Characterization of ligand binding properties of the 5-HT1D receptors cloned from chimpanzee, gorilla and rhesus monkey in comparison with those from the human and guinea pig receptors

'I Get High With a Little Help From My Friends' - How Raves Can Invoke Identity Fusion and Lasting Co-operation via Transformative Experiences

Psychoactive drugs have been central to many human group rituals throughout modern human evolution. Despite such experiences often being inherently social, bonding and associated prosocial behaviors have rarely been empirically tested as an outcome. Here we investigate a novel measure of the mechanisms that generate altered states of consciousness during group rituals, the 4Ds: dance, drums, sleep deprivation, and drugs. We conducted a retrospective online survey examining experiences at a highly ritualized cultural phenomenon where drug use is relatively uninhibited- raves and illegal free parties. Engaging in the 4Ds at raves or free parties was associated with personal transformation for those who experienced the event as awe-inspiring, especially for people with open personalities (n = 481). Without awe, or a ritual context, indulging in the 4Ds was associated with a lack of personal growth, or anomie. A complex SEM revealed that personal transformation following awe-inspiring raves was associated with bonding to other ravers and prosocial behavior toward this group at a cost to self in a simple economic game. Bonding to humanity was not associated with these events. The findings suggest that employing the 4Ds in a ritualized environment - particularly dancing and drug use - can help build meaningful social bonds with associated positive behavioral outcomes.

Introduction: Evidence for entheogen use in prehistory and world religions

This introduction to the special issue reviews research that supports the hypothesis that psychedelics, particularly psilocybin, were central features in the development of religion. The greater response of the human serotonergic system to psychedelics than is the case for chimpanzees’ serotonergic receptors indicates that these substances were environmental factors that affected hominin evolution. These substances also contributed to the evolution of ritual capacities, shamanism, and the associated alterations of consciousness. The role of psilocybin mushrooms in the ancient evolution of human religions is attested to fungiform petroglyphs, rock artifacts, and mythologies from all major regions of the world. This prehistoric mycolatry persisted into the historic era in the major religious traditions of the world, which often left evidence of these practices in sculpture, art, and scriptures. This continuation of entheogenic practices in the historical world is addressed in the articles here. But even through new entheogenic combinations were introduced, complex societies generally removed entheogens from widespread consumption, restricted them in private and exclusive spiritual practices of the leaders, and often carried out repressive punishment of those who engaged in entheogenic practices.

The Mechanisms of Psychedelic Visionary Experiences: Hypotheses from Evolutionary Psychology

Neuropharmacological effects of psychedelics have profound cognitive, emotional, and social effects that inspired the development of cultures and religions worldwide. Findings that psychedelics objectively and reliably produce mystical experiences press the question of the neuropharmacological mechanisms by which these highly significant experiences are produced by exogenous neurotransmitter analogs. Humans have a long evolutionary relationship with psychedelics, a consequence of psychedelics' selective effects for human cognitive abilities, exemplified in the information rich visionary experiences. Objective evidence that psychedelics produce classic mystical experiences, coupled with the finding that hallucinatory experiences can be induced by many non-drug mechanisms, illustrates the need for a common model of visionary effects. Several models implicate disturbances of normal regulatory processes in the brain as the underlying mechanisms responsible for the similarities of visionary experiences produced by psychedelic and other methods for altering consciousness. Similarities in psychedelic-induced visionary experiences and those produced by practices such as meditation and hypnosis and pathological conditions such as epilepsy indicate the need for a general model explaining visionary experiences. Common mechanisms underlying diverse alterations of consciousness involve the disruption of normal functions of the prefrontal cortex and default mode network (DMN). This interruption of ordinary control mechanisms allows for the release of thalamic and other lower brain discharges that stimulate a visual information representation system and release the effects of innate cognitive functions and operators. Converging forms of evidence support the hypothesis that the source of psychedelic experiences involves the emergence of these innate cognitive processes of lower brain systems, with visionary experiences resulting from the activation of innate processes based in the mirror neuron system (MNS).

