D1 dopamine receptor regulation of cell cycle in FGF- and EGF-supported primary cultures of embryonic cerebral cortical precursor cells

A Comparative Analysis of CSF and the Blood Levels of Monoamines As Neurohormones in Rats during Ontogenesis

According to the literature, the cerebrospinal fluid (CSF) in the cerebral ventricles contains numerous neuron-derived physiologically active substances that can function as neurohormones and contribute to volume neurotransmission in the periventricular region of the brain. This study was aimed at carrying out a comparative analysis of CSF and the blood levels of monoamines in rats during ontogenesis as an indicator of age-related characteristics of monoamine transport to body fluids and their function as neurohormones in volume neurotransmission in the periventricular region of the brain. We have shown that CSF in the perinatal period and adulthood contains the most functionally significant monoamines: dopamine, noradrenaline, and serotonin. A comparison of the monoamine levels in the CSF and blood of animals of different age groups revealed that CSF contains monoamines of predominantly neuronal (cerebral) origin and almost no monoamines derived from the general circulation. We also established that monoamines are found in the CSF at physiologically active levels that allow them to act as neurohormones in both reversible volume neurotransmission in the adult brain and irreversible regulation of brain development in the perinatal period.

Morphological Profiling Identifies a Common Mode of Action for Small Molecules with Different Targets

Unbiased morphological profiling of bioactivity, for example, in the cell painting assay (CPA), enables the identification of a small molecule's mode of action based on its similarity to the bioactivity of reference compounds, irrespective of the biological target or chemical similarity. This is particularly important for small molecules with nonprotein targets as these are rather difficult to identify with widely employed target-identification methods. We employed morphological profiling using the CPA to identify compounds that are biosimilar to the iron chelator deferoxamine. Structurally different compounds with different annotated cellular targets provoked a shared physiological response, thereby defining a cluster based on their morphological fingerprints. This cluster is based on a shared mode of action and not on a shared target, that is, cell-cycle modulation in the S or G2 phase. Hierarchical clustering of morphological fingerprints revealed subclusters that are based on the mechanism of action and could be used to predict target-related bioactivity.

Constitutive activity of a G protein-coupled receptor, DRD1, contributes to human cerebral organoid formation

The intricate balance of neural stem cell (NSC) amplification and neurogenesis is central to nervous system development. Dopamine D1 receptor (DRD1) is a typical G protein‐coupled receptor (GPCR) mainly expressed in neurogenic area, with high constitutive activity. The receptor appears in the embryonic period before the formation of mature synaptic contacts, which indicates that dopamine receptor and its constitutive activity play crucial roles in the embryonic brain development. Here, we found that DRD1 was enriched in human NSCs. Inhibition of the receptor activity by its inverse agonists promoted human NSCs proliferation and impeded its differentiation. These results were also mimicked by genetic knockdown of DRD1, which also blocked the effects of inverse agonists, suggesting a receptor‐dependent manner. More interestingly, knock‐in A229T mutant with reduced DRD1 constitutive activity by CRISPR‐Cas9 genome editing technology resulted into increased endogenous human NSCs proliferation. These results were well reproduced in human cerebral organoids, and inhibition of the DRD1 constitutive activity by its inverse agonists induced the expansion and folding of human cerebral organoids. The anatomic analysis uncovered that decreasing the constitutive activity of DRD1 by its inverse agonists promoted the NSCs proliferation and maintenance that led to hindered cortical neurogenesis. Further mechanistic studies revealed that the PKC‐CBP pathway was involved in the regulation by DRD1. Thus, our findings indicate that the constitutive activity of DRD1 and possibly other GPCRs plays an important role in the development of human nervous system.

Sex-Specific Alterations of White Matter Developmental Trajectories in Infants With Prenatal Exposure to Methamphetamine and Tobacco

IMPORTANCE

Methamphetamine is a common illicit drug used worldwide. Methamphetamine and/or tobacco use by pregnant women remains prevalent. However, little is known about the effect of comorbid methamphetamine and tobacco use on human fetal brain development.

