The relation of developmental changes in brain serotonin transporter (5HTT) and 5HT1A receptor binding to emotional behavior in female rhesus monkeys: Effects of social status and 5HTT genotype

Abstract

The goal of the present study was to examine how social subordination stress and 5HTT polymorphisms affect the development of brain serotonin (5HT) systems during the pubertal transition in female rhesus monkeys. We also examined associations with developmental changes in emotional reactivity in response to a standardized behavioral test, the Human Intruder (HI). Our findings provide the first longitudinal evidence of developmental increases in 5HT1A receptor and 5HTT binding in the brain of female primates from pre- to peripuberty. The increase in 5HT1A BPND in these socially housed female rhesus monkeys is a robust finding, occurring across all groups, regardless of social status or 5HTT genotype, and occurring in left and right hemispheres of all prefrontal regions studied, as well as amygdala, hippocampus, hypothalamus, and raphe nuclei. 5HTT BPND also showed an increase with age in raphe, anterior cingulate cortex, and dorsolateral prefrontal cortex. These changes in brain 5HT systems take place as females establish more adult-like patterns of social behavior, as well as during the HI paradigm. Indeed, the main developmental changes in behavior during the HI (increase in freezing and decrease in submission/appeasement) were related to neurodevelopmental increases in 5HT1A receptors and 5HTT, because the associations between these behaviors and 5HT endpoints emerge at peripuberty. We detected an effect of social status on 5HT1A BPND in the hypothalamus and on 5HTT BPND in the orbitofrontal cortex, with subordinates showing higher BPND than dominants in both cases during the pubertal transition. No main effects of 5HTT genotype were observed for 5HT1A or 5HTT BPND. Our findings indicate that adolescence in female rhesus monkeys is a period of central 5HT reorganization, partly influenced by exposure to the social stress of subordination, that likely functions to integrate adrenal and gonadal systems and shape the behavioral response to emotionally challenging social situations.

CRH receptor antagonism reverses the effect of social subordination upon central GABAA receptor binding in estradiol-treated ovariectomized female rhesus monkeys

“…Binding potential (BP ND ) was defined as the ratio at equilibrium of bound flumazenil to that of nondisplacable flumazenil in the tissue of each region. BP ND is a measurement used by our group previously (Embree et al , 2012) that correlates receptor density to experimental conditions (Innis et al , 2007). …”

“…During the experimental period, the YNPRC Field Station acquired a Siemens P4 microPET scanner (Concorde Microsystems, Knoxville, TN, USA) with which the 5 remaining subjects were scanned using identical procedures and staff. Our previously published PET neuroimaging study that was affected by the same change in the YNPRC Imaging Center found instrumentation bias due to differences in the performance of the microPET scanners (Embree et al , 2012). In order to control for this bias we normalized data by calculating the z-distribution for each scanner and converting the mean and variation of the data from the P4 scanner to that of the Focus 220 distribution (Embree et al , 2012).…”

“…Our previously published PET neuroimaging study that was affected by the same change in the YNPRC Imaging Center found instrumentation bias due to differences in the performance of the microPET scanners (Embree et al , 2012). In order to control for this bias we normalized data by calculating the z-distribution for each scanner and converting the mean and variation of the data from the P4 scanner to that of the Focus 220 distribution (Embree et al , 2012). Data from each PET scan were combined into 21 frames and an image reconstructed as previously described (Embree et al , 2012).…”

“…In order to control for this bias we normalized data by calculating the z-distribution for each scanner and converting the mean and variation of the data from the P4 scanner to that of the Focus 220 distribution (Embree et al , 2012). Data from each PET scan were combined into 21 frames and an image reconstructed as previously described (Embree et al , 2012). Both PET images for each subject were summed across frames and then manually rigid-body registered to her structural MRI image using in-house scripts written in IDL (Embree et al , 2012).…”

“…Data from each PET scan were combined into 21 frames and an image reconstructed as previously described (Embree et al , 2012). Both PET images for each subject were summed across frames and then manually rigid-body registered to her structural MRI image using in-house scripts written in IDL (Embree et al , 2012). Regions of interest (ROIs) were manually drawn on an individual subject’s MRI image and then transferred to the PET images (Embree et al , 2012).…”