Sage Journals: Discover world-class research

Abstract

Clinical, genetic and pharmacological evidences suggest an abnormality of the dopaminergic system in the pathogenesis of migraine. Direct evidence of an abnormal metabolism of dopamine in migraine, however, is lacking. Platelets are a useful model to understand brain dopaminergic mechanisms. The present study has been undertaken to study the status of platelet dopamine receptor binding by carrying out radioligand receptor binding assay. Binding of ³H-spiperone to platelet membranes, known to label dopamine (DA)—D2 receptors, was conducted in 20 patients with migraine and an equal number of healthy controls. The equilibrium dissociation constant (Kd) in patients with migraine (1.71 ± 0.19 nM) was found to be significantly lower (P < 0.001) as compared with controls (3.14 ± 0.33 nM). However, no significant change was observed in the maximal number of binding sites (Bmax) in patients with migraine. No relationship of Kd with type of migraine, presence of vomiting, family history, frequency of attack, duration of illness and menstrual migraine was observed. The findings of the present study provide support for the involvement of the dopaminergic system in migraine.

Keywords

Migraine platelets dopamine receptors neurotransmitters

Introduction

The molecular mechanisms of migraine have not yet been fully clarified. The mechanism of migraine is thought to involve activation of the trigeminal nerve (1). Several neurotransmitters and neuromodulators are possibly involved in this and treatment based on some of them is now available (2–4). The role of serotonin and serotonergic receptors in the pathophysiology of migraine is well documented (5). In our earlier studies, of platelet 5-HT _2Areceptors using ³H ketanserin as a radioligand, a significant decrease in the affinity was observed in migraine and a significant reduction in the number of binding sites was found in tension-type headache (6, 7).

The status of dopamine in migraine is still not clear (8, 9), although its involvement was first suggested by Sicuteri in 1977, who hypothesized that there is a monoamine (5-HT and DA) post-synaptic receptor hypersensitivity in areas of the brain involved in pain, vomiting, affect and arterial blood pressure (10). There are circumstantial clinical and pharmacological data to support this. Several prodromal symptoms (mood changes, yawning, drowsiness, food craving), accompanying symptoms (nausea, vomiting, hypotension), and postdromal symptoms (mood changes, drowsiness, tiredness) of a migraine attack may be related to dopaminergic activation (11). Drugs with dopaminergic activity have been employed in the treatment of migraine. DA receptor antagonists are effective in acute attack while DA agonists are employed in prophylaxis (12).

Direct evidence of a dopaminergic abnormality in migraine is, however, difficult to obtain, probably because DA is readily metabolized into norepinephrine by dopamine beta hydroxylase (DBH) and consequently its levels are low and difficult to detect in the serum/plasma and cerebrospinal fluid (13). However, the platelets are discoid cellular components of the blood that are devoid of a nucleus and have a life span of 8–10 days. They take up all the circulating 5-HT and DA released from the autonomic endings and accumulate it in the dense bodies that constitute a neural milieu. The platelet levels of both 5-HT and DA reflect the whole 10-day metabolism of the amines (14). Thus, in addition to their primary function of securing haemostasis, the platelets that can be obtained by a simple venepuncture constitute a useful non-invasive tool to study dopaminergic mechanisms.

The results of studies on platelet DA levels are variable. A recent study reported increased levels of platelet DA in patients suffering from migraine both with and without aura (15); however, in an earlier study the interictal DA levels in the platelets of women with migraine were found to be in the same range as that of control subjects (14). Several studies have evaluated D2 receptor polymorphism in migraine (16–20). Peroutka and colleagues observed that a polymorphism in the Ncol gene that encodes DR D2 was increased in migraine with aura compared with migraine without aura or controls (16). Another study found that only a subgroup of patients who presented with yawning and nausea before or during headache had the DR D2 polymorphism (17). The rest of the studies were negative (18–20). This finding was not confirmed by others (18, 19), except for one study which reported disequilibrium in D2 genotypes in a subgroup of patients having nausea and yawning (20). Thus, the precise role of the D2-like receptor gene polymorphism in migraine is presently not clear. Another study showed a significant genetic association with the dopamine D4 receptor gene in patients having migraine without aura but not migraine with aura. No significant differences were found between control and migraine groups for dopamine transporter gene and DBH polymorphisms (21, 22).