Recognition properties and competitive assays of a dual dopamine/serotonin selective molecularly imprinted polymer

A molecularly imprinted polymer (MIP) with dual dopamine/serotonin-like binding sites (DS-MIP) was synthesized for use as a receptor model of study the drug-interaction of biological mixed receptors at a molecular level. The polymer material was produced using methacrylic acid (MAA) and acrylamide (ACM) as functional monomers, N,N′-methylene bisacrylamide (MBAA) as cross-linker, methanol/water mixture (4:1, v/v) as porogen and a mixture of dopamine (D) and serotonin (S) as templates. The prepared DS-MIP exhibited the greatest rebinding of the template(s) in aqueous methanol solution with decreased recognition in acetonitrile, water and methanol solvent. The binding affinity and binding capacity of DS-MIP with S were found to be higher than those of DS-MIP with D. The selectivity profiles of DS-MIP suggest that the D binding site of DS-MIP has sufficient integrity to discriminate between species of non-optimal functional group orientation, whilst the S binding site of DS-MIP is less selective toward species having structural features and functional group orientations different from S. The ligand binding activities of a series of ergot derivatives (ergocryptine, ergocornine, ergocristine, ergonovine, agroclavine, pergolide and terguride) have been studied with the DS-MIP using a competitive ligand binding assay protocol. The binding affinities of DS-MIP were demonstrated in the micro- or submicro-molar range for a series of ergot derivatives, whereas the binding affinities were considerably greater to natural receptors derived from the rat hypothalamus. The DS-MIP afforded the same pattern of differentiation as the natural receptors, i.e. affinity for the clavines > lysergic acid derivatives > ergopeptines. The results suggest that the discrimination for the ergot derivatives by the dopamine and serotonin sites of DS-MIP is due to the structural features and functional orientation of the phenylethylamine and indolylethylamine entities at the binding sites, and the fidelity of the dopamine and serotonin imprinted cavities.

Naphthyl piperazines with dual activity as 5-HT1D antagonists and 5-HT reuptake inhibitors

SAR around a known molecule with dual 5-HT(1D) antagonist and 5-HT(transporter) inhibitory activity has led to the discovery of molecules with improved dual activity and reduced cross-reactivity toward other aminergic receptors (5-HT(1B), alpha(1), and D(2)).

Serotonin receptor ligands: treatments of acute migraine and cluster headache

Fuelled by the development of the serotonin 5-HT(1B/1D) receptor agonists, the triptans, the last 15 years has seen an explosion of interest in the treatment of acute migraine and cluster headache. Sumatriptan was the first of these agonists, and it launched a wave of therapeutic advances. These medicines are effective and safe. Triptans were developed as cranial vasoconstrictors to mimic the desirable effects of serotonin, while avoiding its side-effects. It has subsequently been shown that the triptans' major action is neuronal, with both peripheral and central trigeminal inhibitory effects, as well as actions in the thalamus and at central modulatory sites, such as the periaqueductal grey matter. Further refinements may be possible as the 5-HT(1D) and 5-HT(1F) receptor agonists are explored. Serotonin receptor pharmacology has contributed much to the better management of patients with primary headache disorders.

New targets in acute migraine treatment

Migraine is a common and highly disabling neurological problem, whose acute treatment was revolutionized by the triptans, serotonin 5-HT1B/1D receptor agonists. Some patients do not respond to triptans, while others are not suitable for them largely because of contraindications based on vascular disease. The exploration of nonvasoconstrictor treatments for acute migraine offers the prospect of dramatic improvements in patient care, as well as important insights into the mechanisms of migraine. Possibilities for such developments include, calcitonin gene-related peptide receptor antagonists, serotonin 5-HT1F and 5-HT1D receptor agonists, glutamate excitatory amino acid receptor antagonists, nitric oxide synthase inhibitors and adenosine A1 receptor agonists. Taken together, the future for migraine and affected patients is bright and promising.

Can we Develop Neurally Acting Drugs for the Treatment of Migraine?

Serotonin (5-HT)(1B/1D) receptor agonists, which are also known as triptans, represent the most important advance in migraine therapeutics in the four millennia that the condition has been recognized. The vasoconstrictive activity of triptans produced a small clinical penalty in terms of coronary vasoconstriction but also raised an enormous intellectual question: to what extent is migraine a vascular problem? Functional neuroimaging and neurophysiological studies have consistently developed the theme of migraine as a brain disorder and, therefore, demanded that the search for neurally acting antimigraine drugs should be undertaken. The prospect of non-vasoconstrictor acute migraine therapies, potential targets for which are discussed here, offers a real opportunity to patients and provides a therapeutic rationale that places migraine firmly in the brain as a neurological problem, where it undoubtedly belongs.

