ABSTRACT
RATIONALE: The expression of sign-tracking (ST) phenotype over goal-tracking (GT) phenotype has been associated to different aspects of impulsive behavior, and depletions of brain serotonin (5-HT) have been shown to selectively increase impulsive action as well as ST. OBJECTIVES: The present study aimed at testing the relationship between reduced brain 5-HT availability and expression of ST phenotype in a genetic model of individual variation in brain 5-HT functionality. Inbred DBA/2J (DBA) mice are homozygous for the allelic variant of the TPH-2 gene causing lower brain 5-HT function in comparison with C57BL/6J (C57) inbred mice. MATERIALS: Young adult (10 weeks) and adult (14 weeks) C57 and DBA mice were trained in a Pavlovian conditioned approach (PCA) paradigm. Lever-directed (ST) and magazine-directed (GT) responses were measured in 12 daily conditioning sessions. In a second experiment, effect of the medial prefrontal cortex (mPFC) 5-HT depletion by the neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) was assessed on acquisition of ST phenotype in adult C57 mice, according to their higher 5-HT functionality compared to DBA mice. RESULTS: Young adult mice of both strains developed ST phenotype, but only adult DBA mice developed ST phenotype. 5-HT depletion in the mPFC of adult C57 mice completely changed their phenotype, as shown by their increased ST. CONCLUSIONS: These findings indicate that ST phenotype can be the expression of a transitory late developmental stage and that genetic factors determine persistence of this phenotype in adulthood. These findings also support a role of 5-HT transmission in PFC in constraining development of ST phenotype.
Subject(s)
Behavior, Animal/physiology , Prefrontal Cortex/metabolism , Serotonin/metabolism , Animals , Conditioning, Classical/physiology , Mice , Mice, Inbred C57BL , Mice, Inbred DBA , Tryptophan Hydroxylase/genetics , Tryptophan Hydroxylase/metabolismABSTRACT
This multidisciplinary research has been subdivided into two parts. The first examines prognosis of the foetus and its weight development in relation to changes in the hormonal curves of HPL and E3 carried out in a batch of 339 3rd term pregnancies. A very high incidence of small-for-date newborns (30-64%) was noted in mothers with low hormonal values and generally a more frequent onset of hypoxia in pregnancy and in labour. The second part assesses the neurological profile of children born to the same mothers examined in the first part up to the 4th year of life. A neurological deficiency of a different extent was evidenced in 33.3% of the children born to mothers with low hormonal values in pregnancy, especially among those born underweight. The neurological deficiency in the control sample was 7.84%.
