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PubMed1986

Potentiation by deprenyl of the autoreceptor-mediated inhibition of [3H]-5-hydroxytryptamine release by 5-methoxytryptamine.

The 5-hydroxytryptamine (5HT) receptor agonist, 5-methoxytryptamine, inhibited in a concentration-dependent manner the electrically-evoked release of 3H-5HT from superfused rat hypothalamic slices, with an IC50 of 560 nmol/l, without affecting the spontaneous outflow of radioactivity. In the presence of the selective monoamine oxidase B (MAO B) inhibitor, (-)-deprenyl (1 mumol/l), the concentration-effect curve for 5-methoxytryptamine was shifted significantly to the left, and the IC50 was decreased to 25 nmol/l. Under the same experimental conditions, the potency of the 5HT receptor agonist lysergic acid diethylamide (LSD) at inhibiting the electrically-evoked release of 3H-5HT was the same in the presence as well as in the absence of (-)-deprenyl. The IC50 values for LSD were 34 nmol/l in the absence of deprenyl, and 31 nmol/l in the presence of the MAO B inhibitor. It is concluded that deprenyl potentiates the inhibition by 5-methoxytryptamine of 3H-5HT release, by preventing its inactivation through MAO B. Since 5-methoxytryptamine may be present in the pineal gland of some species, the potent effects of this 5-HT receptor agonist on serotoninergic neurotransmission may be of physiological relevance.

5-Methoxytryptamine↗

PubMed1994

Effects of LSD on Ca++ currents in central 5-HT-containing neurons: 5-HT1A receptors may play a role in hallucinogenesis.

Drugs that influence the activity of central serotonergic neurons by activating a 5-hydroxytryptamine subtype of receptor (5-HT1A) alter mood and perception. Previously, we demonstrated with whole-cell recordings from acutely isolated 5-HT-containing dorsal raphe (DR) neurons from the adult rat that 5-HT inhibited Ca++ current and activated K+ current in DR neurons. We now show that D-lysergic acid diethylamide (LSD) mimics the actions of 5-HT; it dramatically suppresses Ca++ current in a dose-dependent manner and activates an inwardly rectifying K+ conductance. Spiperone (0.2 microM), a 5-HT1A/5-HT2 antagonist, blocks the effect of both LSD and 5-HT. The nonhallucinogenic structural analog 2-bromo-LSD (2-Bol) at 10 microM has no effect on either Ca++ or K+ current by itself, but it competitively antagonizes both effects of LSD. Inhibition of 5-HT release resulting from 5-HT1A receptor activation may play an integral role in the hallucinogenic actions of LSD by reducing competition between 5-HT and LSD for the postsynaptic 5-HT receptors.

Animals↗

PubMed1977

The effect of LSD on the surface of neuroepithelial cells.

The neuroepithelial cells of 10 control chick embryos and of 22 exposed to lysergic acid diethylamide (LSD) (50 microgram/ml) were examined in scanning electron microscopy (SEM). In specimens exposed to LSD, the cells are swollen and their surface loses its cytoplasmic projections. Labelling techniques applied in transmission electron microscopy (TEM) show that ruthenium red attaches to the surface of the neuroepithelial cells in the form of a continuous dark line in both controls and treated specimens. However, when cationized ferritin or lanthanum is used, the label appears in the form of a continuous line in the controls whereas it is discontinuous in specimens exposed to LSD. These observations suggest that LSD alters the components of the neuroepithelial cell surface in the young chick embryo.

Animals↗

PubMed1995

Effect of a chiral 4-alkyl substituent in hallucinogenic amphetamines.

The potency of hallucinogenic amphetamine derivatives of the 1-(2,5-dimethoxy-4-alkylphenyl)-2-aminopropane type drops dramatically when the length of the 4-alkyl substituent exceeds propyl or when the substituent is branched. This investigation was directed toward evaluating changes in behavioral and biochemical pharmacology resulting from introducing chirality into the 4-alkyl group of such analogues. Two diastereoisomeric derivatives of this class containing a 4-(R or S)-2-butyl substituent, 11a,b, respectively, were studied. A slight but nonsignificant potency difference in d-lysergic acid diethylamide tartrate (LSD)-like discriminative stimulus properties and equal affinity for [125I]-(R)-(2,5-dimethoxy-4-iodophenyl) isopropylamine-labeled serotonin 5-HT2A/C radioligand-binding sites were observed. Thus, the portion of the receptor that interacts with the 4-alkyl substituent on hallucinogenic amphetamines does not present a highly asymmetric environment to the ligand. However, since both test drugs had higher binding affinity but lower LSD-like behavioral potency than the prototype compound with a 4-methyl group ((2,5-dimethoxy-4-methylphenyl)isopropylamine, 2), 11a,b may differ in their receptor agonist efficacy from more behaviorally active compounds such as 2.

