Role of high affinity serotonin receptors in neuronal growth

Sex-specific Disruption of the Prairie Vole Hypothalamus by Developmental Exposure to a Flame Retardant Mixture

Prevalence of neurodevelopmental disorders (NDDs) with social deficits is conspicuously rising, particularly in boys. Flame retardants (FRs) have long been associated with increased risk, and prior work by us and others in multiple species has shown that developmental exposure to the common FR mixture Firemaster 550 (FM 550) sex-specifically alters socioemotional behaviors including anxiety and pair bond formation. In rats, FRs have also been shown to impair aspects of osmoregulation. Because vasopressin (AVP) plays a role in both socioemotional behavior and osmotic balance we hypothesized that AVP and its related nonapeptide oxytocin (OT) would be vulnerable to developmental FM 550 exposure. We used the prairie vole (Microtus ochrogaste) to test this because it is spontaneously prosocial. Using siblings of prairie voles used in a prior study that assessed behavioral deficits resulting from developmental FM 550 exposure across 3 doses, here we tested the hypothesis that FM 550 sex-specifically alters AVP and OT neuronal populations in critical nuclei, such as the paraventricular nucleus (PVN), that coordinate those behaviors, as well as related dopaminergic (determined by tyrosine hydroxylase (TH) immunolabeling) populations. Exposed females had fewer AVP neurons in the anterior PVN and more A13 TH neurons in the zona incerta than controls. By contrast, in FM 550 males, A13 TH neuron numbers in the zona incerta were decreased but only in 1 dose group. These results expand on previous work showing evidence of endocrine disruption of OT/AVP pathways, including to subpopulations of PVN AVP neurons that coordinate osmoregulatory functions in the periphery.

Sex-specific effects of perinatal FireMaster® 550 (FM 550) exposure on socioemotional behavior in prairie voles

The rapidly rising incidence of neurodevelopmental disorders with social deficits is raising concern that developmental exposure to environmental contaminants may be contributory. Firemaster 550 (FM 550) is one of the most prevalent flame-retardant (FR) mixtures used in foam-based furniture and baby products and contains both brominated and organophosphate components. We and others have published evidence of developmental neurotoxicity and sex specific effects of FM 550 on anxiety-like and exploratory behaviors. Using a prosocial animal model, we investigated the impact of perinatal FM 550 exposure on a range of socioemotional behaviors including anxiety, attachment, and memory. Virtually unknown to toxicologists, but widely used in the behavioral neurosciences, the prairie vole (Microtus ochrogaster) is a uniquely valuable model organism for examining environmental factors on sociality because this species is spontaneously prosocial, biparental, and displays attachment behaviors including pair bonding. Dams were exposed to 0, 500, 1000, or 2000 μg of FM 550 via subcutaneous (sc) injections throughout gestation, and pups were directly exposed beginning the day after birth until weaning. Adult offspring of both sexes were then subjected to multiple tasks including open field, novel object recognition, and partner preference. Effects were dose responsive and sex-specific, with females more greatly affected. Exposure-related outcomes in females included elevated anxiety, decreased social interaction, decreased exploratory motivation, and aversion to novelty. Exposed males also had social deficits, with males in all three dose groups failing to show a partner preference. Our studies demonstrate the utility of the prairie vole for investigating the impact of chemical exposures on social behavior and support the hypothesis that developmental FR exposure impacts the social brain. Future studies will probe the possible mechanisms by which these effects arise.

Perinatal MAO Inhibition Produces Long-Lasting Impairment of Serotonin Function in Offspring

In addition to transmitter functions, many neuroamines have trophic or ontogenetic regulatory effects important to both normal and disordered brain development. In previous work (Mejia et al., 2002), we showed that pharmacologically inhibiting monoamine oxidase (MAO) activity during murine gestation increases the prevalence of behaviors thought to reflect impulsivity and aggression. The goal of the present study was to determine the extent to which this treatment influences dopamine and serotonin innervation of murine cortical and subcortical areas, as measured by regional density of dopamine (DAT) and serotonin transporters (SERT). We measured DAT and SERT densities at 3 developmental times (PND 14, 35 and 90) following inhibition of MAO A, or MAO B or both throughout murine gestation and early post-natal development. DAT binding was unaltered within the nigrostriatal pathway, but concurrent inhibition of MAO-A and MAO-B significantly and specifically reduced SERT binding by 10–25% in both the frontal cortex and raphe nuclei. Low levels of SERT binding persisted (PND 35, 90) after the termination (PND 21) of exposure to MAO inhibitors and was most marked in brain structures germane to the previously described behavioral changes. The relatively modest level of enzyme inhibition (25–40%) required to produce these effects mandates care in the use of any compound which might inhibit MAO activity during gestation.

Associations between serotonin transporter and behavioral traits and diagnoses related to anxiety

The role of the serotonin transporter promoter-linked polymorphism (5-HTTLPR) in psychiatric disease remains unclear. Behavioral traits could serve as alternative outcomes that are stable, precede psychopathology, and capture more sub-clinical variation. We test associations between 5-HTTLPR and (1) behavioral traits and (2) clinical diagnoses of anxiety and depression. Second and third generation participants (N=203, 34.2±13.8 years, 54% female) at high- or low- familial risk for depression (where risk was defined by the presence of major depression in the 1st generation) were assessed longitudinally using the Schedule for Affective Disorders and Schizophrenia-lifetime interview, Barratt Impulsiveness Scale-11, Buss-Perry Aggression Questionnaire, and the NEO-Five Factor Inventory. High (but not low)-risk offspring with two risk (short, s) alleles had higher impulsivity (+13%), hostility (+31%) and neuroticism (+23%). SS was associated higher rates of panic (OR=7.05 [2.44, 20.38], p=0.0003) and phobic (OR=2.68[1.04, 6.93], p=0.04), but not other disorders. Impulsivity accounted for 16% of associations between 5-HTTLPR and panic, and 52% of association between 5-HTTLPR and phobias. We show that 5-HTTLPR predicts higher impulsivity, hostility, and neuroticism, and that impulsivity could serve as a useful independent outcome or intermediary phenotype in genetic studies of anxiety.

Developmental exposure to a serotonin agonist produces subsequent behavioral and neurochemical changes in the adult male prairie vole

Autistic spectrum disorders (ASDs) are classified as pervasive developmental disorders characterized by abnormalities in various cognitive and behavioral functions. Although exact underlying causes are still unknown, nearly 30% of autistic patients show elevated blood levels of serotonin (5-HT) and, therefore, various genetic and environmental factors that are known to elevate 5-HT levels may play a role in the development of ASDs. In the present study, we used the socially monogamous male prairie vole (Microtus ochrogaster) as an animal model to examine the effects of perinatal exposure to 5-methoxytryptamine (5-MT), a non-selective serotonin agonist, on subsequent behavioral and neurochemical changes in the brain. 5-MT treated males showed a decrease in affiliation and an increase in anxiety-related behavior, as well as a decrease in the density of 5-HT immunoreactive (ir) fibers in the amygdala and oxytocin-ir and vasopressin-ir cells in the paraventricular nucleus of the hypothalamus, compared to saline treated controls. These data indicate that exposure to 5-HT during early development can induce abnormalities in various neurochemical systems which, in turn, may underlie deficits in social and anxiety-related behaviors. In addition, these data will help to establish the prairie vole model to study the neurobiological underpinnings of complex neuropsychiatric disorders such as ASDs.

