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At least 127 records · Page 7Linked to original sources
PubMed1991

The effects of tianeptine on wet-dog shakes, fore-paw treading and a flexor reflex in rats are consistent with enhancement of 5-hydroxytryptamine uptake.

Tianeptine is a novel antidepressant which uniquely facilitates 5-hydroxytryptamine (5-HT) uptake. When given in a dose of 10 mg/kg to rats pretreated with either carbidopa or phenelzine, it markedly reduced the frequency of wet-dog shakes, fore-paw treading, tremor and hind-limb abduction evoked by L-5-hydroxytryptophan (L-5-HTP) given 30 or 60 min later. This effect of tianeptine was opposite to that of paroxetine, a selective 5-HT uptake inhibitor, which greatly increased the 5-HTP-induced behavioural syndrome. In contrast, tianeptine did not affect behaviours elicited by the 5-HT receptor agonists, 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) or (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI), which are not substrates for the 5-HT uptake process. In spinal animals, tianeptine attenuated an ipsilateral flexor reflex, an effect opposite to that of citalopram, a selective 5-HT uptake inhibitor. These effects of tianeptine are consistent with its ability to increase 5-HT reuptake.

Amphetamines↗
PubMed1992

5-HT2/5-HT1C receptor-mediated facilitatory action on unit activity of ventral horn cells in rat spinal cord slices.

5-Methoxy-N,N-dimethyltryptamine (5-MeODMT) and 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) facilitate motoneuron excitability through 5-HT1C/5-HT2 receptors in rats. Using spinal cord slices prepared from adult rats, we recorded unitary cell discharges, evoked by local stimulation of the adjacent site, extracellularly in the motor nuclei of the ventral horn. 5-MeODMT, DOI, 5-hydroxytryptamine (5-HT), 8-hydroxy-2-(di-N-propylamino)tetralin (8-OH-DPAT) and tandospirone facilitated the probability of firing in the motor nuclei, with 5-MeODMT and DOI being the most potent. The effect of 5-MeODMT was significantly suppressed by ketanserin (a 5-HT2 receptor-selective antagonist), spiperone (a 5-HT1A/5-HT2 receptor antagonist) and cyproheptadine (a 5-HT1C/5-HT2 receptor antagonist), but not by 3-tropanyl-3,5-dichlorobenzoate (MDL 72222, a 5-HT3 receptor-selective antagonist) or pindolol (a 5-HT1A/5-HT1B receptor antagonist). This suggests that 5-HT2 and/or 5-HT1C receptors are involved in the facilitatory effects of 5-HT receptor agonists on the synaptic activity of ventral horn cells.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1993

Intrathecal 5-methoxy-N,N-dimethyltryptamine in mice modulates 5-HT1 and 5-HT3 receptors.

The antinociceptive effects of intrathecally administered 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT), a potent 5-HT receptor agonist, were studied in three behavioral tests in mice: the tail-flick test and the intrathecal substance P and N-methyl-D-aspartic acid (NMDA) assays. Intrathecal administration of 5-MeO-DMT (4.6-92 nmol/mouse) produced a significant prolongation of the tail-flick latency. This action was blocked by 5-HT3 and gamma-aminobutyric acidA (GABAA) receptor antagonists but not by 5-HT2, 5-HT1A, 5-HT1B or 5-HT1S receptor antagonists. Binding studies indicated that 5-MeO-DMT had very low affinity for 5-HT3 receptors. 5-MeO-DMT inhibited biting behavior while increasing scratching behavior induced by intrathecally administered substance P. The inhibition of biting behavior was antagonized by intrathecal co-administration of 5-HT1B and GABAA receptor antagonists while 5-HT1A, 5-HT1S, 5-HT2 and 5-HT3 receptor antagonists had no effect. 5-MeO-DMT-enhanced scratching behavior was inhibited by all the antagonists used except ketanserin and bicuculline, suggesting the involvement of 5-HT1A, 5-HT1B, 5-HT1S, 5-HT3 and GABAA receptors. NMDA-induced biting behavior was inhibited by 5-MeO-DMT pretreatment; this action was antagonized by 5-HT1B, 5-HT3 and GABAA receptor antagonists. The involvement of these receptors in 5-MeO-DMT action suggests that it may promote release of 5-HT (5-hydroxytryptamine, serotonin).

Analgesics↗
PubMed1994

Potentiation of 3,4-methylenedioxymethamphetamine-induced dopamine release and serotonin neurotoxicity by 5-HT2 receptor agonists.

