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Picomole to femtomole per gland/ml levels of 5-methoxytryptamine (5MT) in the pineal gland and serum of the rat and quail were determined, in the absence of a monoamine oxidase inhibitor, by using the ultra-sensitive technique of capillary column gas chromatography/electron-capture negative ion chemical ionization mass spectrometry. Diurnal rhythms of pineal 5MT with high levels at mid-light and low levels at mid-dark were found in both species, while serum 5MT levels showed less or no diurnal variations. The definitive presence of 5MT in the pineal gland and blood circulation provides further evidence that it is potentially a neurohormone. Whether 5MT is implicated in the photoperiodic responses and/or other physiological functions of animals, however, remains to be investigated.

The effects of the 5-HT receptor agonist, 5-methoxytryptamine, on plasma glucose levels were investigated in rats. 5-Methoxytryptamine induced a significant hyperglycemia above the dosage of 1 mg/kg. 5-Methoxytryptamine-induced hyperglycemia was antagonized by pretreatment with the 5-HT1 and 5-HT2 receptor antagonist, methysergide, or the 5-HT2A receptor antagonist, ketanserin, whereas the 5-HT3 and 5-HT4 receptor antagonist, tropisetron, and the 5-HT4 receptor antagonist, SDZ 205-557 (2-methoxy-4-amino-5-chloro-benzoic acid 2-(diethylamino) ethyl ester), showed no effect. In addition, the peripheral 5-HT2 receptor antagonist, xylamidine, reduced 5-methoxytryptamine-induced hyperglycemia. These results suggest that 5-methoxytryptamine-induced hyperglycemia is mediated by the peripheral 5-HT2A receptor, although it has a high affinity for the 5-HT4 receptor. Adrenodemedullation abolished the 5-methoxytryptamine-induced hyperglycemia. 5-Methoxytryptamine did not affect the blood levels of the pancreatic hormones, insulin and glucagon. The hyperglycemia induced by 5-methoxytryptamine was not affected by pretreatment with dexamethasone which inhibits corticosterone release. These results indicate that 5-methoxytryptamine-induced hyperglycemia is elicited by a facilitated adrenaline release from the adrenal gland. Therefore, it is suggested that the 5-HT2A receptor may be partly involved in the pharmacological effects induced by the 5-HT4 receptor agonist, 5-methoxytryptamine. © 1997 Elsevier Science B.V. All rights reserved.

A series of tryptamine analogues has been prepared and tested for their 5-HT1 receptor agonist properties. The incorporation of an alkoxy group at the C-5 position of the indole nucleus resulted in a short-lived and dose-dependent immediate antihypertensive and bradycardic response in anaesthetized spontaneously hypertensive rats (SHR). In addition, a carbomethoxy function at the β-position of the side-chain of the tryptamines significantly increased the mean resting arterial blood pressure (MAP) in pithed rats and also produced contraction of the canine basilar artery in a dose-dependent fashion. Structure-activity relationships (SAR) suggest that the 5-alkoxy group is an important pharmacophore in the production of the antihypertensive effect and that the introduction of a hydroxymethylene group on the side-chain, instead of the carbomethoxy group, changed the receptor affinity profile.

The dinoflagellate Gonyaulax polyedra was previously shown to undergo asexual encystment in response to decreased temperature (15° instead of 20°C rearing temperature) in combination with short-days, a response which can be mimicked by melatonin and, much more efficiently, by 5-methoxytryptamine (= 5-MT). We demonstrate that these cyst-inducing conditions lead to enormous accumulations of the two methoxyindoleamines. The circadian rhythmicity of melatonin is maintained for the two days usually preceding cyst formation, though, at an elevated level. Transiently, very high concentrations of melatonin can occur, eventually exceeding 1 millimolar. These extreme concentrations decay rapidly; during this decline, 5-MT and 5-methoxytryptophol appear in large amounts. The concentrations of 5-MT which are measured during this process are higher than those required for cyst induction by the exogenous indoleamine.

In an attempt to define the role of the pineal hormone melatonin and two analogues (5-methoxytryptamine, 5MT, and 6-hydroxymelatonin, 6HM) in limiting oxidative stress, the present study investigated the changes in glutathione, lipid peroxidation, and the activity of the antioxidant enzyme glutathione peroxidase after exercise (swimming for 60 min) with or without treatment with the indolamines mentioned. Lipid peroxidation was measured by estimating tissue levels of malondialdehyde and 4-hydroxyalkenals; the experimental animals in these studies were male Sprague-Dawley rats. In the liver, swimming exercise increased the levels of reduced glutathione (GSH) and also significantly increasing oxidized glutathione (GSSG), while decreasing the GSH/GSSG ratio, an index directly related to oxidative stress. When the animals were treated with melatonin, the concentrations of GSH and GSSG were also increased after swimming; however, no reduction in the GSH/GSSG ratio appeared. In the animals treated with 6HM the changes were the same as in those treated with melatonin. In muscle as well, the concentration of GSH and the GSH/GSSG ratio were decreased following 60 min of swimming. Pretreatment of the rats with melatonin prevented these effects. Pretreatment of the rats with both 5MT and 6HM also prevented the changes. Brain GSH/GSSG ratio was not affected by either exercise or indolamine administration. Swimming enhanced lipid peroxidation in the liver, muscle and brain; however, this was prevented in animals treated with melatonin or 6HM before swimming. Glutathione peroxidase was significantly elevated after exercise in the brain but not in the liver and muscle. It is concluded that swimming imposes a severe oxidative stress and suggests that melatonin and, to a lesser degree, 5MT and 6HM confer protection against the oxidative damage associated with swimming for 60 min. This mechanism may be reasonably attributed to their indole structure, which possibly allows these molecules to act as free-radical scavengers.

In 1999, a new synthetic tryptamine, 5-MeO-DIPT, became known as a street drug, with the street name of "Foxy" or "Foxy Methoxy". By February 2003, the DEA reported law enforcement seizures and/or reports of abuse in 12 states. We report a case along with an analysis of poison center data on this new drug of abuse.A 19-year-old male was brought to the emergency department following ingestion of a larger than his usual dose of Foxy. Upon arrival, he had hallucinations, hypertension, tachycardia, mydriasis, and catalepsy. Symptoms resolved within two hours after administration of lorazepam and he recovered uneventfully.The AAPCC TESS database contained 41 exposures to "Foxy" between April, 2002 and June, 2003; 26 had moderate or major effects, indicating this drug has significant toxic potential. Given the expanding use of this and other club drugs, the spectrum of toxicity from this new agent will continue to be elucidated.

We have investigated the effects of 5-hydroxytryptamine (5-HT) on electrically induced contractions of rabbit isolated bladder. Electrical field stimulation evoked twitch contractions which were potentiated by 5-HT (0.3-10 microM). The potentiating effect of 5-HT was inhibited by ondansetron (pA2 9.2) and granisetron (pA2 9.1) but not by methysergide or SB 204070 ((1-butyl-4-piperidinyl)methyl 8-amino-7-chloro-1,4-benzodioxan-5-carboxylate hydrochloride). This suggests that the potentiating effect of micromolar concentrations of 5-HT on neuromuscular transmission in rabbit isolated bladder is mediated by 5-HT3 receptors. The receptors involved in the response to lower concentrations of 5-HT, observed in some tissues, remain to be characterised.