Buspirone before prenatal stress protects against adverse effects of stress on emotional and inflammatory pain-related behaviors in infant rats: age and sex differences

Prenatal stress strengthens tonic pain and provokes depression. The serotoninergic system is involved in these processes. We recently showed that maternal buspirone, a 5-HT1A receptor agonist, protects against the adverse effects of in utero stress on depression and pain in adult rat offspring. Using a similar maternal treatment with buspirone, we focus here on the infant stage, which is important for the correction of prenatal abnormalities. Maternal buspirone before restraint stress during the last week of pregnancy decreased the time of immobility in the forced swim test in the infant offspring. Prenatal stress increased formalin-induced pain in the second part of the time-course of the response to formalin in males of middle infancy but in the first part of the response in males of late infancy. The effect was reversed by maternal buspirone. Pain dominated in males of both middle and late infancy but the time-course of formalin pain in infant females revealed a slower development of the processes. The results show that the time-course of formalin-induced pain in infant rats reacts to prenatal stress in an age-dependent and sexually dimorphic manner. Our finding of opposite influences of prenatal stress and buspirone before prenatal stress on formalin-induced pain during the interphase indicates that functional maturity of the descending serotonergic inhibitory system occurs in late infancy males (11-day-olds), and 5-HT1A receptors participate in this process. The data provide evidence that maternal treatment with buspirone prior to stress during pregnancy alleviates depression-like and tonic pain-related behaviors in the infant offspring.

Impact of early administration of sertraline on cognitive and behavioral recovery in the first year after moderate to severe traumatic brain injury

OBJECTIVE

To assess the efficacy of sertraline administered in the first 3 months after moderate to severe traumatic brain injury (TBI) in improving cognitive and behavioral outcomes.

DESIGN

Double-blind, randomized controlled trial.

SETTING

Academic medical center.

PARTICIPANTS

Ninety-nine individuals randomized to placebo (n = 50) or sertraline 50 mg (n = 49) conditions. There were no group differences in age, gender, education, or severity of injury.

INTERVENTIONS

Participants were enrolled an average of 21 days after injury (none > 8 weeks), followed by oral administration of placebo or sertraline 50 mg for 3 months.

MAIN OUTCOME MEASURES

Wechsler Memory Scale-Third Edition Logical Memory, Trail Making Test, Wechsler Adult Intelligence Scale-Third Edition Working Memory Index, Symbol-Digit Modalities Test, Wisconsin Card Sorting Test (64-item), Neurobehavioral Functioning Inventory administered 3, 6, and 12 months after the onset of injury.

RESULTS

Early administration of sertraline did not result in improved cognitive functioning during the year after injury compared with placebo administration. Those receiving placebo performed marginally better than the treatment group on a measure of executive function, but this appeared to be inauthentic. The treatment group followed expected recovery patterns based on existing literature. The placebo group performed better than expected on some measures, primarily due to differential dropout.

CONCLUSIONS

Sertraline does not appear to prevent development of cognitive and behavioral problems following TBI, although this does not negate evidence for the treatment (as opposed to prophylactic) role of sertraline to address emotional and neurobehavioral problems in individuals with TBI.

Maternal buspirone protects against the adverse effects of in utero stress on emotional and pain-related behaviors in offspring

Previous investigations from our laboratory demonstrated that prenatal stress exacerbates inflammatory pain-related behavior in adult rats and that fetal serotonin (5-HT) is involved in this phenomenon. In the present study we test the hypothesis that injections of buspirone, a 5-HT1A agonist, to rat dams before restraint stress during the last week of pregnancy (between pregnant days 15 and 20) can improve the characteristics of emotional and inflammatory pain-related behaviors in the adult offspring. Buspirone was injected to dams between the 9 and 20 days of pregnancy, during restraint stress, five min before it. The depression-like behavior in the forced swim test, formalininduced pain and body weight were investigated in the adult offspring. Prenatal stress exacerbated the licking behavior, the index of formalin-induced pain, and increased the time of immobility, the index of depression-like behavior. Buspirone normalized the licking behavior and profoundly reduced the time of immobility, which indicates differences in the mechanisms of antinociceptive and antidepressant effects of buspirone. The present new findings demonstrate that adverse influences of prenatal stress on emotional and inflammatory pain-related behaviors can be prevented by using prenatal buspirone, which shows long-term anxiolytic, antidepressant and antinociceptive effects. The new fact of body weight decrease in buspirone+stress males is worth noting in the context of the important problem of body weight gain as a common side effect of treatment with antidepressant drugs.

Impact of early administration of sertraline on depressive symptoms in the first year after traumatic brain injury

The potential for sertraline administered in the first 3 months after moderate to severe traumatic brain injury (TBI) to decrease the incidence of depression in the first year after injury was assessed in a double-blinded randomized control trial. Subjects were enrolled an average of 21 days after injury (none >8 weeks) followed by oral administration of placebo (50 subjects) or sertraline 50 mg (49 subjects) for 3 months. Subjects were not depressed at the time of study initiation. Outcome was assessed using the Hamilton Depression Rating Scale (HDRS) and the Depression Scale of the Neurobehavioral Functioning Inventory (NFI). Based on intent-to-treat and efficacy subset analyses, those receiving placebo exhibited significantly greater depressive symptoms than those receiving sertraline during the first 3 months after injury while receiving placebo/drug (10% of placebo group achieving a score of 6 or greater on the HDRS, 0% of the sertraline group; p < 0.023.). There was no significant difference in depressive symptoms during the remainder of the year between the two groups. Sertraline is effective in diminishing depressive symptoms even among those not clinically depressed while the medication is being taken. However, the results do not support the idea that administration early in recovery diminishes the expression of depressive symptoms after the drug is stopped. There is no basis from this study to assume that sertraline administered early in recovery after TBI, when neurotransmitter functioning is often altered, has ongoing effects on the serotonin system after sertraline is discontinued.

Monoamine transporters in human endometrium and decidua

BACKGROUND

Monoamines play important roles in decidualization, implantation, immune modulation and inflammation. Furthermore, monoamines are potent vasoactive mediators that regulate blood flow and capillary permeability. Regulation of the uterine blood flow is important both during menstruation and pregnancy. Adequate monoamine concentrations are essential for a proper implantation and physiological development of pregnancy. Unlike most transmitter substances, monoamines are recycled by monoamine transporters rather than enzymatically inactivated. Their intracellular fate is influenced by their lower affinity for inactivating enzymes than for vesicular transporters located in intracellular vesicles. Thus, cells are capable not only of recapturizing and degrading monoamines, but also of storing and releasing them in a controlled fashion.

METHODS

The general objective of the present review is to summarize the role of the monoamine transporters in the female human reproduction. Since the transporter proteins critically regulate extracellular monoamine concentrations, knowledge of their distribution and cyclic variation is of great importance for a deeper understanding of the contribution of monoaminergic mechanisms in the reproductive process. MEDLINE was searched for relevant publications from 1950 to 2007.

RESULTS

Two families of monoamine transporters, neuronal and extraneuronal monoamine transporters, are present in the human endometrium and deciduas.

CONCLUSIONS

New knowledge about monoamine metabolism in the endometrium during menstruation and pregnancy will increase understanding of infertility problems and may offer new pharmacological approaches to optimize assisted reproduction.