OBJECTIVE

To investigate whether microstructural brain abnormalities reported in children with prenatal methamphetamine and/or tobacco exposure are present at birth before childhood environmental influences.

DESIGN, SETTING, AND PARTICIPANTS

A prospective, longitudinal study was conducted between September 17, 2008, and February 28, 2015, at an ambulatory academic medical center. A total of 752 infant-mother dyads were screened and 139 of 195 qualified neonates were evaluated (36 methamphetamine/tobacco exposed, 32 tobacco exposed, and 71 unexposed controls). They were recruited consecutively from the community.

EXPOSURES

Prenatal methamphetamine and/or tobacco exposure.

MAIN OUTCOMES AND MEASURES

Quantitative neurologic examination and diffusion tensor imaging performed 1 to 3 times through age 4 months; diffusivities and fractional anisotropy (FA) assessed in 7 white matter tracts and 4 subcortical brain regions using an automated atlas-based method.

RESULTS

Of the 139 infants evaluated, 72 were female (51.8%); the mean (SE) postmenstrual age at baseline was 41.5 (0.27) weeks. Methamphetamine/tobacco-exposed infants showed delayed developmental trajectories on active muscle tone (group × age, P < .001) and total neurologic scores (group × age, P = .01) that normalized by ages 3 to 4 months. Only methamphetamine/tobacco-exposed boys had lower FA (group × age, P = .02) and higher diffusivities in superior (SCR) and posterior corona radiatae (PCR) (group × age × sex, P = .002; group × age × sex, P = .01) at baseline that normalized by age 3 months. Only methamphetamine/tobacco- and tobacco-exposed girls showed persistently lower FA in anterior corona radiata (ACR) (group, P = .04; group × age × sex, P = .01). Tobacco-exposed infants showed persistently lower axial diffusion in the thalamus and internal capsule across groups (P = .02).

CONCLUSIONS AND RELEVANCE

Prenatal methamphetamine/tobacco exposure may lead to delays in motor development, with less coherent fibers and less myelination in SCR and PCR only in male infants, but these abnormalities may normalize by ages 3 to 4 months after cessation of stimulant exposure. In contrast, persistently less coherent ACR fibers were observed in methamphetamine/tobacco- and tobacco-exposed girls, possibly from increased dendritic branching or spine density due to epigenetic influences. Persistently lower diffusivity in the thalamus and internal capsule of all tobacco-exposed infants suggests aberrant axonal development. Collectively, prenatal methamphetamine and/or tobacco exposure may lead to delayed motor development and white matter maturation in sex- and regional-specific manners.

Expression and function of dopamine receptors in the developing medial frontal cortex and striatum of the rat

The timeline of dopamine (DA) system maturation and the signaling properties of DA receptors (DRs) during rat brain development are not fully characterized. We used in situ hybridization and quantitative PCR to map DR mRNA transcripts in the medial frontal cortex (mFC) and striatum (STR) of the rat from embryonic day (E) 15 to E21. The developmental trajectory of DR mRNAs revealed distinct patterns of DA receptors 1 and 2 (DRD1, DRD2) in these brain regions. Whereas the mFC had a steeper increase in DRD1 mRNA, the STR had a steeper increase in DRD2 mRNA. Both DR mRNAs were expressed at a higher level in the STR compared with the mFC. To identify the functional properties of DRs during embryonic development, the phosphorylation states of cyclic AMP response element binding protein, extracellular signal-regulated kinase 1/2, and glycogen synthase kinase 3 beta were examined after DR stimulation in primary neuronal cultures obtained from E15 and E18 embryos and cultured for 3 days to ensure a stable baseline level. DR-mediated signaling cascades were functional in E15 cultures in both brain regions. Because DA fibers do not reach the mFC by E15, and DA was not present in cultures, these data indicate that DRs can become functional in the absence of DA innervation. Because activation of DR signal transduction pathways can affect network organization of the developing brain, maternal exposure to drugs that affect DR activity may be liable to interfere with fetal brain development.