New targets in the acute treatment of headache

PURPOSE OF REVIEW

The aim of this article is to review recently identified targets for the acute treatment of primary headache disorders.

RECENT FINDINGS

Calcitonin gene-related peptide (CGRP) receptor blockade has been shown to be an effective acute anti-migraine strategy and is a non-vasoconstrictor in terms of the mechanism of action. It is likely that direct blockade of CGRP release by inhibition of trigeminal nerves would be similarly effective in both migraine and cluster headache. Options for acute treatment based on preclinical work and initial clinical studies include: serotonin 5HT1F and 5HT1D receptor agonists, glutamate excitatory amino acid receptor antagonists, nitric oxide synthase inhibitors and adenosine A1 receptor agonists. Proof of principle studies with octreotide, a somatostatin receptor agonist, demonstrated it to be better than placebo in the acute treatment of cluster headache but not in the acute management of migraine.

SUMMARY

The prospect of a non-vasoconstrictor acute migraine therapy offers a real opportunity to patients, and perhaps more importantly, provides a therapeutic rationale to plant migraine and cluster headache firmly in the brain as neurological problems.

Post-triptan era for the treatment of acute migraine

There now is one realized and several attractive targets for the treatment of acute attacks of migraine that will follow and augment the use of serotonin 5-HT1B/1D receptor agonists, the triptans. Calcitonin gene-related peptide (CGRP) receptor blockade recently has been shown to be an effective acute antimigraine strategy; therefore, blockade of CGRP release by inhibition of trigeminal nerves would seem a logical approach. A number of targets are reviewed in this article including serotonin 5-HT1F and 5-HT1D receptors, adenosine A1 receptors, nociceptin, vanilloid TRPV1 receptors, and anandamide CB1 receptors. Development of one or more such compound offers the exciting prospect of new non-vasoconstrictor treatments for migraine and cluster headache.

Evidence for serotonin (5-HT)1B, 5-HT1D and 5-HT1F receptor inhibitory effects on trigeminal neurons with craniovascular input

Development of serotonin (5HT(1B/1D)) agonists for the acute attack of migraine resulted in considerable interest in their action. The superior sagittal sinus (SSS) was isolated in alpha-chloralose (60 mg/kg, i.p. and 20 mg/kg i.v.i. supplementary 2 hourly) anaesthetised cats. The SSS was stimulated electrically (100 V, 250 micros duration, 0.3 Hz) and neurons of the trigeminocervical complex monitored using electrophysiological methods. To test 5-HT(1B) receptor-mediated activity common carotid blood flow (CCF) was monitored with a transonic flow probe placed around the vessel. Naratriptan (5-HT(1B/1D/1F) receptor agonist) and alniditan (5-HT(1B/1D) receptor agonist) produced reductions in carotid blood flow of 38+/-5% and 42+/-6%, respectively. These effects were attenuated by the 5-HT(1B) receptor antagonist SB224289 (P<0.05). LY344864 (5-HT(1F) receptor agonist) had no effect on CCF. Naratriptan inhibited SSS-evoked activity (61+/-7%), an effect partially inhibited by the 5-HT(1B) receptor antagonist SB224289 (30+/-5%), or by the 5-HT(1D) receptor antagonist BRL-15572 (37+/-6%). There remained an inhibitory effect of naratriptan after both 5-HT(1B) and 5-HT(1D) receptor blockade (22+/-5%). Alniditan inhibited SSS-evoked trigeminal activity (53+/-6%), an effect abolished after 5-HT(1B) and 5-HT(1D) receptor blockade. LY344864 (5-HT(1F) receptor agonist) inhibited SSS-evoked trigeminal activity (28+/-5%), an effect unaltered by either SB224289 or BRL-15572. It can be concluded that there are inhibitory 5-HT(1B), 5-HT(1D) and 5-HT(1F) receptors in the trigeminocervical complex of the cat. 5-HT(1B) receptor-mediated inhibition is the most potent of the three in terms of inhibition of trigeminovascular nociceptive traffic.