The changes of AgNOR parameters of anterior cingulate pyramidal neurons are region-specific in suicidal and non-suicidal depressive patients

The anterior cingulate cortex (AC) is consistently implicated in the pathophysiology of depression. While suicide has been shown in previous reports to be closely related to depression, it is still a distinct phenomenon. The aim to differentiate between depression and suicide was approached by the karyometric analysis of AC pyramidal neurons. The study was performed on paraffin-embedded brains from 20 depressive patients (10 of whom had committed suicide) and 24 matched controls. The karyometric parameters of the layer III and V pyramidal neurons of the dorsal and ventral AC were evaluated bilaterally by Argyrophilic Nucleolar Organiser (AgNOR) silver staining method. Control-specific was the increased nuclear area in ontogenetically younger pyramidal neurons layer III in the left dorsal compared with ventral AC (Wilcoxon test, P<0.01). The decreased AgNOR number per nucleus in these cells in the right ventral AC was depression-specific compared with controls (t-test, P=0.047). On the other hand, the diffuse decrease in AgNOR ratio throughout pyramidal neurons on the left side was specific for suicidal depressive patients compared with non-suicidal patients and controls (ANOVA, P=0.028). The results suggest that regionally differentiated depression- and suicide-specific disturbed function of the most important AC output cells exists in depressive patients.

The tryptophan hydroxylase (TPH) 2 gene unlike TPH-1 exhibits no association with stress-induced depression

BACKGROUND

Serotonin (5-HT) has been implicated in the pathophysiology of several psychiatric disorders including major depression (MD). Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in the biosynthesis of serotonin (5-HT), and might be related to the pathogenesis of MD. Two isoforms are known, TPH-1 and TPH-2. Their association with MD is still debated.

METHODS

A case-control design was used for candidate gene-disease association in 194 patients with stress-induced MD, and 246 healthy controls, all North European Caucasians. Five TPH-2 polymorphisms were analyzed in terms of genotype, allele, and haplotype-based associations.

RESULTS

Neither single marker nor haplotype-based analyses showed significant associations between TPH-2 and MD.

LIMITATIONS

The interpretations are limited by the restricted population size.

CONCLUSIONS

There was no association between TPH-2 gene variants and MD in the same population that had shown a strong association with TPH-1. Hence, the results suggest that in this particular group of stress-induced depression patients TPH-1 appears to be more relevant to MD pathogenesis than TPH-2.

Perinatal exposure to 5-metoxytryptamine, behavioural-stress reactivity and functional response of 5-HT1A receptors in the adolescent rat

Serotonin is involved in a wide range of physiological and patho-physiological mechanisms. In particular, 5-HT1A receptors are proposed to mediate stress-adaptation. The aim of this research was to investigate in adolescent rats: first, the consequences of perinatal exposure to 5-metoxytryptamine (5MT), a 5-HT1/5-HT2 serotonergic agonist, on behavioural-stress reactivity in elevated plus maze, open field and forced swim tests; secondly, whether the behavioural effects induced by perinatal exposure to 5MT on open field and forced swim tests were affected by the selective 5-HT1A receptor agonist LY 228729, a compound able to elicit a characteristic set of motor behaviours on these experimental models, and by the co-administration of the selective and silent 5-HT1A antagonist WAY 100635. Results indicate that a single daily injection of 5MT to, pregnant dams from gestational days 12 to 21 (1mg/kg s.c.), and to the pups from postnatal days 2 to 18 (0.5mg kg s.c.), induce in the adolescent rat offspring: an increase in the percentage of entries and time spent on the open arms in the elevated plus maze; a reduction in locomotor activity and rearing frequency, and an increase in the time spent on the central areas in the open field test; a decrease in immobility and an increase in swimming in the forced swim test. Acute administration of LY 228729 (1.5mg/kg s.c.) strongly decreases rearing frequency and increases peripheral activity in the open field test, and decreases immobility and increases swimming in the forced swim test both in perinatally vehicle and 5MT-exposed offspring. Co-administration of WAY 100635 (0.25mg/kg s.c.) abolishes the effects exerted by LY 228729. These results suggest that, in the adolescent rat, perinatal exposure to 5MT enhances the stress-related adaptive behavioural responses, presumably through a predominant action on presynaptic 5-HT1A receptors and does not deteriorate the functional response of 5-HT1A receptors to selective agonist and antagonist compounds.

Tryptophan hydroxylase-1 gene variants associated with schizophrenia

BACKGROUND

Serotonin (5-HT) has been implicated in the pathophysiology of schizophrenia. Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in the biosynthesis of serotonin (5-HT), and as such it might be related to the pathogenesis of schizophrenia. Two isoforms are known, TPH-1 and TPH-2. TPH-1 association with schizophrenia is debated.

METHODS

A case-control design was employed for gene-disease association in 155 schizophrenic psychosis patients and 253 healthy controls, all North European Caucasians. Six single nucleotide polymorphisms (SNPs) with a haplotype block structure spanning over 23 kb of the total TPH-1 29 kb were analyzed. Linkage disequilibrium and haplotype analyses were performed. Bonferroni correction was used for multiple testing.

RESULTS

Single marker association analyses showed two SNPs significantly associated with schizophrenia. Several haplotypes were associated with the disease. A "sliding window" analysis attributed the strongest disease association to a haplotype configuration localized between the promoter region and intron 3.

CONCLUSIONS

Our data indicate that TPH-1 associates with schizophrenia. It appears that specific combinations of promoter variants vis-à-vis gene transcript variants contribute to genetic predisposition to the disease.

Tryptophan hydroxylase-1 gene variants associate with a group of suicidal borderline women

Alterations in the serotonin (5-HT) system have been related to impulsive aggression and suicidal behavior, common features of the borderline personality disorder (BPD). Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in 5-HT biosynthesis. Two isoforms are known, TPH-1 and TPH-2. TPH-1 has been correlated to various psychiatric and behavioral disorders by gene polymorphism association studies. We aimed to determine whether specific TPH-1 haplotypes associate with BPD. A case-control design was employed. The control group included 98 women without psychiatric history. In all, 95 patients were included, all Caucasian women with a BPD diagnosis who had attempted suicide at least twice during their lifetime. Exclusion criteria were: (i) substance dependence; (ii) dementia or other irreversible organic brain syndromes; (iii) psychotic disorders or major depressive illness with melancholic features; (iv) life-threatening eating disorders. Six single-nucleotide polymorphisms (SNPs) were found at significant linkage disequilibrium across 23 kb of the TPH-1 gene in both patients and controls, suggesting a haplotype block structure. While no individual SNP showed association, several haplotypes associated with the BPD group. In particular, one six-SNP haplotype was absent from the control group while representing about one-quarter of all haplotypes in the BPD group (corrected P<<10(-5)). A 'sliding window' analysis attributed the strongest disease association to haplotype configurations located between the gene promoter and intron 3. We conclude that TPH-1 associates with BPD in suicidal women. Our data support the expectation that haplotype analysis is superior to single locus analysis in gene-disease, case-control association studies.

Formation of the neocortex in mice developing in conditions of prenatal serotonin deficiency

We report here detailed studies of structural changes occurring in the mouse neocortex formed and stratified in conditions of prenatal experimental blockade of serotonin synthesis. Studies were performed using F1(C57BL/CBA) hybrid mice. Endogenous serotonin levels were decreased by exposure of the mice to parachlorophenylalanine, which inhibits the key serotonin synthesis enzyme tryptophan hydroxylase. Offspring brains were studied at 1, 5 and 10 days (n = 10-15 for each time point) of postnatal development. Controls consisted of intact animals at the same periods of development. These experiments showed that prenatal blockade of serotonin synthesis leads to impaired formation of all neocortical layers, impaired growth, development, and differentiation of neurons, and alterations in neuron shape and size. As postnatal development proceeded, significant numbers of neurons died in the brain structures of these animals.

