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Lumilysergic acids.

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Lysergic Acid Diethylamide↗

Receptors for 5-hydroxytryptamine in rabbit blood vessels: activation of alpha adrenoceptors in rabbit thoracic aorta.

Experiments were carried out to identify the receptors mediating the contraction of the rabbit thoracic aorta to 5-hydroxytryptamine (5-HT). Isolated aortic rings were mounted in tissue baths for the measurement of isometric contraction and 5-HT dose-response curves were obtained in the presence and absence of receptor antagonists. Prazosin, 1 X 10(-7) M, or 30-min pretreatment with 1 X 10(-5) M benextramine had no effect on the contractile response of aorta to 5-HT up to 1 X 10(-5) M, whereas 2 brom-D-lysergic acid diethylamide, 1 X 10(-7) M, shifted the 5-HT dose-response curve far to the right. Alpha receptor blockade with either prazosin or benextramine in the presence of 2 brom-D-lysergic acid diethylamide produced a greater blockade than that caused by 2 brom-D-lysergic acid diethylamide alone. When 5-HT dose-response curves were extended to 1 X 10(-3) M, three phases were identified. The first, a dose-related contraction, was mediated exclusively by serotonergic receptors. The second, a relaxation to approximately 40% of maximum, occurred at 1 X 10(-5) M and appeared to result from the rapid development of tachyphylaxis. The third phase was a dose-related contraction to concentrations of 5-HT above 1 X 10(-5) M and was inhibited by either prazosin or pretreatment with benextramine. Similar results were obtained in aortic rings from reserpine-pretreated rabbits. It is concluded that the contractile response to concentrations of 5-HT below 1 X 10(-5) M is mediated exclusively by serotonergic receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Serotonergic and dopaminergic influence of the duration of embryogenesis and intracapsular locomotion of Lymnaea stagnalis L.

The role of the dopaminergic and serotonergic system was studied during the embryonic development of the pond snail Lymnaea stagnalis, with special attention to the effect of dopamine and serotonin as well as their agonists and antagonists on the rotation of the veliger larvae, and to the effect of precursors and inhibitors of the synthetizing enzymes on the duration of the embryonic life. Serotonin, D-lysergic acid diethylamide and N,N-dimethyltryptamine increased at a concentration of 1 microM the rotation by 50%, 90% and 87% respectively, and among them D-Lysergic acid diethylamide was found to be the most potent agonist. Other serotonergic agonists and antagonists enhanced the frequency of the rotation (from 165% to 355%) at higher threshold concentrations in the following rank order: methysergid > tryptamine > 2,5-dimethoxy-4-iodoamphetamine > 5-carboxyamidotryptamine > bromo-lysergic acid diethylamide > 7-methyltryptamine. Application of 1-(2-methoxyphenyl) piperazine decreased the rotation by 76%. The reuptake inhibitor desipramine completely blocked the rotation and killed the embryos. Dopaminergic agonists accelerated the rotation by 62% to 233%, and their effect was ranged as follows: dopamine > apomorphine > m-tyramine approximately equal to p-tyramine. Chlorpromazine at 100 microM concentration killed the embryos. At a concentration of 100 microg/ml, tyrosine, the precursor of DA, slowed down the embryonic development by increasing the duration of the embryonic life from 8 to 10 days. Decarboxylase inhibitors, alpha-methyl-3,4-dihydroxyphenyl-alanine (25 microg/ml) and m-hydroxybenzylhydrazin (5 microg/ml), killed 50% of the embryos, meanwhile the rest hatched ten days later, compared to the control animals. The development was partially blocked by the serotonin precusor L-tryptophane (50 microg/ml). Trytophan hydroxylase blocker, p-chlorphenylalanine (50 microg/ml) resulted in a distortion of the body pattern of the embryos, and prevented the hatching of most (95%) of the animals.

Amphetamines↗

A study of antagonists of 5-hydroxytryptamine and catechol amines on the rat's blood pressure.

The effects of 5-hydroxytryptamine on the blood pressure of anaesthetized rats depended on the dose and the initial level of blood pressure. At medium blood pressure levels, 5-hydroxytryptamine gave a depressor response and sometimes a pressor response which was more evident with large doses. The depressor effect was less apparent or even absent at low, and more pronounced at high, blood pressure levels, and the converse applied to the pressor components. Adenosine also gave a depressor and pressor response. Lysergic acid diethylamide, dihydroergotamine, 1-(3,4-dichlorophenyl)-2-isopropylaminoethanol (a dichloro analogue of isoprenaline), dibenamine and 1-benzyl-5-methoxy-2-methyltryptamine antagonized 5-hydroxytryptamine and catechol amines. Lysergic acid diethylamide and 1-benzyl-5-methoxy-2-methyltryptamine were more effective against 5-hydroxytryptamine, 1-(3,4-dichlorophenyl)-2-isopropylaminoethanol and dibenamine against catechol amines; dihydroergotamine was equally effective against both groups. These antagonists fell into two groups according to their action against the two types of effects (depressor and pressor) of 5-hydroxytryptamine: lysergic acid diethylamide and 1-(3,4-dichlorophenyl)2-isopropylaminoethanol acted preferentially against depressor effects; 1-benzyl-5-methoxy-2-methyltryptamine and dibenamine preferentially against pressor; dihydroergotamine was not assignable to either group. Adenosine was affected similarly, but less than 5-hydroxytryptamine.

Amines↗

Hallucinogens and Drosophila: linking serotonin receptor activation to behavior.

The similarity of mode of action, behavior, and gene response between Drosophila melanogaster and mammalian systems, combined with the power of genetics, have recently made the fly an attractive system to study underlying mechanisms of drug abuse, addiction, and mental disorders. The present studies define the behavioral and molecular effects of the powerful hallucinogen lysergic acid diethylamide in Drosophila. Pharmacological activation of serotonin receptors in the fly by lysergic acid diethylamide induces behaviors not unlike those observed in mammalian systems. These include alterations in visual processing abilities, reduced locomotor activity, and altered gene expression within the brain. Many of these effects are due to activation of the same serotonin receptor subtypes that are thought to be the primary mediators of hallucinogenic drug effects in humans as well as the acute symptoms of schizophrenia.We suggest that Drosophila can be used as a genetically tractable model system to define the molecular events leading from serotonin receptor activation to behavior, possibly revealing new targets for hallucinogenic agents and for the treatment of neuropsychiatric disorders such as schizophrenia.

Animals↗