Action Of Tryptamine Research Articles

Tryptamine as an endogenous modulator of neuronal sensitivity to serotonin

Tryptamine has been studied for its effect on the 5-hydroxytryptamine-induced responses of the dorsal root ganglion neurons in rat with intracellular registration of the membrane potential and conductance and application of drugs from micropipettes under pressure. It was found that tryptamine applied in high concentrations acted like 5-hydroxytryptamine; but in the concentration range when it has no effect on the membrane potential and membrane conductance it either enhanced (10(-7) mol/l) or diminished (10(-5) mol/l) 5-hydroxytryptamine responses mediated by 5-HT1A- but not by 5-HT2-receptors. Harmane acted like tryptamine, but its derivatives either only enhanced or only inhibited the 5-hydroxytryptamine effects. The allosterical nature of 5-hydroxytryptamine-modulating action of tryptamine, harmane and its derivatives is discussed.

A comparison of the effects of tryptamine and 5-hydroxytryptamine on feeding following injection into the paraventricular nucleus of the hypothalamus

The effects of 5-hydroxytryptamine (5-HT) and tryptamine injected into the paraventricular nucleus of the hypothalamus (PVN) on food intake, and on noradrenaline- (NA) induced feeding were examined. In nondeprived rats, 12.5–100 nmol 5-HT reduced the intake of palatable wet mash diet over a 30-minute period. Tryptamine (50 and 100 nmol) was without effect in this paradigm. However, when tryptamine was injected into the PVN of rats pretreated with the monoamine oxidase inhibitor, pargyline, a strong anorectic effect was observed. The action of tryptamine in pargyline-treated rats was not affected by depletion of 5-HT levels in the PVN with PCPA. This indicates that the effect of tryptamine is not mediated by a release of endogenous 5-HT. Tryptamine injected into the PVN potentiated the effect of a low dose of 5-HT on food intake. This effect may be due to a prolongation of the activity of 5-HT resulting from tryptamine competing with 5-HT for the same reuptake system. Tryptamine and 5-HT attenuated the feeding response elicited by injection of 25 nmol NA into the PVN. Both tryptamine and 5-HT were more potent at attenuating the effects of NA than in reducing the intake of the palatable wet mash diet. Overall, the results suggest that tryptamine may act via the serotonergic system in the PVN to affect food intake, but it is a weaker compound than 5-HT in this respect.

Tryptamine impairs the acquisition of a one-way active avoidance task

The effects of intraperitoneal administration of tryptamine to rats pretreated with iproniazid, on the acquisition of an unsignalled one-way active avoidance task, were examined. Tryptamine at 2.5 and 5 mg/kg significantly increased the number of trials required to perform this task to a 9/10 consecutive avoidances criterion, without affecting escape performance. The iproniazid pretreatment had no affect on acquisition, or any other performance variable, of the task. Tryptamine did not significantly affect the avoidance response, or escape response latencies; further tryptamine did not alter gross locomotor activity measured as photocell counts. These results suggest that the acquisition deficit was not the result of nonassociative effects such as changes in response capability, general activity level or nociception. The acquisition deficit induced by tryptamine may involve a direct stimulation of central 5-HT receptors since it was not induced by systemically administered 5-HT, was reversed by the 5-HT antagonists methysergide and metergoline, but was not affected by depletion of brain 5-HT, with PCPA, or by the dopamine antagonist haloperidol. Possible behavioural mechanisms for the action of tryptamine are discussed.

The action of tryptamine on the dog spinal cord and its relationship to the agonistic actions of LSD-like psychotogens.

In chronic spinal dogs, LSD, mescaline, psilocin, 2,5-dimethoxy-4-methylamphetamine, methysergide and tryptamine facilitate the flexor reflex evoked by tetanic electrical stimulation of the toe and induce the stepping reflex. These effects are antagonized by chlorpromazine and cyproheptadine, but not by phenoxybenzamine. 5-Hydroxytryptophan and serotonin also facilitate the flexor reflex and evoke the stepping reflex, but these effects are not antagonized by cyproheptadine. These findings suggest that the mode of action of several LSD-like psychotogens is similar to that of tryptamine and is different from that of serotonin or 5-hydroxytryptophan.

The action of tryptamine and 5-hydroxytryptamine on muscles of sea anemones.

Es wird uber pharmakologische Versuche mit Tryptamin an den Sphinctermuskeln und den ringformigen Muskeln der SeeanemonenCalliactis parasitica undMetridium senile berichtet.