Effects of serotonin on neurite outgrowth from thalamic neurons in vitro

doi:10.1016/S0306-4522(98)00501-6

Neuroscience

Volume 90, Issue 3, May 1999, Pages 967-974

https://doi.org/10.1016/S0306-4522(98)00501-6 Get rights and content

Abstract

Altering levels of serotonin in the primary somatosensory cortex during early postnatal life influences thalamocortical development. Recent in vivo experiments suggest that serotonin may have direct effects on the growth of thalamocortical axons, and the present study was undertaken to determine whether this amine influences process outgrowth from thalamic cells maintained in culture. Ventrobasal thalamic neurons were harvested from newborn rats and maintained in culture for eight days. At the end of this period, 0, 10, 25, 50 or 100 μM serotonin was added to the culture medium. After an additional six days, cultures were fixed and stained with neuron-specific enolase. Quantitative analysis of >500 cells from each condition indicated that 25 μM serotonin, but not the other concentrations of this amine, significantly increased the length of the primary (longest) process growing out from the cell body (P<0.001), the total (summed) length of all processes (P<0.0001), total neurites per cell (P<0.05), number of branch points per cell (P<0.01) and branch points on the primary neurite (P<0.0005).

These results demonstrate that exposing thalamic cells to serotonin increases process outgrowth from them in the absence of their cortical targets.

Section snippets

Substrate preparation

Glass coverslips (12 mm diameter; Fisher) were acid cleaned, sterilized and placed in 0.25 ml of poly-d-lysine (0.01%; 70,000–100,000 mol wt in sterile water; Sigma). After 30 min, excess poly-d-lysine was removed and coverslips were allowed to air dry in a sterile hood. All cultures were grown in neural basal medium (NB; Gibco) that also contained 10% defined supplemented fetal bovine serum (Hyclone).

Culture preparation

Rat pups (Zivic-Miller Laboratories, Sprague–Dawley rats) no more than 12 h old (postnatal day 0,

Controls

An adequate test of the hypothesis that 5-HT influences neurite development by VB neurons in vitro requires that basal levels of 5-HT in the cultures approach zero and that added 5-HT remains available in the culture for the duration of the test period. Both of these conditions were fulfilled in the study. The NB used for the tissue culture experiments contained trace amounts (0.07±10 ng/μl) of 5-HT, as measured by HPLC. Assessment of 5-HT levels in culture wells demonstrated that the amine was

Discussion

The present results demonstrate that increasing concentrations of 5-HT increase process outgrowth for thalamic cells maintained in tissue culture in the absence of their cortical targets. The results suggest a curvilinear relationship between 5-HT concentration and neurite outgrowth. Specifically, the 25 μM 5-HT concentration had the greatest effect on all of the variables analysed, and both lower and higher concentrations were not significantly different from controls with respect to any of the

Conclusions

In summary, the present results indicate that 5-HT significantly influences neurite outgrowth of thalamic neurons, and this effect is independent of any interaction between the axons of these neurons and their cortical targets. The mechanism(s) underlying these effects of 5-HT remain(s) to be determined.

References (35)

M.W. Baker et al.
Serotonin depletors, 5,7-dihydroxytryptamine and p-chlorophenylalanine, cause sprouting in the CNS of the adult snail
Brain Res.
(1993)
C.A. Bennett-Clarke et al.
Patterning of the neocortical projections from the raphe nuclei in perinatal rats: investigation of potential organizational mechanisms
J. comp. Neurol.
(1994)
C.A. Bennett-Clarke et al.
Serotonin 1B receptors in the developing somatosensory and visual cortices are located on thalamocortical axons
Proc. natn. Acad. Sci. U.S.A.
(1993)
C.A. Bennett-Clarke et al.
Effect of serotonin depletion on vibrissae-related patterns of thalamic afferents in the rat's somatosensory cortex
J. Neurosci.
(1994)
C.A. Bennett-Clarke et al.
Thalamocortical afferents in rat transiently express high-affinity serotonin uptake sites
Brain Res.
(1997)
M.E. Blue et al.
A comparison of pattern formation by thalamocortical and serotonergic afferents in the rat barrel field cortex
Cerebral Cortex
(1991)
G. Bruning et al.
Transient expression of the serotonin transporter in the developing mouse thalamocortical system
Acta histochem.
(1997)
O. Cases et al.
Lack of barrels in the somatosensory cortex of monoamine oxidase A-deficient mice: role of a serotonin excess during the critical period
Neuron
(1996)
R.J. D'Amato et al.
Ontogeny of the serotonergic projection to rat neocortex: transient expression of a dense innervation to primary sensory areas
Proc. natn. Acad. Sci. U.S.A.
(1987)
J.A. Daugherty et al.
Effects of neonatal serotonin depletion upon development of rat somatosensory cortex
Soc. Neurosci. Abstr.
(1989)

T.J. Diefenbach et al.

