Serotonin 5-HT1A Receptor Binding Research Articles

Sex-dependent effects of social isolation on the regulation of arginine-vasopressin (AVP) V1a, oxytocin (OT) and serotonin (5HT) 1a receptor binding and aggression

It is widely held that social isolation produces higher rates of mortality and morbidity and has deleterious effects on an individual's sociality. Relatedly, it is widely observed that socially isolated adult rodents display significantly higher levels of aggression when placed in a social situation than do their conspecifics living in social groups. In the following study, we investigated the effects of social isolation on several neurochemical signals that play key roles in the regulation of social behavior in adults. More specifically, we examined the effects of social isolation on vasopressin (AVP) V1a, oxytocin (OT) and serotonin (5-HT)1a receptor binding within the neural circuit controlling social behavior. Male and female Syrian hamsters were housed individually or with two other hamsters for four weeks and were then tested with a same-sex nonaggressive intruder in a neutral arena for 5 min. Social isolation significantly increased aggression in both males and females and altered receptor binding in several brain regions in a sex-dependent manner. For example, V1a receptor binding was greater in socially isolated males in the anterior hypothalamus than it was in any other group. Taken together, these data provide substantial new support for the proposition that the social environment can have a significant impact on the structural and neurochemical mechanisms regulating social behavior and that the amount and type of social interactions can produce differential effects on the circuit regulating social behavior in a sex-dependent manner.

Serotonin receptors and suicide, major depression, alcohol use disorder and reported early life adversity

Serotonin neurotransmitter deficits are reported in suicide, major depressive disorder (MDD) and alcohol use disorder (AUD). To compare pathophysiology in these disorders, we mapped brain serotonin transporter (SERT), 5-HT1A, and 5-HT2A receptor binding throughout prefrontal cortex and in anterior cingulate cortex postmortem. Cases and controls died suddenly minimizing agonal effects and had a postmortem interval ≤24 h to avoid compromised brain integrity. Neuropathology and toxicology confirmed absence of neuropathology and psychotropic medications. For most subjects (167 of 232), a DSM-IV Axis I diagnosis was made by psychological autopsy. Autoradiography was performed in right hemisphere coronal sections at a pre-genual level. Linear model analyses included sex and age with group and Brodmann area as interaction terms. SERT binding was lower in suicides (p = 0.004) independent of sex (females < males, p < 0.0001), however, the lower SERT binding was dependent on MDD diagnosis (p = 0.014). Higher SERT binding was associated with diagnosis of alcoholism (p = 0.012). 5-HT1A binding was greater in suicides (p < 0.001), independent of MDD (p = 0.168). Alcoholism was associated with higher 5-HT1A binding (p < 0.001) but only in suicides (p < 0.001). 5-HT2A binding was greater in suicides (p < 0.001) only when including MDD (p = 0.117) and alcoholism (p = 0.148) in the model. Reported childhood adversity was associated with higher SERT and 5-HT1A binding (p = 0.004) in nonsuicides and higher 5-HT2A binding (p < 0.001). Low SERT and more 5-HT1A and 5-HT2A binding in the neocortex in depressed suicides is dependent on Axis I diagnosis and reported childhood adversity. Findings in alcoholism differed from those in depression and suicide indicating a distinct serotonin system pathophysiology.

Reduced cortical serotonin 5-HT2A receptor binding and glutamate activity in high compulsive drinker rats