The role of dopaminergic signalling during larval zebrafish brain development: a tool for investigating the developmental basis of neuropsychiatric disorders

Neurodevelopment depends on intrinsic and extrinsic factors that influence the overall pattern of neurogenesis and neural circuit formation, which has a direct impact on behaviour. Defects in dopamine signalling and brain morphology at a relatively early age, and mutations in neurodevelopmental genes are strongly correlated with several neuropsychiatric disorders. This evidence supports the hypothesis of a neurodevelopmental origin of at least some forms of mental illness. Zebrafish (Danio rerio) has emerged as an important vertebrate model system in biomedical research. The ease with which intrinsic and extrinsic factors can be altered during early development, the relatively conserved dopaminergic circuit organisation in the larval brain, and the emergence of simple sensorimotor behaviours very early in development are some of the appealing features that make this organism advantageous for developmental brain and behaviour research. Thus, examining the impact of altered dopamine signalling and disease related genetic aberrations during zebrafish development presents a unique opportunity to holistically analyse the in vivo biochemical, morphological and behavioural significance of altered dopamine signalling during a crucial period of development using a highly tractable vertebrate model organism. Ultimately, this information will shed new light on potential therapeutic targets for the treatment of schizophrenia and perhaps serve as a paradigm for investigating the neurodevelopmental origin of other psychiatric disorders.

Prenatal immune challenge compromises the normal course of neurogenesis during development of the mouse cerebral cortex

Maternal infection during pregnancy is an environmental risk factor for the development of severe brain disorders in offspring, including schizophrenia and autism. However, little is known about the neurodevelopmental mechanisms underlying the association between prenatal exposure to infection and the emergence of cognitive and behavioral dysfunctions in later life. By injecting viral mimetic polyriboinosinic-polyribocytidylic acid (Poly I:C) into mice, we investigated the influence of maternal immune challenge during pregnancy on the development of the cerebral cortex of offspring. Our previous study showed that stimulation of the maternal immune system compromised the expression properties of transcription factors and the synaptogenesis of cortical neurons in upper layers but not those in deeper layers. The objective of the current study was to examine further whether maternal immune challenge has an influence on the cellular-biological features of the cortical progenitors that generate distinct cortical neuronal subtypes. We found the following abnormalities in the cortex of mice given the prenatal Poly I:C injection during later stages of cortical neurogenesis. First, proliferative activity and the expression of Pax6, which is a master regulator of the gene expression of transcription factors, were significantly decreased in the cortical progenitors. Second, the laminar allocation and gene expression were significantly altered in the daughter neurons generated at the same birth dates. These results demonstrate that specific abnormalities in the cortical progenitors preceded deficits in neuronal phenotypes. These changes may underlie the emergence of psychiatric brain and behavioral dysfunctions after in utero exposure to an infection.

A transgenic mouse model of neuroepithelial cell specific inducible overexpression of dopamine D1-receptor

