺ channels using cultured neonatal rat TGNs. This paper clarified that zolmitriptan could inhibit HVA Ca²⁺ channels by activating 5HT_1B/1D receptor coupled to G_i/o pathway.

Results

Currents carried by Ba²⁺ passing through HVA Ca²⁺ channels, I_Ba, were recorded from somata of neonatal rat TGNs, small to medium size of 22 to 27 μm in diameter. The peak amplitude of I_Ba in control varied within the range from 230 to 1200 pA (mean ± S.E.M.; 508.5 ± 31.0 pA, n = 37).

Concentration-dependent action of zolmitriptan on IBa

Zolmitriptan was applied to TGNs by superfusion for two minutes. As shown in Fig. 1a, I_Ba was inhibited in the presence of zolmitriptan at 10 μM. Inhibitory actions of zolmitriptan on I_Ba were examined at concentrations between 0.1 and 100 μM (Fig. 1b, the number of cells indicated). Zolmitriptan at lower concentrations slowly started depressing the I_Ba at 10 to 20 s from the onset of application. This depressing action slowly increased but could not reach its maximum in 2 min at concentrations lower than 10 μM. On the other hand, at 100 μM, the I_Ba was very rapidly inhibited within 10 s and completely abolished within one min of the drug application.

Figure 1

Inhibition of HVA I_Ba by zolmitriptan. (a) Typical illustration of I_Ba elicited in response to command pulses from −60 mV to 10 mV for 40 ms. I_Ba was inhibited by 2 min application of 10 μM zolmitriptan. (b) The average time course of I_Ba inhibition by zolmitriptan at four different concentrations. Superfusing application of zolmitriptan started at t = 0 and lasted for 120 s during the period indicated by horizontal bar. Mean value of the relative amplitude of I_Ba compared to the control I_Ba at t = 0 was plotted on ordinate (I_Ba ratio) against time on abscissa. The number of neurons examined is indicated for the respective concentrations. S.E.M. value was not indicated. (c) Concentration-inhibition relationship for zolmitriptan. Bar graph shows the relative amplitude of I_Ba at two minutes after application of zolmitriptan compared to the control. (*p < 0.05 **p < 0.01).

As noticed from Fig. 1b, this inhibitory effect of zolmitriptan on I_Ba lasted after the end of the drug application and afterwards became more marked, attaining to its peak. Then, it should be noted that the inhibitory action of zolmitriptan on I_Ba could be hardly washed out. Therefore, the inhibitory effect of the drug was compared by using the I_Ba ratio (see Method and figure legend) at 2 min after the onset of the application. The I_Ba ratios were 0.96 ± 0.06 (0.1 μM, n = 4), 0.81 ± 0.08 (1 μM, n = 6), 0.75 ± 0.07 (5 μM, n = 6), 0.71 ± 0.06 (10 μM, n = 12), 0.40 ± 0.12 (40 μM, n = 8), and 0.00 ± 0.00 (100 μM, n = 3), and compared with the I_Ba ratio of control group without zolmitriptan (0.97 ± 0.03, n = 3), as summarised in Fig. 1c, showing the concentration-inhibition relationship for the action of zolmitriptan on I_Ba.

Action of zolmitriptan, inhibited by a 5HT_1B/1D antagonist

Since triptans are known to act as 5-HT_1B/1D agonists, we examined whether or not the zolmitriptan-induced inhibition on I_Ba could be blocked by a 5-HT_1B/1D receptor antagonist, GR127935. The preparations were pretreated with GR127935 for 2 min; no direct actions of the antagonist on I_Ba were observed at 0.3 μM. Following GR127935 application for more than 2 min, zolmitriptan (5 and 10 μM) was added to the superfusate. The I_Ba ratios with 10 μM zolmitriptan were 0.71 ± 0.06 (without GR127935, n = 12), 0.72 ± 0.10 (0.1 μM GR127935, n = 6), 1.10 ± 0.04 (0.3 μM GR127935, n = 4), as summarized in Fig. 2. It was shown that the zolmitriptan-induced inhibition of I_Ba was significantly reduced by GR127935 at 0.3 μM. On the other hand, the I_Ba ratios with 5 μM zolmitriptan were 0.75 ± 0.07 (without GR127935, n = 6), 0.84 ± 0.13 (0.1 μM GR127935, n = 4), showing no significant inhibition. These data suggested that zolmitriptan inhibited I_Ba by activating 5-HT_1B/1D receptors. It should be added that GR127935 at concentrations higher than 1 μM occasionally inhibited I_Ba.