Serotonin2A receptors and glutamate signaling have been implicated in the pathophysiology and treatment of compulsive spectrum disorders. Schedule-Induced Polydipsia (SIP), characterized by excessive drinking under intermittent food reinforcement schedules, is a valid model for studying the compulsive phenotype in rats. We explored the expression, function, and neurochemistry of 5-HT2A receptors in the frontal cortex (FC) of rats with individual differences to compulsivity. Rats were selected for high (HD) versus low (LD) drinking on SIP. First, we measured 5-HT2A, 5-HT1A, and mGlu2/3 receptors and serotonin transporter binding in different brain regions. Second, we assessed the effect of microinfusion into the medial prefrontal cortex (mPFC) of the 5-HT2A/C receptor agonist DOI, the mGlu2/3 agonist LY379268, and the combination of DOI with the 5-HT2A receptor antagonist M100907 and the 5-HT2C receptor antagonist SB242084. Finally, we measured the serotonin and glutamate efflux in mPFC in basal condition and after DOI local application. The compulsive HD rats showed a specific reduction of 5-HT2A receptor binding in FC compared to LD rats. The highest dose of DOI reduced compulsive drinking in HD rats on SIP, whereas LY379268 did not induce any significant effect. The 5-HT2A receptor antagonist M100907 reversed the DOI induced reduction on compulsive drinking in HD rats while blocking the 5-HT2C receptor did not affect SIP. Compulsive HD rats showed increased serotonin and decreased glutamate efflux in basal conditions that were modified by the DOI application. These findings indicate that reduced 5-HT2A receptor binding and glutamate neurochemical mechanisms may underlie compulsive behavior vulnerability.

Predicting targets of compounds against neurological diseases using cheminformatic methodology.

Recently developed multi-targeted ligands are novel drug candidates able to interact with monoamine oxidase A and B; acetylcholinesterase and butyrylcholinesterase; or with histamine N-methyltransferase and histamine H3-receptor (H3R). These proteins are drug targets in the treatment of depression, Alzheimer's disease, obsessive disorders, and Parkinson's disease. A probabilistic method, the Parzen-Rosenblatt window approach, was used to build a "predictor" model using data collected from the ChEMBL database. The model can be used to predict both the primary pharmaceutical target and off-targets of a compound based on its structure. Molecular structures were represented based on the circular fingerprint methodology. The same approach was used to build a "predictor" model from the DrugBank dataset to determine the main pharmacological groups of the compound. The study of off-target interactions is now recognised as crucial to the understanding of both drug action and toxicology. Primary pharmaceutical targets and off-targets for the novel multi-target ligands were examined by use of the developed cheminformatic method. Several multi-target ligands were selected for further study, as compounds with possible additional beneficial pharmacological activities. The cheminformatic targets identifications were in agreement with four 3D-QSAR (H3R/D1R/D2R/5-HT2aR) models and by in vitro assays for serotonin 5-HT1a and 5-HT2a receptor binding of the most promising ligand (71/MBA-VEG8).

The effects of chronic alcohol self-administration on serotonin-1A receptor binding in nonhuman primates

BackgroundPrevious studies have found interrelationships between the serotonin system and alcohol self-administration. The goal of this work was to directly observe in vivo effects of chronic ethanol self-administration on serotonin 5-HT1A receptor binding with [18F]mefway PET neuroimaging in rhesus monkeys. Subjects were first imaged alcohol-naïve and again during chronic ethanol self-administration to quantify changes in 5-HT1A receptor binding. MethodsFourteen rhesus monkey subjects (10.7–12.8 years) underwent baseline [18F]mefway PET scans prior to alcohol exposure. Subjects then drank gradually increasing ethanol doses over four months as an induction period, immediately followed by at least nine months ad libidum ethanol access. A post [18F]mefway PET scan was acquired during the final three months of ad libidum ethanol self-administration. 5-HT1A receptor binding was assayed with binding potential (BPND) using the cerebellum as a reference region. Changes in 5-HT1A binding during chronic ethanol self-administration were examined. Relationships of binding metrics with daily ethanol self-administration were also assessed. ResultsWidespread increases in 5-HT1A binding were observed during chronic ethanol self-administration, independent of the amount of ethanol consumed. A positive correlation between 5-HT1A binding in the raphe nuclei and average daily ethanol self-administration was also observed, indicating that baseline 5-HT1A binding in this region predicted drinking levels. ConclusionsThe increase in 5-HT1A binding levels during chronic ethanol self-administration demonstrates an important modulation of the serotonin system due to chronic alcohol exposure. Furthermore, the correlation between 5-HT1A binding in the raphe nuclei and daily ethanol self-administration indicates a relationship between the serotonin system and alcohol self-administration.