Discovery of a protein sequence in the N-terminal region of the human neuronal alpha7 nicotinic acetylcholine receptor involved in homomeric interactions

The neuronal nicotinic acetylcholine receptor subunit, alpha7, can form homopentameric receptor/ion channel complexes. Potential contributions of its N-terminal region to homomeric interactions were investigated, in comparison with the corresponding region of an analogous heteromeric subunit, alpha3. Recombinant chimeras were prepared upon engineering the N-terminal alpha7 (M1-V224) or alpha3 (M1-S232) sequence into the background of another homomeric mouse 5-hydroxytryptamine3 (5-HT)(3) receptor. The alpha7/5-HT(3) chimera, when expressed heterologously in a human epithelial cell line, SH-EP1, robustly expressed alpha-bungarotoxin binding sites as homooligomers while the alpha3/5-HT(3) did not produce epibatidine (non-selective ligand) binding sites, and did not interfere the alpha7/5-HT3 phenotype, upon co-expression. Yeast two hybrid assays with the N-terminal regions showed positive responses between alpha7:alpha7, but not between alpha7:alpha3 and alpha3:alpha3. Similar assays with the alpha7 N-terminal region and its five smaller fragments (G23-N46, D47-N90, V91-N133, S134-M182and Q183-V224) revealed that the G23-N46 sequence is involved in homomeric interactions. Replacement of the corresponding region of the alpha3/5-HT(3) chimera with the alpha7 G23-N46 sequence conferred a dominant negative role on the chimera, by abolishing the alpha7/5-HT(3) phenotype. These results support the view that the G23-N46 portion of the alpha7 N-terminal region may contribute to receptor homooligomerizations.

Neurogenic inflammation in the context of migraine

Despite considerable research into the pathogenesis of idiopathic headaches, such as migraine, the pathophysiological mechanisms underlying them remain poorly understood. Although it is well established that the trigeminal nerve becomes activated during migraine, the consequences of this activation remain controversial. One theory, based on preclinical observations, is that activation of trigeminal sensory fibers leads to a painful neurogenic inflammation within the meningeal (dural) vasculature mediated by neuropeptide release from trigeminal sensory fibres and characterized by plasma protein extravasation, vasodilation, and mast cell degranulation. Effective antimigraine agents such as ergots, triptans, opioids, and valproate inhibit preclinical neurogenic dural extravasation, suggesting that this activity may be a predictor of potential clinical efficacy of novel agents. However, several clinical trials with other agents that inhibit this process preclinically have failed to show efficacy in the acute treatment of migraine in man. Alternatively, it has been proposed that painful neurogenic vasodilation of meningeal blood vessels could be a key component of the inflammatory process during migraine headache. This view is supported by the observation that jugular plasma levels of the potent vasodilator, calcitonin gene-related peptide (CGRP) are elevated during the headache and normalized by successful sumatriptan treatment. Preclinically, activation of trigeminal sensory fibers evokes a CGRP-mediated neurogenic dural vasodilation, which is blocked by dihydroergotamine, triptans, and opioids but unaffected by NK1 receptor antagonists that failed in clinical trials. These observations suggest that CGRP release with associated neurogenic dural vasodilation may be important in the generation of migraine pain, a theory that would ultimately be tested by the clinical testing of a CGRP receptor antagonist.

The pharmacology of headache

Headache is a common problem which besets most of us at some time or the other. The pharmacology of headache is complex in an overall sense but can be understood in terms of the anatomy and physiology of the pain-producing structures. Migraine can be used as a template to understand the activation of nociceptive systems in the head and thus their neurotransmitter mediation and modulation. In recent years, the role of serotonin (5-HT) in headache pharmacology has been unravelled in the context of both understanding its role in the nociceptive systems related to headache and by exploiting its 5-HT1 receptor subtypes in headache therapeutics. The pharmacology of the head pain systems, as they are known and as they might evolve, are explored in the context of both, the anatomy and physiology of trigeminovascular nociception and in the context of clinical questions, such as those of efficacy, headache recurrence and adverse events.