Early neonatal and postweaning social emotional deprivation interferes with the maturation of serotonergic and tyrosine hydroxylase-immunoreactive afferent fiber systems in the rodent nucleus accumbens, hippocampus and amygdala

The impact of early emotional experience on the development of serotonergic and dopaminergic fiber innervation of the nucleus accumbens, hippocampal formation and the amygdala was quantitatively investigated in the precocious rodent Octodon degus. Two animal groups were compared: 1) degus which were repeatedly separated from their parents during the first three postnatal weeks, after weaning they were individually reared in chronic social isolation and 2) controls which were reared undisturbed with their families. In the deprived animals 5-hydroxytryptamine-immunoreactive fiber densities were increased in the core region of the nucleus accumbens (up to 126%), in the central nucleus of the amygdala (up to 112%) and in the outer subregion of the dentate gyrus stratum moleculare (up to 149%), whereas decreased fiber densities were detected in the dentate subgranular layer (down to 86%) and in the stratum lacunosum of the hippocampal cornu ammonis region 1 (down to 86%). Tyrosine hydroxylase-immunoreactive fiber densities were increased in the core (up to 115%) and shell region (up to 113%) of the nucleus accumbens of deprived animals, whereas decreased fiber densities (down to 84%) were observed in the hilus of the dentate gyrus. In the stratum granulosum and subgranular layer the fiber densities increased up to 168% and 127% respectively. In summary, these results indicate that the postnatal establishment of the monoaminergic innervation of limbic areas is modulated in response to early emotional experience, and that this environmental morphological adaptation is highly region specific.

Haplotype analysis reveals tryptophan hydroxylase (TPH) 1 gene variants associated with major depression

BACKGROUND

Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in the biosynthesis of serotonin (5-HT) and might be related to the pathogenesis of major depression (MD). Two isoforms are known, TPH-1 and TPH-2. Tryptophan hydroxylase-1 association with MD is still debated.

METHODS

A single nucleotide polymorphism (SNP) screening strategy was used to define TPH-1 haplotypes spanning over 23 kilobase (kb) of the 29 kb gene length. Genotyping was performed in 228 MD patients and 253 healthy control subjects.

RESULTS

Six SNPs were found at linkage disequilibrium in both patients and control subjects, suggesting a haplotype block structure. Single marker association analyses showed only one SNP significantly associated with MD. Several haplotypes were associated with MD. When all six locus haplotypes were divided into two groups, above or below a 5% threshold, the compound haplotype group below a 5% frequency resulted as associated with the disease (31.6% vs. 18.0% in control subjects, p < 10(-5)). A "sliding window" analysis attributed the strongest disease association to a haplotype configuration localized between introns 7 and 8 (p < 10(-5)).

CONCLUSIONS

Haplotype analysis indicates that TPH-1 associates with MD. The most common TPH-1 variants appear to carry no risk, while some of the less frequent variants might contribute to genetic predisposition to MD.

Maternal ethanol administration inhibits 5-hydroxytryptamine synthesis and tryptophan hydroxylase expression in the dorsal raphe of rat offspring

Maternal ethanol consumption during pregnancy has a detrimental effect on the central nervous system (CNS) development of fetus. 5-Hydroxytryptamine (5-HT) is an important neurotransmitter and/or neuromodulator in the mammalian CNS. Tryptophan hydroxylase (TPH) is the rate limiting enzyme of 5-HT synthesis. Ethanol is known to induce neuropsychiatric disorders by alteration of the central serotonergic system. In the present study, the effects of maternal ethanol intake on the 5-HT synthesis and the TPH expression in the dorsal raphe of rat offspring were investigated. The present results show that the synthesis of 5-HT and the expression of TPH in the dorsal raphe of rat offspring were suppressed by maternal ethanol intake and that the suppressive effect of alcohol was more potent in the 5 weeks old rat pups compared to the 3 weeks old rat pups. Based on the present study, it can be suggested that the pathogenesis of ethanol-induced neuropsychological disorders involves ethanol-induced suppression on the 5-HT synthesis and the TPH expression in the dorsal raphe of offspring.

Separation-induced receptor changes in the hippocampus and amygdala of Octodon degus: influence of maternal vocalizations

Relatively little is known about the basic mechanisms that play a role in the vulnerability of the developing brain toward adverse environmental influences. Our study in the South American rodent Octodon degus revealed that repeated brief separation from the parents and exposure to an unfamiliar environment induces in the hippocampal formation of male and female pups an upregulation of D1 and 5-HT1A receptor density in the stratum radiatum and stratum lacunosum moleculare of the CA1 region. In the CA3 region, only the 5-HT1A receptors were upregulated; no changes were observed for D1 receptors in this region. GABA(A) receptor density in the hippocampus and amygdala was downregulated (nonsignificant trend) after parental separation. The acoustic presence of the mother during parental separation suppressed the D1 and 5-HT1A receptor upregulation in some regions of the hippocampus; no such suppressing influence was observed for the GABA(A) receptors. In the basomedial amygdala, the maternal calls enhanced the separation-induced 5-HT1A receptor upregulation in the male pups, whereas in the female pups the separation-induced receptor densities were not only suppressed by the maternal call but further downregulated, compared with the control group. These results demonstrate that early adverse emotional experience alters aminergic function within the hippocampus and amygdala and that the mother's voice, a powerful emotional signal, can modulate these effects in the developing limbic system.

Altered zincergic innervation of the developing primary somatosensory cortex in monoamine oxidase-A knockout mice

Genetic inactivation of monoamine oxidase-A (MAO-A) significantly elevates levels of serotonin (5-HT) during early development and causes a disruption in the compartmented organization of thalamocortical axon terminals in layer 4 of the somatosensory cortex. In order to determine whether corticocortical innervation of the primary somatosensory cortex is also affected by this mutation, we examined the distribution of zinc-containing axon terminals (terminals known to originate from within the cortex) in the developing somatosensory cortex of MAO-A knockout mice, at postnatal days (PD) 3, 5, 6, 8, 10, 12, 15, 28, and 60. In layer 4 of wild-type mice, histochemical staining for zinc respected barrel-specific compartments at all ages beyond PD 5. By contrast, zinc staining in MAO-A knockout mice did not exhibit signs of barrel compartmentation at any age. Across cortical layers, substantial developmental changes in the distribution of zinc-containing terminals were observed in wild-type mice up until PD 12, at which time the mature lamina-specific pattern of zinc staining was achieved. Similar changes were observed in the somatosensory cortex of MAO-A knockout mice, except that its developmental time course was significantly compressed, with zincergic innervation achieving a mature appearance by PD 8. These results provide evidence that an excess of monoamines, most likely 5-HT, dramatically perturbs the columnar organization of intracortical zincergic afferents in layer 4 and significantly accelerates the appearance of a mature laminar pattern of zinc-containing corticocortical terminals.

Amantadine to improve neurorecovery in traumatic brain injury-associated diffuse axonal injury: a pilot double-blind randomized trial

BACKGROUND

Traumatic brain injury (TBI) caused by a high-speed transportation accident results in a mechanism of injury commonly described as diffuse axonal injury (DAI), which is associated with a reduction in dopamine turnover in the brain. Because of its affect on both dopamine and N-methyl-D-aspartate (NMDA) channels, amantadine has been the subject of considerable interest and clinical use in acute TBI.

PARTICIPANTS

In this study, 35 subjects, who had a TBI in a transportation accident and were initially seen with a Glasgow Coma Scale score of 10 or less within the first 24 hours after admission, were randomly assigned to a double-blind, placebo-controlled, crossover design trial.

MAIN OUTCOME MEASURES

Amantadine, 200 mg, or placebo was each administered for 6 weeks (12 weeks total) to patients who were recruited consecutively.

