Are the monoamines involved in shaping conduct ...(t is the one associated with vulnerabili...)

Date:9/13/2009

t is the one associated with vulnerability for antisocial behaviour in females (Nilsson et al., 2008) (see figure 1). This is in line with a marked sex difference between the gene variants with regard to changes in blood flow in specific brain regions as a response to emotional stimuli, using fMRI, which has been shown by the group of Meyer-Lindenberg.

Genetic influences on impulsiveness and sensation seeking

Our findings raise a number of questions:

• How are stable factors such as personality and temporal factors and current mood or appetite related to each other if brain serotonin activity is involved in both?

• How can platelet MAO-B activity be associated with a stable factor such as impulsiveness?

The view on the first question is that the personality, which is a life-long characteristic of the individual, is mainly a consequence of the size or capacity of the brain monoamine systems, while state-dependent factors such as mood are dependent on the current activity, large or small, in the system. It is obvious that an impulsive, sensation-seeking person, as well as a more introvert and monotony-resistant individual can be in a high or low mood, depending on the current situation.

Probably events during life development explain the associations between MAO gene variants and personality. During foetal development, high levels of serotonin have been shown to be an effective inhibitor of the growth of the serotonin system. Hence, gene variants inferring a low rate of inactivation of serotonin, especially during foetal life, will lead to a small or low-capacity brain serotonin system in the adult. Both experiments with animals, using serotonin specific neurotoxins, and studies on humans, e.g. by measuring levels of degradation products of serotonin in the cerebrospinal fluid, have shown that a reduced or low capacity of the brain serotonin system is linked to a personality characterised by
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Contact: Sonja Mak s.mak@update.europe.at 431-405-5734 European College of Neuropsychopharmacology Source:Eurekalert

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