Figure 2

GR127935 modulation on zolmitriptan-sensitive I_Ba. (a) GR127935, 5HT_1B/1D antagonist, depressed the inhibition of I_Ba by zolmitriptan (10 μM). Bar graph shows that the zolmitriptan-induced inhibition of I_Ba was significantly reduced by pretreatment with 0.3 μM of the antagonist GR127935 (*p < 0.05). I_Ba ratio is the value that I_Ba (test) was divided by I_Ba (control). Inset shows the time course of GR127935 and zolmitriptan application. I_Ba (control) and I_Ba (test) were recorded as shown in the chart. (b) Typical illustration of I_Ba in control (left), in the presence of 0.3 μM GR127935 (center), and 10 μM zolmitriptan added on 0.3 μM GR127935 (right).

Action of zolmitriptan, mediated by G-protein pathway

It is widely accepted that some of 5-HT receptor subtypes are G-protein coupled. Possible involvement of G-protein pathways in the present action of zolimitriptan was tested by using pertussis toxin (PTX, an irreversible inhibitor of Gi/_o proteins). When cultured TGNs were treated overnight with PTX (500 ng/ml), zolmitriptan at 10 μM could not exert an inhibitory effect on I_Ba; the amplitude of I_Ba in control was almost the same as that of I_Ba in the presence of zolmitriptan; that is I_Ba ratio = 1.0 as shown in Fig. 3. Thus, PTX pretreatment prevented the inhibition of I_Ba by zolmitriptan, while I_Ba was depressed by zolmitriptan without the PTX pretreatment. This significant change induced by PTX indicated the role of G-proteins in the zolmitriptan inhibition of I_Ba.

Figure 3

PTX modulation on zolmitriptan-sensitive I_Ba. PTX treatment prevented the inhibition of I_Ba by zolmitriptan (10 μM). Bar graph shows that the zolmitriptan-induced inhibition of I_Ba was significantly reduced by overnight treatment of 500 ng/ml PTX (*p < 0.05). Recording of I_Ba (control) and I_Ba (test) in the presence of zolmitriptan were made according to the same time course shown in the inset of figure 2. I_Ba ratio means I_Ba (test)/I_Ba (control).

Pharmacological profile of I_Ba, sensitive to zolmitriptan

Characteristics of I_Ba inhibited by zolmitriptan were pharmacologically determined by using a variety of selective Ca²⁺ channel blockers. Indeed, four types of HVA Ca²⁺ channels are known to be expressed in TGNs; that is, N-type, P/Q-type, R-type, and L-type channels. In the present experiments, therefore, ω-conotoxin GVIA (ω-CgTx, 1 μM), ω-agatoxin IVA (ω-Aga, 0.2 μM), SNX-482 (0.1 μM), and nicardipine (10 μM) were used to examine possible contribution of each Ca²⁺ channel to the zolmitriptan-sensitive I_Ba, respectively. It is confirmed that all four Ca²⁺ blockers reduced I_Ba; ratios of I_Ba in the presence of Ca²⁺ blockers to control I_Ba were 0.42 ± 0.05 (ω-CgTx, n = 5); 0.58 ± 0.04 (ω-Aga, n = 4); 0.84 ± 0.05 (SNX-482, n = 7); and 0.43 ± 0.08 (nicardipine, n = 4).