RESULTS

There was an improvement in the Mini-Mental Status (MMSE) scores of 14.3 points (P =.0185), Disability Rating Scale (DRS) score of 9.8 points (P =.0022), Glasgow Outcome Scale (GOS) score of 0.8 points (P =.0077), and in the FIM Cognitive score (FIM-cog) of 15.1 points (P =.0033) in the group that received amantadine during the first 6 weeks (group 1), but there was no improvement in the second 6 weeks on placebo (P >.05). In group 2 (active drug second 6 weeks), there was an improvement in the MMSE of 10.5 points, in the DRS of 9.4 points (P =.0006), in the GOS of 0.5 points (P =.0231), and in the FIM-cog of 11.3 points (P =.0030, Wilcoxon signed rank) spontaneously in the first 6 weeks on placebo (P =.0015). However, group 2 gained a statistically significant additional 6.3 points of recovery in the MMSE (P =.0409), 3.8 points in the DRS (P =.0099), 0.5 points in the GOS (P =.4008), and 5.2 points in the FIM-cog (P =.0173, Wilcoxon signed rank) between the sixth week and the twelfth week of treatment on the active drug.

CONCLUSIONS

There was a consistent trend toward a more rapid functional improvement regardless of when a patient with DAI-associated TBI was started on amantadine in the first 3 months after injury.

Developmental effects of prenatal cocaine exposure on 5-HT1A receptors in male and female rat offspring

Prenatal cocaine exposure results in behavioral abnormalities throughout development in rats, but little is known regarding the biological mechanisms underlying these abnormalities. Pregnant rats received subcutaneous twice-daily injections (1 ml/kg) of normal saline or 15 mg/kg of cocaine hydrochloride throughout gestation (gestation days 1-20). Following delivery, pups were placed with untreated surrogates. Male and female pups were killed on postnatal days 30, 60 or 120 for assessment of 5-HT(1A) receptor development in the forebrain, diencephalon, midbrain and pons using radiolabel immunocytochemistry. Findings revealed gender and age differences in developmental regulation of 5-HT(1A) receptors, indicating that male rats are more susceptible to long-term consequences of prenatal cocaine exposure in comparison to females. This study also demonstrates gender-specific development of serotonin (5-HT(1A)) receptors across postnatal ages, demonstrating a fundamentally different pattern of development of 5-HT(1A) receptors between males and females.

Altered dendritic spine density in animal models of depression and in response to antidepressant treatment

Olfactory bulbectomy, neonatal clomipramine administration, and maternal deprivation have been employed as animal models of depression. Each model is unique with respect to the experimental manipulations required to produce "depressive" signs, expression and duration of these signs, and response to antidepressant treatments. Dendritic spines represent a possible anatomical substrate for the enduring changes seen with depression and we have previously shown that chronic antidepressant drug exposure alters the density of hippocampal dendritic spines in an enduring fashion. The purpose of the present study was to determine whether persistent alteration of hippocampal spine density is a common element in each of these different models of depression and whether such alterations could be reversed with chronic antidepressant treatment. The results show that olfactory bulbectomy reduced spine density in CA1, CA3, and dentate gyrus compared to sham-operated controls. Chronic treatment with amitriptyline, a tricyclic antidepressant, reversed the bulbectomy- induced reduction in dendritic spine density in CA1, CA3, and dentate gyrus, whereas treatment with mianserin, an atypical antidepressant, reversed this reduction only in dentate gyrus. On the other hand, neither neonatal clomipramine administration nor maternal deprivation affected hippocampal dendritic spine density. Repeated neonatal handling, however, as a control or as part of the maternal deprivation procedure, elevated spine density in dentate gyrus. These data suggest that long-lasting alterations in hippocampal dendritic spine density contribute to the neural mechanism underlying the olfactory bulbectomy model of depression, but not the neonatal clomipramine or maternal deprivation models.

Functional implications of neurotransmitter expression during axonal regeneration: serotonin, but not peptides, auto-regulate axon growth of an identified central neuron

We studied the regenerative properties of one of two electrically coupled molluscan neurons, the serotonergic cerebral giant cells (CGCs) of Lymnaea stagnalis, after axotomy. The CGCs play a crucial role in feeding behavior, and when both cells are disconnected from their target neurons, animals no longer feed. When one CGC was permanently disconnected from its targets and the other was reversibly damaged by a nerve crush, the latter one regenerated over a period of 2 weeks to reform functional synapses with specific target neurons. At the same time, recovery of the feeding behavior was observed. After the crush, neuropeptide gene expression in the CGC was downregulated to approximately 50%. Serotonin synthesis, on the other hand, remained unaffected, suggesting that serotonin might have an active role in regeneration. In primary neuron culture, CGCs failed to extend neurites in the presence of serotonin; in cells that extended neurites in the absence of serotonin, focally applied serotonin, but not neuropeptides, induced growth cone collapse. Using serotonin-sensitive sniffer cells, we show that CGC neurites and growth cones release serotonin in culture. Finally, both the spontaneous and stimulation-induced release of serotonin from CGCs in culture resulted in growth cone collapse responses that could be blocked by the serotonin receptor antagonist methysergide. Our data suggest that auto-released serotonin is inhibitory to CGC neurite outgrowth in vitro. During regeneration in vivo, serotonin release might fine-tune axon guidance and branching by inducing local collapse responses in extending neurites.

Regional changes in density of serotonin transporter in the brain of 5-HT1A and 5-HT1B knockout mice, and of serotonin innervation in the 5-HT1B knockout

5-HT1A knockout (KO) mice display an anxious-like phenotype, whereas 5-HT1B KOs are over-aggressive. To identify serotoninergic correlates of these altered behaviors, autoradiographic measurements of 5-HT1A and 5-HT1B serotonin (5-HT) receptors and transporter (5-HTT) were obtained using the radioligands [3H]8-OH-DPAT, [125I]cyanopindolol and [3H]citalopram, respectively. By comparison to wild-type, density of 5-HT1B receptors was unchanged throughout brain in 5-HT1A KOs, and that of 5-HT1A receptors in 5-HT1B KOs. In contrast, decreases in density of 5-HTT binding were measured in several brain regions of both genotypes. Moreover, 5-HTT binding density was significantly increased in the amygdalo-hippocampal nucleus and ventral hippocampus of the 5-HT1B KOs. Measurements of 5-HT axon length and number of axon varicosities by quantitative 5-HT immunocytochemistry revealed proportional increases in the density of 5-HT innervation in these two regions of 5-HT1B KOs, whereas none of the decreases in 5-HTT binding sites were associated with any such changes. Several conclusions could be drawn from these results: (i) 5-HT1B receptors do not adapt in 5-HT1A KOs, nor do 5-HT1A receptors in 5-HT1B KOs. (ii) 5-HTT is down-regulated in several brain regions of 5-HT1A and 5-HT1B KO mice. (iii) This down-regulation could contribute to the anxious-like phenotype of the 5-HT1A KOs, by reducing 5-HT clearance in several territories of 5-HT innervation. (iv) The 5-HT hyperinnervation in the amygdalo-hippocampal nucleus and ventral hippocampus of 5-HT1B KOs could play a role in their increased aggressiveness, and might also explain their better performance in some cognitive tests. (v) These increases in density of 5-HT innervation provide the first evidence for a negative control of 5-HT neuron growth mediated by 5-HT1B receptors.

