Vanilloid Receptor VR1 Research Articles

Use of vanilloids in urologic disorders.

The bladder is an organ rich in vanilloid targets: dense unmyelinated c-fibers partially responsible for bladder sensation and response to noxious stimuli. Drugs such as capsaicin and resiniferatoxin (RTX) interact with the VR1 vanilloid receptor subtype to initially excite then subsequently desensitize the c-fibers. This chapter examines the literature describing the use of vanilloid receptor agonists in the treatment of the following urological disorders: neurogenic bladder (NGB), overactive bladder (OAB), and interstitial cystitis/painful bladder syndrome (IC/PBS). Review of the literature was performed using Pubmed and the following key words "capsaicin," "resiniferatoxin (RTX)," and "neurogenic bladder," "overactive bladder (OAB)," and "interstitial cystitis," "painful bladder syndrome." Articles focusing on randomized trials comparing intravesical administration of a vanilloid receptor agonist to placebo and those in English were reviewed. We conclude that capsaicin and RTX do appear to provide some acceptable treatment results in patients with neurogenic bladder, though larger studies are needed to confirm this. Although efficacy has been shown in some studies, currently the use of vanilloids cannot be recommended for routine use in patients with OAB as the need for catheterization may cause the risk to outweigh the benefit of treatment. Similarly, for the treatment of BPS, vanilloid receptor agonists lack strong evidence for efficacy or tolerability; larger studies are needed to define their role. Understanding how vanilloids are able to impact these disorders, however, may help further elucidate their underlying pathophysiological processes.

New satiety hormone nesfatin-1 protects gastric mucosa against stress-induced injury: Mechanistic roles of prostaglandins, nitric oxide, sensory nerves and vanilloid receptors

Nesfatin-1 belongs to a family of anorexigenic peptides, which are responsible for satiety and are identified in the neurons and endocrine cells within the gut. These peptides have been implicated in the control of food intake; however, very little is known concerning its contribution to gastric secretion and gastric mucosal integrity. In this study the effects of nesfatin-1 on gastric secretion and gastric lesions induced in rats by 3.5h of water immersion and restraint stress (WRS) were determined. Exogenous nesfatin-1 (5–40μg/kg i.p.) significantly decreased gastric acid secretion and attenuated gastric lesions induced by WRS, and this was accompanied by a significant rise in plasma NUCB2/nefatin-1 levels, the gastric mucosal blood flow (GBF), luminal NO concentration, generation of PGE2 in the gastric mucosa, an overexpression of mRNA for NUBC2 and cNOS, as well as a suppression of iNOS and proinflammatory cytokine IL-1β and TNF-α mRNAs. Nesfatin-1-induced protection was attenuated by suppression of COX-1 and COX-2 activity, the inhibition of NOS with L-NNA, the deactivation of afferent nerves with neurotoxic doses of capsaicin, and the pretreatment with capsazepine to inhibit vanilloid VR1 receptors. This study shows for the first time that nesfatin-1 exerts a potent protective action in the stomach of rats exposed to WRS and these effects depend upon decrease in gastric secretion, hyperemia mediated by COX-PG and NOS-NO systems, the activation of vagal and sensory nerves and vanilloid receptors.

Chronic Opioid Potentiates Presynaptic but Impairs Postsynaptic N-Methyl-d-aspartic Acid Receptor Activity in Spinal Cords: IMPLICATIONS FOR OPIOID HYPERALGESIA AND TOLERANCE

Chronic Opioid Potentiates Presynaptic but Impairs Postsynaptic N-Methyl-d-aspartic Acid Receptor Activity in Spinal Cords: IMPLICATIONS FOR OPIOID HYPERALGESIA AND TOLERANCE

Enantioselective synthesis of 3( S)-hydroxy polygodial derivatives and evaluation of their vanilloid activity

The enantioselective synthesis of 3( S)-hydroxy polygodial and its acetyl derivative is described. The construction of the 3-hydroxy drimane skeleton was based on the titanium-catalyzed radical cyclization of (10 S)-10, 11-epoxy-farnesyl acetate. Only underivatized 3( S)-hydroxy polygodial showed activity in assays on VR1 vanilloid receptor in HEK cells transfected with the human VR1.