After pretreatment with each of blockers for 2 min, zolmitriptan (10 μM) was added to the superfusing solutions, and I_Ba ratios were obtained (see inset of Fig. 4). When pretreated with ω-CgTx, the I_Ba ratio was 0.55 ± 0.02 (n = 5); with ω-Aga, 0.89 ± 0.05 (n = 4); with SNX-482, 0.80 ± 0.03 (n = 7); and with nicardipine, 0.28 ± 0.15 (n = 4) (Fig. 4). The I_Ba ratios after pretreatment with ω-Aga or SNX-482 seemed to be larger than the ratio 0.71 ± 0.06 (10 μM zolmitriptan without Ca²⁺ blockers) in Fig. 1c, suggesting a possibility that Ca²⁺ channels sensitive to ω-Aga or SNX-482 likely contributed to the blockade of zolmitriptan I_Ba inhibition. Indeed, significant difference was detected between ω-Aga and ω-CgTx or nicardipine, and also between SNX-482 and nicardipine (Fig. 4), indicating that blockade of P/Q-type and R-type Ca²⁺ channels with ω-Aga and SNX-482 reduced the inhibition of I_Ba by zolmitriptan. Therefore, it is likely that P/Q-type and R-type channels could be inhibited by zolmitriptan by acting on 5-HT_1B/1D receptors through G proteins pathways.

Figure 4

Pharmacological characteristics of zolmitriptan-sensitive I_Ba. Bar graph shows that inhibition of I_Ba was significantly reduced with ω-Aga, compared to those with ω-CgTx and nicardipine, Aand with SNX-482, compared to that with nicardipine (*p < 0.05). I_Ba (control) after pretreatment with Ca²⁺ blockers and I_Ba (test) 2 min after adding zolmitriptan were recorded as indicated in the inset. I_Ba ratio was obtained by I_Ba (test)/I_Ba (control).

Discussion

The present experiments demonstrated modulating actions by zolmitriptan on I_Ba of the rat isolated TGNs. Zolmitriptan inhibited HVA Ca²⁺ currents carried by Ba²⁺ in a concentration-dependent manner within the concentration range between 0.1 μM and 100 μM by acting on 5HT_1B/1D receptor through G_i/o protein-coupled pathway.

5HT receptors are divided into 7 families, 5HT_1~7 receptors, on the basis of their amino acid sequences and other properties. 5HT₁ receptors are further subdivided according to their physiological functions, binding affinity and other features [12]. The present study showed that GR127935, a potent 5HT_1B/1D receptor antagonist abolished the effect of zolmitriptan, meaning that zolmitriptan acted on 5HT_1B/1D receptor.

5HT_1B and/or _1D subtypes are known as G-protein mediated receptors. In the present study, pretreatment with PTX inhibited the I_Ba inhibition by zolmitriptan, indicating the involvement of G_i/o protein coupled pathway. This observation might be compatible with the previous reports that an increase in intracellular Ca²⁺ level by 5HT₁ receptor is associated with activation of G_i/G_o protein coupled pathway [13,14] and that the modulation of neuronal voltage-gated Ca²⁺ channel is mediated by receptors coupled to PTX-sensitive G proteins [15,16]. In this context, possible involvement of stimulatory of G-proteins (G_s) in the zolmitriptan action should be further investigated by using cholera toxin. A recent report shows that sumatriptan could activate the other second messenger MAPK pathway leading to changes in intracellular Ca²⁺ changes [17]. This possibility for the action of zolmitriptan remains to be considered in future.

It is reported that triptans, antimigraine drugs might inhibit the release of vasoactive neuropeptide from trigeminovascular nerve endings and also inhibit transmission of nociceptive impulses to second-order neurons of the trigeminocervical complex, resulting in the antimigraine effect of triptan [18]. It is known that the trigeminal ganglion possesses small to medium size 5HT_1B/1D receptor positive peptidergic neurons [4,5] and furthermore that antimigraine drugs could block synaptic transmission between meningeal nociceptors and central trigeminal neurons presynaptically [7]. All of these suggest that HVA Ca²⁺ channels, highly responsible to neurotransmitter release from presynaptic terminal, might be involved in the antimigraine effects of triptans. Indeed the present study showed that HVA I_Ba of TGNs was affected by zolmitriptan, a 5HT_1B/1D agonist, strongly advocating the idea that triptans inhibited neurotransmitter release from peripheral or central presynaptic terminal through HVA Ca²⁺ channels.