Potential involvement of S100B in the protective effects of a serotonin-1a agonist on ethanol-treated astrocytes

Previously, this laboratory found that the offspring of rats that consumed ethanol on a chronic basis prior to parturition exhibited a significant reduction in serotonin (5-HT) neurons and in astrocytes proximal to these neurons. This laboratory also showed that maternal treatment with a 5-HT(1A) agonist during the latter part of gestation prevented the reduction of 5-HT neurons and most of the astrocyte abnormalities. The present in vitro studies extended our prior in vivo work by examining the potential involvement of S100B with the protective effects of a 5-HT(1A) agonist, i.e., buspirone, on astrocytes. Astrocyte cultures were either maintained in chemically defined media in the presence and absence of ethanol and buspirone or in conditioned media that was generated by ethanol- and buspirone-treated astrocytes. A mouse monoclonal antibody to S100B was used to assess the potential involvement of S100B with the protective effects of buspirone. Additional in vitro studies measured the direct effects of S100B and ethanol on astrocyte proliferation. These investigations demonstrate that in vitro ethanol exposure reduces the number of astrocytes, and that treatment with the 5-HT(1A) agonist buspirone prevents the ethanol-associated reduction in astrocyte number. The protective effects of buspirone appear to be mediated by factors that are secreted by astrocytes; such factors likely include S100B. In addition, added S100B prevents an ethanol-associated reduction in [(3)H]-thymidine incorporation into proliferating astrocytes.

Relationship between central serotonergic function and aggression in prepubertal boys: effect of age and attention-deficit/hyperactivity disorder

Data indicate that diminished central serotonergic (5-HT) function is related to aggression in adults, but discrepant findings in children suggest that age or the presence of attention-deficit/hyperactivity disorder (ADHD) may influence this relationship. This study examined whether age or ADHD affects the association between 5-HT and aggression in 7-11-year old clinically-referred boys. Forty-six boys were divided into non-aggressive ADHD, aggressive ADHD, and aggressive non-ADHD groups based on responses to interviews and ratings of behavior. Central 5-HT function was assessed by measuring the prolactin response to a 1-mg/kg oral dose of D,L-fenfluramine. There was no significant difference in the prolactin response across the three groups of boys. Furthermore, when examined dimensionally, prolactin response was largely unrelated to ratings of aggression, even after controlling for ADHD. Finally, age was not associated with prolactin response, and had no effect on the relationship between prolactin response and aggression. This study provides further evidence that there is no clear relationship between central 5-HT function and aggression in disruptive boys. Moreover, these data do not confirm the hypothesis that age or the presence of ADHD influence the relationship between 5-HT and childhood aggression.

Chronic fluoxetine administration to juvenile rats prevents age-associated dendritic spine proliferation in hippocampus

The density of dendritic spines, the postsynaptic sites of most excitatory synapses, increases during the first 2 postnatal months in rat hippocampus. Significant alterations in hippocampal levels of serotonin and norepinephrine impact synaptic development during this time period. In the present study, dendritic spine density was studied in the hippocampus (CA1) and dentate gyrus of juvenile rats acutely and chronically exposed to antidepressant drugs that act on serotonin and norepinephrine. One group of 21-day-old rats was given a single injection of a serotonin specific re-uptake inhibitor (fluoxetine or fluvoxamine), a norepinephrine-specific re-uptake inhibitor (desipramine), or saline and killed after 24 h. A second group of rats was injected daily, beginning on postnatal day (PN) 21, for 3 weeks. This group was further subdivided into rats that were killed 1 day or 21 days after the last injection. Golgi analysis showed that a single injection of fluvoxamine produced a significant increase in dendritic spine density in stratum radiatum of CA1 and in the dentate gyrus. Further, acute treatment with all three antidepressants increased the total length of secondary dendrites in CA1, with fluoxetine and desipramine increasing the number of secondary dendrites as well. In fluoxetine-treated animals killed on days 42 or 62 (1 or 21 days post-treatment, respectively), dendritic spine density remained at levels present in CA1 at 21 days. These results show that acute antidepressant treatment can impact dendritic length and spine density, and raise the possibility that chronic fluoxetine treatment arrests spine development into young adulthood.

In utero exposure to serotonergic drugs alters neonatal expression of 5-HT(1A) receptor transcripts: a quantitative RT-PCR study

In embryonic rat brain, serotonin (5-HT) acts as a differentiation signal for 5-HT neurons and their target cells during midgestation. Serotonin receptors expressed during this period include the 5-HT(1A) subtype, which may mediate some of these developmental effects. Using the highly sensitive method of competitive RT-PCR, we quantified the effects of maternal treatment with either p-chlorophenylalanine (pCPA; which depletes 5-HT in embryonic rat brain) or 5-methoxytryptamine (5-MT; a general 5-HT(1) /5-HT(2) agonist) from embryonic day E12-17 on expression of 5-HT(1A) receptor mRNA transcripts in brains of offspring at postnatal day 4 (PND 4). In offspring of both pCPA and 5-MT treated mothers, 5-HT(1A) transcripts were significantly reduced compared to vehicle controls, although effects of pCPA were greater than those of 5-MT. These results indicate that either under-stimulation of 5-HT(1A) receptors (due to pCPA-induced 5-HT depletion) or over-stimulation (by the agonist 5-MT) during prenatal development significantly reduced expression of 5-HT(1A) receptor transcripts in neonatal offspring. This may occur by disruption of 5-HT(1A) gene transcription or by post-transcriptional mechanisms (such as altered translation or turnover of mRNA). Whatever the mechanism, reductions in 5-HT(1A) receptor transcripts following in utero exposure to serotonergic drugs could significantly impact the number of 5-HT(1A) receptors expressed in neonatal rat brain. Whether such effects will persist into adulthood remains to be determined.

Plasticity of 5-hydroxytryptamine(1B) receptors during postnatal development in the rat visual cortex

The distribution of 5-hydroxytryptamine1A and 5-hydroxytryptamine1B receptors in the visual cortex was studied by quantitative autoradiography during postnatal development. Overall, receptor densities increased throughout development, but exhibited regional rearrangements, particularly in the case of 5-hydroxytryptamine1B receptors. Neonatal treatment with 5,7-dihydroxytryptamine, which causes selective degeneration of serotoninergic neurons, had no effect on the density of 5-hydroxytryptamine1A receptors in the visual cortex. However, a transient increase in 5-hydroxytryptamine1B at postnatal days 10-12 was observed after this treatment, suggesting a regulation of postsynaptic receptors. Neonatal enucleation resulted in a marked increase in 5-hydroxytryptamine1B binding sites in all layers of the visual cortex by P16, whereas it had no effect upon 5-hydroxytryptamine1A binding sites. These results show that both receptor subtypes do not exhibit striking transient features in the visual cortex during postnatal development, but rather undergo discrete reorganizations. 5-Hydroxytryptamine1B receptors show changes in density after either neonatal degeneration of serotoninergic neurons or enucleation, indicating that the serotoninergic system involving this receptor subtype can exhibit some postnatal plasticity in the visual cortex.

Changes in the physiological roles of neurotransmitters during individual development

The classical neurotransmitters (acetylcholine and biogenic monoamines) are multifunctional substances involved in intra- and intercellular signaling at all stages of ontogenesis in multicellular animals. A cyclical scheme is proposed to describe age-related changes in neurotransmitter functions at different stages of development from oocyte maturation to neuron formation. This may reflect not only the temporospatial organization of neurotransmitter processes, but also the origin of the functions of acetylcholine and biogenic monoamines from the protosynapses of the cleaved embryo to neuronal synapses.