This study examined effects of 5-methoxytryptamine (5-MOT), an agonist at 5-HT4 and 5-HT2B receptors, on the contractile response and acetylcholine release in rat stomach fundus strips. 5-MOT (10−9 − 10−5 M) produced a concentration-dependent increase in the contraction, while it evoked acetylcholine release in a ‘bell-shaped’ concentration-dependent manner. Atropine reduced 5-MOT (10−8 − 10−6 M)-induced contractions, but it had little effect on the contractions evoked by higher concentrations. 5-MOT-induced contraction and acetylcholine release were inhibited by SDZ 205–557 (2-methoxy-4-amino-5-chloro-benzoic acid 2-[diethylamino] ethyl ester), a 5-HT4 receptor antagonist. In the presence of atropine, both SDZ 205–557 and yohimbine, a 5-HT2B receptor antagonist, inhibited the contraction. In the presence of tetrodotoxin, the contraction was inhibited by yohimbine, but not by SDZ –557. These results suggest that the contractile action of 5-MOT in rat stomach fundus involves atropine-sensitive and atropine-resistant components. The sensitive contraction appears to be mediated through 5-HT4 receptors located on cholinergic neurons, whereas the resistant contraction is mediated through 5-HT4 receptors located on non-cholinergic neurons and through 5-HT2B receptors.

A sensitive method for the measurement of endogenous 5-methoxytryptamine in brain tissue has been developed using capillary column gas chromatography-electron-capture negative-ion chemical ionization mass spectrometry. 5-Methoxytryptamine was first converted to N-[2H3]acetyl-5-methoxytryptamine by reaction with hexa-deuterated acetic anhydride, followed by reaction with pentafluoropropionic anhydride to yield the highly electron-capturing 3,3'-spirocyclic pentafluoro-propionyl indolenine derivative. Quantitative analysis was carried out by selected-ion monitoring of the [M-HF].- and [M-HF-DF].- ion intensity of the 3.3'-spirocyclic pentafluoropropionyl indolenine derivative, using 5-methoxy-[alpha, alpha, beta, beta-2H4]tryptamine as the internal standard. The presence of 5-methoxytryptamine in the brain tissue was demonstrated. In the absence of a monoamine oxidase inhibitor, the mean +/- S.D. levels of 5-methoxytryptamine in the rat and quail whole brain were found to be 30 +/- 6 and 347 +/- 52 pg/g, respectively. The possible physiological functions of 5-methoxytryptamine as a neuromodulator and/or neurotransmitter have to be considered.

The effects of GYKI-46 903 ((+)endo-4-propionyloxy-6-(4-fluorophenyl)-1-azabicyclo [3.3.1]non-6-ene HCl), on 5-HT3 receptors have been studied and compared with ondansetron in peripheral organs in vitro and in vivo, and in a receptor binding assay in membranes prepared from rat cerebral cortex. GYKI-46 903 was found to be a non-competitive antagonist at 5-HT3 receptors present in non-stimulated longitudinal muscle strip of guinea-pig ileum (pD2' against serotonin = 5.54), and also in 5-methoxytryptamine-pretreated electrically stimulated ileal preparations (pD2' against serotonin = 5.26). On the contrary, ondansetron was found to be a competitive antagonist for 5-HT3 receptors; the pA2 value against serotonin was 7.40 in non-stimulated ileum, and it was 7.08 in electrically stimulated ileal preparation pretreated with 5-methoxytryptamine. In displacement studies, the pIC50 values of GYKI-46 903 and ondansetron against [3H]granisetron binding to rat cerebral cortex membranes were 6.91 and 8.58 respectively. GYKI-46 903, when administered by intravenous infusion, antagonized the decrease in heart rate evoked by serotonin (Bezold-Jarisch reflex) in anaesthetized rats, and the maximal reversal was less than 50%. This was in striking contrast with ondansetron, which, after intravenous injection, completely antagonized the serotonin-induced bradycardia with an ID50 value of 3.28 ug/kg. These data classify GYKI-46 903 as a non-competitive antagonist for 5-HT3 receptors.

Melatonin, secreted by the pineal gland at night, inhibits pubertal development of rats and presumably men. In addition, it may directly suppress prostate growth in the adult rat. To investigate the possibility for a causal relationship between the age-related decline in melatonin production and increase in prevalence of benign prostate hypertrophy (BPH) in man, the presence of melatonin binding sites in human BPH tissue was examined. In vitro autoradiography indicated specific 125I-labeled melatonin (125I-melatonin) binding in the prostate, localized to the glandular epithelium. Separation and subcellular fractionation indicated that these sites were associated with the microsomal fraction of the epithelial cells. Kinetic and equilibrium 125I-melatonin binding experiments revealed that the binding was time dependent and reversible, with an apparent half saturation at 140 pmol/L. Competition experiments indicated high and low affinity melatonin binding sites; binding was inhibited by melatonin (IC50 1 nmol/L and 1 micromol/L, respectively) and partially by the putative melatonin antagonist, N-(2,4 dinitrophenyl)-5-methoxytryptamine (ML-23; IC50 0.1 nmol/L). Serotonin and 6-hydroxymelatonin were less potent, whereas up to 0.1 mmol/Lol/L of 5-methoxytryptamine, 6-methoxymelatonin, and tryptamine caused only a partial reduction in specific binding. The guanine nucleotide analogs, guanosine 5'-O-[3-thiotriphosphate] and guanosine 5'-O-[2-thio-diphosphate, inhibited specific 125I-melatonin binding, whereas 5'-guanylyl imidodiphosphate was less potent. The results indicate putative melatonin receptors in the human prostate epithelium.

1. The aim of this study was to characterize the receptors mediating the atropine-resistant neurogenic contraction to 5-hydroxytryptamine (5-HT) in the longitudinal muscle of the guinea-pig proximal colon and to determine the type of tachykinin receptors involved in the contractile response to 5-HT by the use of selective antagonists. 2. In the presence of atropine (0.3 microM), guanethidine (5 microM), hexamethonium (100 microM), ketanserin (0.1 microM) and indomethacin (3 microM), 5-HT (0.01-3 microM) produced concentration-dependent neurogenic contractions of colonic strips and at 0.3 microM produced a maximal effect (pEC50 = 7.39 +/- 0.09, n = 18). The 5-HT4 receptor stimulant, 5-methoxytryptamine (5-MeOT, 0.03-10 microM) also produced neurogenic contractions with similar maximum effect to those of 5-HT (pEC50 = 6.89 +/- 0.16). 3. The 5-HT4 receptor antagonist, DAU 6285 (3 microM) shifted the concentration-response curves to both 5-HT and 5-MeOT to the right without significant depression of the maximum, but the 5-HT1/5-HT2 receptor antagonist, metitepine (0.1 microM) and the 5-HT3 receptor antagonist, ondansetron (0.3 microM) had no effect on the control curves to 5-HT and 5-MeOT. 4. The selective NK1 receptor antagonist, FK 888 (1 microM) markedly attenuated the contractions to 5-HT and 5-MeOT. In contrast, the selective NK2 receptor antagonist, SR 48968 (10 nM) and the selective NK3 receptor antagonist, SR 142801 (10 nM) had no effect on the contractions to 5-HT and 5-MeOT. 5. These results indicate that the 5-HT-induced atropine-resistant neurogenic contraction of guinea-pig proximal colon is due to activation of 5-HT4 receptors, presumably located on excitatory motor neurones, innervating the longitudinal muscle. The contraction evoked by activation of the 5-HT4 receptors is mediated primarily via NK1 receptors but not NK2 or NK3, suggesting that the 5-HT4 receptor-mediated contraction is evoked indirectly via tachykinin release from tachykinin-releasing excitatory neurones.