DA receptors have been demonstrated on human blood platelets (23–25). According to the IUPHAR classification there are five subtypes of DA receptors (26). D1 and D5 are grouped together as DA-D1-like receptors while D2, D3 and D4 are included in DA-D2-like receptors. The D2-like receptor family can be studied with ³H spiroperidol or ¹²⁵I iode-benzamide (27). In view of the conflicting data regarding DA and migraine (8, 9), the present study has been undertaken to investigate the D2 receptor binding in platelets using ³H spiperone as a radioligand and haloperidol as a competitor. ³H spiperone was chosen as a radioligand because tritium has a long half life of approximately 12 years (28) as compared with ¹²⁵I, which has a short half life of 60 days (29). Haloperidol is a specific competitor for dopaminergic sites so it was also used simultaneously to determine the extent of non-specific binding.

Patients and methods

Twenty patients with migraine attending the Headache Clinic in the Neurology Outpatients Department of King George's Medical University were included. The diagnosis of migraine was based on the criteria given by the International Headache Society (30). A detailed history was taken according to a predesigned proforma and complete physical examination was done. The severity of pain in the attacks was graded on a three-point scale: 1 = mild headache, does not interfere with the patient's daily routine; 2 = moderate headache, interferes with the daily routine but patient can continue his work; 3 = severe headache, patient has to take bed rest. Twenty healthy controls comprising of paramedical staff and relatives of the patients were also included. The patient characteristics of the subjects included in the study are given in Table 1.

Table 1

Patient characteristics

Clinical features	Migraine	Controls
Number	20	20
Age (years)
Mean ±s.e.m.	28.5 ± 2.4	29.1 ± 1.9
Range	18–45	18–44
Sex (M : F)	7:13	9:11
Type
With aura	4	–
Without aura	16	–
Duration of disease (years)
Mean ±s.e.m.	6.25 ± 0.49	–
Range	3–10	–
Time since last attack (days)
Mean ±s.e.m.	7.5 ± 0.32	–
Range	6–10	–
Family history positive	10	–

None of the subjects included in the study were suffering from hypertension, diabetes mellitus, ischaemic heart disease or any psychiatric illness that may affect dopamine receptor assay. Drugs like aspirin, psychotropics and anti-depressants were not allowed for at least 7 days prior to collection of blood samples.

Collection of blood samples

Nine ml of blood was collected by venepuncture from the antecubital vein using a disposable plastic syringe with a 20-gauge needle, between 09.00 and 10.00, and immediately transferred to plastic tubes containing 1 ml of 3.8% sodium citrate. It was transported to the Indian Institute of Toxicology Research, Lucknow, within 30 min of collection for biochemical assay. The blood samples were collected at least 5 days after the last attack of migraine, and in women they were taken during the early follicular phase in the first week.

Preparation of platelet membrane

The method of Khanna et al. (23) was followed for preparation of platelet-rich plasma (PRP) and platelet membrane. The citrated blood (0.129 M, pH 6.5, 9:1 v/v) was gently mixed and centrifuged at 200 × g for 10 min. The supernatant PRP was transferred into another plastic tube and centrifuged at 12 000 × g for 10 min at 4°C. The platelet pellet obtained was washed twice with 5 mM Tris-HCI buffer (pH 7.4) and the platelet suspension was homogenized and centrifuged at 50 000 × g for 10 min at 4°C. The platelet membrane fraction was finally suspended in tris HCI buffer (50 mM, pH 7.5).

Platelet counts

Platelet counts were done in a Naeubeur haemocytometer in duplicate. For platelet counts 0.1 mL of PRP was taken out in plastic tubes and added to 1.9 mL of formyl citrate.