5-HT2A and mGlu2 receptor binding levels are related to differences in impulsive behavior in the Roman Low- (RLA) and High- (RHA) avoidance rat strains

The Roman Low- and High-Avoidance rat strains (RLA-I vs RHA-I) have been bidirectionally selected and bred according to their performance in the two-way active avoidance response in the shuttle-box test. Numerous studies have reported a pronounced divergence in emotionality between the two rat strains including differences in novelty seeking, anxiety, stress coping, and susceptibility to addictive substances. However, the underlying molecular mechanisms behind these divergent phenotypes are not known. Here, we determined impulsivity using the 5-choice serial reaction time task and levels of serotonin transporter (SERT), 5-HT2A and 5-HT1A receptor binding using highly specific radioligands (3H-escitalopram, 3H-MDL100907 and 3H-WAY100635) and mGlu2/3 receptor binding (3H-LY341495) using receptor autoradiography in fronto-cortical sections from RLA-I (n=8) and RHA-I (n=8) male rats. In the more impulsive RHA-I rats, 5-HT2A, 5-HT1A and SERT binding in the frontal cortex was significantly higher compared to RLA-I rats. In contrast, mGlu2/3 receptor binding was decreased by 40% in RHA-I rats compared to RLA-I rats. To differentiate between mGlu2 and mGlu3 receptor protein levels, these were further studied using western blotting, which showed non-detectable levels of mGlu2 receptor protein in RHA rats, while no differences were observed for mGlu3 receptor protein levels. Collectively, these data show general congenital differences in the serotonergic system and a pronounced difference in mGlu2 receptor protein levels. We suggest that the differences in the serotonergic system may mediate some of the phenotypic characteristics in this strain such as hyper-impulsivity and susceptibility to drug addiction.

Brain-derived neurotrophic factor genotype status impacts on hippocampal serotonin 5-HT1A receptor binding

Brain-derived neurotrophic factor genotype status impacts on hippocampal serotonin 5-HT1A receptor binding

Development of brainstem 5-HT1A receptor-binding sites in serotonin-deficient mice

The sudden infant death syndrome is associated with a reduction in brainstem serotonin 5-hydroxytryptamine (5-HT) and 5-HT(1A) receptor binding, yet it is unknown if and how these findings are linked. In this study, we used quantitative tissue autoradiography to determine if post-natal development of brainstem 5-HT(1A) receptors is altered in two mouse models where the development of 5-HT neurons is defective, the Lmx1b(f/f/p) , and the Pet-1⁻/⁻ mouse. 5-HT(1A) receptor agonist-binding sites were examined in both 5-HT-source nuclei (autoreceptors) and in sites that receive 5-HT innervation (heteroreceptors). In control mice between post-natal day (P) 3 and 10, 5-HT(1A) receptor binding increased in several brainstem sites; by P25, there were region-specific increases and decreases, refining the overall binding pattern. In the Lmx1b(f/f/p) and Pet-1⁻/⁻ mice, 5-HT(1A)-autoreceptor binding was significantly lower than in control mice at P3, and remained low at P10 and P25. In contrast, 5-HT(1A) heteroreceptor levels were comparable between control and 5-HT-deficient mice. These data define the post-natal development of 5-HT(1A)-receptor binding in the mouse brainstem. Furthermore, the data suggest that 5-HT(1A)-heteroreceptor deficits detected in sudden infant death syndrome are not a direct consequence of a 5-HT neuron dysfunction nor reduced brain 5-HT levels. To elucidate the developmental relationship between serotonin (5-HT) levels and 5-HT(1A) receptors in the brainstem, we examined 5-HT(1A) binding in two 5-HT-deficient mouse models. In nuclei containing 5-HT neurons, 5-HT(1A) binding was decreased (autoreceptors), while binding was maintained in projection sites (heteroreceptors). Thus, brainstem 5-HT(1A)-heteroreceptor-binding sites do not appear developmentally sensitive to reduced brain 5-HT levels.

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

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 the left and right hemispheres of all prefrontal regions studied, as well as the 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.