It is important to determine which subtypes of HVA Ca²⁺ channels might essentially contribute to the release of different neurotransmitters from various classes of neurons. Some paper mentioned simply about HVA Ca²⁺ subtype on trigeminal neurons, but there is no consensus about which subtypes mainly contribute yet. Ebersberger et al shows that discharge patterns of trigeminal second order neurons with dural input are different in the presence of each HVA Ca²⁺ subtype blockade [19], On the other hand, Hong et al showed that N- and P/Q-channels are important for the release of CGRP from perivascular TGNs [20] and the release of CGRP is shown to be prevented when N-, P/Q- or L- channels are blocked on trigeminal vascular neuron [9]. The present study demonstrated that the inhibition of zolmitriptan-sensitive I_Ba in small-medium TGNs depended mainly on activation of P/Q- and R-type channels.

P/Q-type Ca²⁺ channels are reported to locate in all brain structure [18] and also in the trigeminal ganglia [8]. Furthermore, α-eudesmol, a P/Q-type channel blocker, inhibits the release of a neuropeptide from perivascular trigeminal sensory nerves [21]. These observations may support our present findings that P/Q-type channels might be possible sites on which zolmitriptan could act in cultured neonatal rat TGNs. Although N-type is also known to locate in DRG neurons [22 –24], a few studies show the N-type channel dominance in TGNs. The present study with ω-CgTx also could not statistically demonstrate an appreciable involvement of N-type channels in the inhibition of zolmitriptan-sensitive I_Ba of cultured rat TGNs.

R-type Ca²⁺ channels are shown to locate presynaptically in the central nervous system, but the transmitter release mediated by R-type channels is less efficient than that by P/Q-and N-type channels [25]. In the process of development, R-type channels are replaced by P/Q-type ones in the central synaptic transmission [26]. There are similar results for Ca²⁺ channel subtypes obtained from neonatal and adult TGNs; in neonatal 4% are provided with P/Q-type while 15% with R-type one [8]; in adult 40% with P/Q-type while 5% to R-type [27]. In this context, the present study, for the first time, demonstrated possible involvement of R- as well as P/Q-type channels in the actions of zolmitriptan on the cultured neonatal rat TGNs.

Although zolmitriptan (0.1~100 μM) inhibited I_Ba of cultured TGNs, it is difficult to determine the effective concentration of zolmitriptan acting in vivo on the trigeminal ganglion. Sumatriptan is reported to induce discharges in dural primary afferent neurons at concentrations between 0.24 and 24 μM [28] and also cause vasocontraction in rat isolated vena portae smooth muscle at concentrations between 0.001 and 10 μM [29]; these indicate that actions of two triptans could be exerted at similar concentrations.

Conclusion

Zolmitriptan inhibited I_Ba in a concentration-dependent manner by acting on 5HT_1B/1D receptor. P/Q- and possibly R-type calcium channels contributed to the inhibition of I_Ba by zolmitriptan. G_i/o protein pathway were involved. Although this action of zolmitriptan on HVA Ca²⁺ channels might explain the antimigraine effect, more detailed research of second messenger pathway would reveal the further mechanism leading to antinociceptive effect of triptans and pain pathway of migraine.