Design principles of sensory receptors

EDITORIAL article Front. Cell. Neurosci., 07 July 2010Sec. Cellular Neurophysiology Volume 4 - 2010 | https://doi.org/10.3389/fncel.2010.00025

P6.4 Autonomic neurons expressing cannabinoid and vanilloid receptors in postnatal development

Cannabinoids are cell membrane-derived signalling molecules that are released from nerves, blood cells and endothelial cells, and have diverse biological effects. Endogenous cannabinoids and their cannabinoid CB1 and CB2 receptors, are present from the early stages of gestation and play a number of vital roles for the developing organism. The majority of afferent neurons have vanilloid VR1 receptors. The aim of this work was to immunocytochemically investigate the development of the neurons containing CB1, CB2 and VR1 receptors in the nodose ganglion of vagus nerve (GNVN), in the spinal ganglia (SG) and sympathetic ganglia of rats of different ages.

CB1 Cannabinoid Receptor Inhibition: Promising Approach for Heart Failure?

Endocannabinoids are part of a novel signaling system, along with their cellular receptors and several proteins implicated in their synthesis, release, transport, and degradation. The endocannabinoids are endogenous lipid mediators generated by almost all cell types both in the brain and in the peripheral tissues, which have a wide range of biological effects similar to those of marijuana. 2-Arachidonoylglycerol and arachidonoyl ethanolamide (anandamide) are the 2 best characterized endocannabinoids. Their effects are mediated by 2 G protein–coupled receptors, CB1 and CB2, as well as additional, as-yet unidentified ones.1 2-Arachidonoylglycerol binds to both CB2 and CB1 receptors, whereas arachidonoyl ethanolamide has higher affinity for CB1 receptors and may also bind to vanilloid VR1 receptors. The tissue levels of endocannabinoids are determined by the balance between their biosynthesis (involving phospholipase D– and diacyl-glycerol lipase–dependent and other pathways), cellular uptake, and degradation by fatty acid amide hydrolase and/or monoacylglycerol lipases.1,2 Both CB2 and CB1 receptors are negatively coupled to adenylate cyclase through Gi/o proteins but can also signal via protein kinases A and C, mitogen-activated protein kinases, and cyclooxygenase 2 pathways, among others.1,3 The CB1 receptor is widely distributed in the central nervous system1 and at lower levels in various peripheral tissues (eg, myocardium,4–6 human coronary artery endothelial and smooth muscle cells,7,8 adipose tissue,9,10 and the liver10–12). Initially it was thought that CB2 receptors were expressed only in immune and hematopoietic cells, but recent studies have also established their presence in the myocardium,6 human coronary endothelial and smooth muscle cells,7,8 brain,13 and liver.12 Modulation of the endocannabinoid system (ECS) may be therapeutically exploited in various cardiovascular (CV) disorders ranging from circulatory shock, stroke, atherosclerosis and restenosis, and hypertension, to cirrhotic cardiomyopathy, myocardial infarction, and chronic heart failure.1,14,15

TRPV1 Gene Required for Thermosensory Transduction and Anticipatory Secretion from Vasopressin Neurons during Hyperthermia

Increases in core body temperature promote thermoregulatory cooling by stimulating sweat production and preemptive renal water reabsorption through the release of vasopressin (VP, antidiuretic hormone). The mechanism by which the hypothalamus orchestrates this anticipatory VP release during hyperthermia is unknown but has been linked to a central thermosensory mechanism. Here, we report that thermal stimuli spanning core body temperatures activate a calcium-permeable, ruthenium red- and SB366791-sensitive nonselective cation conductance in hypothalamic VP neurons. This response is associated with a depolarizing receptor potential and an increase in action potential firing rate, indicating that these neurons are intrinsically thermosensitive. The thermosensitivity of VP neurons isolated from trpv1 knockout (Trpv1(-/-)) mice was significantly lower than that of wild-type counterparts. Moreover, Trpv1(-/-) mice showed an impaired VP response to hyperthermia in vivo. Channels encoded by the trpv1 gene thus confer thermosensitivity in central VP neurons and contribute to the thermal control of VP release in vivo.

