Development Of Tyrosine Hydroxylase Research Articles

Laminin deficits induce alterations in the development of dopaminergic neurons in the mouse retina.

Genetically modified mice lacking the beta2 laminin chain (beta2null), the gamma3 laminin chain (gamma3 null), or both beta2/gamma3 chains (compound null) were produced. The development of tyrosine hydroxylase (TH) immunoreactive neurons in these mouse lines was studied between birth and postnatal day (P) 20. Compared to wild type mice, no alterations were seen in gamma3 null mice. In beta2 null mice, however, the large, type I TH neurons appeared later in development, were at a lower density and had reduced TH immunoreactivity, although TH process number and size were not altered. In the compound null mouse, the same changes were observed together with reduced TH process outgrowth. Surprisingly, in the smaller, type II TH neurons, TH immunoreactivity was increased in laminin-deficient compared to wild type mice. Other retinal defects we observed were a patchy disruption of the inner limiting retinal basement membrane and a disoriented growth of Müller glial cells. Starburst and AII type amacrine cells were not apparently altered in laminin-deficient relative to wild type mice. We postulate that laminin-dependent developmental signals are conveyed to TH amacrine neurons through intermediate cell types, perhaps the Müller glial cell and/or the retinal ganglion cell.

Early social deprivation alters monoaminergic afferents in the orbital prefrontal cortex of octodon degus

The influence of early parental deprivation on the development of tyrosine hydroxylase- and 5-hydroxytryptamine-immunoreactive fiber innervation of subregions of the orbital prefrontal cortex (ventrolateral orbital, lateral orbital and agranular insular cortex) was quantitatively investigated in the precocious lagomorph Octodon degus. Forty-five-day-old degus from two groups were compared: 1) degus which were repeatedly separated from their parents during the first three postnatal weeks, and after weaning they were reared in social isolation; and 2) degus which were reared undisturbed in their families. Compared with the normal control animals the ventrolateral orbital prefrontal cortex and agranular insular cortex of the deprived animals displayed significantly increased density of tyrosine hydroxylase-immunoreactive fibers (up to 172% in the ventrolateral orbital prefrontal cortex and up to 143% in the agranular insular cortex). The lateral orbital prefrontal cortex showed increased 5-hydroxytryptamine-positive fiber densities (up to 118%). This altered balance between the serotonergic and dopaminergic cortical innervation in the orbital prefrontal cortex may reflect an anatomical and functional adaptation, which may be triggered by an altered activity of these transmitter systems during the phases of parental separation and social isolation.

Maternal separation followed by early social deprivation affects the development of monoaminergic fiber systems in the medial prefrontal cortex of Octodon degus

The influence of early postnatal socio-emotional deprivation on the development of tyrosine hydroxylase- and 5-hydroxytryptamine-immunoreactive fiber innervation in the medial prefrontal cortex was quantitatively investigated in the precocial rodent Octodon degus. Forty-five-days-old degus from two groups were compared: (i) degus which were repeatedly separated from their mothers during the first three postnatal weeks and after weaning reared in complete isolation; and (ii) degus which were reared under normal undisturbed social conditions. The two monoaminergic fiber systems in the four subregions of the medial prefrontal cortex responded differentially to the deprivation. While the infralimbic cortex was the only subregion that displayed an increase in 5-hydroxytryptamine-positive fiber densities (129.2%) but no changes in tyrosine hydroxylase-immunoreactive fibers, the precentral medial (82.2%), anterior cingulate (74.6%) and prelimbic cortex (86.9%) showed significantly reduced tyrosine hydroxylase-positive fiber innervation, but no changes in 5-hydroxytryptamine-immunoreactive fiber densities. The number of tyrosine hydroxylase-positive somata in the ventral tegmental area and in the substantia nigra remained unchanged. In cortical areas the number of tyrosine hydroxylase-immunoreactive somata was increased (depending on the medial prefrontal cortex subregion between 241.8% and 398.7%) in deprived animals. This altered balance between the serotonergic and dopaminergic cortical innervation in the different subregions of the medial prefrontal cortex may reflect a counter-regulative anatomical and functional adaptation, which may be triggered by an altered activity of these transmitter systems during the phases of maternal separation and social isolation.