Method

Animal preparation

All procedures were carried out in accordance with the guidelines for Animal Experimentation in Tokyo Medical and Dental University (No.0060010). Wistar rats (0–7 days after birth, Saitama Experimental Animals Supply Inc., Japan) were anesthetized by pentobarbital (i.p.). After the decapitation of the rats, trigeminal ganglia were dissected and treated with papain (20.3 units/ml) in low-Ca²⁺ and low-Mg²⁺ Krebs' solution for 30 min at 37°C, washed with modified Krebs' solution and triturated using fire-polished Pasteur pipettes. Neurons were plated onto poly-L-lysine pretreated 35 mm dishes. The plating medium contained Dulbecco's modified Eagle's medium with 10% calf serum. The TGNs were kept in culture in modified Krebs' solution saturated with 5% CO₂ at 37°C for 2 hours to one day before experiment. The ionic composition of the modified Krebs' solution was (mM): NaCl, 117; KCl, 4.7; CaCl₂, 2.5; MgCl₂, 1; glucose, 11; 3-(N-morpholino) propanesulfonic acid (MOPS), 25; and pH 7.2 adjusted with NaOH. The low-Ca²⁺ and low-Mg²⁺ Krebs' solution was made by adding EDTA (2.5 mM) to the modified Krebs' solution.

Electrophysiological recording

Membrane currents were recorded from somata of cultured TGNs in the whole-cell voltage clamp configuration of patch clamp technique with an Axopatch 1D amplifier (Axon Instrument). Currents were filtered low-pass at 2 Hz by the built-in Bessel filter, and recorded on a chart recorder (San-ei) for later analysis. Patch pipettes were pulled from borosilicate glass capillaries (Harvard) using a puller (Narishige co.), and had input resistance of 5–10 MΩ after polishing. The ionic composition of the patch pipette solution was (mM): CsCl, 100; MOPS, 40; MgCl₂, 1; EGTA, 10; CaCl₂, 1; ATP, 2 and pH 7.2 adjusted with KOH. A series resistance of the recording system was not electrically compensated.

Currents carried by Ba²⁺ passing through HVA Ca²⁺ channels, I_Ba, were evoked by depolarizing voltage step command pulse to +10 mV for 40 ms from a holding potential of −60 mV every 10 s. For isolating Ba²⁺ currents an external solution was used, containing (mM): TEA-Cl 140; CsCl, 2.5; BaCl₂, 2.5; MgCl₂, 1; Glu, 11; HEPES, 10 and pH 7.3 adjusted with TEA-OH. The amplitude of I_Ba was determined as the difference between the baseline and the peak inward current during each command pulse.

External solutions were applied continuously via a polyethylene tube mounted on a micromanipulator and the tip of the tube was positioned within 10 mm of the recorded neurons. External solution was kept at 37° C. The capacity of chamber was 150 μl and the flow rate of solution was 2 ml/min.

Materials

Zolmitriptan was a gift from Astrazeneca. Zolmitriptan was dissolved in dimethylsulfoxide (DMSO) and stored at −20°C. More dilute solutions were made daily dissolved in external solution before every experiment. ω-CgTx, ω-Aga and SNX-482 were purchased from Peptide Institute. Nicardipine was from Sigma. GR127935 was from Tocris.

Data analysis

All data are expressed as means ± S.E.M. I_Ba ratio of Fig. 1b was expressed as the relative amplitude in response to each step command pulse compared to control values, and I_Ba ratios shown in Fig 1c, 2, 3, 4 were expressed as the relative amplitude after 120 s zolmitriptan application compared to control values in the absence of zolmitriptan. Statistical significance was assessed with Student's t-test for simple comparisons and Bonferroni-type multiple t-test for multiple comparison. Differences of P < 0.05 were considered to be significant.

Competing interests

The author(s) declare that they have no competing interests.

Authors' contributions

T. Morikawa conceived of the study, participated in design of the study, carried out cell-culture and electrophysiological experiments, performed the statistical analysis, and prepared the manuscript as a main investigator. Y Matsuzawa participated in experiments and discussion. K Makita participated in design of the study and did the entire summary and discussion from the viewpoint of the pain clinic. Y Katayama conceived of the study, performed in design of the study, helped to prepare the manuscript and gave financial support of the present study and approval of this version to be published. All authors read and approved the final manuscript.