Receptor binding assay

Assay of ³H-siperone binding to platelet membranes

Binding assay for dopamine (DA)—D2 receptors in platelet membranes was carried out following the standard protocol as described by Khanna et al. (23). Briefly, binding tubes containing assay buffer (15.4 mM Tris-HCl pH 7.4, 50 μM ketanserin), platelet membrane protein (150–300 ug / tube) and ³H-spiperone (Specific activity 15 Ci / mmole, Perkin Elmer, USA) at varying concentrations (0.1 × 10⁻⁹ M to 10 × 10⁻⁹ M) in a final volume of 1 mL were incubated at 37°C for 15 min. The tubes were placed in ice after the incubation was over and contents filtered on glass fibre discs (Whatman GF/B, 25 mm diameter). The filters were washed twice with 5 mL cold Tris-HCl buffer, dried and counted in vials containing 5 mL scintillation fluid, using a scintillation counter (Packard, USA) at an efficiency of 40–50% for tritium. Control incubations containing haloperidol (1 × 10⁻⁶ M) were carried out simultaneously to determine the extent of non-specific binding. The binding was expressed as pmoles ³H-spiperone bound/gm protein. Binding affinity (Kd) and number of receptor binding sites (Bmax) were determined by non-linear regression analysis.

Assay of protein content

Protein was determined following the method of Lowry et al. (31) using bovine serum albumin as reference standard.

Chemicals and source

³H-spiperone (15 Ci / mmole) was procured from M/s Perkin Elmer, USA. Haloperidol and Ketanserin were procured from M/s Sigma—RBI, USA. All other chemicals used in the assay were of analytical grade and obtained from the local source.

Data analysis

The data were analysed by the method of Scatchard (32), plotting bound/free (B/F) vs. bound (B), and finally analysed by nonlinear regression analysis, and the equilibrium dissociation constant (Kd) and the maximal number of binding sites (Bmax were obtained. The values of Kd and Bmax are expressed as mean ±s.e.m..

Statistical analysis

The independent student's t-test was used to compare the mean values between migraine and controls. A univariate analysis of the various clinical features with the binding characteristics (Kd, Bmax) was done. The value of the correlation coefficient (r) was also calculated for the binding characteristics with age, duration of disease, frequency of attacks and time since last attack. A P-value less than 0.05 was considered significant.

Results

The platelet count in PRP in patients with migraine (2.56 ± 0.05 cells/10⁸ mm³) and controls (2.48 ± 0.08 cells/10⁸ mm³) did not show any statistically significant difference. The platelet dopamine D2 receptor binding characteristics are depicted in Table 2. In four migraineurs and four controls no platelet binding was detected. The Kd in migraineurs (1.71 ± 0.19 nM) was significantly lower as compared with control subjects (3.14 ± 0.33 nM) while the Bmax did not show any significant difference (migraineurs 473.31 ± 39.31 pmole ligand bound /gm protein; controls 408.38 ± 30.58 pmole ligand bound/gm protein). It can be observed from the scatterplot (Fig. 1) that there are two outliers in the control group. Analysis of the data for Kd and Bmax after excluding these two subjects reveals that in controls the Kd was 2.78 ± 0.25 nM while the Bmax was 406.50 ± 25.78 pmole ligand bound/gm protein. The Kd in migraine was still significantly lower as compared with controls (P < 0.01).

Table 2

Platelet dopamine D2 receptor binding in migraine

Group	Binding characteristics
Group	Kd (nM)	Bmax (pmole ligand bound/gm protein)
Migraine
Males	1.40 ± 0.35	499.75 ± 58.78
Females	1.81 ± 0.20	464.50 ± 45.97
Total	1.71 ± 0.19	473.31 ± 39.31
Control
Males	2.81 ± 0.32	399.50 ± 43.4
Females	3.34 ± 0.50	413.70 ± 39.31
Total	3.14 ± 0.36	408.38 ± 30.58

∗P < 0.001 as compared with controls.

Values are expressed as mean ±s.e.m.

In four migraineurs and four controls no platelet binding was detected.