The effects of the 5-HT2 receptor agonists 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) and 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) on 3,4-methylenedioxymethamphetamine (MDMA)-induced dopamine release and 5-HT depletion in the striatum were studied. The MDMA-induced increase in the extracellular concentration of dopamine in the striatum was enhanced significantly in rats treated with either DOI (2 mg/kg, ip.) or 5-MeODMT (15 mg/kg, ip.), as assessed using in vivo microdialysis. Neither DOI nor 5-MeODMT alone altered the extracellular concentration of dopamine in the striatum. The striatal concentration of 5-HT was decreased, but not significantly, 7 days following a single administration of MDMA (10 mg/kg, sc.). However, 7 days following the concomitant treatment with DOI and MDMA the striatal concentration of 5-HT was significantly less than that in rats treated with MDMA alone or the vehicle-treated controls. It is concluded that activation of 5-HT2 receptors is an important determinant of the acute increase in extracellular dopamine and, consequently, the long-term depletion of brain 5-HT produced by MDMA.

Amphetamines↗
PubMed1996

The antiaggressive potency of (-)-penbutolol involves both 5-HT1A and 5-HT1B receptors and beta-adrenoceptors.

The relative importance of 5-HT1A and beta-adrenergic activities in the antiaggressive effects of (-)-penbutolol was studied in male mice. (-)-Penbutolol had high affinity for 5-HT1A receptors and beta-adrenoceptors, and antagonized the 5-methoxy-N,N-dimethyltryptamine (5-MeODMT)-induced 5-HT syndrome and the 8-hydroxy-2-(di-n-propylamin)tetralin (8-OH-DPAT)-induced discriminatory stimulus in rats. (-)-Penbutolol abolished aggressive behaviour (ED50 = 56 mumol/kg), and reversed the antiaggressive effects of 8-OH-DPAT and 1-(3-trifluoromethylphenyl)piperazine (TFMPP) (ED50 = 8.1 and 2.1 mumol/kg, respectively). (N-[2-[4-(2-Methoxyphenyl)-1-piperazinyl]ethyl-N-(2-pyridinyl) cyclohexanecarboxamide (WAY 100635) reversed the antiaggressive effects of 8-OH-DPAT (ED50 = 0.012 mumol/kg), but did not affect the antiaggressive effects of TFMPP. The antiaggressive effect of a submaximal dose of 8-OH-DPAT was markedly potentiated by beta-adrenoceptor antagonists without 5-HT1A receptor affinity, whereas (-)-penbutolol was effective at only one dose (4.5 mumol/kg). In conclusion, the 5-HT1A receptor antagonistic potency of (-)-penbutolol in aggressive mice is attenuated by beta-adrenoceptor-induced facilitation of serotonergic neurotransmission.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1985

Activity of serotonin-containing neurons in nucleus raphe magnus in freely moving cats.

Serotonergic neurons were recorded in the nucleus raphe magnus in freely moving cats and were initially identified on-line by their characteristic slow and regular spontaneous activity during quiet waking (3.42 +/- 0.33 spikes/s; mean +/- SE). Discharge rates of these serotonergic neurons were highest during active waking (4.49 +/- 0.40 spikes/s), intermediate during slow-wave sleep (middle: 2.14 +/- 0.23 spikes/s), and lowest during REM sleep (0.20 +/- 0.03 spikes/s). Although these cells fired at a rate 31.3% higher during active waking than during quiet waking, their activity displayed no correlation with phasic elevations of the nuchal EMG or overt body movements. In addition, no relationship was observed between the activity of these neurons during slow-wave sleep and the occurrence of sleep spindles in the cortical EEG or pontogeniculooccipital waves recorded from the lateral geniculate nucleus. Serotonergic neurons of nucleus raphe magnus were also relatively unresponsive to phasic auditory and visual stimuli, with about half of the cells examined showing weak excitatory responses. These neurons did respond, however, to the administration of a small dose of the serotonin specific agonist, 5-methoxy-N,N-dimethyltryptamine (250 micrograms/kg, i.m.) with a mean decrease in unit activity of 73.6 +/- 4.5%. The results of this study are compared with those previously reported for serotonergic neurons in the dorsal raphe nucleus, nucleus centralis superior, and nucleus raphe pallidus of freely moving cats.

Acoustic Stimulation↗
PubMed1985

11C-labeling of indolealkylamine alkaloids and the comparative study of their tissue distributions.

