Abstract

The administration of 5-hydroxytryptophan (5HTP) to dogs, cats, rabbits, rats and mice produced somatic, autonomic and behavioral effects which grossly resembled those of lysergic acid diethylamide. These effects were associated with a rise in the serotonin levels in the blood, the central nervous system and peripheral tissues.

In dogs and cats low doses of 5HTP decreased spontaneous activity. Larger doses caused excitement and disorientation accompanied by evidence of depressant effects on certain reflexes, motor control and sensory functions. Behavioral effects observed included disorientation, fear and sham rage in dogs and cats, respectively. Rodents given intermediate doses showed excitement and increased spontaneous activity. Large doses produced excitement followed by depression in all species.

5HTP produced mydriasis, piloerection, tachycardia, salivation, lacrimation, tachypnea, retching, vomiting and increased intestinal motility.

5HTP also produced a marked rise in the concentration of serotonin in the rat uterus. Much of this serotonin was found to be pharmacologically inactive.

The possible functional significance of serotonin in the brain was discussed and it was suggested that 5HTP may prove useful in studying the function of serotonin.