Molecular cloning, sequence analysis and pharmacological properties of the porcine 5-HT(1D) receptor

A cDNA encoding the full-length 5-HT(1D) receptor derived from porcine cerebral cortex was amplified, cloned and sequenced, using guinea-pig 5-HT(1D) receptor coding sequence oligonucleotide primers in reverse transcription-polymerase chain reaction (RT - PCR). The 5' and 3' ends of the porcine 5-HT(1D) receptor cDNA were verified by inverse PCR. Sequence analysis of porcine 5-HT(1D) receptor cDNA revealed an open reading frame of 1134 nucleotides encoding a polypeptide of 377 amino acids having 92% homology with the human 5-HT(1D) receptor and 88 - 90% homology with other species homologues. The porcine 5-HT(1D) receptor cDNA was further subcloned into a mammalian expression vector pcDNA3 and expressed in monkey Cos-7 cells. Radioligand binding assays using either [(3)H]-5-CT or [(3)H]-GR125743 on Cos-7 cell membranes showed that pK(i) values of 14 serotonin ligands were highly correlated with those obtained with the human 5-HT(1D) receptor. Nonetheless, a selective antagonist at the human 5-HT(1D) receptor, BRL15572, only poorly recognized the porcine homologue. Using membranes from cells co-expressing the porcine 5-HT(1D) receptor and rat G(alphail)Cys(351) Ile protein, it was shown that 5-HT and zolmitriptan increased, while ketanserin decreased basal [(35)S]-GTPgammaS binding. The potency of zolmitriptan in the [(35)S]-GTPgammaS binding assay (pEC(50): 8. 46+/-0.08) agreed with its affinity in displacing the radioligands [(3)H]-5-CT and [(3)H]-GR125743 (pK(i): 8.38+/-0.15 and 8.67+/-0.08, respectively). In conclusion, we have established the cDNA sequence and pharmacology of the cloned porcine 5-HT(1D) receptor. This information would be useful in exploring the role of divergent amino acid residues in the receptor-ligand interaction as well as the role of 5-HT(1D) receptor in pathophysiological processes relevant for novel drug discovery in diseases such as migraine.

Advantages of heterologous expression of human D2long dopamine receptors in human neuroblastoma SH-SY5Y over human embryonic kidney 293 cells

The human D2long dopamine receptor when expressed heterologously in a human neuronal cell line, SH-SY5Y, produced more robust functional signals than when expressed in a human embryonic kidney cell line, HEK293. Quinpirole (agonist)-induced GTPgamma(35)S binding and high affinity sites were 3 - 4 fold greater in SH-SY5Y than in HEK293 cells. N-type Ca(2+) channel currents present in SH-SY5Y cells, but not HEK293 cells, were inhibited potently by quinpirole with a half-maximal inhibitory concentration of 0.15+/-0.03 nM. Inhibition of adenylyl cyclases by agonists, on the other hand, was of similar potency and efficacy in the two cell lines. GTPgamma(35)S-Bound Galpha subunits from quinpirole-activated and solubilized membranes were monitored upon immobilization with various Galpha-specific antibodies. Galpha(i) and Galpha(o) subunits were highly labelled with GTPgamma(35)S in SH-SY5Y cells, but only Galpha(i) subunits were labelled in HEK293 cells. The additional G(o) coupling in SH-SY5Y cells could arise, at least in part, from the presence of G(o) coupled-effectors, such as the N-type Ca(2+) channel, and may contribute to robust agonist-induced GTPgamma(35)S binding, which is a reliable means for measuring ligand intrinsic efficacy. It appears that expression of neuronal G protein-coupled receptors in neuronal environments could reveal additional functional characteristics that are absent in non-neuronal cell lines. This appears to be due to, at least in part, to the presence of neuron-specific effectors. These findings underscore the importance of the cellular environment in which drug actions are examined, particularly in the face of intensive efforts to develop drugs for G protein-coupled receptors of various origins.

Agonist-induced GTPgamma35S binding mediated by human 5-HT(2C) receptors expressed in human embryonic kidney 293 cells