Dopamine and its receptors appear in the brain during early embryonic period suggesting a role for dopamine in brain development. In fact, dopamine receptor imbalance resulting from impaired physiological balance between D1- and D2-receptor activities can perturb brain development and lead to persisting changes in brain structure and function. Dopamine receptor imbalance can be produced experimentally using pharmacological or genetic methods. Pharmacological methods tend to activate or antagonize the receptors in all cell types. In the traditional gene knockout models the receptor imbalance occurs during development and also at maturity. Therefore, assaying the effects of dopamine imbalance on specific cell types (e.g. precursor versus postmitotic cells) or at specific periods of brain development (e.g. pre- or postnatal periods) is not feasible in these models. We describe a novel transgenic mouse model based on the tetracycline dependent inducible gene expression system in which dopamine D1-receptor transgene expression is induced selectively in neuroepithelial cells of the embryonic brain at experimenter-chosen intervals of brain development. In this model, doxycycline-induced expression of the transgene causes significant overexpression of the D1-receptor and significant reductions in the incorporation of the S-phase marker bromodeoxyuridine into neuroepithelial cells of the basal and dorsal telencephalon indicating marked effects on telencephalic neurogenesis. The D1-receptor overexpression occurs at higher levels in the medial ganglionic eminence (MGE) than the lateral ganglionic eminence (LGE) or cerebral wall (CW). Moreover, although the transgene is induced selectively in the neuroepithelium, D1-receptor protein overexpression appears to persist in postmitotic cells. The mouse model can be modified for neuroepithelial cell-specific inducible expression of other transgenes or induction of the D1-receptor transgene in other cells in specific brain regions by crossbreeding the mice with transgenic mouse lines available already.

Early exposure to nicotine during critical periods of brain development: Mechanisms and consequences

Tobacco use during pregnancy continues to be a major problem with more than 16% of pregnant women in the United States continuing to smoke during pregnancy. Tobacco smoke is known to contain more than 4,000 different chemicals, and while many of these compounds have the potential to interfere with proper neurodevelopment, there is direct evidence that nicotine, the major psychoactive substance present in tobacco, acts as a neuroteratogen. Nicotine activates, and subsequently desensitizes, neuronal nicotinic acetylcholine receptor subtypes (AChRs), which are expressed in the developing central nervous system (CNS) prior to the in-growth of cholinergic neurons. Nicotinic AChRs are present by the first trimester of development in both humans and rodents, and activation of these receptors by acetylcholine is thought to play a critical role in CNS development. The purpose of the current review is to provide an overview of the role that nicotinic AChRs play in the developing CNS and to describe the effects of nicotine exposure during early development on neuronal cell biology, nicotinic AChR expression and neurotransmitter system (e.g., dopamine, norepinephrine, serotonin) function. In particular, differences that occur as a result of the timing and duration of nicotine exposure will be discussed. Emphasis will be placed on preclinical studies examining particular periods of time which correspond to periods of prenatal development in humans (i.e., first, second and third trimesters). Finally, the effects of early nicotine exposure on neurobehavioral development as it pertains to specific disorders, i.e., attention deficit hyperactivity disorder (ADHD), depression and addiction, will be discussed.

Lower diffusion in white matter of children with prenatal methamphetamine exposure

BACKGROUND

Methamphetamine use is a common problem among women of childbearing age, leading to an increasing number of children with prenatal methamphetamine exposure. Whether microstructural brain changes associated with prenatal methamphetamine exposure can be detected with diffusion tensor imaging (DTI) is unknown.

METHOD

Twelve-direction DTI was performed in 29 methamphetamine-exposed and 37 unexposed children ages 3-4 years on a 3-T MRI scanner. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were determined in the corpus callosum (genu and splenium) and bilaterally in the frontal and parietal white matter (WM), basal ganglia (caudate, putamen, globus pallidus), and thalamus.

RESULTS

Children with prenatal methamphetamine exposure had lower ADC in the frontal (right: -2.1%, p = 0.04; left: -2.0%, p = 0.09) and parietal WM (right: -3.9%, p = 0.002; left: -3.3%, p = 0.02) compared to unexposed children. The methamphetamine-exposed children also showed a trend for higher FA in the left frontal WM (+4.9%, p = 0.06) compared to the unexposed children.

CONCLUSION

Since less myelination and higher dendritic or spine density have been reported in animals exposed to methamphetamine, lower diffusion in our children may reflect more compact axons or greater dendritic or spine density associated with prenatal methamphetamine exposure. These findings suggest alterations in white matter maturation in these children exposed to methamphetamine in utero.