In segments of human right atrial appendages preincubated with [3H]noradrenaline and superfused with physiological salt solution containing desipramine and corticosterone, we determined the effects of 5-hydroxytryptamine (5-HT) receptor agonists and antagonists on tritium overflow evoked by transmural electrical stimulation (2 Hz). Tritium overflow was inhibited by 5-HT, 5-carboxamidotryptamine (5-CT), 5-methoxytryptamine (5-MeOT), 5-methoxy-3(1,2,3,6-tetrahydro-4-pyridinyl)-1H indole succinate (RU 24969) and sumatriptan. Yohimbine and oxymetazoline (in the presence of idazoxan) also inhibited tritium overflow. The inhibitory potency of the drugs was significantly correlated with their affinity for 5-HTID receptors in human brain and for cloned human 5-HT1D alpha and 5-HT1D beta receptors, but not with their affinity for 5-HT1B, 5-HT1E, 5-HT1F, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT3, 5-HT5A, 5-HT5B and 5-HT7 receptors. The potency order 5-CT5-HT5-MeOT is opposite to the order of affinities reported for 5-HT6 binding sites. The preferential 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetraline (up to 0.3 microM) and the selective 5-HT4 receptor agonist cisapride (up to 1 microM) failed to inhibit tritium overflow. L-694,247, a potent 5-HT1D beta receptor agonist, did not inhibit tritium overflow, but counteracted the inhibitory effect of 5-HT. Ketanserin at a concentration which should block 5-HT1D alpha but not 5-HT1D beta receptors and methiothepin at a concentration which may be assumed to block both 5-HT1D alpha and 5-HT1D beta receptors antagonized the inhibitory effect of 5-HT. Propranolol and ondansetron did not modify the 5-HT-induced inhibition of release. In conclusion, noradrenaline release in human right atrial appendages is inhibited via 5-HT receptors which are located on the noradrenergic axon terminals. These inhibitory presynaptic 5-HT receptors belong to the 5-HT1D subfamily. The ability of ketanserin to antagonize the inhibitory effect induced by activation of these receptors suggests that they can be subclassified as 5-HT1D alpha.

Dinoflagellates are the causative agents of red tides with worldwide occurrence and can be induced to encyst by in doleamines such as melatonin and 5-methoxytryptamine (5-MOT). This biological response may be mediated via indoleamine-binding proteins or receptors. Here we report the initial characterization of the signal transduction mechanisms by which indoleamines induce encystment of dinoflagellates. In particular, we explored the possible involvement of G proteins and cAMP in cyst formation. Both melatonin and 5-MOT promoted the encystment of Gonyaulax tamarensis and Crypthecodinium cohnii. Exposure of dinoflagellates to dibutyryl cAMP, which directly activates cAMP-dependent pathways, did not affect the ability of indoleamines to promote encystment. However, dibutyryl cAMP dose-dependently diminished the indoleamine-induced suppression of cell growth. Exposure of dinoflagellates to the bacterial toxins from Vibrio cholerae and Bordetella pertussis had no effect on the indoleamine-induced encystment response, indicating the lack of involvement of Gs or Gi-like proteins. Moreover, [32P]ADP ribosylation of dinoflagellate membranes by either toxin failed to identify substrate proteins. These results suggest that although the indoleamine-induced encystment of dinoflagellates may involve a G-protein-coupled signal transduction pathway, the identity of the G protein concerned may be distinct from those that regulate adenylyl cyclases in mammalian cells.

Synthesis and release of the pineal hormone melatonin is in all vertebrates primarily regulated by the light/dark cycle. In pineal organs of teleost fish, like in other non-mammalian vertebrates, melatonin formation is regulated by a direct photoreception of the pineal organ. We performed measurements in explanted, perifused pineal organs of the rainbow trout, Oncorhynchus mykiss, to examine whether melatonin can influence its own production. For this purpose we have continuously perifused isolated pineal organs under light- and dark-adapted conditions and measured the release of melatonin and other methoxy-indoles by HPLC with electrochemical detection. Addition of 2-iodomelatonin to the perifusate in a concentration of 2 ng/ml significantly inhibited melatonin release in light-, as well as in dark-adapted organs. The release of 5-methoxytryptamine and 5-methoxytryptophol was also significantly reduced in light-adapted organs. These results indicate that extracellular melatonin may act as a paracrine or autocrine feedback signal and may be important for the illumination-dependent melatonin production.

The 5-HT receptor mediating postjunctional relaxation of precontracted guinea-pig ileum has been characterized using several agonists and antagonists. Substance P precontracted tissues were potently relaxed by 5-HT (5-hydroxytryptamine, serotonin), 5-CT (5-carboxamidotryptamine) and several other indoles. The rank order of potency, with pEC50 values in parentheses, was 5-CT (7.6)5-methoxytryptamine (5.7)5-HT (5.5)alpha-methyl-5-HT (4.7)2-methyl-5-HT (4.0) = tryptamine (4.0) = N,N-dimethyl-tryptamine (4.0) = N,N-dimethyl-5-HT (4.0) = dipropyl-5-CT (4.0) = sumatriptan (4.0). 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)-tetralin) acted as a potent (6.3), but partial, agonist with respect to 5-HT. The responses to 5-CT were antagonized by several compounds with the following rank order of affinity, with pKB values in parentheses: LSD (lysergic acid diethylamide; 8.1) = mesulergine (7.8)methysergide (7.6) = spiperone (7.6)clozapine (7.3)(-)-pindolol (6.0)ketanserin (6.0) = ondansetron (6.0) = GR 113808 ([1-(2-methane-sulphonamido-ethyl)-piperidin-4-yl]-methyl-in dole-3- carboxylate maleate;6.0). The relaxant responses to 5-HT were also resistant to tetrodotoxin. These data are consistent with a functional 5-HT receptor, mediating relaxation of guinea-pig ileum, which exhibits an operational profile similar to that of the cloned guinea-pig 5-ht7 receptor. This study, therefore, provides evidence for a functional correlate of the 5-ht7 gene product.

Intracellular electrophysiological methods were used to examine the effects of 5-hydroxytryptamine (5-HT), 5-carboxamidotryptamine (5-CT), 5-methoxytryptamine (5-MeOT), 4-amino-5-chloro-2-methoxy-N-(4-[1-azabicyclo[3,3,1]nonyl]) benzamide hydrochloride (renzapride), cis-4-amino-5-chloro-N[1-[3- (4-fluorophenoxy)propyl]-3-methoxy-4-piperidinyl[-2-methoxybenzamide monohydrate (cisapride) and endo-N-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2,3-dihydro-3- (1-methyl)ethyl-2-oxo-1 H-benzimidazole-1-carboxamidehydrochloride (BIMU 8) on noncholineric slow excitatory postsynaptic potentials (slow EPSPs) in myenteric afterhyperpolarization (AH) neurons of guinea pig ileum. 5-HT (0.01-1 microM) and 5-CT (0.001-0.1 microM) produced a concentration-dependent inhibition of slow EPSPs. The 5-HT1A receptor antagonist 1-(2-methoxyphenyl)-4-[4-(2-phthalimidobutyl]piperazine (NAN-190) produced rightward shifts in 5-HT and 5-CT concentration-response curves; facilitation of slow EPSPs was never observed. 5-MeOT caused a depolarization and inhibited spike afterhyperpolarizations in a concentration-dependent manner but this effect was not blocked by the 5-HT3/5-HT4 receptor antagonist, tropisetron (1 microM). Renzapride (0.01-0.3 microM), cisapride (0.01-1.0 microM) and BIMU 8 (0.01-1.0 microM) did not change the membrane potential of any neuron tested. Renzapride and BIMU 8 did not change the amplitude of slow EPSPs. In 13 of 19 neurons cisapride did not change the amplitude of slow EPSPs; in 6 neurons cisapride (1 microM) reversibly inhibited the slow EPSP. Responses to substance P which mimicked the slow EPSP were not affected by cisapride.(ABSTRACT TRUNCATED AT 250 WORDS)