Synergistic Effect between Maternal Infection and Adolescent Cannabinoid Exposure on Serotonin 5HT1A Receptor Binding in the Hippocampus: Testing the “Two Hit” Hypothesis for the Development of Schizophrenia

Infections during pregnancy and adolescent cannabis use have both been identified as environmental risk factors for schizophrenia. We combined these factors in an animal model and looked at their effects, alone and in combination, on serotonin 5HT1A receptor binding (5HT1AR) binding longitudinally from late adolescence to adulthood. Pregnant rats were exposed to the viral mimic poly I:C on embryonic day 15. Adolescent offspring received daily injections of the cannabinoid HU210 for 14 days starting on postnatal day (PND) 35. Hippocampal and cortical 5HT1AR binding was quantified autoradiographically using [3H]8-OH-DPAT, in late adolescent (PND 55), young adult (PND 65) and adult (PND 90) rats. Descendants of poly I:C treated rats showed significant increases of 15–18% in 5HT1AR in the hippocampus (CA1) compared to controls at all developmental ages. Offspring of poly I:C treated rats exposed to HU210 during adolescence exhibited even greater elevations in 5HT1AR (with increases of 44, 29, and 39% at PNDs 55, 65, and 90). No effect of HU210 alone was observed. Our results suggest a synergistic effect of prenatal infection and adolescent cannabinoid exposure on the integrity of the serotoninergic system in the hippocampus that may provide the neurochemical substrate for abnormal hippocampal-related functions relevant to schizophrenia.

Serotonin 5-HT1A receptor binding sites in the brain of the pigeon (Columba livia)

Present knowledge about the serotonergic system in birdbrains is very limited, although the pigeon was used as an animal model in various studies focused on the behavioral effects of serotonergic transmission. In the mammalian brain the 5-HT(1A) receptor is the most widespread serotonin receptor type, and is involved in various functions. Less is known about the distribution of 5-HT(1A) receptors in the avian species. Therefore, we analyzed serotonin 5-HT(1A) receptor binding sites in the pigeon brain using quantitative in vitro receptor autoradiography with the selective radioligand [³H]-8-hydroxy-2-(di-n-propylamino)tetralin ([³H]-8-OH-DPAT). The receptor is differentially distributed throughout the pigeon brain. High levels of 5-HT(1A) receptors are found in the nucleus pretectalis (PT). Moderate densities were detected in the tectum, as well as in the telencephalic nidopallium and hyperpallium. Very low levels were found in the hippocampal formation, the amygdaloid complex, the basal ganglia, and several thalamic nuclei. Furthermore, local variations in 5-HT(1A) receptor densities support the concept of further subdivisions of the entopallium. The regional distribution patterns of 5-HT(1A) receptors mostly display a similar distribution as found in homologue brain structures of mammals.

Age, Sex, and Reproductive Hormone Effects on Brain Serotonin-1A and Serotonin-2A Receptor Binding in a Healthy Population

There is a need for rigorous positron emission tomography (PET) and endocrine methods to address inconsistencies in the literature regarding age, sex, and reproductive hormone effects on central serotonin (5HT) 1A and 2A receptor binding potential (BP). Healthy subjects (n=71), aged 20-80 years, underwent 5HT1A and 2A receptor imaging using consecutive 90-min PET acquisitions with [(11)C]WAY100635 and [(18)F]altanserin. Logan graphical analysis was used to derive BP using atrophy-corrected distribution volume (V(T)) in prefrontal, mesiotemporal, occipital cortices, and raphe nucleus (5HT1A only). We used multivariate linear regression modeling to examine BP relationships with age, age(2), sex, and hormone concentrations, with post hoc regional significance set at p<0.008. There were small postsynaptic 5HT1A receptor BP increases with age and estradiol concentration in women (p=0.004-0.005) and a tendency for small 5HT1A receptor BP declines with age and free androgen index in men (p=0.05-0.06). Raphe 5HT1A receptor BP decreased 4.5% per decade of age (p=0.05), primarily in men. There was a trend for 15% receptor reductions in prefrontal cortical regions in women relative to men (post hoc p=0.03-0.10). The significant decline in 5HT2A receptor BP relative to age (8% per decade; p<0.001) was not related to sex or hormone concentrations. In conclusion, endocrine standardization minimized confounding introduced by endogenous hormonal fluctuations and reproductive stage and permitted us to detect small effects of sex, age, and endogenous sex steroid exposures upon 5HT1A binding. Reduced prefrontal cortical 5HT1A receptor BP in women vs men, but increased 5HT1A receptor BP with aging in women, may partially explain the increased susceptibility to affective disorders in women during their reproductive years that is mitigated in later life. 5HT1A receptor decreases with age in men might contribute to the known increased risk for suicide in men over age 75 years. Low hormone concentrations in adults <50 years of age may be associated with more extreme 5HT1A receptor BP values, but remains to be studied further. The 5HT2A receptor declines with age were not related to sex or hormone concentrations in this sample. Additional study in clinical populations is needed to further examine the affective role of sex-hormone-serotonin receptor relationships.