The 5-HT(2C) receptor as heterologously expressed in various mammalian cells mediates inositol 1,4,5-triphosphate (IP(3)) signal by activating G(q/11) subtypes of G proteins, but minimally promotes agonist-induced GTPgamma35S binding in membranes due to slow GTP turnover rates of the G proteins. Here we discovered robust (over 200%) agonist-induced GTPgamma35S binding mediated by the human receptor expressed in human embryonic kidney (HEK) 293 cells, and investigated its pharmacology. Agonists concentration-dependently increased GTPgamma35S binding in isolated membranes, which was competitively blocked by antagonists. Intrinsic efficacies of agonists from GTPgamma35S binding were comparable to those from IP(3) measurement. Pertussis toxin treatment largely blocked serotonin-induced GTPgamma35S binding, serotonin high affinity sites by 70% without altering the total binding sites, and reduced IP(3) release by 40%. GTPgamma35S-bound Galpha subunits from serotonin-activated membranes were mainly Galpha(i), judging from immobilization studies with various Galpha-specific antibodies. Inhibition of forskolin-stimulated cAMP formation, however, was not observed. Apparently, the 5-HT(2C) receptor-mediated GTPgamma35S binding is a unique phenotype observed in HEK293 cells, reflecting its coupling to pertussis toxin-sensitive G(i) subtypes, which contribute to the IP(3) signal, along with pertussis toxin-insensitive G(q/11) subtypes.

Efficient functional coupling of the human D3 dopamine receptor to G(o) subtype of G proteins in SH-SY5Y cells

1 The D3 dopamine receptor presumably activates Gi/Go subtypes of G-proteins, like the structurally analogous D2 receptor, but its signalling targets have not been clearly established due to weak functional signals from cloned receptors as heterologously expressed in mostly non-neuronal cell lines. 2 In this study, recombinant human D3 receptors expressed in a human neuroblastoma cell line, SH-SY5Y, produced much greater signals than those expressed in a human embryonic kidney cell line, HEK293. Quinpirole, a prototypic agonist, markedly inhibited forskolin-stimulated cyclic AMP production and Ca2+-channel (N-type) currents in SH-SY5Y cells, and enhanced GTPgamma35S binding in isolated membranes, nearly ten times greater than that observed in HEK293 cell membranes. 3 GTPgamma35S-bound Galpha subunits from quinpirole-activated and solubilized membranes were monitored upon immobilization with various Galpha-specific antibodies. Galphao subunits (not Galphai) were highly labelled with GTPgamma35S in SH-SY5Y, but not in HEK293 cell membranes, despite their abundance in the both cell types, as shown with reverse transcription-polymerase chain reaction and Western blots. N-type Ca2+ channels and adenylyl cyclase V (D3-specific effector), on the other hand, exist only in SH-SY5Y cells. 4 More efficient coupling of the D3 receptor to Go subtypes in SH-SY5Y than HEK293 cells may be attributed, at least in part, to the two D3 neuronal effectors only present in SH-SY5Y cells (N-type Ca2+-channels and adenylyl cyclase V). The abundance of Go subtypes in the both cell lines seems to indicate their availability not a limiting factor.

Differential pharmacology between the guinea-pig and the gorilla 5-HT1D receptor as probed with isochromans (5-HT1D-selective ligands)

1. Both the 5-HT1D and 5-HT1B receptors are implicated in migraine pathophysiology. Recently isochromans have been discovered to bind primate 5-HT1D receptors with much higher affinity than 5-HT1B receptors. In the guinea-pig, a primary animal model for anti-migraine drug testing, however, isochromans bound the 5-HT1D receptor with lower affinity than the gorilla receptor. 2. This species-specific pharmacology was investigated, using site-directed mutagenesis on cloned guinea-pig receptors heterologously expressed in human embryonic kidney 293 cells. Mutations of threonine 100 and arginine 102 at the extracellular side of transmembrane II of the guinea-pig 5-HT1D receptor to the corresponding primate residues, isoleucine and histidine, respectively, enhanced its affinity for isochromans to that of the gorilla receptor, with little effects on its affinities for serotonin, sumatriptan and metergoline. Free energy change from the R102H mutation was about twice as much as that from the T100I mutation. 3. For G protein-coupling, serotonin marginally enhanced GTPgamma35S binding in membranes expressing the guinea-pig 5-HT1D receptor and its mutants, but robustly in membranes expressing the gorilla receptor. Sumatriptan enhanced GTPgamma35S binding in the latter nearly as much as serotonin, and several isochromans by 30-60% of serotonin. 4. We discovered key differences in the function and binding properties of guinea-pig and gorilla 5-HT1D receptors, and identified contributions of I100 and H102 of primate 5-HT1D receptors to isochroman binding. Among common experimental animals, only the rabbit shares I100 and H102 with primates, and could be useful for studying isochroman actions in vivo.