Objectives The aim was to examine the biological activity of 5-methoxytryptamine derivatives at the 5-hydroxytryptamine (5-HT)4 receptor to explore the effect of substitution on the aliphatic amine of the 5-methoxyamine scaffold. Methods Three compounds were tested for affinity at the 5-HT4 receptor by radioligand binding and functional activity using guinea-pig ileum and human colon circular muscle preparations and also in the mouse whole gut transit test. Key findings The three compounds all had agonist properties at the 5-HT4 receptor but their efficacy differed in the different functional tests. Compound 3 had the highest affinity for the 5-HT4 receptor and was a full agonist at relaxing human colon circular muscle with efficacy closest to 5-HT. Compounds 1 and 2 were partial agonists in this assay with lower efficacies; compound 2 was a full agonist in the guinea-pig ileum assay whereas compound 3 was a partial agonist. Compounds 1 and 2 also showed activity in the mouse gut transit assay while compound 3 had no activity. Conclusions Of the compounds tested, compound 3 was the most promising 5-HT4 receptor agonist and the results highlight the value of using human tissue in functional tests when assessing compounds for potential activity.

There is no general agreement yet on the antioxidant effect of pineal indoles against lipid peroxidation. Accordingly, the main goal of the present work was to study the antioxidant activity of melatonin (MLT), N-acetylserotonin (NAS), 5-HO-tryptophan (5HO-TRP) and 5-methoxytryptamine (5MTP) in two different lipid systems with high content of polyunsaturated fatty acids (PUFAs): triglycerides (rich in 20:5 n-3, 22:6 n-3) dissolved in chloroform and sonicated liposomes made of retinal lipids (rich in 22:6 n-3). In the triglyceride-chloroform-system the peroxidation reaction was initiated by cumene hydroperoxide (CHP) whereas liposomes were peroxidized with Fe. 2+. The techniques employed at the present work were: (1) TBARS production, (2) DPPH assay, (3) determination of conjugated dienes production and (4) analysis of fatty acid profile by GC-MS. Butylated hydroxytoluene (BHT) was employed as a reference because of its well known antioxidant capacity. Our results showed that MLT and 5MTP were unable to protect PUFAs against lipid peroxidation in both systems, whereas NAS and 5HO-TRP were better antioxidants that BHT in the triglyceride-system but ineffective in the liposome-system. We conclude that the antioxidant behaviour of pineal indoles depends not only on their functional groups but also on the assay system and could be explained by the polar paradox theory. Fil: Fagali, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Catala, Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina

5-MeO-DALT (N,N-diallyl-5-methoxytryptamine) is a psychoactive substance, sold primarily over the Internet as a 'research chemical' or 'plant food'. Although details for the synthesis of this tryptamine have been available since 2004, its use as a hallucinogenic drug has been reported only occasionally in on-line user fora. It is controlled in only a few countries world-wide. There is little scientifically-based literature on the pharmacological, physiological, psychopharmacological, toxicological and epidemiological characteristics of 5-MeO-DALT. Here we review what is known about these aspects. We also report what we believe to be the first death involving the use of this substance. The case involved a man in his mid-20s who died in mid-2010. The coroner concluded that the deceased "died from injuries sustained after being hit by a lorry whilst under the influence of 5-MeODALT". It is critical that any other cases, including non-fatal instances, are documented so that a scientific evidence-base can be established for this drug.

Purpose The objective of this study was to compare the effects of two neuroprotective agents; melatonin, a free radical scavenger and topiramate, AMPA/kainate receptor antagonist, administered alone or in combination in neonatal hypoxic-ischemic model. Methods After being anesthetized, 7-day-old pups underwent ischemia followed by exposure to hypoxia. The pups were divided into 4 groups in order to receive the vehicle, melatonin, topiramate and combination of topiramate and melatonin. These were administered intraperitoneally for three times; the first before ischemia, the second after hypoxia and the third 24 hours after the second dose. After sacrification, infarct volume and apoptosis were evaluated. Results Percent infarcted brain volume was significantly reduced in rats which received drugs compared with those which received the vehicle. The number of TUNEL positive cells per unit area in hippocampus and cortex were markedly reduced in drug treated groups compared with control group. No significant differences were found regarding percent infarcted brain volume and number of TUNEL positive cells among drug-treated groups. Conclusions Melatonin and topiramate, administered either alone or in combination significantly reduced the percent infarcted brain volume and number of TUNEL positive cells suggesting that these agents may confer benefit in treatment of infants with hypoxic-ischemic encephalopathy.

Seven new amides of 5-methoxytryptamine were synthesized and tested for radioprotective activity in mice. One of them, the heptafluorobutyramide 4 , is moderately active (57 % survivors), the rest demonstrate little or no activity. Of twelve compounds that had been found to exhibit high radioprotective activity by ip injection, only two [ p -aminopropiophenone ( 9 ) and ts ethylene ketal 8 ] retain that high activity (92–95 % survivors) when administered orally. Three are moderately active: p -aminobenzonitrile ( 10 ,55%), 5- methoxytryptamine octanoic amide ( 11 , 50 %), and p -aminobenzophenone ( 12 ,48 %).

We examined the effect of 5-hydroxytryptamine (5-HT) on Na+ and Cl- flux (J) and short-circuit current (Isc) in human jejunal mucosa. Segments of jejunum, taken at the time of gastric bypass surgery, were stripped of the seromuscular layers (and attached neural ganglia) and mounted as flat mucosal sheets in Ussing chambers under short-circuit conditions. 5-HT (0.1-100 microM) produced a concentration-dependent rise in Isc (mean effective concn = 2.5 microM). Using 22Na and 36Cl, we measured flux across control tissues and in those exposed to 5-HT. 5-HT decreased both net JNa and JCl and increased Isc (-1.1 +/- 0.6, -1.7 +/- 0.6, and 0.6 +/- 0.1 mueq.cm-2.h-1, respectively). Thus the 5-HT-induced rise in Isc could be accounted for by reduced net JNa and JCl. 5-HT induced a significant (P < 0.05) Cl- secretion (serosal-to-mucosal flux) when glucose was included in the buffer bathing the mucosal surface. Neither tetrodotoxin, the adrenergic receptor antagonists prazosin and propranolol, nor the cholinergic receptor antagonists atropine and hexamethonium inhibited the change (delta) in Isc induced by 5-HT. 5-Methoxytryptamine (5-MeOT) and zacopride, known 5-HT4 receptor agonists, induced significant delta Isc. The 5-HT receptor antagonists N-acetyl-5-hydroxytryptophyl-5-hydroxytryptamine (5-HT1P), ketanserin (5-HT2), and ICS-205-930 (preferential for 5-HT3 at 0.1 microM had no effect on delta Isc.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of benzodiazepines (BZP) on melatonin release was investigated in the pineal gland of the rainbow trout, Oncorhynchus mykiss, maintained under in vitro perifusion culture conditions. Melatonin and the methoxyindoles 5-methoxytryptophol (5-MTOL), 5-methoxyindoleacetic acid (5-MIAA), and 5-methoxytryptamine (5-MT) were determined directly in samples of the superfusion medium by HPLC with electrochemical detection. Melatonin release was significantly increased by addition of diazepam and clonazepam in a dose-related and reversible manner. The effects of benzodiazepines were more pronounced in light-adapted pineal organs, when melatonin secretion is low, than under scotopic conditions. When the perifusion medium was replaced by a medium containing low calcium, high magnesium concentrations, melatonin release was considerably decreased by 70% in light-adapted and 20% in dark-adapted pineal organs. Addition of diazepam to low Ca2+, high Mg(2+)-medium reversed the decrease of melatonin release and produced a clear rise in its secretion rate. Addition of the BZP antagonist flumazenil to the perifusion medium slightly decreased melatonin release in the light- and dark-adapted state, whereas the peripheral receptor antagonist PK 11195 did not alter melatonin release. The effect of diazepam is reduced by simultaneous addition of flumazenil to the superfusion medium, suggesting that the effects of diazepam are receptor-mediated. The methoxyindoles 5-MTOL, 5-MIAA, and 5-MT showed no significant changes of their release pattern after diazepam application in light- and dark-adapted pineal organs. These results suggest that BZP can influence melatonin production and release by an intrapineal action possibly on the melatonin synthesizing photoreceptor cell.