Amphetamines↗

PubMedDate not supplied

Role of the serotonin 5-HT(2A) receptor in learning.

This study reviews the role of the serotonin 5-HT2A receptor in learning as measured by the acquisition of the rabbit's classically conditioning nictitating membrane response, a component of the eyeblink response. Agonists at the 5-HT2A receptor including LSD (d-lysergic acid diethylamide) enhanced associative learning at doses that produce cognitive effects in humans. Some antagonists such as BOL (d-bromolysergic acid diethylamide), LY53,857, and ketanserin acted as neutral antagonists in that they had no effect on learning, whereas others (MDL11,939, ritanserin, and mianserin) acted as inverse agonists in that they retarded learning through an action at the 5-HT2A receptor. These results were placed in the context of what is known concerning the anatomical distribution and electrophysiological effects of 5-HT2A receptor activation in frontal cortex and hippocampus, as well as the role of cortical 5-HT2A receptors in schizophrenia. It was concluded that the 5-HT2A receptor demonstrates constitutive activity, and that variations in this activity can produce profound alterations in cognitive states.

Animals↗

PubMed1979

An analysis of some perceptual effects of morphine, chlorpromazine, and LSD.

Male albino rats were trained to detect either a pure tone or a weak footshock embedded in white noise by utilizing a discrete-trial two-choice, successive discrimination procedure. The effects of morphine, chlorpromazine (CPZ), and lysergic acid diethylamide (LSD) were then analyzed on several measures of performance. Morphine (2.5--10 mg/kg) produced a nonspecific decrease in accuracy of discrimination on trials when the stimulus was presented as well as on trials when no stimulus occurred. Morphine was also followed by dose-dependent decreased in speed to initiate trials and by increases in intersubject variability. CPZ (1.0--4.0 mg/kg) caused a decrease in accuracy only on no-stimulus trials and, like morphine decreased speed to initiate trials. LSD (0.04--0.16 mg/kg/ decreased overall accuracy in a nonspecific manner (i.e., when shock and tone discriminations were considered together) and decreased speed by producing periods of nonresponding.

Acoustic Stimulation↗

PubMed1981

Inhibition of sympathetic activity by stimulating in the raphe nuclei and the role of 5-hydroxytryptamine in this effect.

The possibility that the putative transmitter 5-hydroxytryptamine (5-HT) is involved in the mediation of long latency to onset raphe-spinal inhibition of sympathetic preganglionic neurones was investigated in anaesthetized cats by stimulating sites located in nucleus raphe pallidus and obscurus and recording sympathetic discharge in T3 or T10 white rami evoked either reflexively or by intraspinal stimulation at cervical level. Several putative 5-HT antagonists were administered intravenously (i.v.) or topically to the spinal cord. In 7 cats lysergic acid diethylamide (LSD) in a dose range 25-50 microgram/kg i.v. or 0.6 microgram topically, reversibly reduced the raphe spinal inhibition by 40-100%. Topical application was more effective than i.v. administration. In 5 cats stimulating within the ventromedial reticular formation at sites unlikely to involved 5-HT neurones produced a short latency to onset inhibition which was unaffected by LSD. Methysergide, cinanserin and cyproheptadine depressed sympathetic discharge in the absence of brain stimulation in cats with CNS intact and in unanaesthetized decerebrate spinal cats. The results are discussed in the light of the known actions of the putative 5-HT antagonists.

Adrenergic Fibers↗

PubMed1957

The action of 5-hydroxytryptamine and some of its antagonists on the umbilical vessels of the human placenta.