Chronic cocaine exposure in the fetal rhesus monkey: consequences for early development of dopamine neurons

The effects of cocaine on the development of neurons containing tyrosine hydroxylase (TH) were investigated in fetal rhesus macaques. Pregnant monkeys were treated with cocaine 3 mg/kg or saline i.m., four times a day from day 18 of pregnancy until days 40 or 60. Cocaine concentration in plasma from females thus treated was approximately 800 ng/ml 10-20 min following injection. At the time of C-section, plasma levels of cocaine in fetal blood were 231 +/- 70 ng/ml. The brains from 40 and 60 d old fetuses were examined using immunocytochemistry and in situ hybridization. The appearance of neurons containing TH by day 40 of gestation was not different between control and cocaine-treated fetal monkeys. In both groups (N = 3 each) TH-IR neurons and TH mRNA were located in the mesencephalon and dorsal hypothalamus by day 40, and fiber projections extended to the developing striatum. Also in the day 60 fetuses, the TH-IR neurons were distributed similarly in both groups (N = 5 each), but the TH mRNA content, measured by quantitative in situ hybridization, was reduced in the substantia nigra (SN) and ventral tegmental area (VTA) after cocaine treatment. These data suggest that exposure to cocaine in fetal life does not affect the development of TH or the expression of its mRNA on day 40 of gestation. By day 60, however, the expression of TH mRNA was significantly reduced. This latter effect can be explained by reduced dopamine synthesis in the cocaine-treated fetuses.

Development of tyrosine hydroxylase-, dopamine- and dopamine β-hydroxylase-immunoreactive neurons in a teleost, the three-spined stickleback

The development of catecholaminergic neuronal systems in the brain of a teleost, the three-spined stickleback, was studied through embryonic to early larval stages by immunocytochemistry using specific antibodies against dopamine, tyrosine hydroxylase and dopamine β-hydroxylase. By analysing the spatiotemporal patterns of development for the catecholaminergic nuclei, possible homologies with nuclei in amniote brains have been identified. The noradrenergic neurons in the isthmus region of the rostral rhombencephalon originate in the same manner as the A4–A7 + subcoeruleus group in mammals. Their developmental characteristics show the largest similarities with the subcoeruleus group of birds and mammals, although some features are shared with developing A6 (locus coeruleus) neurons. Catecholaminergic neurons never appear during development in the ventral mesencephalon of the three-spined stickleback. A group of large dopaminergic neurons that accompany the cerebrospinal fluid (CSF)-contacting neurons follows the border between the hypothalamus and the ventral thalamus into the caudal hypothalamus, where they are continuous with the dopaminergic neurons in the posterior tuberculum. They are thus topologically comparable with the dopaminergic neurons of the zona incerta in mammals. The dopaminergic CSF-contacting neurons that line the median, lateral and posterior recesses of the third ventricle do not contain tyrosine hydroxylase-immunoreactivity at any developmental stage. This indicates that they take up and accumulate exogenous dopamine or l-dihydroxyphenylalanine, and do not synthesize dopamine from tyrosine at any developmental stage. Tyrosine hydroxylase-immunoreactive neurons appear in the pineal organ on the day of hatching (120 h post-fertilization). They were still observed in 240-h-old larvae, but are absent in the pineal organ of adult sticklebacks. The initial appearance and subsequent differentiation of catecholaminergic neurons in the stickle-back embryo follow essentially the same spatial and temporal pattern as in amphibian, avian and mammalian embryos. This observation supports the hypothesis that morphologically, topologically and chemically similar monoaminergic neurons in different vertebrate classes are homologous.

Developmental regulation of tyrosine hydroxylase in the mediobasal hypothalamus

In the adult rodent the mediobasal hypothalamus (MBH) interacts extensively with the pituitary gland to regulate a variety of endocrine functions. The dopaminergic (DA) neurons of the mature MBH are influenced by numerous transmitters and hormones, however, little is known about developmental regulation of this system. Ontogeny of DA neurons was examined in vivo and in explant culture by monitoring tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis. The influence of the depolarizing agent, veratridine, was examined to determine whether development of TH in the MBH is regulated by depolarizing signals as in other CA neurons. Veratridine elicited a significant increase in TH activity in cultures of MBH. Adult MBH neurons are influenced by hormones such as estradiol. We investigated the possible role of estradiol in regulating the ontogeny of MBH DA neurons in culture. We developed a steroid-depleted culture medium to rigorously define the effects of steroids on the developing system. This enabled us to determine that estradiol does not appear to influence TH during embryonic development, though estrogen receptors are present at this stage. These results were confirmed in vivo by injecting neonates with moxestrol, a synthetic estrogen which is not sequestered by α-fetoprotein. This treatment did not elicit any change in TH. Our observations suggest that although estrogen regulates TH in the adult MBH, this hormone does not play a role in developmental regulation of TH in this brain region. In contrast, however, depolarizing signals appear to be a widespread mechanism for regulation of TH in numerous neuronal populations.