The involvement of visceral afferent fibers and 5-HT3 or 5-HT4 receptors in the vomiting induced by oral administration of copper sulfate was investigated in beagle dogs. Vomiting induced by copper sulfate (100 mg/kg) was inhibited markedly by bilateral abdominal vagotomy and bilateral greater splanchnic nerve section. The vomiting induced by copper sulfate was inhibited by blocking 5-HT4 receptors with high doses (1 and 3 mg/kg, i.v.) of ICS 205-930. On the other hand, blocking 5-HT3 receptors with MDL 72222 (0.5 and 5 mg/kg, i.v.) or low doses (0.01 and 0.1 mg/kg, i.v.) of ICS 205-930 had no apparent effect on the vomiting induced by copper sulfate. Oral administration of a 5-HT4 receptor agonist, 5-methoxytryptamine (5-MT), caused vomiting at a dose of 100 mg/kg, and the vomiting was inhibited markedly by abdominal visceral nerve section or a high dose (1 mg/kg, i.v.), but not a low dose (0.01 mg/kg, i.v.), of ICS 205-930. Intravenous administration of 5-MT (10 mg/kg) failed to induce vomiting. These results suggest that the abdominal visceral afferent fibers and possibly peripheral 5-HT4 receptors play an important role in the vomiting induced by oral administration of copper sulfate in dogs.

In Gonyaulax polyedra, 5-methoxytryptamine (5-MT), 5-fluorotryptamine (5-FT) and 6-fluorotryptamine (6-FT) are similarly potent stimulators of bioluminescence. When given in long-days (light/dark cycle of 16:8 hr), 5-methoxytryptamine is a strong inducer of cyst formation, leading to complete encystment of the entire cell population down to concentrations of 5 × 10−6 M, whereas 5- and 6-fluorotryptamines only elicit incomplete encystment, especially with regard to the capability of the individual cells to form cyst walls (5-FT: about one half of cells; 6-FT: maximally 1 5 ); the fluorotryptamines lead, however, to an immobilization of cells and retractions of the protoplast from the theca (6-FT ⩾ 5 × 10−6 M; 5-FT ⩾ 10−5 M). Gonyaulax extracts catalyse photo-oxidatin of the three indoleamines: 5-MT leads to an accumulation of the homologous 5-methoylated kynuramine, whereas only minor amounts of fluorinated kynuramines were obtained. In a superoxide anion-generating system, 5-MT and 5-FT are predominantly oxidized to substituted kynuramines; 6-FT undergoes the homologous reaction, but is further converted into a non-fluorescent product.

The purpose of this study was to compare the 5-hydroxytryptamine (5-HT) receptor subtypes involved in secretion of water and electrolytes (sodium, potassium, and chloride) induced by luminally administered serotonin in rat jejunum and ileum in vivo. Ketanserin partially inhibited and ICS 205-930 totally inhibited serotonin-evoked secretion. Ketanserin induced mild basal secretion while ICS 205-930 alone reduced basal absorption. There were no differences in the effects of ketanserin or ICS 205-930 on serotonin-induced secretion by rat jejunum versus ileum. Neither N-acetyl-5-hydroxytryptophyl-5-hydroxytryptophanamide nor methysergide altered the secretory effect of serotonin in rat ileum. The substituted benzamides, cisapride, and BRL 24924, and the 5-HT4 agonist, 5-methoxytryptamide, induced water and electrolyte secretion. While BRL 24924 did not alter the subsequent serotonin-induced secretory fluxes, cisapride slightly inhibited the induced secretion. These results suggest that (1) in both segments of the intestine, 5-HT2, 5-HT3, and/or 5-HT4 receptor subtypes are involved in the regulation of intestinal transport of water and electrolytes under basal conditions; (2) serotonin-induced water and electrolyte secretion is mediated by pathways involving 5-HT2, 5-HT3, and 5-HT4 receptor subtypes in both rat jejunum and ileum; (3) 5-HT1 receptors do not seem to be involved in the mediation of intestinal water and electrolyte transport; (4) these effects are similar to those described for systemically administered 5-HT.

1. The involvement of neurokinins in the non-cholinergically-mediated contractile response induced by stimulation of 5-HT3 and 5-HT4 receptors has been examined in the longitudinal muscle-myenteric plexus preparation of the guinea-pig ileum. 2. The 5-HT3 receptor agonist, 2-methyl-5-hydroxytryptamine (2-methyl-5-HT), showed a lower potency in this preparation than the more selective 5-HT4 receptor agonist 5-methoxytryptamine. The effect of both drugs was markedly reduced by atropine. 3. Substance P (SP) and neurokinin B (NKB) produced biphasic concentration-response curves in the preparation. Neurokinin A (NKA), the NK1 receptor agonist, [Sar9,Met(O2)11]SP and the NK3 receptor agonist, senktide yielded monophasic concentration-response curves. 4. After desensitization of the NK1 receptor with SP or [Sar9,met(O2)11]SP, in the presence of atropine, the contractile response to 2-methyl-5-HT was entirely blocked. Desensitization of NK3 receptors with NKB, also in the presence of atropine, fully suppressed the 5-HT4 receptor-mediated contraction evoked by 5-methoxytryptamine. 5. In preparations prelabelled with [3H]-choline, SP produced a concentration-dependent increase in tritium overflow, an index of [3H]-acetylcholine release, while an inverse relationship was found with NKB. At low neurokinin concentrations, the releasing effect of NKB was much more marked. 6. It is suggested that in the response to 5-HT3 receptor stimulation, there is a role for SP and acetylcholine. NKB appears to be preferentially involved in the release of acetylcholine elicited by stimulation of 5-HT4 receptors.

The response of a cell line of Xenopus laevis melanophores to serotonin was examined. Serotonin increased intracellular levels of cAMP and induced pigment dispersion in the cells. The responses depended on both the concentration of serotonin applied and on the time for which the cells were exposed to serotonin. Using a recently described, microtiter-plate-based bioassay, a series of serotonin receptor ligands were evaluated as agonists or antagonists at the melanophore serotonin receptor. The pharmacological profile suggests the presence of a receptor which shares some properties with but appears different from other previously described serotonin receptors.