Figure 1

Scattergram showing the binding characteristics (a) Kd and (b) Bmax of ³H spiperone to platelet membrane in migraine (•) and controls (o). A significant decrease was observed in the Kd in migraineurs (P < 0.001).

A univariate analysis did not reveal any significant difference in Kd or Bmax with respect to age, sex, duration of illness, frequency of attacks, time since last attack, type of migraine, family history, vomiting, and menstrual migraine (Table 3). The correlation coefficient (r) of Kd and Bmax with age, duration of disease, frequency of attacks and time since last attack was also not significant (Table 4).

Table 3

Univariate analysis of platelet dopamine D2 receptor binding with various clinical features of migraine

Group	n	Binding characteristics
Group	n	Kd (nM)	Bmax (pmole ligand bound/gm protein)
Age
< 30 years	7	1.67 ± 0.25	396.86 ± 59.18
≥ 30 years	9	1.74 ± 0.25	532.78 ± 37.97
Sex
Male	4	1.40 ± 0.35	499.75 ± 58.78
Female	12	1.81 ± 0.20	464.50 ± 45.97
Duration of disease
< 5 years	6	1.93 ± 0.27	436.00 ± 64.79
≥ 5 years	10	1.58 ± 0.22	495.70 ± 45.35
Frequency of attacks
< 5/month	7	1.69 ± 0.20	500.5 ± 52.45
≥ 5/month	9	1.73 ± 0.29	446.13 ± 53.02
Time since last attack
< 7 days	7	1.67 ± 0.18	417.82 ± 29.15
≥ 7 days	9	1.76 ± 0.18	544.74 ± 39.78
Type of migraine
With aura	4	1.53 ± 0.26	444.25 ± 10.69
Without aura	12	1.77 ± 0.22	483.00 ± 49.16
Family history
Positive	8	1.42 ± 0.25	452.88 ± 43.02
Negative	8	2.00 ± 0.20	493.75 ± 61.74
Vomiting
Present	8	1.57 ± 0.28	429.25 ± 35.87
Absent	8	1.85 ± 0.22	517.38 ± 62.78
Menstrual migraine
Present	3	1.86 ± 0.44	400.67 ± 42.06
Absent	9	1.86 ± 0.25	485.78 ± 59.17

Table 4

Correlation of platelet dopamine D2 receptor binding with various clinical features

Clinical features	Correlation coefficient (r)
Clinical features	Kd	Bmax
Age	0.20	0.49
Duration of disease	−0.04	0.20
Frequency of attacks	0.06	0.07
Time since last attack	0.24	0.47

Discussion

Activation of the DA D2 receptor has been proposed to play a modifying role in the pathophysiology of migraine (33), so the present study was carried out using ³H spiperone as a radioligand because in earlier studies from our laboratory specific binding sites to ³H spiperone on the platelets had been demonstrated (23). Alterations in platelet ³H spiperone binding in patients with schizophrenia and Parkinson's disease have also been demonstrated (34, 35). The blood samples were collected at the same time of the menstrual cycle in all the female subjects to avoid the variations in receptor binding due to the menstrual period (36).

The findings of the present study show that there is a significant decrease in the equilibrium constant (Kd) of ³H spiperone binding to platelets in patients with migraine; however, there was no change in the maximal number of binding sites (Bmax). The decrease in Kd did not have any significant correlation with the clinical features of migraine such as age, sex, duration of disease, frequency of attacks, time since last attack, type of migraine, family history, vomiting and menstrual migraine.

Binding of ³H-spiperone to platelet membranes is known to label dopamine D2 receptors. Reduced Kd implies increased affinity of the platelet D2 receptors to dopamine, so that the platelets take up dopamine from all the body circulation, which may lead to an increase in platelet dopamine levels. The platelet dopamine levels, however, were not measured in the present study. The results of a recent study where plasma and platelet levels of dopamine were measured show that plasma levels of dopamine were not detected by the multichannel electrochemical high performance liquid chromatography (HPLC) system. The platelet levels of dopamine were higher in both types of migraine as compared with controls, but the difference was significant only in migraine without aura (15). In an earlier study by D'Andrea et al. in which platelet catecholamines were estimated in women with migraine, the levels of interictal platelet DA levels were found in the same range as controls. Subgroup analysis, however, revealed that patients having migraine without aura had higher platelet DA levels as compared with those with aura and controls (14).