The vasoconstrictor action of 5-hydroxytryptamine (5-HT) in the human placental preparation is about 10 times stronger than that of adrenaline and is antagonized by anti-adrenaline compounds like phentolamine. Both 5-HT and adrenaline are antagonized by yohimbine and chlorpromazine. Specific and strong anti-5-HT action is demonstrated for lysergic acid diethylamide (LSD) and tryptamine. Both LSD and tryptamine in larger doses have a vasoconstrictor action. Mescaline has no certain modifying effect on the action of 5-HT, but itself causes vasoconstriction in large doses. The antihistamine drug phenbenzamine in histamine blocking doses abolishes the action of 5-HT in half the preparations tested. The ganglionic blocking agent trimetaphan in large doses antagonizes the action of 5-HT added subsequently, and also, to a lesser degree, the effect of adrenaline. Hexamethonium and tetraethylammonium bromides are ineffective in this preparation. No certain modifying action of reserpine on subsequently added 5-HT could be demonstrated, and the same was true for heparin even in very high concentrations.

Antihypertensive Agents↗

PubMed1987

5-Hydroxytryptophol and 5-hydroxyindoleacetic acid levels in rat brain: effects of various drugs affecting serotonergic transmitter mechanisms.

The effect of various pharmacological treatments on the levels of free and total 5-hydroxytryptophol (5-HTOL) and 5-hydroxyindoleacetic acid (5-HIAA) in rat brain were investigated using a gas chromatographic-mass spectrometric technique. The disappearance of 5-HTOL following monoamine oxidase (MAO) inhibition induced by pargyline was more rapid (t1/2 10-15 min) than that of 5-HIAA (t1/2 30-40 min) in all regions investigated, indicating a rapid turnover of 5-HTOL. The selective MAO-A inhibitor chlorgyline produced a more pronounced reduction of 5-HTOL than of 5-HIAA, while the MAO-B inhibitor deprenyl was without effect on both serotonin metabolites. The MAO-A inhibitor amiflamine which is selective for serotonin neurons, was also more effective in reducing free 5-HTOL levels than of 5-HIAA levels, suggesting that the formation of 5-HTOL is closely associated with serotonin neurons. Neonatal treatment with the serotonin neurotoxin 5, 7-dihydroxytryptamine (5,7-HT) led to a more pronounced reduction of 5-HTOL levels in cerebral cortex than that of 5-HIAA levels, while the increase of 5-HTOL levels in pons-medulla was more marked than of 5-HIAA levels. Probenecid treatment increased several fold both conjugated 5-HTOL and 5-HIAA levels in brain tissue. An increase was also noted for free 5-HTOL, although of less magnitude. Treatment with the serotonin receptor active agents methiothepin and d-lysergic acid diethylamide produced similar alterations of free 5-HTOL and 5-HIAA. The present results have demonstrated that free 5-HTOL has a rapid turnover in rat brain and that free 5-HTOL levels may serve as a useful index for serotonin turnover.

Animals↗

PubMed1985

Discriminative stimulus properties of clonidine: substitution by ergot derivatives.

Bromocriptine, lergotrile and lisuride but not apomorphine, ergonovine or lysergic acid diethylamide (LSD) mimicked clonidine in rats trained to discriminate this compound (0.02 mg/kg) from saline. BC 105, ketanserin and haloperidol failed to block the clonidine cue. Yohimbine was an effective antagonist of clonidine but not of the lisuride substitution for clonidine. Since dopamine does not appear to be involved in the stimulus effects of clonidine, the behavioral similarities between clonidine and some ergots may be related to alpha-adrenoceptor stimulation; however, the role of blood pressure changes in the stimulus effects of all of these compounds should not be overlooked.

Adrenergic alpha-Agonists↗

PubMed1960

Analgesic antipyretic drugs as antagonists of bradykinin.