Five indolealkylamines (N,N-dimethyltryptamine, N-methyltryptamine, bufotenine, O-methylbufotenine, N,N,N-trimethyltryptamine iodide) were labeled with 11C by use of 11CH3I. The labeled compounds were synthesized with a radiochemical yield of 2-50% (based on trapped 11CH3I) in 20-35 min with radiochemical purities of more than 92%. The tissue distributions of these labeled compounds were investigated in rats. In all cases, the accumulations in the liver, lung and small intestine were high. [11C]DMT and [11C]OMB also accumulated to a large extent in the brain, where their accumulation was retained. Brain uptake of three other radiopharmaceuticals was low. [11C]DMT is the radiopharmaceutical of choice for the study of the serotonin action mechanism in the brain, because it has the highest radiochemical yield and the highest brain uptake of these 11C-labeled compounds.

Animals↗
PubMed1982

Comparative discriminative stimulus effects of 5-methoxy-N,N-dimethyltryptamine and LSD.

Rats were trained to discriminate injections of either 5-OMe DMT (1.5 mg/kg) or LSD (0.096 mg/kg) from saline in a two-lever drug discrimination task. After stable discrimination performances were attained (greater than 85%) in each group, dose-response generalizations between the two groups of animals were examined. The results revealed that the 5-OMe DMT-stimulus response generalized to LSD and that the LSD-stimulus response generalized to 5-OMe DMT. Furthermore, both the 5-OMe DMT-stimulus and the LSD-stimulus could be significantly attenuated by the serotonin antagonist BC-105. However, the pattern of the dose-related antagonism by BC-105 was different between the drug stimuli. It was concluded that while the discriminative stimulus effects of 5-OMe DMT and LSD may be mediated via a common serotonergic system, the receptor interaction of these agents within that pharmacological system may be somewhat different.

Animals↗
PubMed1982

Hallucinogens as discriminative stimuli: a comparison of 4-OMe DMT and 5-OMe DMT with their methythio counterparts.

Rats, trained to discriminate 1.5 mg/kg of the hallucinogenic agent 5-methoxy-N,N-dimethyltryptamine (5-OMe DMT) from saline in a two-lever drug discrimination task, were challenged with various doses of the 4-methoxy, 4-methylthio and 5-methylthio derivatives of DMT. The 5-OMe DMT cue was found to generalize to all three of these agents; the order of potency is 5-OMe greater than 5-SMe greater than 4-OMe greater than 4-SMe DMT.

Animals↗
PubMed1982

Inhibition of prolactin release by stimulation of presynaptic serotonin autoreceptors.

The effects of 5-methoxy-N,N-dimethyltryptamine (5-MeODMT), a serotonin agonist with a preferential action on presynaptic autoreceptors, on prolactin release in male rats was determined. Basal serum prolactin levels were not altered after administration of 1.0, 2.0, 5.0, 10.0 or 20.0 mg/kg of 5-MeODMT. Pretreatment with 5-MeODMT reduced prolactin release by agents that depend on serotonergic neurotransmission for part of their prolactin release stimulation. Prolactin release in response to L-5-hydroxytryptophan (5-HTP) or morphine was significantly reduced by pretreatment of the rats with 5-MeODMT. The results of this experiment indicate that 5-MeODMT acts as a presynaptic serotonin autoreceptor stimulant and not as a post-synaptic serotonin agonist on the neuronal systems that control prolactin release.

Animals↗
PubMed1984

Acute and chronic effects of LSD and 5-MeODMT on raphe-evoked dorsal root potentials in the cat.

Both acute and chronic effects of lysergic acid diethylamide (LSD) and 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) on the dorsal root potential (DRP), evoked by stimulation of the nucleus raphe magnus of the cat, were examined. Single injections of LSD potentiated while those of 5-MeODMT inhibited the raphe-evoked DRP. The electrophysiologic response produced by each drug correlates well in dosage and time-course with their reported behavioral effects. Following four consecutive daily injections of LSD, complete tolerance developed to the potentiating effect of LSD on this potential. A similar pretreatment schedule with 5-MeODMT failed to alter its acute inhibitory effect on the DRP. These results correlate well with the development of tolerance to the behavioral effects of LSD and 5-MeODMT. This system may thus provide a unique electrophysiological model to examine the effects of these drugs.

Action Potentials↗
PubMed1984

Evidence for 5-HT2 involvement in the mechanism of action of hallucinogenic agents.