1. The 5-HT4 receptor has only recently been identified but has yet to be cloned. This paper describes the pharmacology of a potent and selective 5-HT4 receptor antagonist, GR113808, which will be useful in the further characterization of this receptor. 2. On the guinea-pig ascending colon, GR113808 (1 nM-0.1 microM) behaved as an antagonist of 5-hydroxytryptamine (5-HT)-induced contraction, producing rightward displacements of the concentration-effect curve to 5-HT and a concentration-related depression of the maximum effect. However, the compound had no effect on cholecystokinin (CCK-8)-induced contraction in concentrations up to 1 microM. 3. In the guinea-pig colon preparation, onset and offset of the antagonism by GR113808 of 5-HT-induced contraction was examined. Incubation of the tissues for either 15 min, 30 min or 60 min produced similar rightward displacements of the concentration-effect curves to 5-HT, with no increase in the degree of depression of the maxima with increasing time of incubation. Experiments examining offset of antagonism (0.01 microM) demonstrated that washout for 30 min was required to reverse fully the effects of the antagonist. 4. Potency estimates in the colon for GR113808 were made by determining approximate pA2 values (30 min) using the Gaddum equation. The values obtained were 9.2, 9.7 and 9.2 when tested against the agonists 5-HT, 5-methoxytryptamine and R,S-zacopride respectively. 5. On the carbachol-contracted tunica muscularis mucosae preparation of the rat thoracic oesophagus, GR113808 behaved as an antagonist of 5-HT-induced relaxation, producing no reduction in maximum response. Analysis of these data yielded a pA2 of 9.3. GR1 13808 also antagonised the relaxant effects of 5-methoxytryptamine (pA2 = 9.0) and R,S-zacopride (pA2 = 9.4). The compound had no effect on isoprenaline-induced relaxation of the carbachol-contracted oesophagus at a concentration of 1 MicroM.6. In tests of selectivity, GR113808 had only low affinity for 5-HT3 receptors (pKi = 6.0) and had no functional activity at either 5-HT2 or 5-HT1-like receptors on vascular smooth muscle preparations. In a range of binding assays, GRi 13808 was shown to have no appreciable affinity for any other receptor type investigated.7. In the anaesthetized piglet, GRI13808 was a potent antagonist of 5-methoxytryptamine-induced tachycardia (mean DRo = 97.2 microg kg-1 h-1). The compound was ineffective against isoprenaline-induced tachycardia.8. The present results are discussed in comparison with those for existing antagonists at the 5-HT4receptor. The results of this study indicate that GRI13808 will be a valuable antagonist for studying 5-HT4 receptor mechanisms in vitro and in vivo and validate its use as a radioligand for determining 5-HT4 receptor distribution.

Twenty-six title compounds with the ethylamine part of tryptamine or 5-methoxytryptamine fixed in an anticlinal ecliptic conformation were synthesized for assaying them at the different known serotonin receptors. Several alkylation methods have been improved and adapted for the space consuming norbornane system. The structures were fully elucidated by high-field NMR spectroscopy. All 1H- and 13C-signals could be assigned by means of 1H-1H- and 13C-1H-correlation spectroscopy (COSY). Selektivitat sterisch fixierter Tryptamin- und 5-Methoxytryptamin-derivate an Serotoninrezeptorsubtypen, 1. Mitt: Synthese von N-Alkyl- und N,N-Dialkyl-3-indolylbicyclo[2.2.1]heptan-2-aminen Sechsundzwanzig Titelverbindungen wurden dargestellt, um sie pharmakologisch an verschiedenen Serotoninrezeptortypen zu prufen. In diesen Verbindungen liegt der Ethylaminteil des Tryptamins bzw. 5-Methoxytryptamins in anticlinal ekliptisch fixierter Konformation vor. Hierzu wurden verschiedene Alkylierungsmethoden optimiert und an die Erfordernisse des sterisch anspruchsvollen Norbornansystems angepast. Alle Strukturen wurden durch Hochfeld-NMR-Spektroskopie gesichert. Durch 1H-1H-und 13C-1H-Korrelationsspektroskopie (COSY) konnten alle Protonen- und Kohlenstoffresonanzen des Norbornansystems zweifelsfrei zugeordnet werden.

The goal was to develop a rat model for determination of the effects of intrathecally administered drugs on the peripherally induced pruritic behaviors. After chronic intrathecal catheterization, a serotonin derivative (5-methoxytryptamine: MeOT, 200 μg on both sides) was injected into the lower leg skin. After the first period (phase 0: 0-30 min) MeOT injection was repeated and opioid antagonist naltrexone (10 μg), NMDA receptor antagonists ketamine (10-100 μg), kynurenic acid (1-10 μg) or their combinations were injected intrathecally. The second observational period lasted for 60 min (phases I and II, 30-60 and 60-90 min, respectively). MeOT produced pruritic behavior with high degree of interindividual differences. The second MeOT injection caused an enhanced pruritic behavior in Phase I. Naltrexone decreased the pruritic activity, while neither doses of ketamine influenced the effects of MeOT. The higher doses of kynurenic acid resulted in notable decreases in the pruritic behavior. The combinations of naltrexone with ketamine or kynurenic acid produced a prolonged antipruritic effect. Our data suggest an important direction for the development of a new itch model in rats that focuses on the spinal mechanism of itching. Besides, the results revealed the role of the spinal opioid and NMDA receptors in this process.

Autistic spectrum disorders (ASDs) are classified as pervasive developmental disorders characterized by abnormalities in various cognitive and behavioral functions. Although exact underlying causes are still unknown, nearly 30% of autistic patients show elevated blood levels of serotonin (5-HT) and, therefore, various genetic and environmental factors that are known to elevate 5-HT levels may play a role in the development of ASDs. In the present study, we used the socially monogamous male prairie vole (Microtus ochrogaster) as an animal model to examine the effects of perinatal exposure to 5-methoxytryptamine (5-MT), a non-selective serotonin agonist, on subsequent behavioural and neurochemical changes in the brain. 5-MT treated males showed a decrease in affiliation and an increase in anxiety-related behavior, as well as a decrease in the density of 5-HT immunoreactive (ir) fibers in the amygdala and oxytocin-ir and vasopressin-ir cells in the paraventricular nucleus of the hypothalamus, compared to saline treated controls. These data indicate that exposure to 5-HT during early development can induce abnormalities in various neurochemical systems which, in turn, may underlie deficits in social and anxiety-related behaviors. In addition, these data will help to establish the prairie vole model to study the neurobiological underpinnings of complex neuropsychiatric disorders such as ASDs.

The study of indralin radioprotective properties at its joint application with cystamine and mexamine was carried out in the experiments on inbred mice and rats. The mice and rats were exposed to whole-body y-irradiation at a dose of 9.0 and 9.5 Gy, correspondingly. A combined parenteral administration ofindralin and cystamine at a dose of 25 mg/kg showed ponentiaton of indralin radioprotective properties up to a level of the ED50 effect versus the absence of or a weak radioprotective effect in the case of their separate application. In the experiments on rats, indralin (50 mg/kg) and mexamine (12 mg/kg) injected intraperitoneally almost completely eliminated the animal mortality from the intestinal syndrome of acute radiation sickness amounting in the control radiation group to 60% on the 7th day after exposure to radiation at a dose of 9.5 Gy. However, at the above conditions, radioprotectors at these doses had a low-level radioprotective action at the onset of the bone marrow syndrome of acute radiation sickness. Combined application of indralin and mexamine at the same doses and at the same conditions led to a radiation protection 50% as high as in the case when radioprotectors were applied separately at a double dose.