Dopamine, cocaine and the development of cerebral cortical cytoarchitecture: a review of current concepts

Exposure of the developing fetus to cocaine produces lasting adverse effects on brain structure and function. Animal models show that cocaine exerts its effects by interfering with monoamine neurotransmitter function and that dopamine is cocaine's principal monoamine target in the fetal brain. This review will examine the role of dopamine receptor signaling in the regulation of normal development of the cerebral cortex, the seat of higher cognitive functions, and discuss whether dopamine receptor signaling mechanisms are the principal mediators of cocaine's deleterious effects on the ontogeny of cerebral cortical cytoarchitecture.

Elevated dopamine levels during gestation produce region-specific decreases in neurogenesis and subtle deficits in neuronal numbers

Dopamine levels in the fetal brain were increased by administering the dopamine precursor 3,4-dihydroxy-l-phenylalanine (l-DOPA) to pregnant mice in drinking water. The l-DOPA exposure decreased bromodeoxyuridine (BrdU) labeling in the lateral ganglionic eminence and frontal cortical neuroepithelium but not medial or caudal ganglionic eminences. The regional differences appear to reflect heterogeneity in precursor cells' responses to dopamine receptor activation. Relative numbers of E15-generated neurons were decreased at postnatal day 21 (P21) in the caudate-putamen, nucleus accumbens and frontal cortex but not globus pallidus in the l-DOPA group. TUNEL labeling did not show significant differences on P0, P7 or P14 in the caudate-putamen or frontal cortex, suggesting that cell death was not altered. Although virtually all cells in the P21 brains that were labeled with the E15 BrdU injection were NeuN-positive, stereological analyses showed no significant changes in total numbers of NeuN-positive or NeuN-negative cells in the P21 caudate-putamen or frontal cortex. Thus persisting deficits in neuronal numbers were evident in the l-DOPA group only by birth-dating analyses and not upon gross histological examination of brain sections or analysis of total numbers of neurons or glia. One explanation for this apparent discrepancy is that l-DOPA exposure decreased cell proliferation at E15 but not at E13. By E15, expansion of the neuroepithelial precursor pool is complete and any decrease in cell proliferation likely produces only marginal decreases in the total numbers of cells generated. Our l-DOPA exposure model may be pertinent to investigations of neurological dysfunction produced by developmental dopamine imbalance.

Dopamine receptor activation modulates GABA neuron migration from the basal forebrain to the cerebral cortex

GABA neurons of the cerebral cortex and other telencephalic structures are produced in the basal forebrain and migrate to their final destinations during the embryonic period. The embryonic basal forebrain is enriched in dopamine and its receptors, creating a favorable environment for dopamine to influence GABA neuron migration. However, whether dopamine receptor activation can influence GABA neuron migration is not known. We show that dopamine D1 receptor activation promotes and D2 receptor activation decreases GABA neuron migration from the medial and caudal ganglionic eminences to the cerebral cortex in slice preparations of embryonic mouse forebrain. Slice preparations from D1 or D2 receptor knock-out mouse embryos confirm the findings. In addition, D1 receptor electroporation into cells of the basal forebrain and pharmacological activation of the receptor promote migration of the electroporated cells to the cerebral cortex. Analysis of GABA neuron numbers in the cerebral wall of the dopamine receptor knock-out mouse embryos further confirmed the effects of dopamine receptor activation on GABA neuron migration. Finally, dopamine receptor activation mobilizes striatal neuronal cytoskeleton in a manner consistent with the effects on neuronal migration. These data show that impairing the physiological balance between D1 and D2 receptors can alter GABA neuron migration from the basal forebrain to the cerebral cortex. The intimate relationship between dopamine and GABA neuron development revealed here may offer novel insights into developmental disorders such as schizophrenia, attention deficit or autism, and fetal cocaine exposure, all of which are associated with dopamine and GABA imbalance.