D'Andrea et al. also measured platelet DA levels in patients with cluster headache during the active period as well as in remission and interestingly found an increase in platelet DA in the active as well as the remission phase (15). Castillo et al. measured plasma monoamine levels by HPLC in patients with tension-type headache and found lower DA levels in patients as compared with controls. A positive correlation was observed between DA levels and severity of depression (37). Platelet DA D2 receptor binding has not yet been studied in other types of headaches. However, it seems less likely that abnormalities in DA D2 receptor binding can be used as a biological marker for migraine. It is more plausible that impairment in the dopaminergic system may represent an abnormal biochemical phenotypic trait of primary headaches.

There was no change in the Bmax of platelet DA-D2 receptors in the present study. In contrast to this an increased density of D₃, D₄and D₅ receptors has been demonstrated on the peripheral blood lymphocytes of migraineurs, suggesting hypo function of dopaminergic activity (38, 39).

Dopamine has vasoactive effects on blood vessels in vitro and in vivo, depending on the vascular bed and dose, which are mediated by specific dopamine receptors (27). Our results suggest that DA D2 receptors may be involved in migraine; however, the exact cascade of events that link abnormal neurotransmission to the manifestation of head pain and the accompanying symptoms is yet to be fully understood. Activation of brainstem dopaminergic structures has been proposed during migraine attacks by Cao et al., who observed an increase in baseline T₂-weighted signal intensities in the red nucleus and substantic nigra before the onset of visually triggered migraine (40). D1 and D2 receptors have been found in the rat trigeminocervical complex using antibodies specific to the individual receptors (41). Microiontophoretic application of dopamine is able to inhibit reversibly the rate of neuronal firing of durally activated neurons in the trigeminocervical complex in response to L-glutamate. The implication is that the dopaminergic response in the trigeminocervical complex is predominantly mediated via D2 receptors. The platelet has many similarities with the neuron and they have been proposed to be a peripheral model to study dopaminergic mechanisms (42–44). So extrapolation of the findings of the present study to the brain would mean that the D2 receptors in the brainstem have increased affinity to DA resulting in an increase in dopamine levels in the neurons. This may explain the symptoms such as nausea, vomiting, gastro kinetic changes, hypotension, etc. Supportive evidence is provided by Castillo et al., who demonstrated that the DA metabolite 3,4 dihydrophenylacetic acid (DOPAC) is increased in the cerebrospinal fluid of migraineurs and DOPAC levels correlated well with the severity of pain (45).

One of the limitations of our findings is the small sample size, which may be the reason why we did not observe any correlation between the clinical features and platelet ³H spiperone binding. In contrast to this, Del Zompo reported changes in the DR D2 gene polymorphism only in the subgroup of patients with migraine without aura having yawning and nausea (15). It is possible that a larger sample size may bring out alterations in ³H spiperone binding in relation to the clinical features of migraine. Despite its limitations our study provides support for the involvement of DA in migraine.

References

1 Goadsby

Lipton

Ferrari

. Migraine—a current understanding and treatment. N Engl J Med 2002; 346:257–70.

2 Humphrey

Feniuk

. Mode of action of the anti-migraine drug sumatriptan. Trends Pharmacol Sci 1991; 12:444–6.

Olesen

Diener

Husstedt

Goadsby

Hall

Meier

Calcitonin gene-related peptide receptor antagonist BIBN 4096 BS for the acute treatment of migraine. N Engl J Med 2004; 350:1104–10.

Mannix

Rapoport

Fan

Assaid

Furtek

Efficacy and tolerability of a novel oral CGRP antagonist MK-0974, in the acute treatment of migraine. Cephalalgia 2007; 27:759.