Neurite branch development of an identified serotonergic neuron from embryonic Helisoma: evidence for autoregulation by serotonin

Devl Biol.

(1995)

M. Fujimiya et al.

Postnatal development of serotonin nerve fibers in the somatosensory cortex of mice studied by immunohistochemistry

J. comp. Neurol.

(1986)

J.I. Goldberg et al.

Expression and function of the neurotransmitter serotonin during development of Helisoma nervous system

Devl Biol.

(1989)

K. Goslin et al.

Changes in the distribution of GAP-43 during the development of neuronal polarity

J. Neurosci.

(1990)

P.G. Haydon et al.

Serotonin selectively inhibits growth cone motility and synaptogenesis of specific identified neurons

Science

(1984)

P.G. Haydon et al.

The regulation of neurite outgrowth cone motility, and electrical synaptogenesis by serotonin

J. Neurobiol.

(1987)

M. Igarashi et al.

Ligand-induced growth cone collapse: amplification and blockade by variant GAP-43 peptides

J. Neurosci.

(1995)

Cited by (67)

Serotonin and development
2020, Handbook of Behavioral Neuroscience
Citation Excerpt :
There are also effects on the cortex itself. Excess serotonin at this time leads to loss of the typical barrel-like patterns of cells in somatosensory cortex (Cases et al., 1996; Lieske, Bennett-Clarke, & Rhoades, 1999). There is a reduced columnar organization and aberrant communications within the cortex (Erzurumlu & Gaspar, 2012; Miceli et al., 2013).
Serotonin is the most widely distributed monoamine in the mammalian brain and plays an extensive role both in adult brain function and in development of the immature brain. These two components of serotonin's actions coexist throughout life, in varying amounts. During brain development, serotonin regulates its own final terminal density (autoregulation) cortical and circuitry development and specific connections between the thalamus and cortex. Increasingly, these properties are being studied in animal models so that selective serotonin receptor actions at critical periods are known. By understanding these receptor effects, and knowing selective pharmacological agents for these receptors, there will be an increasing understanding of the potential utility of developmental pharmacology—that is using pharmacotherapy to improve the outcome of developmental disorders related to serotonin deficits, including autism, sudden infant death syndrome, fetal alcohol syndrome, rare genetic syndromes, and the effects of early childhood adversity.
Serotonin depletion increases seizure susceptibility and worsens neuropathological outcomes in kainate model of epilepsy
2017, Brain Research Bulletin
Citation Excerpt :
However, because the inhibiting effect of pCPA on 5-HT synthesis, albeit reversible, can last for several days or even weeks (Park et al., 1994), the possibility that serotonin depletion additionally affect the “maturation” stages of epileptogenesis cannot be excluded. Indeed, serotonin is crucial for many form of neuronal and synaptic plasticity, including, fiber outgrowth (Lieske et al., 1999), neurogenesis (Diaz et al., 2013), synaptogenesis (Mogha et al., 2012) and long-term potentiation (Sarnyai et al., 2000), which have all been implicated in epilepsy (Pitkänen and Sutula, 2002). Whatever the case, it is clear from this experiment and prior studies that serotonin neurotransmission plays modulatory roles in three major aspects of epilepsy, including (1) susceptibility to the initial insult, (2) seizure susceptibility, including to later-life spontaneous seizures, and (3) seizure frequency during the chronic phase of epilepsy.
Serotonin is implicated in the regulation of seizures, but whether or not it can potentiate the effects of epileptogenic factors is not fully established. Using the kainic acid model of epilepsy in rats, we tested the effects of serotonin depletion on (1) susceptibility to acute seizures, (2) development of spontaneous recurrent seizures and (3) behavioral and neuroanatomical sequelae of kainic acid treatment. Serotonin was depleted by pretreating rats with p-chlorophenylalanine. In different groups, kainic acid was injected at 3 different doses: 6.5 mg/kg, 9.0 mg/kg or 12.5 mg/kg. A single dose of 6.5 mg/kg of kainic acid reliably induced status epilepticus in p-chlorophenylalanine-pretreated rats, but not in saline-pretreated rats. The neuroexcitatory effects of kainic acid in the p-chlorophenylalanine-pretreated rats, but not in saline-pretreated rats, were associated with the presence of tonic-clonic convulsions and high lethality. Compared to controls, a greater portion of serotonin-depleted rats showed spontaneous recurrent seizures after kainic acid injections. Loss of hippocampal neurons and spatial memory deficits associated with kainic acid treatment were exacerbated by prior depletion of serotonin. The present findings are of particular importance because they suggest that low serotonin activity may represent one of the major risk factors for epilepsy and, thus, offer potentially relevant targets for prevention of epileptogenesis.
How serotonin receptors regulate morphogenic signalling in neurons
2017, Progress in Neurobiology
Serotonin (5-hydroxytrympamine or 5-HT) is one of the phylogenetically oldest neurotransmitters, and the serotonergic system is among the earliest developed neuronal systems. Serotonin is critically involved in regulating multiple physiological functions, acting via a heterogenic receptor family that includes G protein-coupled receptors and ligand-gated ion channels. Although serotonergic neurons comprise a widely distributed and complex network that targets nearly every brain structure, serotonin-mediated signalling is under strict temporal and spatial control. Imbalance in serotonergic signalling is implicated in many pathophysiological conditions, including schizophrenia, Alzheimer’s disease, depression, and anxiety. In addition to its well-established role as a neurotransmitter, serotonin is involved in many aspects of neural development, including neurite outgrowth, somatic morphology regulation, growth cone motility, synaptogenesis, and control of dendritic spine shape and density. The morphogenic effects of serotonin are developmentally regulated, and serotonin availability during sensitive developmental stages can modulate the formation and functions of behaviourally relevant neuronal networks in adulthood. Here we provide an overview of the molecular mechanisms responsible for the morphogenic effects of serotonin elicited by its different receptors in neurons. We also discuss the role of serotonin receptor-mediated morphogenic signalling in the development and maintenance of pathophysiological conditions.