Dopamine receptor mRNA and protein expression in the mouse corpus striatum and cerebral cortex during pre- and postnatal development

The outcome of dopaminergic signaling and effectiveness of dopaminergic drugs depend on the relative preponderance of each of the five dopamine receptors in a given brain region. The separate contribution of each receptor to overall dopaminergic tone is difficult to establish at a functional level due to lack of receptor subtype specific pharmacological agents. A surrogate for receptor function is receptor protein or mRNA expression. We examined dopamine receptor mRNA expression by quantitative reverse transcription real-time PCR in the striatum, globus pallidus, frontal cortex and cingulate cortex of embryonic and postnatal mice. Samples of each region were collected by laser capture microdissection. D1- and D2-receptor mRNAs were the most abundant in all the regions of the mature brain. The D1-receptor was predominant over the D2-receptor in the frontal and cingulate cortices whereas the situation was reversed in the striatum and globus pallidus. In the proliferative domains of the embryonic forebrain, D3-, D4- and D5-receptors were predominant. In the corpus striatum and cerebral cortex, the D3- and D4-receptors were the only receptors that showed marked developmental regulation. By analyzing D1 receptor protein expression, we show that developmental changes in mRNA expression reliably translate into changes in protein levels, at least for the D1-receptor.

Characterization of mouse striatal precursor cell lines expressing functional dopamine receptors

Dopamine and its receptors appear in the developing brain early in the embryonic period and dopamine receptor activation influences proliferation and differentiation of neuroepithelial precursor cells. Since dopamine D(1) and D(2) receptor activation produces opposing effects on precursor cell activity, dopamine's overall effects may correlate with relative numbers and activity of each receptor subtype on the precursor cells. Dopamine receptor expression and activity in individual precursor cells in the intact brain are difficult to ascertain. Therefore, cell lines with known receptor expression profiles can be useful tools to study dopamine's influence on neuroepithelial cells. We report characterization of dopamine receptor expression and activity profiles in three mouse striatal precursor cell lines and suggest that these cell lines can be valuable tools to study dopamine's effects on striatal precursor cell proliferation and differentiation.

Dopamine regulates cell cycle regulatory proteins via cAMP, Ca(2+)/PKC, MAPKs, and NF-kappaB in mouse embryonic stem cells

This study examined the effect of dopamine on DNA synthesis and its related signal cascades in mouse embryonic stem (ES) cells. Dopamine inhibited DNA synthesis in both a dose- and time-dependent manner. Dopamine, SKF 38393 (D1 receptor agonist), and quinpirole (D2 receptor agonist) decreased the level of [(3)H]-thymidine incorporation. The level of cyclic adenosine 3, 5-monophosphate (cAMP) was increased by SKF 38393 but not by quinpirole. The protein kinase C (PKC) protein was translocated from the cytosolic fraction to the membrane compartment by dopamine. Dopamine also increased [Ca(2+)](i), which was blocked by EGTA (an extracellular Ca(2+) chelator), BAPTA-AM (an intracellular Ca(2+) chelator), nifedipine (a L-type Ca(2+) channel blocker), SQ 22536 [an adenylyl cyclase (AC) inhibitor] and neomycin [a phospholipase C (PLC) inhibitor]. Dopamine, SKF 38393, and quinpirole increased the level of p44/42 mitogen-activated protein kinases (MAPKs), p38 MAPK, and stress-activated protein kinase/Jun-N-terminal kinase (SAPK/JNK) phosphorylation. Dopamine also increased level of H(2)O(2) formation and activated the transcription factor family NF-kappaB. Moreover, SKF 38393, quinpirole, and dopamine inhibited cell cycle regulatory proteins, which is consistent with the change in the level of [(3)H]-thymidine incorporation observed. The dopamine-induced decrease in cyclin E, cyclin-dependent protein kinase-2 (CDK-2), and cyclin D1, CDK-4 were blocked by pertussis toxin (G protein inhibitor), SQ 22536, neomycin, bisindolylmaleimide I (PKC inhibitor), SB 203580 (p38 MAPK inhibitor), PD 98059 (p44/42 inhibitor), and SP 600125 (SAPK/JNK inhibitor). In conclusion, dopamine inhibits DNA synthesis in mouse ES cells via the cAMP, Ca(2+)/PKC, MAPKs, and NF-kappaB signaling pathways.