The anandamide transport inhibitor AM404 reduces ethanol self‐administration

The endocannabinoid system mediates in the pharmacological actions of ethanol and genetic studies link endocannabinoid signaling to alcoholism. Drugs activating cannabinoid CB1 receptors have been found to promote alcohol consumption but their effects on self-administration of alcohol are less clear because of the interference with motor performance. To avoid this problem, a novel pharmacological approach to the study of the contribution of the cannabinoid system in alcoholism may be to use drugs that locally amplify the effects of alcohol on endogenous cannabinoids. In the present study we addressed this model by studying the effects of the anandamide transport inhibitor N-(4-hydroxyphenyl) arachidonoyl-ethanolamide (AM404) on both ethanol self-administration and reinstatement of alcohol-seeking behavior in rats. The results show that AM404 significantly reduced ethanol self-administration in a dose-dependent manner but failed to modify reinstatement for lever pressing induced by the stimulus associated with alcohol. This effect was not due to a motor depressant effect and was not related to a decrease in general motivational state, as it was not effective in other reward paradigms such as lever pressing for a saccharin solution. The mechanism of action of AM404 does not involve cannabinoid CB1 receptors as the CB1-selective antagonist SR141716A did not block the reduction of ethanol self-administration induced by the anandamide uptake blocker. Moreover, 3-(1,1-dimethylheptyl)-(-)-11-hydroxy-delta 8-tetrahydrocannabinol (HU-210), a classical cannabinoid receptor agonist, did not affect ethanol self-administration. The effects of AM404 are not mediated by either vanilloid VR1 receptors or cannabinoid CB2 receptors because it is not antagonized by either the VR1 receptor antagonist capsazepine or the CB2 antagonist AM630. These results indicate that AM404 may be considered as an innovative approach to reduce alcohol consumption.

Enantioselective synthesis of 1-( R)-hydroxypolygodial and its 9α epimer, 1-( R)-hydroxyisotadeonal

The enantioselective synthesis of 1-( R)-hydroxypolygodial and its epimer at C-9 is described. α-Ionone was the starting material. Key steps of these syntheses included a Corey–Bakshi–Shibata oxazaborolidine-mediated reduction and a stereoselective Diels–Alder reaction. No vanilloid activity was detected for both compounds in assays on VR1 vanilloid receptor in HEK cells transfected with the human VR1.

Reduced Anxiety, Conditioned Fear, and Hippocampal Long-Term Potentiation in Transient Receptor Potential Vanilloid Type 1 Receptor-Deficient Mice

The transient receptor potential vanilloid type 1 channel (TRPV1) (formerly called vanilloid receptor VR1) is known for its key role of functions in sensory nerves such as perception of inflammatory and thermal pain. Much less is known about the physiological significance of the TRPV1 expression in the brain. Here we demonstrate that TRPV1 knock-out mice (TRPV1-KO) show less anxiety-related behavior in the light-dark test and in the elevated plus maze than their wild-type littermates with no differences in locomotion. Furthermore, TRPV1-KO mice showed less freezing to a tone after auditory fear conditioning and stress sensitization. This reduction of conditioned and sensitized fear could not be explained by alterations in nociception. Also, tone perception per se was unaffected, as revealed by determination of auditory thresholds through auditory brainstem responses and distortion-product otoacoustic emissions. TRPV1-KO showed also less contextual fear if assessed 1 d or 1 month after strong conditioning protocols. These impairments in hippocampus-dependent learning were mirrored by a decrease in long-term potentiation in the Schaffer collateral-commissural pathway to CA1 hippocampal neurons. Our data provide first evidence for fear-promoting effects of TRPV1 with respect to both innate and conditioned fear and for a decisive role of this receptor in synaptic plasticity.

The Endogenous Cannabinoid Anandamide Produces δ-9-Tetrahydrocannabinol-Like Discriminative and Neurochemical Effects That Are Enhanced by Inhibition of Fatty Acid Amide Hydrolase but Not by Inhibition of Anandamide Transport