5 Schwedt

. Serotonin and migraine: the latest developments. Cephalalgia 2007; 27:1301–7.

Shukla

Khanna

Pradeep

Husain

Tandon

Nag

Platelet ³H-ketanserin binding in migraine. Cephalagia 2001; 21:567–72.

Shukla

Husain

Tandon

Khanna

Nag

Dikshit

Platelet ³H ketanserin binding in tension-type headache. Headache 2003; 43:103–8.

8 Akerman

Goadsby

. Dopamine and migraine: biology and clinical implications. Cephalalgia 2007; 27:1308–14.

9 Gladstone

. Dopamine and migraine: trigeminovascular nociception, genetics and therapeutics. Cephalalgia 2007; 27:1315–20.

10.

10 Sicuteri

. Dopamine, the second putative protagonist in headache. Headache 1977; 17:129–31.

11.

11 Fanciullacci

Alessandri

Del Rosso

. Dopamine involvement in the migraine attack. Funct Neurol 2000; 15 (Suppl. 3):171–81.

12.

12 Siow

Young

Silberstein

. Neuroleptics in headache. Headache 2005; 45:358–71.

13.

13 Cooper

Bloom

Roth

. The biochemical basis of neuropharmacology, 5th edn. New York, NY: Oxford University Press 1986.

14.

14 D'Andrea

Welch

Nagel-Leiby

Grunfeld

Joseph

. Platelet catecholamines in migraine. Cephalalgia 1989; 9:3–5.

15.

15 D'Andrea

Granella

Perini

Farruggio

Leone

Bussone

. Platelet levels of dopamine are increased in migraine and cluster headache. Headache 2006; 46:585–91.

16.

16 Peroutka

Wilhoit

Jones

. Clinical susceptibility to migraine with aura is modified by dopamine D2 receptor (DRD2) Ncol alleles. Neurology 1997; 49:6.

17.

Del Zompo

Cherchi

Palmas

Ponti

Bocchetta

Gessa

Association between dopamine receptor genes and migraine without aura in a Sardinian sample. Neurology 1998; 51:781–6.

18.

18 Dichgans

Forderreuther

Deiterich

Pfaffenrath

Gasser

. The D2 receptor Ncol allele: absence of allelic association with migraine with aura. Neurology 1998; 51:928.

19.

19 Shepherd

Lea

Hutchins

Jordan

Brimage

Griffiths

. Dopamine receptor genes and migraine with and without aura: an association study. Headache 2002; 42:346–51.

20.

Rebaudengo

Rainero

Pariziale

Rossina

Pavandli

Rubino

Lack of interaction between a polymorphism in the dopamine D2 receptor gene and the clinical features of migraine. Cephalalgia 2004; 24:503–7.

21.

Mochi

Cevoli

Cortelli

Pierangeli

Soriani

Scapoli

A genetic association study of migraine with dopamine receptor 4, dopamine transporter and dopamine-beta hydroxylase genes. Neurol Sci 2003; 23:301–5.

22.

22 McCallum

Fernandez

Quinlan

Macartney

Lea

Griffiths

. Association study of a functional variant in intron 8 of the dopamine transporter gene and migraine susceptibility. Eur J Neurol 2007; 14:706–7.

23.

23 Khanna

Agrawal

Seth

. 3H Spiroperidol binding sites in platelets. Biochem Biophys Res Commun 1987; 146:983–8.

24.

24 De Keyser

De Waele

Convents

Ebinger

Vauquelin

. Identification of D1-like dopamine receptors on human blood platelets. Life Sci 1988; 42:1797–806.

25.

25 Ricci

Bronzeth

Mannino

Migninl

Moroseth

Tayebati

Amenta

. Dopamine receptors in human platelets. Naunyn Schmiedebergs Arch Pharmacol 2001; 363:376–82.

26.

26 Schwartz

. Dopamine receptors, In: Girdlestone

, ed. The IUPHAR compendium of receptor characterization and classification. London: IUPHAR Media 1998:141–51.

27.

