Gene tied to excitable personality.
One version of the so-called D4 dopamine receptor gene, or D4DR, appears frequently in people who report high levels of "novelty seeking," according to two independent studies reported in the January Nature Genetics.
Some investigators conceive of novelty seeking as a discrete personality trait. People scoring high on this characteristic enjoy exploring new environments, are excitable and quick-tempered, and seek out thrilling sensations. Those scoring low are reflective, deliberate, and orderly.
"This work provides the first replicated association between a specific genetic locus involved in neurotransmission and a normal personality trait," contend Richard P. Ebstein of Sarah Herzog Memorial Hospital in Jerusalem and his colleagues. Ebstein's group performed one of the newly reported studies.
Both investigations took inspiration from a theory advanced by C. Robert Cloninger of Washington University School of Medicine in St. Louis. Cloninger argues for the existence of four independent temperamental traits-novelty seeking, harm avoidance, reward dependence, and persistence (SN: 3/5/94, p. 152).
Based on animal and earlier clinical studies, Cloninger proposed that the way brain cells handle the chemical messenger dopamine shapes an individual's propensity for novelty seeking.
Ebstein's group administered Cloninger's personality questionnaire to 124 unrelated Israeli adults, most of them Ashkenazi or Sephardic Jews. Each volunteer also donated a blood sample for genetic analysis.
Volunteers scoring high in novelty seeking were much more likely to bear a slightly longer form of the D4DR gene than low novelty seekers, the scientists maintain. The D4DR gene helps to regulate the formation of one class of receptors, or molecular gateways, for dopamine transmission in the brain. The longer gene may endow a person with receptors that respond to dopamine by promoting novelty-seeking behavior, Ebstein and his colleagues theorize.
In the other study, Jonathan Benjamin of the National Institute of Mental Health in Bethesda, Md., and his coworkers recruited 315 people in the United States, most of them pairs of male siblings. Volunteers completed a questionnaire that yielded scores on five personality traits-extroversion, openness to experience, neuroticism (being prone to distress and impulsiveness), agreeableness, and conscientiousness. Many psychologists currently favor this classification.
No single trait of the five showed an association with any D4DR variation. However, the long version of the D4DR gene corresponded to a substantially elevated frequency of answers to individual questions that signify novelty-seeking behavior, Benjamin's group asserts.
In a commentary accompanying the new results, Cloninger argues that they support the further use of his personality model for studying the genetics and neurobiology of personality.
Genetics alone does not determine personality, however. An individual's mix of temperamental traits affects responses to the environment and underscores character development throughout adulthood, Cloninger theorizes. In his model, character consists of commitments to goals, cooperativeness, and spiritual beliefs that transcend the self.
The identification of genes contributing to temperament may help to unravel the roots of some psychiatric disorders, Cloninger adds. For instance, a predisposition to novelty seeking may play a role in some cases of schizophrenia, he suggests. One antipsychotic drug, clozapine, specifically targets D4 dopamine receptors, which schizophrenic patients often possess in unusually high numbers. However, prior studies have found that the same patients do not exhibit a preponderance of any particular form of the D4DR gene.
It may be useful to reexamine D4DR in groups of schizophrenics to find how often the longer variety occurs together with novelty seeking, Cloninger contends.
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|Title Annotation:||Science News of the Week|
|Date:||Jan 6, 1996|
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