Hypogastric ganglion perinatal development: evidence for androgen specificity via androgen receptors

The hypogastric ganglion (HG) has previously been shown to be sensitive to both the organizational and activational influences of testosterone. The current investigations examined whether testosterone exerts similar effects prenatally, whether these events are specifically controlled by androgen, and whether androgens might directly masculinize the HG. Prenatal treatment with an anti-androgen, flutamide, resulted in significant decreases in the adult levels of tyrosine hydroxylase (TH) activity, an index of postsynaptic noradrenergic ontogeny 3, and choline acetyltransferase (ChAT) activity, a marker for presynaptic terminal formation. In addition, testosterone propionate and dihydrotestosterone benzoate reversed the effects of neonatal castration on the development of TH and ChAT activities. In contrast estradiol benzoate was unable to restore enzyme activities. To determine whether the above observations might be produced by direct effects on the HG, androgen cytosol receptor characteristics were studied. Competition and saturation analyses demonstrate that the affinity and specificity of the androgen cytosol receptor in the HG are similar to that displayed in the pituitary, which has previously been shown to contain androgen receptors. These results suggest that the adult levels of TH and ChAT activities are organized during prenatal and early postnatal development. In addition, the organization of the HG appears to be androgen specific. The presence of cytosol androgen receptors suggests that the organizational effects of androgens are possibly induced by a direct mechanism.

Immunohistochemical studies on the development of tyrosine hydroxylase- and serotonin-immunoreactive neurons in fetal dorsal raphe tissue transplanted into the anterior eye chamber of adult rats.

Pieces of tissue containing dorsal raphe nuclei of fetal rat brains were transplanted into the anterior eye chambers of adult rats. The differences between the developmental patterns of catecholaminergic and serotonergic neurons--especially the extension of their axonal processes--in the grafts were immunohistochemically examined using tyrosine hydroxylase (TH) and serotonin antisera. At an early stage after transplantation (3 days), TH-positive neurons appeared in grafts that had and had not been pretreated with a monoamine oxidase inhibitor (MAOI, Nialamide), while serotonin-positive neurons were demonstrated only in the grafts that had undergone MAOI pretreatment. Morphological differences in the growth pattern in the experimental milieu between the TH and serotonin neurons were also demonstrated: at this early stage, the somata of the TH neurons were multipolar and stellate shaped and possessed several distinct processes, while the serotonin neurons were ovoid shaped and lacked such processes. One week to 1 month after transplantation, the number of TH-positive fibers gradually increased, but their distribution was restricted to the area surrounding the cell bodies of the TH neurons in the graft. However, the processes of the serotonin neurons formed a dense plexus in the graft, and a small number of these fibers extended into the host iris 1 week after transplantation. By one month after the operation, the density of the serotonin fibers had gradually increased throughout the graft, and protruding serotonin fibers formed a network of varicose fibers in the host uveal tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Ontogeny of the dopamine and cyclic adenosine-3′: 5′ -monophosphate-regulated phosphoprotein (DARPP-32) in the pre- and postnatal mouse central nervous system

The ontogeny of a dopamine and cyclic adenosine-3′:5′-monophosphate-regulated phosphoprotein with an apparent molecular weight of 32 kilodaltons (DARPP-32) has been studied in the central nervous system of the prenatal, newborn and adult mouse.DARPP-32-immunoreactive somata were first identified at day 12 of gestation, in the primary olfactory cortex and in the ventrolateral medulla oblongata. On day 14 of gestation, neurons containing DARPP-32-like immunoreactivity became apparent in the caudate nucleus, olfactory tubercle, nucleus accumbens, frontoparietal cortex and the ventral medulla oblongata. During the period up to and including birth, the number of cell bodies and fibres in all these areas increased markedly. In addition, DARPP-32-positive neurons became visible in the olfactory nucleus, the arcuate nucleus, and DARPP-32-positive cells appeared in the choroid plexus of the lateral, third and fourth ventricles. DARPP-32-containing fibres could be seen in the median eminence, the ventrolateral thalamus, and in the striatonigral projection, descending in the internal capsule to ramify extensively in the substantia nigra. Only in the cerebellum and suprachiasmatic nucleus did the development of DARPP-32-like immunoreactivity occur postnatally.The development of tyrosine hydroxylase, the rate-limiting enzyme for catecholamine synthesis, was simultaneously examined. The arrival of the tyrosine hydroxylase-containing projection to the caudate nucleus, the olfactory tubercle and the nucleus accumbens apparently occurred 1–2 days after the appearance of DARPP-32-immunoreactive cells within these regions. In the ventral and ventrolateral medulla oblongata, and the primary olfactory cortex, no tyrosine hydroxylase innervation was seen near the DARPP-32-positive neurons at days 12–14. The organization of the DARPP-32-containing somata of the caudate nucleus into aggregates of 5–15 neurons was partly paralleled spatially by an increased density of tyrosine hydroxylase-positive fibres.Many DARPP-32-immunoreactive cells in the immature mouse brain are present by the day of birth, particularly in the areas known to receive a dopaminergic innervation. The development of these presumptive dopaminoceptive DARPP-32-containing neurons does not seem to be dependent on the presence, however, of a dopaminergic input, since in all regions examined DARPP-32-LI preceded the appearance of tyrosine hydroxylase-like immunoreactivity by at least 1–2 days. Indeed, the results suggest that the existence of DARPP-32-like immunoreactivity in cell bodies and dendrites may be a pre-requisite for the formation or subsequent stabilization of dopaminergic synapses.