Cannabinoid administration increases 5HT1A receptor binding and mRNA expression in the hippocampus of adult but not adolescent rats

The endocannabinoid and serotonin systems share a high level of overlap in terms of the physiological processes that they regulate, however, little is known about their functional interactions particularly during adolescence, a vulnerable period for both the development of psychosis and for initiation to substance use. In the present study, the effects of cannabinoid treatment on serotonin 5HT1A receptor density and mRNA expression were investigated in two age groups: Adolescent (postnatal day 35) and adult (postnatal day 70) rats were injected with the synthetic cannabinoid HU210 (25, 50 or 100 μg/kg) or vehicle for 1, 4 or 14 days and sacrificed 24 h after the last injection. 5HT1A receptor density was measured in different brain regions using [ 3H]8-OH-DPAT quantitative autoradiography whereas mRNA expression was measured in adjacent brain sections. Higher levels of both serotonin 5HT1A receptor binding and mRNA expression were observed in limbic regions in adolescent control animals compared to adults. 5HT1A receptor density was increased by 23% in the CA1 region of the hippocampus of adult rats treated with 100 μg/kg HU210 for 4 days compared to vehicle treated controls. The same treatment increased mRNA expression by 27% and by 14% in the CA1 region and dentate gyrus of the hippocampus respectively. 5HT1A receptor density was increased by 22% in the CA1 of adult animals treated with 50 μg HU210, by 26% in the dentate gurus of adult rats treated with 100 μg for 14 days. By contrast, 5HT1A receptor density or mRNA expression was not affected in the brain of adolescent animals in any of the brain regions examined. These results suggest that cannabinoid treatment has differential effects on serotonin-related neurochemistry in adolescent compared to adult rats. The effects in the adult brain may compromise hippocampal function and could account for the cognitive deficits seen in habitual heavy cannabis users.

Moderate perinatal arsenic exposure alters neuroendocrine markers associated with depression and increases depressive-like behaviors in adult mouse offspring

Arsenic is one of the most common heavy metal contaminants found in the environment, particularly in water. We examined the impact of perinatal exposure to relatively low levels of arsenic (50 parts per billion, ppb) on neuroendocrine markers associated with depression and depressive-like behaviors in affected adult C57BL/6J mouse offspring. Whereas most biomedical research on arsenic has focused on its carcinogenic potential, a few studies suggest that arsenic can adversely affect brain development and neural function. Compared to controls, offspring exposed to 50 parts per billion arsenic during the perinatal period had significantly elevated serum corticosterone levels, reduced whole hippocampal CRFR 1 protein level and elevated dorsal hippocampal serotonin 5HT 1A receptor binding and receptor-effector coupling. 5HT 1A receptor binding and receptor-effector coupling were not different in the ventral hippocampal formation, entorhinal or parietal cortices, or inferior colliculus. Perinatal arsenic exposure also significantly increased learned helplessness and measures of immobility in a forced swim task. Taken together, these results suggest that perinatal arsenic exposure may disrupt the regulatory interactions between the hypothalamic–pituitary–adrenal axis and the serotonergic system in the dorsal hippocampal formation in a manner that predisposes affected offspring to depressive-like behavior. These results are the first to demonstrate that relatively low levels of arsenic exposure during development can have long-lasting adverse effects on behavior and neurobiological markers associated with these behavioral changes.