Reelin plays an important role in the regulation of synaptic plasticity in adulthood. Administration of 5-metoxytryptamine (5MT), an agonist of serotonin receptors, during natal and neonatal periods results in decreased reelin expression. In adulthood, reelin is expressed by GABAergic neurons.The purpose of this study was to reveal the effect of elevated serotonergic stimulation on the expression of reelin and glutamate decarboxylase (GAD1) in adulthood as well as on depressive behavior and spatial cognitive abilities in adult female rats.Rats were injected with 5MT. A forced swimming test was used for evaluation of the depressive behavior and Morris water maze test was used for evaluation of spatial cognition. Brains were used for measuring the expression of reelin and GAD1.We found a significant decrease in reelin expression in the cerebellum and prefrontal cortex of 5MT-treated rats. GAD1 expression was decreased in the cerebellum of 5MT-treated rats. 5MT-treated rats reached a lower immobility score in the forced swimming test. The Morris water maze test did not reveal any significant differences.We have shown that administration of serotonin receptor agonist resulted in a decreased RELN and GAD1 expression in the cerebellum of adult female rats. We propose that this phenomenon might be relevant in the pathogenesis of autism (Fig. 3, Ref. 38). Full Text in free PDF www.bmj.sk.

5-Methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) is a designer hallucinogen derived from tryptamine and is reportedly abused and involved in criminal activities. For the detection of 5-MeO-DIPT use, a liquid chromatography-tandem mass spectrometric method for 5-MeO-DIPT and its metabolites, 5-hydroxy-N,N-diisopropyltryptamine (5-OH-DIPT) and 5-methoxy-N,N-isopropyltryptamine (5-MeO-IPT) was developed and validated in rat urine. The urine samples were pretreated by protein precipitation with acetonitrile and introduced into a BDS HYPERSIL C(18) column (50 × 2.0 mm, 5 μm) for chromatographic separation. Mobile phases consisted of methanol, water, and 1% formic acid, and gradient elution was used at a flow rate of 0.2 mL/min. For the MS detection, multiple-reaction monitoring analysis was adopted. The linear range was 0.01-10 μg/mL, and the lower limit of quantification was 10 ng/mL for all analytes. The intra- and interday accuracies and precisions met the criteria (15%). The developed method was successfully applied to the drug-treated rat urine.

The bioluminescent dinoflagellateGonyaulax polyedra contains various indoleamines, in particular, melatonin and 5-methoxytryptamine, as well as enzymes of their biosynthetic pathway. Melatonin exhibits a high-amplitude circadian rhythm characterized by a dramatic increase shortly after the onset of darkness. The maximum of melatonin is followed by a peak of 5-methoxytryptamine. These 5-methoxylated indoleamines seem to be involved in the mediation of the information ‘darkness’.G. polyedra shows a short-day response, which consists in the formation of asexual cysts. Light break experiments demonstrate the photoperiodic nature of this reaction. Cells become sensitive to short days only upon exposure to a lowered temperature (

An efficient synthesis of [fluoroacetyl-18F]fluoromelatonin (Nω-[18F]Fluoroacetyl-5-methoxytryptamine) starting from [18F]fluoride and ethyl p-toluensulfonyloxyacetate is described. The total time required for its synthesis is ca. 90 min. The radiochemical yield, purity and specific activity (end of bombardment) of the desired compound are 14.2%,>98%, and 540 mCi/μmol, respectively.

The effects of N-bromoacetyl 5-methoxytryptamine (BraMT) and some related bromoacyl melatonin and tryptamine derivatives on 2-[125I]iodomelatonin (2-[125I]aMT) binding in chicken brain membranes were examined. All analogues displaced specific binding to chicken brain membranes in a concentration-dependent manner. Preincubation of chicken brain membranes with BraMT (10(-8)M) did not significantly alter either 2-[125I]aMT binding site affinity (Kd) or density (Bmax). SDS polyacrylamide gel electrophoresis of chicken brain membrane proteins preincubated with 2-[125I]BraMT indicated that numerous proteins were labelled. The incorporation of radiolabel into these proteins was not blocked by melatonin, 2-iodomelatonin or N-(1,4 dinitrophenyl)-5-methoxytryptamine (ML-23), but was reduced by BraMT. In contrast to previous reports on hamster and rat brain membranes, the present results provide no evidence that BraMT or 2-[125I]BraMT affinity labels specific melatonin binding proteins in chicken brain.

The effects of melatonin on proliferation and on the induction of melanogenesis in rodent melanoma cells were investigated. It was found that melatonin at low concentrations (0.1-10 n M ) inhibited cell growth but had no effect on melanogenesis, while at high concentrations (⩾0.1 μ M it inhibited the induction of melanogenesis but not cell growth. These effects were specific since corresponding concentrations of the direct precursor and product of melatonin degradation N -acetylserotonin ( N -Ac-5HT) and 5-methoxytryptamine (5MT), respectively, did not have any effect on cell proliferation or melanogenesis. At very high concentration (100 μ M ) both N -Ac-5HT and melatonin could stimulate melanoma proliferation while 5MT inhibited it. The demonstration of differential and unparalleled effects of melatonin on cell proliferation and melanogenesis suggests that melatonin can regulate or modify both processes via different mechanisms.

The binding of [ 3 H]5-hydroxytryptamine (5-HT) to rat enteric membranes was inhibited by the inclusion of 5-HT 2-methyl-5-HT, 5-hydroxytryptophan, N,N,N-triethyltryptamine and 2-Br-N,N-diethyltryptamine in the incubation buffer. In contrast, tryptamine, 5-methoxytryptamine and 2-methyl-N,N-diethyltryptamine enhanced binding. Ascorbate and dithiothreitol facilitated and reduced binding at low and high concentrations respectively. Methysergide, tropisetron, paroxetine and pargyline failed to modify binding. However, following the establishment of [ 3 H]5-HT binding, the subsequent addition of 5-HT and other agents failed to displace [ 3 H]5-HT binding. Heat treatment of the membrane preparation also failed to modify [ 3 H]5-HT binding. The latter findings of an irreversible and heat-insensitive binding indicate that the apparently high affinity ‘specific’ labelling of [ 3 H]5-HT to rat enteric membranes does not represent receptor-bound [ 3 H]5-HT. The complex interaction between [ 3 H]5-HT and other agents may reflect oxidative events and problematic binding.

Melatonin deacetylase, an enzyme activity recently discovered in the Xenopus laevis retina, regulates local melatonin levels. The deacetylase occurs in retina, retinal pigment epithelium, and skin, all sites of melatonin action, and is widely distributed among vertebrates. We have solubilized the enzyme from Xenopus retina and pigment epithelium using nonionic detergents, and have developed a specific enzyme assay. We have characterized the enzyme and now report that the deacetylase is relatively specific for melatonin and is inhibited by the melatonin precursor N-acetylserotonin and the product of the deacetylase, 5-methoxytryptamine. Inhibition of deacetylase activity by eserine (physostigmine) suggests a relationship between deacetylase and cholinesterase activities. However, among a variety of cholinesterase inhibitors tested, only eserine inhibits the deacetylase. Furthermore, eserine is much less potent as an inhibitor of the deacetylase than the cholinesterases, and purified cholinesterases failed to deacetylate melatonin. We also show that melatonin deacetylase and aryl acylamidase (an enzyme related to cholinesterases) activities are differentially extractable from Xenopus ocular tissues, and that they exhibit different pH optima and inhibition profiles. Our results provide an initial characterization of the Xenopus retinal melatonin deacetylase, and indicate that deacetylase activity is distinct from cholinesterase and aryl acylamidase activities.