27 Kuhar

Minneman

Muly

. Catecholamines, In: Siegel

, ed. Basic neurochemistry, molecular cellular and medical aspects, 7th edn. Edinburgh: Elsevier Press 2006:211–25.

28.

28 Lucas

Unterweger

. Comprehensive review and critical evaluation of the half life of tritum. J Res Natl Inst Stand Technol 2000; 105:541–9.

29.

29 True

. Preparation of iodinated radioligand. Curr Protoc Neurosi 2001; Appendix 3:Appendix 3A.

30.

30 The Headache Classification Committee of the International Headache Society. The International Classification of Headache Disorders, 2nd edition. Cephalalgia 2004; 24 (Suppl. 1):1–160.

31.

31 Lowry

Rosebrough

Farr

Randall

. Protein measurement with the folin phenol reagent. J Biol Chem 1951; 193:265–75.

32.

32 Scatchard

. The attraction of proteins for small molecule and ions. Ann N Y Acad Sci 1949; 51:660–72.

33.

33 Peroutka

. Molecular variation within the dopamine receptor DRD2 gene in migraine. J Headache Pain 2000; 1 (Suppl.): 147–51.

34.

34 Sethi

Kumar

Agarwal

Seth

Trivedi

. 3H spiperone binding in platelet membranes: a possible biological marker for schizophereria. Acta Psychiatr Scand 1986; 186–90.

35.

35 Khanna

Maheshwari

Nag

Seth

. Usefulness of platelet neurotransmitter receptors in Parkinson's disease. Eur J Pharmacol 1990; 183:531.

36.

Martignoni

Blandini

Melzid'Eril

D'Andrea

Sances

Costa

The influence of gender in the evaluation of platelet and plasma catecholamines. Life Sci 1993; 52:1995–2004.

37.

37 Castillo

Martinez

Leira

Lema

Noya

. Plasma monoamines in tension-type headache. Headache 1994; 34:531–5.

38.

Barbanti

Fabbrini

Ricci

Paola Pascali

Bronzetti

Amenta

Migraine patients show an increased density of dopamine D3 and D4 receptors on lymphocytes. Cephalalgia 2000; 20:15–19.

39.

Barbanti

Bronzetti

Ricci

Cerbo

Fabrini

Buzzi

Increased density of dopamine D5 receptor in peripheral blood lymphocytes of migraineurs: a marker for migraine. Neurosci Lett 1996; 207:73–6.

40.

40 Cao

Aurora

Nagesh

Patel

Welch

. Functional MRI-BOLD of brainstem structures during visually triggered migraine. Neurology 2002; 59:72–8.

41.

41 Bergerot

Storer

Goadsby

. Dopamine inhibits trigemino-vascular transmission in the rat. Ann Neurol 2007; 61:251–62.

42.

42 Malmgren

Hasselmark

. The platelet and the neuron: two cells in focus in migraine. Cephalalgia 1988; 8:7–24.

43.

43 Campbell

Marangos

Murphy

Pearse

AGE

. Neuron specific enolase (NSE) in human blood platelets: implications for neuronal model. Rec Adv Neuropsychopharmacol 1981; 31:203–11.

44.

44 Husain

Khanna

Roy

Tandon

Pradeep

Seth

. Platelet dopamine receptors and oxidative stress parameters as markers of manganese toxicity. Hum Exp Toxicol 2001; 20:631–6.

45.

45 Castillo

Martinez

Suarez

Naveiro

Lema

Noya

. Cerebrospinal fluid tyrosine and 3, 4 dihydroxyphenylacetic acid levels in migraine patients. Cephalalgia 1996; 16:56–61.

Platelet Dopamine: D2 Receptor Binding in Patients with Migraine

Abstract

Keywords

Introduction

Patients and methods

Collection of blood samples

Preparation of platelet membrane

Platelet counts

Receptor binding assay

Assay of 3H-siperone binding to platelet membranes

Assay of protein content

Chemicals and source

Data analysis

Statistical analysis

Results

Discussion

References

Assay of ³H-siperone binding to platelet membranes