Serotonin depletion during synaptogenesis leads to decreased synaptic density and learning deficits in the adult rat: a possible model of neurodevelopmental disorders with cognitive deficits

Studies in the past have revealed serotonin to play a role in regulating the development and maturation of the mammalian brain, largely through the release of the astroglial protein S-100beta. S-100beta plays a role in neurite extension, microtubule and dendritic stabilization and regulation of the growth associated protein GAP-43, all of which are key elements in the production of synapses. Depletion of serotonin, and thus of S-100beta, during synaptogenesis should lead to a loss of synapses and the behaviors dependent on those synapses. The current study was undertaken to test this hypothesis. In order to assess the influence of serotonin we have looked at the synaptic density in the adult after depletion, by using immunodensitometry of synaptic markers (synaptophysin and MAP-2) and by studying behaviors thought to be highly dependent on synaptic plasticity and density. Male Sprague-Dawley rats were depleted of serotonin on postnatal days (PND) 10-20 by treating with the tryptophan hydroxylase inhibitor parachlorophenylalanine (PCPA; 100 mg/kg, s.c.). On PND's 30 and 62, animals were perfused for immunodensitometry. Littermates were used for behavioral testing. At PND 55-62, the animals were tested in an interchangeable maze with olfactory cues and in an eight-arm radial maze. Our results show a loss of both synaptic markers in the hippocampus on PND 30. At PND 62, the only remaining loss was of the dendritic marker MAP-2. The animals had deficits in both behaviors tested, suggestive of spacial learning deficits and of the failure to extinguish learned behaviors or to re-learn in a new set. Our findings show the long-term consequences of interfering with the role of serotonin in brain development on the morphology and function of the adult brain. These findings may have implications for human diseases, including schizophrenia, thought to be related to neurodevelopmental insults such as malnutrition, hypoxia, viruses or in utero drug exposure. Moreover, they provide further insights into the functioning of serotonin and S-100beta in development and aging.

Age-related changes in the association between serotonergic function and aggression in boys with ADHD

The results of several studies have indicated an inverse relationship between central serotonergic (5-HT) mechanisms and aggression in animals and adults, but studies in children have yielded conflicting results. This study assessed 5-HT function, using a fenfluramine (FEN) challenge procedure, in an attempt to replicate a previously reported enhancement of the prolactin (PRL) response to FEN in aggressive relative to nonaggressive ADHD boys. The study failed to replicate the previous finding. Samples from both studies were then examined to reconcile the discrepant findings. The samples differed significantly in age. The entire group (n = 50) was then divided into older and younger subgroups and reanalyzed using a two-way (age-group x aggression) analysis of covariance (ANCOVA) controlling for plasma medication level. The ANCOVA generated a significant age-group x aggression interaction. Young aggressive boys had a significantly greater PRL response to FEN than young nonaggressive boys, but no such difference existed in the older age-group. These findings raise the possibility of different developmental trajectories in 5-HT function between aggressive and nonaggressive boys.

From oocyte to neuron: do neurotransmitters function in the same way throughout development?

1. Classical neurotransmitters (such as acetylcholine, biogenic amines, and GABA) are functionally active throughout ontogenesis. 2. Based on accumulated evidence, reviewed herein, we present an hypothetical scheme describing developmental changes in this functional activity, from the stage of maturing oocytes through neuronal differentiation. This scheme reflects not only the spatio-temporal sequence of these changes, but also the genesis of neurotransmitter functions, from "protosynapses" in oocytes and cleaving embryos to the development of functional neuronal synapses. 3. Thus, it appears that neurotransmitters participate in various forms of intra- and intercellular signalling throughout all stages of ontogenesis.

Hypoxia and brain development

Hypoxia threatens brain function during the entire life-span starting from early fetal age up to senescence. This review compares the short-term, long-term and life-spanning effects of fetal chronic hypoxia and neonatal anoxia on several behavioural paradigms including novelty-induced spontaneous and learning behaviours. Furthermore, it reveals that perinatal hypoxia is an additional threat to neurodegeneration and decline of cognitive and other behaviours during the aging process. Prenatal hypoxia evokes a temporary delay of ingrowth of cholinergic and serotonergic fibres into the hippocampus and neocortex, and causes an enhanced neurodegeneration of 5-HT-ir axons during aging. Neonatal anoxia suppresses hippocampal ChAT activity and up-regulates muscarinic receptor sites for 3H-QNB and 3H-pirenzepine binding in the hippocampus in the early postnatal age. The altered development of axonal arborization and pre- and postsynaptic cholinergic functions may be an important underlying mechanism to explain the behavioural deficits. As far as the cellular mechanisms of perinatal hypoxia is concerned, our primary aim was to study the putative importance of Ca2+ homeostasis of developing neurons by means of pharmacological interventions and by measuring the development of immunoexpression of Ca(2+)-binding proteins. We assessed that nimodipine, an L-type calcium channel blocker, prevented or attenuated the adverse behavioural and neurochemical effects of perinatal hypoxias, while it enhanced the early postnatal development of ir-Ca(2+)-binding proteins. The results are discussed in the context of different related research areas on brain development and hypoxia and ischaemia.

Protective effects of maternal buspirone treatment on serotonin reuptake sites in ethanol-exposed offspring

Previous work in this laboratory demonstrated that in utero ethanol exposure is associated with abnormal development of the serotonergic system. Specific abnormalities included deficiencies of serotonin (5-HT) and its metabolites, and cortical 5-HT reuptake sites. The concentration of 5-HT1A receptors was also altered. The serotonin deficit was detected in the fetal ethanol-exposed brain, at an age when 5-HT would normally function as an essential trophic factor. Thus, it was hypothesized that the early 5-HT ethanol-associated deficit of an essential trophic factor (e.g. 5-HT) could contribute to subsequent developmental abnormalities in serotonergic neurons. In the present investigation we used quantitative autoradiography (QAR) to more fully characterize the developmental abnormalities in 5-HT reuptake sites in developing offspring of ethanol-fed rats. In addition, we attempted to overcome the potential negative impact of the ethanol-associated deficit of fetal 5-HT, by administering a 5-HT1A agonist, buspirone, to pregnant rats. These investigations demonstrated that postnatal (PN) 19 and/or 35 day ethanol-exposed offspring had a significant decrease in [3H]citalopram binding to 5-HT reuptake sites in the frontal cortex, parietal cortex, lateral hypothalamus, substantia nigra, medial septum, and striatum. In contrast, [3H]citalopram binding was increased in the dorsal raphe on PN5 and in the median raphe on PN19. No significant ethanol-associated changes were detected in the hippocampus CA3 region or in the amygdala. When [3H]citalopram binding was compared in the offspring of saline- and buspirone-treated dams, it appeared that maternal treatment with buspirone prevented or reversed most of the ethanol-associated developmental abnormalities in 5-HT reuptake sites. Buspirone prevented the decline in binding of [3H]citalopram in the frontal cortex, lateral hypothalamus, substantia nigra and medial septum. Similarly, buspirone treatment prevented the ethanol-associated increase in binding in the dorsal and median raphe. Additional experiments are needed to elucidate the impact of maternal buspirone treatment on the development of other neurotransmitter systems in offspring.

Lack of barrels in the somatosensory cortex of monoamine oxidase A-deficient mice: role of a serotonin excess during the critical period

In a transgenic mouse line (Tg8) deficient for the gene encoding monoamine oxidase A (MAOA), we show that the primary somatosensory cortex (S1) lacks the characteristic barrel-like clustering of layer IV neurons, whereas normal pattern formation exists in the thalamus and the trigeminal nuclei. No barrel-like patterns were visible with tenascin or serotonin immunostaining or with labeling of thalamocortical axons. An excess of brain serotonin during the critical period of barrel formation appears to have a causal role in these cortical abnormalities, since early administration of parachlorophenylalanine, an inhibitor of serotonin synthesis, in Tg8 pups restored the formation of barrels in S1, whereas inhibition of catecholamine synthesis did not. Transient inactivation of MAOA in normal newborns reproduced a barrelless phenotype in parts of S1.