Differential ontogeny of three putative catecholamine cell types in the postnatal rat retina

The development of tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) in the rat retina was investigated using the indirect immunofluorescence technique. Two types of TH-positive cells were found. The first appeared at postnatal day 2, in the vitreal half of the inner nuclear layer (INL). Single fibres from these neurones, bifurcating in and innervating layer 3 of the inner plexiform layer (IPL) were seen at day 4. This first type of TH-positive cell was most numerous at day 15, but thereafter disappeared before adulthood. At day 5, a more intensely staining TH-immunoreactive neurone became visible, occupying a more proximal part of the INL, and projecting multiple fibres to layer 1 of the IPL. In contrast, PNMT-positive cells, in the vitreal half of the INL and in the ganglion cell layer (GCL), sending single varicose axons to layer 3 of the IPL, were first apparent only at day 10, achieving a disposition similar to that of the adult by days 15–16 postnatal. Analysis of adjacent sections stained with antibodies to TH and PNMT revealed that neither type of TH-positive neurone also contained PNMT-like immunoreactivity. It is concluded that although both of the rate-limiting enzymes of the catecholamine synthetic pathway are present in the developing rat retina, they occur in 3 mutually exclusive populations of neurones.

Differential and independent manifestation within co-containing neurones of neuropeptide Y and tyrosine hydroxylase during ontogeny of the rat central nervous system

The development of tyrosine hydroxylase- and neuropeptide Y-immunoreactive cell bodies in the foetal rat brain was analyzed immunohistochemically using antibodies raised against tyrosine hydroxylase and neuropeptide Y. Possible co-existence of these two substance within the same neurones was investigated by comparison of adjacent sections. In the ventral medulla oblongata, neurones containing both neuropeptide Y- and tyrosine hydroxylase-like immunoreactivity were demonstrable in and around the lateral reticular nucleus as early as the 17th day of gestation. The total number and the proportion of cells exhibiting this co-existence increased from this stage up to birth. In the nucleus of the solitary tract in the dorsal medulla oblongata, NPY-immunoreactive cells bodies were first visualized at day 13 of gestation. However, although tyrosine hydroxylase-immunoreactive cells could also be seen within the nucleus at this and later ages, they occupied a different, more caudal and medial part. Consequently, no neurones containing both neuropeptide Y and tyrosine hydroxylase were apparent up to the day of birth. Finally, in the locus coeruleus, tyrosine hydroxylase-immunoreactive neurones were also demonstrable at day 13 of gestation. In this case, however, no neuropeptide Y-immunoreactive somata could be seen in the nucleus until day 21. The present study indicates that the existence of neuropeptide Y and tyrosine hydroxylase in co-containing neurones is not inextricably linked, and suggests that the factors controlling the synthesis of these two substances are not identical.

Time of appearance during development of differences in nigrostriatal tyrosine hydroxylase activity in two inbred mouse strains

The greater activity of tyrosine hydroxylase (TH) in substantia nigra and corpus striata of adult BALB/cJ than CBA/J mice, is attributable to differences in the number of dopamine neurons in the ventral midbrain tegmentum. To determine if strain differences in TH activity develop postnatally we have measured the development of TH in the midbrain (SN) and in the corpus striatum (CS). In the midbrain neonatal TH activity was 20% of adult levels. Thereafter, TH activity increased rapidly achieving adult levels by 11 days. A 25% ‘overshoot’ above adult values at 15 days was followed by a gradual decrease to adult activity at 4 weeks. In the CS neonatal activity was about 10% of adult levels and increased slowly to reach adult values at 4 weeks. Striatal choline acetyltransferase (CAT) activity in the neonate was only 3.7% of adult values and at 21 days had only reached 70% of adult activity. Neonatal glutamic acid decarboxylase (GAD) activity was relatively high in both brain regions and increased gradually to adult activity by 4 weeks. Strain differences in TH activity were not present at birth but first appeared at 9 days in SN and 11 days in CS. Once established, the differences were maintained. These results suggest that strain differences in TH are most probably a consequence of differences in postnatal neuron survival, although the possibility that some neurons lose their phenotypic expression of TH cannot be excluded.