Differential effect of dopamine on mitosis in early postnatal albino and pigmented rat retinae

Insufficient levels of L-DOPA, released from the retinal pigment epithelium (RPE), in albino animals are considered responsible for the abnormal development of the underlying neural retina. L-DOPA normalizes retinal neurogenesis by reducing levels of cell proliferation either by acting on the cells directly or by being converted into dopamine. Here we report the effects of dopamine on mitosis in early postnatal neural retinae from albino and pigmented rats, using 4D (x, y, z and time) confocal microscopy. Exogenous dopamine significantly prolongs mitosis in retinae from albino, but not pigmented, animals. As fewer cells move into and divide in the ventricular zone (VZ) in the presence of dopamine, we conclude that the overall cell cycle is affected. The D1 receptor blocker, SCH 23390, inhibits these effects. Thus, the differential effects of dopamine on neural retinae from pigmented and albino rats in vitro must result from the activation of D1 receptors, which are present in the retina from birth. Immunohistochemical labeling of D1 receptors shows that the pattern of their distribution is similar between pigmentation phenotypes, but levels of expression may be elevated in albinos. Labeling is most intense in the inner plexiform layer but is present throughout the neuroblastic layer. These findings are discussed in light of previous reports of reduced catecholamine levels in the albino retina.

Influence of dopamine on precursor cell proliferation and differentiation in the embryonic mouse telencephalon

Dopamine and its receptor binding sites appear in the brain early in the embryonic period raising the possibility that dopamine may influence brain development. We show that one component of dopamine's role in brain development is its ability to influence proliferation and differentiation of progenitor cells in the neostriatum and the dorsomedial prefrontal cortex on embryonic day 15 in mice. Dopamine and a D1-like receptor agonist reduce the relative proportion of progenitor cells incorporating the S phase marker bromodeoxyuridine. A D2-like agonist produces the opposite effect. Both the effects are evident in the lateral ganglionic eminence, neuroepithelial precursor of the neostriatum and in the neuroepithelium of the dorsomedial prefrontal cortex. Neostriatal progenitor cells are more responsive than cortical progenitor cells to the effects of dopamine receptor activation. Furthermore, progenitor cells in the ventricular zone are more responsive to D1-like agonists and progenitors in the subventricular zone more so to D2-like agonists. Thus, dopamine's developmental effects show regional and progenitor cell type specificity, presumably due to heterogeneity in the distribution of its receptor binding sites.

Dopamine D3 receptor stimulation promotes the proliferation of cells derived from the post-natal subventricular zone

In the adult mammalian brain, neural stem cells persist in the subventricular zone (SVZ) where dopamine D3 receptors are expressed. Here, we demonstrate that addition of 1 microm apomorphine increases cell numbers in post-natal SVZ cell cultures. This effect was prevented by a co-treatment with haloperidol, sulpiride or U-99194A, a D3-preferring antagonist, and mimicked by the dopamine D3 receptor selective agonist 7-hydroxy-dipropylaminotetralin (7-OH-DPAT). EC50 values were 4.04 +/- 1.54 nm for apomorphine and 0.63 +/- 0.13 nm for 7-OH-DPAT, which fits the pharmacological profile of the D3 receptor. D3 receptors were detected in SVZ cells by RT-PCR and immunocytochemistry. D3 receptors were expressed in numerous beta-III tubulin immunopositive cells. The fraction of apoptotic nuclei remained unchanged following apomorphine treatment, thus ruling out any possible effect on cell survival. In contrast, proliferation was increased as both the proportion of nuclei incorporating bromo-deoxyuridine and the expression of the cell division marker cyclin D1 were enhanced. These findings provide support for a regulatory role of dopamine over cellular dynamics in post-natal SVZ.