Serotonin transporter polymorphisms (5-HTTLPR) in emotion processing. Implications from current neurobiology.
2014, Progress in Neurobiology
Citation Excerpt :
A growing amount of evidence indicates that 5-HT balance is crucial for the development, differentiation and maturation of nerve cells and networks in brain areas that control sensorial input, stimulus processing and motor response. Some examples of this are: (1) 5-HT modulates projections from the cell bodies of thalamocortical glutaminergic neurons in cultures that involve serotonin receptors; (2) 5-HT contributes to differentiation of cortical glutaminergic neurons via one of the 5-HT receptor subgroups (Lieske et al., 1999); and (3) exposure to 5-HT increases the likelihood of long-term potentiation in the visual cortex (Kojic et al., 2000). Others have shown that basal epigenetic factors, such as higher DNA methylation levels within the CpG sites of the serotonin transporter promoter is directly associated with increased depressive symptomatology, Increased methylation of the gene sequence could repress the expression of the 5-HTTLPR (Zhao et al., 2013).
The candidate gene approach directly tests the effects of genetic variation within a potentially contributing gene in an association study. However, the candidate gene approach is limited by how much is known about the biology of the disease being investigated. The serotonin transporter gene SLC6A4 has been studied more than any other single candidate gene in the field of neurobiology. Transcription of the serotonin transporter gene is modulated by a polymorphic region, 5-HTTLPR, near the promoter. 5-HTTLPR genotype has been associated with individual variation in emotion processing, brain structure, and brain function. We present an updated review of the biological literature on the serotonin transporter polymorphism. Recent imaging and behavioral studies of the role of 5-HTTLPR genotype in emotion processing are discussed in light of new biological findings related to 5-HTTLPR variation. We also examine the clinical implications of discoveries about the role of serotonin and 5-HTTLPR genotype in neural plasticity and behavioral malleability.
Gαz regulates BDNF-induction of axon growth in cortical neurons
2014, Molecular and Cellular Neuroscience
The disruption of neurotransmitter and neurotrophic factor signaling in the central nervous system (CNS) is implicated as the root cause of neuropsychiatric disorders, including schizophrenia, epilepsy, chronic pain, and depression. Therefore, identifying the underlying molecular mechanisms by which neurotransmitter and neurotrophic factor signaling regulates neuronal survival or growth may facilitate identification of more effective therapies for these disorders. Previously, our lab found that the heterotrimeric G protein, Gz, mediates crosstalk between G protein-coupled receptors and neurotrophin signaling in the neural cell line PC12. These data, combined with Gαz expression profiles – predominantly in neuronal cells with higher expression levels corresponding to developmental times of target tissue innervation – suggested that Gαz may play an important role in neurotrophin signaling and neuronal development. Here, we provide evidence in cortical neurons, both manipulated ex vivo and those cultured from Gz knockout mice, that Gαz is localized to axonal growth cones and plays a significant role in the development of axons of cortical neurons in the CNS. Our findings indicate that Gαz inhibits BDNF-stimulated axon growth in cortical neurons, establishing an endogenous role for Gαz in regulating neurotrophin signaling in the CNS.
Placenta-derived hypo-serotonin situations in the developing forebrain cause autism
2013, Medical Hypotheses
Autism is a pervasive developmental disorder that is characterized by the behavioral traits of impaired social cognition and communication, and repetitive and/or obsessive behavior and interests. Although there are many theories and speculations about the pathogenetic causes of autism, the disruption of the serotonergic system is one of the most consistent and well-replicated findings. Recently, it has been reported that placenta-derived serotonin is the main source in embryonic day (E) 10–15 mouse forebrain, after that period, the serotonergic fibers start to supply serotonin into the forebrain. E 10–15 is the very important developing period, when cortical neurogenesis, migration and initial axon targeting are processed. Since all these events have been considered to be involved in the pathogenesis of autism and they are highly controlled by serotonin signals, the paucity of placenta-derived serotonin should have potential importance when the pathogenesis of autism is considered. I, thus, postulate a hypothesis that placenta-derived hypo-serotonin situations in the developing forebrain cause autism. The hypothesis is as follows. Various factors, such as inflammation, dysfunction of the placenta, together with genetic predispositions cause a decrease of placenta-derived serotonin levels. The decrease of placenta-derived serotonin levels leads to hypo-serotonergic situations in the forebrain of the fetus. The paucity of serotonin in the forebrain leads to mis-wiring in important regions which are responsible for the theory of mind. The paucity of serotonin in the forebrain also causes over-growth of serotonergic fibers. These disturbances result in network deficiency and aberration of the serotonergic system, leading to the autistic phenotypes.