Footnotes

List of Abbreviation

Acknowledgements

This study was supported in part by Grant-in-Aid for Scientific Research (No. 13307056 to Y.K.)

References

1. Goadsby

Edvinsson

: The trigeminovascular system and migraine: studies characterizing cerebrovascular and neuropeptide changes seen in humans and cats. Ann Neurol 1993, 33:48–56.

2. Longmore

Shaw

Smith

Hopkins

McAllister

Pickard

Sirinathsinghji

Butler

Hill

: Differential distribution of 5HT1D- and 5HT1B-immunoreactivity within the human trigemino-cerebrovascular system: implications for the discovery of new antimigraine drugs. Cephalalgia 1997, 17:833–842.

3. Bonaventure

Voorn

Luyten

Jurzak

Schotte

Leysen

: Detailed mapping of serotonin 5-HT1B and 5-HT1D receptor messenger RNA and ligand binding sites in guinea-pig brain and trigeminal ganglion: clues for function. Neuroscience 1998, 82:469–484.

4. Potrebic

Ahn

Skinner

Fields

Basbaum

: Peptidergic nociceptors of both trigeminal and dorsal root ganglia express serotonin 1D receptors: implications for the selective antimigraine action of triptans. J Neurosci 2003, 23:10988–10997.

5. Ma

Hill

Sirinathsinghji

: Colocalization of CGRP with 5-HT1B/1D receptors and substance P in trigeminal ganglion neurons in rats. Eur J Neurosci 2001, 13:2099–2104.

6. Goadsby

Knight

: Inhibition of trigeminal neurones after intravenous administration of naratriptan through an action at 5-hydroxy-tryptamine (5-HT1B/1D) receptors. Br J Pharmacol 1997, 122:918–922.

7. Levy

Jakubowski

Burstein

: Disruption of communication between peripheral and central trigeminovascular neurons mediates the antimigraine action of 5HT1B/1D receptor agonists. Proc Natl Acad Sci USA 2004, 101:4274–4279.

8. Ikeda

Matsumoto

: Classification of voltage-dependent Ca2+ channels in trigeminal ganglion neurons from neonatal rats. Life sciences 2003, 73:1175–1187.

9. Akerman

Williamson

Goadsby

: Voltage-dependent calcium channels are involved in neurogenic dural vasodilatation via a presynaptic transmitter release mechanism. Br J Pharmacol 2003, 140:558–566.

10.

10. Sun

Dale

: Differential inhibition of N and P/Q Ca2+ currents by 5-HT1A and 5-HT1D receptors in spinal neurons of Xenopus larvae. J Physiol 1998, 510:103–120.

11.

11. Sun

Dale

: G-proteins are involved in 5-HT receptor-mediated modulation of N- and P/Q- but not T-type Ca2+ channels. J Neurosci 1999, 19:890–899.

12.

12. Tepper

Rapoport

Sheftell

: Mechanisms of action of the 5-HT1B/1D receptor agonists. Arch Neurol 2002, 59:1084–1088.

13.

13. Zgombick

Borden

Cochran

Kucharewicz

Weinshank

Branchek

: Dual coupling of cloned human 5-hydroxytryptamine1D alpha and 5-hydroxytryptamine1D beta receptors stably expressed in murine fibroblasts: inhibition of adenylate cyclase and elevation of intracellular calcium concentrations via pertussis toxin-sensitive G protein(s). Mol Pharmacol 1993, 44:575–582.

14.

14. Adham

Borden

Schechter

Gustafson

Cochran

Vaysse

Weinshank

Branchek

: Cell-specific coupling of the cloned human 5-HT1F receptor to multiple signal transduction pathways. Naunyn Schmiedebergs Arch Pharmacol 1993, 348:566–575.

15.

15. Holz

Rane

Dunlap

: FTP-binding proteins mediate transmitter inhibition of voltage-dependent calcium channels. Nature 1986, 319:670–672.