We have studied the regional distribution of 5-hydroxytryptamine (5-HT) receptor subtypes in fresh circular segments of human cerebral, middle meningeal, and temporal arteries. Vasomotor responses induced by a series of 5-HT agonists and antagonists with some degree of selectivity were studied by using a sensitive in vitro system. Nine 5-HT agonists were examined for contractile effects on the arteries. In cerebral and meningeal arteries 5-carboxamidotryptamine (5-CT) was more potent than 5-HT. The opposite order of potency (5-HT-5-CT) was found in temporal arteries. In the cerebral arteries 5-methoxytryptamin (5-MeOHT) was more potent than sumatriptan while sumatriptan was more potent than 5-MeOHT in meningeal and temporal arteries. The 5-HT1, receptor antagonist, methiothepin, competitively antagonized 5-CT-induced contractions in cerebral arteries, with a PA2, value of 9.05. 5-HT-induced contractions were competitively antagonized by ketanserin (5-HT2) in the temporal arteries PA2, value of 9.06). Methiothepin and ketanserin had non-competitive antagonistic effects in the middle meningeal arteries. The 5-HT3, selective antagonist ondansetron did not cause any shift of the contractions induced by 2-methyl-5-HT in the temporal, cerebral and middle meningeal arteries. These results suggest that the cerebral arteries mainly contain 5-HTid., or 5-HT1,-like receptors, and the temporal artery 5-HT2, receptors; the data further indicate the presence of both receptor subtypes in the middle meningeal artery.

To further understand the relationship between melatonin (MT) and deltorphins (Dels) in pain modulation, two chimeric peptides (Del I-5-methoxytryptamine and Del II-5-methoxytryptamine) both containing 5-methoxytryptamine at the carboxyl-terminal of Dels mimicking MT were designed, synthesized and characterized by tail-flick assay in mice. Results showed that intracerebroventricular (i.c.v.) administration of Del I-5-methoxytryptamine (YaFDVVG-X, X is 5-methoxytryptamine, 5, 50 nmol/kg) or Del II-5-methoxytryptamine (YaFEVVG-X, X is 5-methoxytryptamine, 5, 50 nmol/kg) produced stronger analgesia than deltorphins (Del I or Del II alone), and acting even longer and stronger than cocktails containing Del I or Del II (50 nmol/kg) and MT (50 nmol/kg). Naloxone (i.p., 100 nmol/kg) could totally block the analgesic effects induced by the chimeric peptides, while luzindole (specific antagonist of melatonin receptor, i.p., 250 nmol/kg) could only partially inhibit the effects down to that induced by Dels alone. Interestingly, Del I-5-methoxytryptamine and Del II-5-methoxytryptamine act weaker with δ receptor than Dels in vitro but could induce much longer analgesia through co-activating δ opioid receptor and melatonin receptor.

The metabolism of melatonin in the central nervous system is of interest for several reasons. Melatonin enters the brain either via the pineal recess or by uptake from the blood. It has been assumed to be also formed in some brain areas. Neuroprotection by melatonin has been demonstrated in numerous model systems, and various attempts have been undertaken to counteract neurodegeneration by melatonin treatment. Several concurrent pathways lead to different products. Cytochrome P(450) subforms have been demonstrated in the brain. They either demethylate melatonin to N-acetylserotonin, or produce 6-hydroxymelatonin, which is mostly sulfated already in the CNS. Melatonin is deacetylated, at least in pineal gland and retina, to 5-methoxytryptamine. N(1)-acetyl-N(2)-formyl-5-methoxykynuramine is formed by pyrrole-ring cleavage, by myeloperoxidase, indoleamine 2,3-dioxygenase and various non-enzymatic oxidants. Its product, N(1)-acetyl-5-methoxykynuramine, is of interest as a scavenger of reactive oxygen and nitrogen species, mitochondrial modulator, downregulator of cyclooxygenase-2, inhibitor of cyclooxygenase, neuronal and inducible NO synthases. Contrary to other nitrosated aromates, the nitrosated kynuramine metabolite, 3-acetamidomethyl-6-methoxycinnolinone, does not re-donate NO. Various other products are formed from melatonin and its metabolites by interaction with reactive oxygen and nitrogen species. The relative contribution of the various pathways to melatonin catabolism seems to be influenced by microglia activation, oxidative stress and brain levels of melatonin, which may be strongly changed in experiments on neuroprotection. Many of the melatonin metabolites, which may appear in elevated concentrations after melatonin administration, possess biological or pharmacological properties, including N-acetylserotonin, 5-methoxytryptamine and some of its derivatives, and especially the 5-methoxylated kynuramines.

The aim of this study was to determine whether pineal indoles affect cyclic nucleotide levels in mammary gland slices of BALB/c adult mice. Melatonin at 0.1 nM-10 microM concentrations decreased cAMP and augmented cGMP concentration in murine mammary gland slices in the presence of a phosphodiesterase inhibitor (1 mM theophylline), an index of cyclic nucleotide synthesis. Melatonin-induced changes in cyclic nucleotide levels were significantly larger at the end of the light period (2000) than in the morning (at 1000). Indole-induced inhibition of cyclic AMP levels by mammary slices exhibited the following order of potency: 5-methoxytryptamine > melatonin > or = 6-hydroxymelatonin > serotonin, N-acetylserotonin > 5-hydroxytryptophol. The order of potency for indole-induced augmentation of cyclic GMP levels was: 5-methoxytryptamine > melatonin > 6-hydroxymelatonin > serotonin, N-acetylserotonin, 5-hydroxytryptophol. When melatonin or 5-methoxytryptamine (10 nM) were examined for their effects on cAMP and cGMP levels in mammary glands of mice killed at six different time intervals during the 24-hr cycle, the activity was maximal during night. The data demonstrate that 5-methoxytryptamine and melatonin decreased cAMP and increased cGMP levels in mammary gland slices. Methoxyindole-induced changes in cyclic nucleotide synthesis in murine mammary glands exhibit the time-dependency known to occur in several other melatonin-influenced responses.

Changes in mechanical events and intracellular levels of cAMP induced by the activation of the 5-HT4 receptor were investigated in the rat esophagus tunica muscularis mucosae preparation. Serotonin (5-HT) and 5 methoxytryptamine (5-MOT; 5-HT4 agonist) caused concentration-related relaxation responses, while 5-carboxamidotryptamine (5-CT; 5-HT1 agonist), 1-(2,5-dimethoxy-4-iodophenyl)-2-amino-propane (DOI; 5-HT2 agonist) and 2-methyl-serotonin (2-methyl-5-HT; 5-HT3 agonist) were less active. The prokinetic agents, cisapride and renzapride also induced concentration-dependent relaxation of rat esophagus which was intermediate to 5-HT and 5-MOT in potency. The relaxation was not due to activity at receptors other than the 5-HT4 since methysergide (5-HT1 and 5-HT2 antagonist) and granisetron (5-HT3 antagonist) did not block the relazant response to 5-HT while ICS 205930 (5-HT4 antagonist) antagonized this response (pA2 = 6.45). Serotonin also caused concentration-related increases in tunica muscularis mucosae cAMP with the rank order of efficacy of 5-HT agonists in raising tissue cAMP levels reflecting their relaxant activities (5HT⩾5-MOT>5-CT>DOI = 2-methyl-5-HT = control). Enhancement of cAMP concentrations was also observed following renzapride treatment. This cAMP relaxation response was specific for 5-HT4 receptor actication as demonstrated by the lack of ICS 205930 inhibition of rat esophagus relaxation caused by isoproterenol, 16,16-dimethyl-prostaglandin E2 and forskolin. ICS 205930 (10−5 M) alone, however, significantly decreased tissue cAMP, emphasizing its lack of selectivity as an antagonist for blocking the 5-HT4-mediated rise in cAMP. These data suggest that the activation of the putative 5-HT4 receptor mediates rat esophagus relaxation via generation of cAMP.