The antagonism between analgesic antipyretic drugs and bradykinin was examined quantitatively, using the bronchoconstrictor response of guinea-pigs in vivo. The dose of bradykinin required to overcome antagonism by calcium acetylsalicylate increased with the dose of acetylsalicylate given, the ratio being roughly constant. Fifty times the quantity of acetylsalicylate which just antagonized bradykinin did not modify bronchoconstriction due to small doses of histamine, 5-hydroxytryptamine, or acetylcholine. A method of measuring the potency of this anti-bradykinin action was developed. Acetylsalicylic acid, phenylbutazone, amidopyrine, and phenazone had a high potency; paracetamol, cinchophen, sodium salicylate, and acetanilide had a moderate potency; and phenacetin, salicylamide, and 4-hydroxyisophthalic acid had little or none. Cortisone, hydrocortisone, aldosterone, amodiaquine, and morphine were ineffective or their action was non-specific. In sensitized guinea-pigs, an injection of antigen caused bronchospasm. This response was greatly lessened by pretreatment with mepyramine, but was not affected by calcium acetylsalicylate, lysergic acid diethylamide, or atropine. Acetylsalicylic acid, phenylbutazone, and amidopyrine did not specifically antagonize the action of bradykinin on the capillaries of guinea-pig skin in vivo, on guinea-pig ileum in vitro or on rat duodenum in vitro.

Acetaminophen↗

PubMed2003

Characterization of the discriminative stimulus properties of centrally administered (-)-DOM and LSD.

Despite the plausible assumption that the effects of hallucinogens predominantly arise in the central nervous system, most studies of these drugs in intact subjects have been conducted following systemic administration. The objective of the present investigation was to characterize the stimulus effects of (-)2,5-dimethoxy-4-methylamphetamine ((-)-DOM) following intracerebroventricular administration. Chronic indwelling cannulae were implanted into the lateral ventricle of male Fischer 344 rats trained to discriminate systemically administered (-)-DOM or lysergic acid diethylamide (LSD) from saline. Time-course and dose-response relationships for (-)-DOM and LSD administered intracerebroventricularly were established. For both LSD and (-)-DOM, central administration did not change the pretreatment times required for the maximal stimulus effects to occur. However, the onset of the stimulus effect was more rapid following intracerebroventricular administration. Following pretreatment periods that maximize drug-appropriate responding, central administration of (-)-DOM and LSD was approximately 2.4- and 1.5-times more potent, respectively, than systemic administration. The results of this study are consistent with the assumption that the stimulus effects of (-)-DOM and LSD are centrally mediated.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗

PubMed1992

Determination of drugs from urine by on-line immunoaffinity chromatography-high-performance liquid chromatography-mass spectrometry.

A method for rapid extraction and identification of drugs in urine is described. The system utilizes a high-performance protein G immunoaffinity column coupled to a reversed-phase analytical column by use of a trapping column and switching valve. A small amount of antibody (5 micrograms drug-specific) is used for each analysis to extract either propranolol or lysergic acid diethylamide (LSD) from human urine. Urine diluted with phosphate-buffered saline is pumped directly through the protein G column thus eliminating time- and solvent-consuming sample preparation procedures. On-line ultraviolet or mass spectral analysis provides the means of drug detection and identification. With ultraviolet detection propranolol may be detected in spiked urine at the 250 pg/ml level. A Hewlett-Packard mass spectrometer modified for atmospheric pressure ionization and equipped with an ion spray source allows detection of propranolol in urine at 2.5 ng/ml and LSD at 500 pg/ml using single ion monitoring. The potential applicability of the technique for drug confirmations is discussed.

Chromatography, Affinity↗

PubMed1984

Experimental CNS ischemia: serotonin antagonists reduce or prevent damage.

We tested three serotonin antagonists--lysergic acid diethylamide (LSD), 2-bromolysergic acid diethylamide (BOL), and cinanserin--for effects on experimental spinal cord ischemia in the rabbit. Blood flow to spinal cord was obstructed. Drugs were administered before or after initiation of occlusion, and flow was later restored. When LSD was given 5 minutes after the onset of occlusion, the duration of ischemia required to produce neurologic abnormality was prolonged, but this protection was temporary. BOL and cinanserin treatment 5 minutes after the onset of ischemia was beneficial because neurologic improvement was permanent, and pretreatment with these drugs also markedly reduced damage. Therefore, several serotonin antagonists can prevent or reduce spinal cord damage when administered before or after the onset of ischemia.

Animals↗

PubMed1983

The 5-hydroxytryptamine receptor of blood platelets.