16.

16. Dolphin

: G protein Modulation of Voltage-gated Calcium Channels. Pharmacological Reviews 2003, 55:607–627.

17.

17. Durham

Russo

: Stimulation of the calcitonin gene-related peptide enhancer by mitogen-activated protein kinases and repression by an antimigraine drug in trigeminal ganglia neurons. J Neurosci 2003, 23:807–815.

18.

18. Pietrobon

Striessnig

: Neurobiology of migraine. Nature Reviews 2003, 4:386–398.

19.

19. Ebersberger

Portz

Meissner

Schaible

Richter

: Effects of N-, P/Q- and L-type calcium channel blockers on nociceptive neurones of the trigeminal nucleus with input from the dura. Cephalalgia 2004, 24:250–261.

20.

20. Hong

Kim

Rhim

Lee

: Effect of omega-conotoxin GVIA and omega-agatoxin IVA on the capsaicin-sensitive calcitonin gene-related peptide release and autoregulatory vasodilation in rat pial arteries. J Cereb Blood Flow Metab 1999, 19:53–60.

21.

21. Asakura

Kanemasa

Minagawa

Kagawa

Yagami

Nakajima

Ninomiya

: alpha-eudesmol, a P/Q-type Ca (2+) channel blocker, inhibits neurogenic vasodilation and extravasation following electrical stimulation of trigeminal ganglion. Brain Res 2000, 873:94–101.

22.

22. Soeda

Tatsumi

Katayama

: Neurotransmitter release from growth cones of rat dorsal root ganglion neurons in culture. Neuroscience 1997, 77:1187–1199.

23.

23. Sutton

Martin

Pinnock

Lee

Scott

: Gabapentin inhibits high-threshold calcium channel currents in cultured rat dorsal root ganglion neurones. Br J Pharmacol 2002, 135:257–265.

24.

24. McDowell

: Fentanyl decreases Ca2+ currents in a population of capsaicin-responsive sensory neurons. Anesthesiology 2003, 98:223–231.

25.

25. Kamp

Krieger

Henry

Hescheler

Weiergraber

Schneider

: Presynaptic ‘Ca2.3-containing’ E-type Ca channels share dual roles during neurotransmitter release. Eur J Neurosci 2005, 21:1617–1625.

26.

26. Iwasaki

Momiyama

Uchitel

Takahashi

: Developmental changes in calcium channel types mediating central synaptic transmission. J Neurosci 2000, 20:59–65.

27.

27. Borgland

Connor

Christie

: Nociceptin inhibits calcium channel currents in a subpopulation of small nociceptive trigeminal ganglion neurons in mouse. J Physiol 2001, 536:35–47.

28.

28. Strassman

Levy

: The anti-migraine agent sumatriptan induces a calcium-dependent discharge in meningeal sensory neurons. Neuroreport 2004, 15:1409–1412.

29.

29. Datte

Offoumou

: Involvement of nitric oxide in fading of 5-hydroxytryptamine-induced vasocontraction in rat isolated vena portae smooth muscle. J Pharm Pharm Sci 2004, 23:1–7.

Antimigraine Drug,Zolmitriptan,Inhibits High-Voltage Activated Calcium Currents in a Population of Acutely Dissociated Rat Trigeminal Sensory Neurons

Abstract

Background

Results

Conclusion

Background

Results

Concentration-dependent action of zolmitriptan on IBa

Action of zolmitriptan, inhibited by a 5HT1B/1D antagonist

Action of zolmitriptan, mediated by G-protein pathway

Pharmacological profile of IBa, sensitive to zolmitriptan

Discussion

Conclusion

Method

Animal preparation

Electrophysiological recording

Materials

Data analysis

Competing interests

Authors' contributions

Footnotes

List of Abbreviation

Acknowledgements

References

Action of zolmitriptan, inhibited by a 5HT_1B/1D antagonist

Pharmacological profile of I_Ba, sensitive to zolmitriptan