Enhancement by serotonin of the growth in vitro of antennal lobe neurons of the sphinx moth Manduca sexta

Cell culture experiments have been used to examine the effects of serotonin [5-hydroxytryptamine (5-HT)] on the morphological development of antennal lobe (AL) neurons in the brain of the sphinx moth, Manduca sexta. The majority of cells used in this study were from animals at stage 5 of the 18 stages of metamorphic adult development. 5-HT did not affect the survival of M. sexta AL neurons in culture, but did increase the numbers of cells displaying features characteristic of certain cell types. Three morphologically distinct cell types were examined in detail. The principal effect of 5-HT on these neurons was enhancement of cell growth. The magnitude of responses to this amine was cell-type specific. Site-specific responses to 5-HT were apparent also in one cell type. Our results suggest that the effects of 5-HT can change during the course of metamorphic development. These changes coincide temporally with the development of fast, sodium-based action potentials.

Adrenocorticotropic hormone activation of adenylate cyclase in raphe neurons: multiple regulatory pathways control serotonergic neuronal differentiation

The RN46A cell line was derived from embryonic day 13 rat medullary raphe cells by infection with a retrovirus encoding the temperature-sensitive mutant of SV40 large T antigen (tsT-ag). The RN46A cell line is neuronally restricted and constitutively differentiates following a shift to nonpermissive temperature. Differentiated RN46A cells express low levels of tryptophan hydroxylase (TPH) but no detectable levels of serotonin (5-HT). Treatment of cultures with the adrenocorticotropic hormone peptide ACTH4-10 up-regulates the expression of TPH immunoreactivity in differentiated RN46A cells, but 5-HT synthesis requires initial treatment with ACTH4-10, followed by partial membrane depolarizing conditions. Up-regulation of TPH by ACTH4-10 is apparently due to activation of adenylate cyclase, whereas the increased 5-HT synthesis with membrane depolarization can be blocked with the voltage-sensitive Ca(2+)-channel blockers nifedipine and omega-conotoxin. ACTH4-10 treatment also markedly up-regulates the expression of the 5-HT reuptake transporter, as do dibutyryl cyclic AMP and forskolin; chronic membrane depolarization has no effect on 5-HT reuptake. The expression of the high-affinity 5-HT1A receptor is increased threefold by ACTH4-10 treatment during differentiation and fivefold by differentiation under partial membrane depolarizing conditions. Combining ACTH4-10 treatment and membrane depolarization does not increase expression of the 5-HT1A receptor further. 5-HT release is constitutive in ACTH-treated RN46A cells and linked to spontaneous synaptic vesicle fusion in RN46A cells. Considered with previous results, these data indicate that multiple effectors, ACTH, brain-derived neurotrophic factor, and membrane depolarization, have both distinct and overlapping effects that regulate specific elements of the serotonergic neuronal phenotype during differentiation and maturation.

The role of receptor/channel activity in neuronal cell migration

Confocal laser microscopy, in conjunction with carbocyanine dyes and calcium-sensitive fluorescent indicators, was used in slices and explant cultures of developing cerebellum to study cellular mechanisms underlying a motility of neuronal cell migration. The results indicate that a combination of voltage- and ligand-activated ion channels cooperatively regulates Ca2+ influx into the migrating cells. We suggest that molecules, present in the local cellular milieu, affect cell motility by activating specific ion channels and second messengers that influence polymerization of stiff and contractile cytoskeletal proteins. This early interaction between postmitotic neurons and surrounding cells controls the rate of their movements, sculpts their shapes, establishes their positions, and, therefore, indirectly determines their identities to prior formation of synaptic connections.

Postnatal development of hippocampal and neocortical cholinergic and serotonergic innervation in rat: effects of nitrite-induced prenatal hypoxia and nimodipine treatment

Postnatal development of ingrowing cholinergic and serotonergic fiber patterns were studied in the rat hippocampus and parietal cortex employing a histochemical procedure for acetylcholinesterase as a cholinergic fiber marker, and immunocytochemistry of serotonin for serotonergic fiber staining. The rat pups were killed at postnatal days 1, 3, 5, 7, 10, and 20. The development of cholinergic and serotonergic innervation was described and the fiber density quantified under normal conditions and after long-term prenatal anemic hypoxia induced by chronic exposure to sodium nitrite. Furthermore, a third group was studied in which the nitrite hypoxia was combined with a simultaneous treatment with the Ca(2+)-entry blocker nimodipine to test the neuroprotective potential of this drug. Quantitative measurement of fiber density from postnatal day 1 to day 20 yielded the following results: (i) both neurotransmitter systems revealed an age-dependent and an anatomically-organized developmental pattern; (ii) the serotonergic innervation of the dorsal hippocampus preceded that of cholinergic afferentation in postnatal days 1-3; (iii) prenatal hypoxia induced a transient delay in the innervation of parietal neocortex and dentate gyrus for both neurotransmitter systems, but left the innervation of the cornu ammonis unaffected; and (iv) the hypoxia-induced retardation of cholinergic and serotonergic fiber development was prevented by concomitant application of the Ca(2+)-antagonist nimodipine during the hypoxia. The results indicate that prenatal hypoxia evokes a temporary delay in the cholinergic and serotonergic fiber outgrowth in cortical target areas in a region-specific manner. The hypoxia-induced growth inhibition is prevented by the calcium antagonist nimodipine, which supports the importance of the intracellular Ca2+ homeostasis of cells and growth cones in regulating axonal proliferation.

Lack of evidence for serotonergic effect on the cellular development of the olfactory bulb in the postnatal rat

Serotonin has been postulated to influence several developmental parameters. The potential role of serotonin in the development of the rat olfactory bulb, a simple cortical structure, was determined following selective depletion of serotonin to the olfactory bulb of neonate rats. In the neonate, 5,7-dHT was injected into the anterior olfactory nucleus to selectively destroy serotonergic axons leading to the bulb. Following survival of 5 days to 3 months, the rats were sacrificed and analyzed by immunocytochemical markers, Nissl stain, Golgi impregnation, and image analysis. The serotonin depletions had no significant effect on the cytoarchitecture of the bulb or on neuronal or glial cell growth. In addition, the depletions did not affect neuronal migration or differentiation (overall length of dendrites, branch points, or dendritic spines) of cell populations in the bulb. These findings suggest that serotonin does not, by itself, affect the overall development of cellular elements in the bulb, although this study does not rule out the possibility that serotonin may affect other parameters of development.

Cocaine-induced deficits in ACTH and corticosterone responses in female rat progeny

The objective of this study was to determine whether prenatal exposure to cocaine could produce functional changes in central serotonergic systems mediating neuroendocrine responses in female progeny. Pregnant rats were administered either saline or (-) cocaine (15 mg/kg, SC, b.i.d.) from gestational day 13-20. Progeny were fostered to nontreated lactating dams at birth. Central serotonergic function was determined by the ability of a serotonin releaser, p-chloroamphetamine (PCA), to stimulate plasma adrenocorticotropin (ACTH), corticosterone, and renin secretion in female progeny at postnatal day (PD) 30. Prenatal cocaine did not alter basal levels of ACTH, corticosterone, or renin. In contrast, ACTH and corticosterone responses to the 5-HT releaser PCA were significantly attenuated (-28% to 43%) in cocaine progeny, while the renin response to PCA was unaffected. These data suggest that cocaine administration during pregnancy can produce long-term selective alterations in neuroendocrine responses mediated by central serotonergic systems in prepubescent female progeny.