The affinities (Ki values) of twenty two psycho-active agents, including LSD, 5-OMe DMT and a series of phenalkylamine derivatives, for cortical 5-HT1 and 5-HT2 binding sites were compared with two measures of behavioral activity. It was found that a significant correlation (r = 0.938) exists between the 5-HT2 binding affinities of these agents and their ED50 values as determined in tests of stimulus generalization using 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) as the training drug. Furthermore, for fifteen of these agents where human data were available, a significant correlation (r = 0.924) also exists between 5-HT2 binding affinities and their human hallucinogenic potencies. The results of this study suggest that the mechanism of action of these agents involves 5-HT2-related events.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗
PubMed1985

Development of selective tolerance to the serotonin behavioral syndrome and suppression of locomotor activity after repeated administration of either 5-MeODMT or mCPP.

Repeated administration to rats of the 5-HT1A-selective agonist 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) produced tolerance to the ability of a test dose of 5-MeODMT to produce the serotonin behavioral syndrome, but not to the ability of a test dose of the 5-HT1B-selective agonist m-chlorophenylpiperazine (mCPP) to decrease locomotor activity. Conversely, repeated administration of mCPP produced tolerance to the ability of a test dose of mCPP to decrease locomotor activity, but not to the ability of a test dose of 5-MeODMT to elicit the serotonin behavioral syndrome. The lack of cross-tolerance between these two selective agonists is consistent with the idea that the serotonin behavioral syndrome and suppression of locomotor activity are mediated by different subtypes of the 5-HT1 receptor.

Animals↗
PubMed1991

Antagonism by 8-hydroxy-2(di-n-propylamino)tetraline and other serotonin agonists of muscarinic M1-type receptors coupled to inositol phospholipid breakdown in human IMR-32 and SK-N-MC neuroblastoma cells.

IMR-32 and SK-N-MC cells were found to contain [3H]quinuclidinyl benzilate specific binding sites inhibited by pirenzepine in a manner suggesting the presence of both M1-type and M2-type muscarinic receptor recognition sites. Neither cell had detectable [3H]8-OH-DPAT binding sites. Carbachol stimulated the rate of inositol phospholipid breakdown in IMR-32 and SK-N-MC human neuroblastoma cells with an EC50 value of about 50 microM in both cases. Pirenzepine inhibited the carbachol (100 microM)-stimulated inositol phospholipid breakdown in both cells with Hill slopes of unity and IC50 values of 15 nM (IMR-32) and 12 nM (SK-N-MC). The 5-HT1A receptor agonist 8-OH-DPAT competitively inhibited carbachol-stimulated inositol phospholipid breakdown with pA2 values of 5.78 (IMR-32) and 5.61 (SK-N-MC). These values are consistent with the inhibitory potency of 8-OH-DPAT towards [3H]quinuclidinyl benzilate binding in these cells. The 5-HT agonists 5-MeODMT and buspirone at micromolar concentrations inhibited carbachol-stimulated breakdown in IMR-32 cells. The inhibition by 8-OH-DPAT and 5-MeODMT was not affected by preincubation with (-)alprenolol. 5-HT (10-100 microM) was without effect on either basal or carbachol-stimulated breakdown. It is concluded that IMR-32 and SK-N-MC neuroblastoma cells express muscarinic M1-type but not serotoninergic receptors coupled to phosphoinositide-specific phospholipase C. 8-OH-DPAT acts as a weak antagonist at these muscarinic receptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1993

Evidence for 5-HT2 receptor involvement in the stimulation of preovulatory LH and prolactin release and ovulation in normal cycling rats.

The participation of serotonin (5-HT) in the control of LH secretion and ovulation has been reported in numerous pharmacological experiments, although the results have been contradictory. In this study to determine the physiological involvement of 5-HT2 receptors in the control of preovulatory LH and prolactin (PRL) release and ovulation, ketanserin (KET), a selective 5-HT2 receptor antagonist, was administered to normal cycling rats. Oral administration of KET at 10 mg/kg BW between 0900h and 1300h on the day of proestrus completely blocked ovulation, while the administration after 1500h did not. The ovulation was confirmed 2 days after treatment with KET. There was no consistent effect on the number of ova ovulated. Co-administration of KET with 5-methoxy-N,N-dimethyltryptamine (5-MeDMT), a 5-HT agonist, at a dose of 2 mg/kg BW ip reversed KET-induced inhibition of ovulation. The highest rate (89%) of reversal was obtained by co-administration at 1500h. KET administered at 1100h completely blocked the preovulatory surge of LH and PRL observed in control animals at 1800h. The present study suggests that 5-HT stimulates preovulatory LH and PRL surge and ovulation via 5-HT2 receptor under physiological conditions and that the effect of 5-HT depends on the critical period and the 24-hour periodicity.

Animals↗