Correlation between serotonin synthesis and 5-HT1A receptor binding in the living human brain: A combined α-[11C]MT and [18F]MPPF positron emission tomography study

Serotonin (5-HT) is one of the major neurotransmitters and has been implicated in a wide variety of cerebral functions. Several lines of evidence indicate that 5HT1A receptors exert a negative feedback in the synthesis and release of serotonin. While most of what is known about serotonin comes from studies in animals, much less empirical evidence exists about the serotonergic system in the living human brain. This study aims to assess the correlation between serotonin synthesis and 5-HT1A receptor binding using positron emission tomography (PET) in humans. Six healthy male volunteers underwent 2 PET scans in the same day: one measuring α-[11C]MT K⁎ [ml/g/min] trapping constant (a measure of serotonin synthesis) and one measuring 5-HT1A receptor binding potential BPND with [18F]MPPF. Volumes of interest (VOIs) selected a priori included: anterior cingulate cortex (ACC), anterior insula, hippocampus, amygdala, thalamus, hypothalamus and midbrain raphe nuclei. Correlation analyses were conducted voxel-by-voxel and with manually traced VOIs. A significant negative correlation between serotonin synthesis and 5-HT1A binding potential was found bilaterally in hippocampus and anterior insula and in the left ACC. The combination of [18F]MPPF and α-[11C]MT PET offers a means to investigate key determinants of 5-HT neurotransmission under physiological and psychopathological conditions in the human brain in vivo.

Measurement of Serotonin 5-HT1A Receptor Binding Using Positron Emission Tomography and [carbonyl-11C]WAY-100635—Considerations on the Validity of Cerebellum as a Reference Region

[Carbonyl-(11)C]WAY-100635 has been used extensively in positron emission tomography (PET) imaging of serotonin 1A receptors (5-HT1A) in vivo in the human brain. Specific binding to receptors is usually estimated using compartmental modeling with arterial plasma input function. The use of reference tissue input (cerebellum) enables quantification without the need of arterial blood sampling, but the accuracy of this method is highly dependent on the validity of the reference region in terms of both specific and nonspecific binding. In this paper, we report exceptionally high uptake of [carbonyl-(11)C]WAY-100635 in the gray matter of cerebellum in one healthy male subject, which was reproducible in repeated PET scanning and most likely represents specific binding to 5-HT1A receptors in cerebellar gray matter. Serotonin 1A receptors are transiently expressed in the human cerebellum during early childhood and usually level off until adolescence but may persist in some individuals. As a methodological implication, the results of this study with regard to test-retest characteristics of [carbonyl-(11)C]WAY-100635 measurements in healthy volunteers using both arterial plasma and reference tissue input functions support the use of cerebellar white matter as reference region, to avoid the potential bias originating from binding of [carbonyl-(11)C]WAY-100635 to 5-HT1A receptors in cerebellar gray matter.

Search for correlations between serotonin 5-HT1A receptor expression and cognitive functions—a strategy in translational psychopharmacology

Animal studies and studies of human aging have suggested that the serotonin 5-HT1A receptor may serve as a biomarker for cognitive functioning and a target for pharmacological treatment of cognitive deficits. The purpose of this positron emission tomography (PET) study was to search for relationships between interindividual variability in serotonin 5-HT1A receptor binding potential (BP) and cognitive functioning. Twenty-four male control subjects, age 20-55 years, were examined with [11C]WAY100635 PET and a battery of cognitive tests. 5-HT1A receptor binding potential were calculated for the raphe nuclei, the hippocampus and the neocortex. Correlation coefficients between BP and cognitive performance were obtained for each region. There was a severalfold of variability in 5-HT1A BP between individuals. We found no significant correlation between regional [11C]WAY100635 binding and cognitive performance. The results do not provide support for involvement of the 5-HT1A receptor in cognitive functioning in man and question the predictive validity of some currently used animal models in translational neuroscience.

