Platelet monoamine oxidase activity predicts alcohol sensitivity and voluntary alcohol intake in rhesus monkeys

Abstract

Platelet monoamine oxidase B (MAO-B) has been proposed to be a biological marker for the properties of monoamine systems, with low activity being associated with vulnerability for high scores on personality traits such as sensation seeking, monotony avoidance, and impulsiveness, as well as for vulnerability for alcoholism. In the present study, platelet MAO-B activity was analysed in 78 rhesus macaques, and its relation to voluntary alcohol intake and behaviours after intravenous alcohol administration was observed. Monkeys with low platelet MAO-B activity had low levels of 5-hydroxyindole acetic acid in cerebrospinal fluid and showed excessive aggression after alcohol administration. A novel finding was that animals with low platelet MAO-B activity showed less intoxication following alcohol administration. As we have shown previously, they also voluntarily consumed more alcohol. We here replicate results from studies on both humans and non-human primates, showing the utility of platelet MAO as a marker for risk behaviours and alcohol abuse. Furthermore, we link platelet MAO activity to alcohol sensitivity.

Figure 1.

CSF 5-HIAA levels were lower in animals with low platelet MAO-B activity (t = −2.39, P <0.05). Box plot with whiskers showing largest and smallest observation. The boxes represent the lower and the upper quartiles with the median value marked as a line within the boxes.

Figure 2.

A: Motoric intoxication scores were lower in monkeys with low platelet MAO-B activity than in monkeys with high platelet MAO-B activity (t = −2.10, P <0.05). Reported as frequency. B: Monkeys with low platelet MAO-B activity showed more aggressive behaviour after alcohol infusion (t = 4.55, P <0.001). Stare threats. C: Monkeys with low platelet MAO-B activity consumed more alcohol than monkeys with high MAO-B activity (t = 2.15, P <0.05). Mean alcohol intake per day during the two-weeks period. Box plots with whiskers showing largest and smallest observation. The boxes represent the lower and the upper quartiles with the median value marked as a line within the boxes.