Anandamide is an endogenous ligand for brain cannabinoid CB(1) receptors, but its behavioral effects are difficult to measure due to rapid inactivation. Here we used a drug-discrimination procedure to test the hypothesis that anandamide, given i.v. or i.p., would produce discriminative effects like those of delta-9-tetrahydrocannabinol (THC) in rats when its metabolic inactivation was inhibited. We also used an in vivo microdialysis procedure to investigate the effects of anandamide, given i.v. or i.p., on dopamine levels in the nucleus accumbens shell in rats. When injected i.v., methanandamide (AM-356), a metabolically stable anandamide analog, produced clear dose-related THC-like discriminative effects, but anandamide produced THC-like discriminative effects only at a high 10-mg/kg dose that almost eliminated lever-press responding. Cyclohexyl carbamic acid 3'-carbamoyl-biphenyl-3-yl ester (URB-597), an inhibitor of fatty acid amide hydrolase (FAAH), the main enzyme responsible for metabolic inactivation of anandamide, produced no THC-like discriminative effects alone but dramatically potentiated discriminative effects of anandamide, with 3 mg/kg anandamide completely substituting for the THC training dose. URB-597 also potentiated the ability of anandamide to increase dopamine levels in the accumbens shell. The THC-like discriminative-stimulus effects of anandamide after URB-597 and methanandamide were blocked by the CB1 receptor antagonist rimonabant, but not the vanilloid VR1 receptor antagonist capsazepine. Surprisingly, the anandamide transport inhibitors N-(4-hydroxyphenyl)-eicosa-5,8,11,14-tetraenamide (AM-404) and N-(3-furylmethyl)eicosa-5,8,11,14-tetraenamide (UCM-707) did not potentiate THC-like discriminative effects of anandamide or its dopamine-elevating effects. Thus, anandamide has THC-like discriminative and neurochemical effects that are enhanced after treatment with a FAAH inhibitor but not after treatment with transport inhibitors, suggesting brain area specificity for FAAH versus transport/FAAH inactivation of anandamide.

Anandamide administration alone and after inhibition of fatty acid amide hydrolase (FAAH) increases dopamine levels in the nucleus accumbens shell in rats

Although endogenous cannabinoid systems have been implicated in the modulation of the rewarding effects of abused drugs and food, little is known about the direct effects of endogenous ligands for cannabinoid receptors on brain reward processes. Here we show for the first time that the intravenous administration of anandamide, an endogenous ligand for cannabinoid receptors, and its longer-lasting synthetic analog methanandamide, increase the extracellular dopamine levels in the nucleus accumbens shell of awake, freely moving rats, an effect characteristic of most drugs abused by humans. Anandamide produced two distinctly different effects on dopamine levels: (1) a rapid, transient increase that was blocked by the cannabinoid CB1 receptor antagonist rimonabant, but not by the vanilloid VR1 receptor antagonist capsazepine, and was magnified and prolonged by the fatty acid amide hydrolase (FAAH) enzyme inhibitor, URB597; (2) a smaller delayed and long-lasting increase, not sensitive to CB1, VR1 or FAAH blockade. Both effects were blocked by infusing either tetrodotoxin (TTX, 1 microm) or calcium-free Ringer's solution through the microdialysis probe, demonstrating that they were dependent on the physiologic activation of dopaminergic neurotransmission. Thus, these results indicate that anandamide, through the activation of the mesolimbic dopaminergic system, participates in the signaling of brain reward processes.

Vanilloid VR1 receptor is involved in rimonabant‐induced neuroprotection

Recently, a potential neuroprotective effect of rimonabant, independent of the CB1 receptor interaction, has been proposed. In the present study, the role of transient receptor potential channel vanilloid subfamily member 1, named VR1, on neuroprotective effect of rimonabant, on global cerebral ischemia in gerbils, was investigated. Rimonabant (0.05-3 mg kg-1), given i.p. 5 min after recirculation, dose dependently antagonized the ischemia-induced decrease in electroencephalographic (EEG) total spectral power and restored relative frequency band distribution 7 days after ischemia. Rimonabant (0.125-0.5 mg kg-1) fully prevented ischemia-induced hyperlocomotion 1 day after ischemia and memory impairment evaluated in a passive avoidance task, 3 days after ischemia. At 7 days after ischemia, the survival of pyramidal cells, in the CA1 subfield, was respectively 91 and 96%, in the animals given rimonabant 0.25 and 0.5 mg kg-1, compared to the vehicle group. Higher doses were not protective. The protection induced by rimonabant followed a bell-shaped curve, the maximal active doses being 0.25 and 0.5 mg kg-1. Capsazepine (0.01 mg kg-1), a selective VR1 vanilloid receptor antagonist, completely reversed rimonabant-induced neuroprotective effects against EEG flattening, memory impairment and CA1 hippocampal neuronal loss. These findings suggest that VR1 vanilloid receptors are involved in rimonabant's neuroprotection even if other mechanisms can contribute to this effect.