Measurement of serotonin 5-HT1A receptor binding using positron emission tomography and [carbonyl-11C]WAY-100635—considerations on the validity of cerebellum as a reference region

Measurement of serotonin 5-HT1A receptor binding using positron emission tomography and [carbonyl-11C]WAY-100635—considerations on the validity of cerebellum as a reference region

Altered Brain Serotonin 5-HT1A Receptor Binding After Recovery From Anorexia Nervosa Measured by Positron Emission Tomography and [Carbonyl11C]WAY-100635

Previous studies have shown that women with anorexia nervosa (AN), when ill and after recovery, have alterations of serotonin (5-HT) neuronal activity and core eating disorder symptoms, such as anxiety. To further characterize the 5-HT system in AN, we investigated 5-HT1A receptor activity using positron emission tomography imaging because this receptor is implicated in anxiety and feeding behavior. To avoid the confounding effects of malnutrition, we studied 13 women who had recovered from restricting-type AN (mean age, 23.3 +/- 5.2 years) and 12 women who had recovered from bulimia-type AN (mean age, 28.6 +/- 7.3 years) (>1 year normal weight, regular menstrual cycles, no bingeing or purging). These subjects were compared with 18 healthy control women (mean age, 25.1 +/- 5.8 years). Intervention The 5-HT1A receptor binding was measured using positron emission tomography imaging and a specific 5-HT1A receptor antagonist, [carbonyl-11C]WAY-100635. Specific 5-HT1A receptor binding was assessed using the binding potential measure. Binding potential values were derived using both the Logan graphical method and compartmental modeling. The binding potential in a region of interest was calculated with the formula: binding potential = distribution volume of the region of interest minus distribution volume of the cerebellum. Women recovered from bulimia-type AN had significantly (P<.05) increased [11C]WAY-100635 binding potential in cingulate, lateral and mesial temporal, lateral and medial orbital frontal, parietal, and prefrontal cortical regions and in the dorsal raphe compared with control women. No differences were found for women recovered from restricting-type AN relative to controls. For women recovered from restricting-type AN, the 5-HT1A postsynaptic receptor binding in mesial temporal and subgenual cingulate regions was positively correlated with harm avoidance. We observed increased 5-HT1A receptor binding in women who had recovered from bulimia-type AN but not restricting-type AN. However, 5-HT1A receptor binding was associated with a measure of anxiety in women recovered from restricting-type AN. These data add to a growing body of evidence showing that altered serotonergic function and anxiety symptoms persist after recovery from AN. These psychobiological alterations may be trait related and may contribute to the pathogenesis of AN.

Association of serotonin 5-HT2A receptor binding and the T102C polymorphism in depressed and healthy Caucasian subjects.

Serotonin 5-HT2A receptor (5-HT2A) binding is reported to be altered in individuals with suicidal behavior, mood disorders, and aggressive-impulsive traits. Genetic association with major depression, suicidal behavior, and aggressive-impulsive traits has not been established. This study examines the possible association of the 5-HT2A gene C102T polymorphism with the receptor binding kinetics, and clinical overt phenotypes. The study population included 63 healthy volunteers and 152 subjects with mood disorders, 56 of whom had a history of suicide attempts. All were Caucasian. Platelet 5-HT2A binding kinetics (Bmax and KD) were assayed and adjusted for seasonal variation. All subjects were genotyped for the T102C polymorphism. Clinical phenotype was determined by structured clinical interview. The TT genotype was associated with higher Bmax in all subjects (F=3.53, df=2,211; p=0.03), controlling for diagnosis. Bonferroni-adjusted post hoc testing showed higher binding in the TT compared with TC genotype in the control group (F=7.56, df=2,60, p=0.001), but not in the mood-disordered subjects. No difference was found in genotype and allele distribution between the mood-disordered subjects, with and without suicide attempt history, and controls. Bmax was not related to a diagnosis of mood disorders. The TT genotype appears associated with higher platelet 5-HT2A Bmax in the healthy population, but this genotypic effect appears absent in mood disorders and unrelated to psychopathology.