Hypodipsia, stereotypy and hyperactivity induced by beta-phenylethylamine in the water-deprived rat.

beta-Phenylethylamine (PEA) is an endogenous constituent of human, rat and other mammalian brain tissue. It is rapidly metabolised by type B monoamine oxidase, and there is evidence for specific binding sites for PEA in rat brain. In the first experiment, the effects of systemically-administered PEA (3.125-50.0 mg/kg) on water consumption in water deprived male rats were investigated. PEA produced a depression of drinking within the first 15 min following its administration, with a strong linear relation between drug dose and the degree of depression. In the following 45 min, there was evidence of a dose-related recovery in the drinking. In the second experiment, the effects of PEA on activity in water-deprived rats were investigated. PEA at 12.5 m/kg produced behavioral stimulation, which was particularly evident in measures of total horizontal activity. At higher doses, 25.0 and 50.0 mg/kg, PEA induced a behavioral stereotypy syndrome, associated with a depression of horizontal and vertical activities. Relationships between the hypodipsic effect of PEA and its ability to produce psychomotor stimulation at a moderate dose level, and stereotypy at higher dose levels are considered.