The endocannabinoid arachidonyl ethanolamide (anandamide) increases pulmonary arterial pressure via cyclooxygenase-2 products in isolated rabbit lungs

Several cannabinoids elicit systemic vasodilation, mainly via CB1 cannabinoid and vanilloid receptors. However, effects in the pulmonary circulation are unknown. Using the isolated, ventilated, buffer-perfused rabbit lung, we have shown that the endocannabinoids arachidonyl ethanolamide (anandamide) and 2-arachidonyl glycerol (2-AG) dose-dependently increase pulmonary arterial pressure (+19.9 +/- 3.4 mmHg, 5 microM, and +39.5 +/- 10.8 mmHg, 0.4 microM, respectively). 2-AG induced lung edema. The CB1 receptor antagonist AM-251 (0.1 and 5 microM) and the VR1 vanilloid receptor antagonist capsazepine (10 microM) failed to reduce anandamide's effects. The metabolically stable anandamide and 2-AG analogs R-methanandamide and noladin ether, Delta9-tetrahydrocannabinol, and the synthetic cannabinoid HU-210, which is no arachidonic acid product, were without effect. The unspecific cyclooxygenase (COX) inhibitor aspirin (100 microM, P < 0.001) and the specific COX-2 inhibitor nimesulide (10 microM, P < 0.01) completely prevented pulmonary hypertension after 5 microM anandamide. COX-2 RNA was detected in rabbit lungs. The synthetic thromboxane receptor antagonist SQ 29,548 was without effect, but the specific EP1 prostanoid receptor antagonist SC-19220 (100 microM) inhibited the pressure increase after anandamide (P < 0.05). PCR analysis detected fatty acid amidohydrolase (FAAH), an enzyme that degrades endocannabinoids, in rabbit lung tissue. Furthermore, the specific FAAH inhibitor methyl arachidonyl fluorophosphonate (0.1 microM) blocked pressure effects of anandamide (P < 0.01). Finally, anandamide (99 +/- 55 pmol/g) and 2-AG (19.6 +/- 8.4 nmol/g) were found in native lungs. We conclude that anandamide increases pulmonary arterial pressure via COX-2 metabolites following enzymatic degradation by FAAH into arachidonic acid products.

Fluorescent leukotriene B4: potential applications

Leukotriene B4 (LTB4) is a potent lipid mediator of inflammation that acts primarily via a seven-transmembrane-spanning, G-protein-coupled receptor denoted BLT1. Here, we describe the synthesis and characterization of fluorescent analogs of LTB4 that are easy to produce, inexpensive, and without the disadvantages of a radioligand. Fluorescent LTB4 is useful for labeling LTB4 receptors for which no antibodies are available and for performing one-step fluorescence polarization assays conducive to high-throughput screening. We found that orange and green fluorescent LTB4 were full agonists that activated the LTB4 receptor BLT1 with EC50 values of 68 and 40 nM, respectively (4.5 nM for unmodified LTB4). Flow cytometric measurements and confocal imaging showed that fluorescent LTB4 colocalized with BLT1. Fluorescence polarization measurements showed that orange fluorescent LTB4 bound to BLT1 with a Kd of 66 nM and that this binding could be displaced by unlabeled LTB4 and other BLT1-specific ligands. Fluorescent LTB4 analogs were also able to displace tritiated LTB4. Orange fluorescent LTB4 binding to enhanced green fluorescent protein-tagged BLT1 could be observed using fluorescence resonance energy transfer. In addition to being a useful alternative to radiolabeled LTB4, the unique properties of fluorescently labeled LTB4 allow a variety of detection technologies to be used.

Functional Vanilloid Receptor VR1 Is Expressed on Megakaryocytes and Platelets, and Acts as a Sensor for Hypertheimia Generating Endocannabinoids.