Blood platelets show specific, high affinity binding of 3H-5-hydroxytryptamine, 3H-ketanserin and 3H-D-lysergic acid diethylamide. 5-HT-antagonists are considerably more potent than agonists regarding both the displacement of specifically bound 3H-ketanserin and the shape change reaction mediated by the 5-HT-receptor. The latter depends on a rise of free intracellular Ca2+. The binding site for 3H-ketanserin and the site at which the 5-HT-induced shape change is triggered show the characteristics of a 5-HT2-receptor whose intracellular mediator seems to be Ca2+. The 5-HT2-receptor of platelets may be used as a partial model for that in neurons; however, it remains to be elucidated whether Ca2% is a mediator of the latter.

Animals↗

PubMedDate not supplied

Antagonist properties of d-LSD at 5-hydroxytryptamine2 receptors.

The hallucinogenic agent d-lysergic acid diethylamide (d-LSD) interacts with a number of serotonin (5-hydroxytryptamine [5-HT]) receptor subtypes in the central nervous system. It has been hypothesized that hallucinosis is produced by agonist activity at 5-HT2 receptors. There exist, however, numerous data from radioligand binding, cellular, smooth muscle, and behavioral studies that suggest that d-LSD is a potent 5-HT2 antagonist. These data are reviewed in this report. In addition, d-LSD displays agonist activity at 5-HT1A and 5-HT1C receptor subtypes, as determined in biochemical studies. At the present time, agonist interactions at 5-HT1C receptors, as opposed to 5-HT2 receptors, appears to be a more likely "common mechanism of action" of hallucinogenic agents.

Animals↗

PubMed1995

Role of alpha 1-adrenoceptors and 5-HT2 receptors in serotonin-induced contraction of rat prostate: autoradiographical and functional studies.

Urinary obstruction from benign prostatic hyperplasia is a common clinical problem possibly associated with excessive prostatic constriction around the urethra. These studies compared adrenergic and serotonergic functional activity to specific alpha 1 and serotonin (5-hydroxytryptamine; 5-HT) binding sites in the rat prostate. Isolated, left ventral lobes of the rat prostate were removed and examined for in vitro contraction. Norepinephrine-induced contraction of the rat prostate was competitively blocked by prazosin with an apparent antagonist dissociation constant (pKB) of 8.13. 5-HT also contracted the rat prostate. However, in the presence of prazosin, maximum 5-HT contraction was reduced by half suggesting that high concentrations of 5-HT can activate alpha 1 receptors in the prostate. The concentration-response curve to 5-HT in the presence of 1 microM prazosin was competitively inhibited by the 5-HT2 receptor antagonist LY53857 (6-methyl-1-(1-methylethyl)ergoline-8-carboxylic acid 2-hydroxyl-1-methylpropylester (Z)-2-butenedioate (1:1)) (pKB = 9.02). Autoradiographic studies with [125I]LSD (2-iodo-lysergic acid diethylamide) documented the presence of 5-HT2 receptors since significant displacement of the radioligand occurred with 5-HT and LY53857, but not with prazosin. The alpha 1-adrenoceptor ligand [125I]HEAT ([beta-(4-hydroxy-3-iodophenyl)ethylaminomethyl]-tetralone) confirmed the presence of alpha 1-adrenoceptors in the rat prostate since significant displacement of the radioligand occurred with prazosin, but not 5-HT or LY53857. The inability of prazosin to displace [125I]LSD and the inability of 5-HT to displace [125I]HEAT suggest that 5-HT cannot directly interact with alpha 1-adrenoceptors in the prostate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-1 Receptor Antagonists↗

PubMed1975

Therapeutic usefulness of hallucinogenic drugs as a function of their chemical structure.

D-lysergic acid diethylamide (LSD) displays (1) the phenylethylamine pattern present in mescaline, cyclazocine and catecholamines and (2) the 4-substituted tryptamine structure of psilocybin which is a serotonin analog. Hence (a) Naloxone--a blocker of the LSD-like side effects of cyclazocine--should (and does) block effects of LSD, and (b) cross-tolerance may be present between LSD and cyclazocine but not between mescaline and psilocybin. Even though LSD binds subcortically, its effect on regional perfusion of the brain and, presumably, function is primarily cortical and, since the perfusion shifts evoked by psilocybin are confined to subcortical regions, we assume that other compounds with the phenylethylamine structure such as mescaline, also may selectively affect cortical activity.

Binding Sites↗