View all citing articles on Scopus

View full text

Effects of serotonin on neurite outgrowth from thalamic neurons in vitro

Abstract

Section snippets

Substrate preparation

Culture preparation

Controls

Discussion

Conclusions

Serotonin depletors, 5,7-dihydroxytryptamine and p-chlorophenylalanine, cause sprouting in the CNS of the adult snail

Brain Res.

Patterning of the neocortical projections from the raphe nuclei in perinatal rats: investigation of potential organizational mechanisms

J. comp. Neurol.

Serotonin 1B receptors in the developing somatosensory and visual cortices are located on thalamocortical axons

Proc. natn. Acad. Sci. U.S.A.

Effect of serotonin depletion on vibrissae-related patterns of thalamic afferents in the rat's somatosensory cortex

J. Neurosci.

Thalamocortical afferents in rat transiently express high-affinity serotonin uptake sites

Brain Res.

A comparison of pattern formation by thalamocortical and serotonergic afferents in the rat barrel field cortex

Cerebral Cortex

Transient expression of the serotonin transporter in the developing mouse thalamocortical system

Acta histochem.

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

Neuron

Ontogeny of the serotonergic projection to rat neocortex: transient expression of a dense innervation to primary sensory areas

Proc. natn. Acad. Sci. U.S.A.

Effects of neonatal serotonin depletion upon development of rat somatosensory cortex

Soc. Neurosci. Abstr.

Neurite branch development of an identified serotonergic neuron from embryonic Helisoma: evidence for autoregulation by serotonin

Devl Biol.

Postnatal development of serotonin nerve fibers in the somatosensory cortex of mice studied by immunohistochemistry

J. comp. Neurol.

Expression and function of the neurotransmitter serotonin during development of Helisoma nervous system

Devl Biol.

Changes in the distribution of GAP-43 during the development of neuronal polarity

J. Neurosci.

Serotonin selectively inhibits growth cone motility and synaptogenesis of specific identified neurons

Science

The regulation of neurite outgrowth cone motility, and electrical synaptogenesis by serotonin

J. Neurobiol.

Ligand-induced growth cone collapse: amplification and blockade by variant GAP-43 peptides

J. Neurosci.