Recent investigations have been revealing that platelet can sense shear stress and cold stimulation. These mechanical and physical stimuli alter the platelet functions, including induction of activation and irreversible dysfunction. These data may suggest that platelets, most small-sized cells, can efficiently circulate in the microcirculatory vasculature, and can sense the peripheral physical conditions including temperature.Here we show that human megakaryocytic cell line, MEG-01 and platelets express vanilloid receptor VR1, a receptor for capsaicin. It has been identified that VR1 is linked to thermal sensor, and this can sense hyperthermia around 43 °. Therefore we examined the physiological significance of VR1 expressed on MEG-01 and platelets.First we identified the expression of VR1 on human platelets and MEG-01 by immunoblotting, flowcytometer and RT-PCR, and identified the expression of VR1 on these cells. Hyperthermia stimulation of MEG-01 at 40–43 ° generated a endocannabinoids, 2-arachidonylglycerol(2-AG) and anandamide. Since this effect of hyperthermia stimulation was abolished by the incubation with capsazepine, an antagonistic analogue of capsaicin, it was suggested that the effect of hyperthermia might through VR1. It is well known that 2-AG and anandamide act on their specific receptors, CB1, CB2 and VR1 expressed on various cell-types, and act as an endocannabinoids, and accomplish diverse physiological functions, including vessel dilatation. Hyperthermia stimulation also affected the cell-cycle and induced G1-phase arrest in MEG-01 cells, partially through autocrine manner of generated endocannabinoids by acting of CB1 and CB2 receptors. Moreover prolonged hyperthermia stimulation up to 6 hours induced cellular apoptosis in MEG-01 by releasing cytocrome C and resulting caspase cascade activation.Based on these results, we hypothesize that VR1 on platelets may act as a hyperthermal sensor and generate endocannabinoid, and this may regulate the diverse systems including vessel functions.

The gastrointestinal pharmacology of cannabinoids: an update

Recent work in the field of gastrointestinal pharmacology of cannabinoids has focused on enteric endocannabinoid and endovanilloid systems and their modulation in pathophysiological conditions. CB(1) receptor immunoreactivity was detected on enteric cholinergic neurones and vasoactive intestinal peptide-containing submucosal ganglion cells, on discrete nuclei of the dorsovagal complex (involved in emesis) and on central and peripheral vagal terminals, thus controlling gastroesophageal reflux and gastrointestinal motility. CB(1) receptor activation by endocannabinoids inhibited induced fluid secretion and inflammation in animal models and reduced proliferation of cultured colorectal cancer cells. Endocannabinoids also activate cannabinoid CB(2) and vanilloid VR1 receptors in certain inflammatory states. Thus endocannabinoid metabolism could provide a useful therapeutic target for many gastrointestinal disorders.

Defective Adult Neurogenesis in CB1 Cannabinoid Receptor Knockout Mice

Pharmacological studies suggest a role for CB1 cannabinoid receptors (CB1R) in regulating neurogenesis in the adult brain. To investigate this possibility, we measured neurogenesis by intraperitoneal injection of bromodeoxyuridine (BrdU), which labels newborn neurons, in wild-type and CB1R-knockout (CB1R-KO) mice. CB1R-KO mice showed reductions in the number of BrdU-labeled cells to approximately 50% of wild-type (WT) levels in dentate gyrus and subventricular zone (SVZ), suggesting that CB1R activation promotes neurogenesis. To test this further, WT mice were given the CB1R antagonist N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboximide hydrochloride (SR141716A) before measuring neurogenesis with BrdU. SR141716A paradoxically increased the number of BrdU-labeled cells by approximately 50% in SVZ; another CB1R antagonist, 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-1-piperidinyl-1H-pyrazole-3-carboxamide (AM251), had a similar effect. To investigate this discrepancy, SR141716A was given to CB1R-KO mice, in which it still stimulated neurogenesis, indicating involvement of a non-CB1 receptor. Action at one such non-CB1, SR141716A-sensitive site, the VR1 vanilloid receptor, was tested by administering SR141716A to VR1-KO mice, in which the ability of SR141716A to enhance neurogenesis was abolished. Thus, CB1 and VR1 receptors both seem to have roles in regulating adult neurogenesis.

Basic Science: Prejunctional and Presynaptic Trigeminovascular Targets: What Preclinical Evidence Is There?

Inhibition of trigeminovascular nociceptive traffic by a prejunctional/presynaptic mechanism is an attractive approach for the treatment of migraine. It has been shown that blocking the presumed postsynaptic actions of calcitonin gene‐related peptide (CGRP) is an effective acute antimigraine strategy, so that blockade of CGRP release by presynaptic inhibition also seems promising. A number of targets are reviewed including serotonin 5‐HT1F and 5‐HT1D receptor agonists, adenosine A1 receptor agonists, nociceptin, and vanilloid VR1 receptors. For each, the preclinical rationale for their involvement in prejunctional/presynaptic mechanisms is reviewed. Development of one or more such compounds offers the exciting prospect of new nonvasoconstrictor treatments for migraine and cluster headache.