Influence of adrenal epinephrine on postnatal development of tyrosine hydroxylase activity in the superior cervical ganglion.

The effects of bilateral adrenalectomy on postnatal development of tyrosine hydroxylase (TH) activity in the superior cervical ganglion were examined in the rat. Adrenalectomy on day 12 blocked further developmental rise of TH activity, while adrenalectomy on day 7 did not affect normal development of enzyme activity when examined on day 12. The effect of adrenalectomy could be reversed by replacement with daily injections of epinephrine, but not by similar replacement with corticosterone. Chronic administration of SKF 64139, a specific inhibitor of adrenal phenylethanolamine N-methyl-transferase activity that depletes circulating epinephrine levels, also led to a cessation of normal development of TH activity. Similar to adrenalectomy, the effect of SKF 64139 could be observed only after 2 weeks of postnatal development. From these data, it appears that after 2 postnatal weeks, further developmental rise of TH activity in the sympathetic ganglion is an epinephrine-dependent process.

Metabolic requirements for differentiation of embryonic sympathetic ganglia cultured in the absence of exogenous nerve growth factor

The embryonic mouse superior cervical ganglion (SCG) in culture was employed to define the role of ongoing metabolic processes in morphological and biochemical development. The 14 gestational day SCG does not require added nerve growth factor (NGF) for differentiation in vitro. Consequently, its use allows study of intraganglionic regulation of neuronal growth in the absence of complicating, exogenous growth factors. Ganglia were cultured without added NGF, in medium containing various metabolic inhibitors; neurite elaboration and development of tyrosine hydroxylase (T-OH) activity, a biochemical marker of adrenergic maturation, were evaluated. Neurite elaboration proceeded normally with inhibition of RNA synthesis by actinomycin D, or of protein synthesis by cycloheximide or puromycin. In contrast, inhibition of RNA or protein synthesis prevented normal development of T-OH activity. However, neurites and T-OH developed normally in the presence of DNA synthesis inhibition by cytosine arabinoside, which markedly reduced the nonneuronal cell population. These observations suggest that neurite elaboration and the ontogenetic increase in T-OH activity are regulated differently in ganglia cultured in the absence of exogenous NGF. Moreover, the initial outgrowth of neurites and increase in T-OH activity may occur independent of peripherally migrating support cells in this embryonic ganglion.

Development of Tyrosine Hydroxylase Activity in Dissociated Cerebral Cell Cultures

The present study describes the development of tyrosine hydroxylase (TH) activity in dissociated cerebral cell cultures. Cerebral hemispheres from 8-day-old chick embryos were mechanically dissociated

Effects of hypothyroidism on the enzymes for biogenic amines in the developing rat brain

The effects of neonatal radiothyroidectomy on the development of tyrosine hydroxylase (TH), DOPA-decarboxylase (DOPAdC), 5-hydroxytryptophan-decarboxylase (5-HTPdC), catechol-O-methyl transferase (COMT), and monoamine oxidase (MAO) in cerebral hemispheres (CH) and brainstem (BS) of rats have been studied in homogenates and subcellular fractions at two critical developmental stages. At 13 days of age, DOPAdC, 5-HTPdC, COMT and MAO activities were decreased in the CH of hypothyroid animals whereas TH activity tended to be increased. These changes were particularly evident in the subcellular compartments displaying the highest relative specific activity (RSA) of the individual enzymes. Less severe changes were observed in 32 day old rats perhaps because the brain had adapted to the hormonal deficiency. The RSA of the various enzymes was little affected by hypothyroidism and age. The preponderance of the synthesis over catabolism, as reflected by increased TH and decreased MAO and COMT activities, suggests an enzymatic compensatory response to hypothyroidism to normalize the levels of catecholamines, and probably serotonin, available to the brain.

EFFECTS OF DEXAMETHASONE ON NEUROTRANSMITTER ENZYMES IN CHROMAFFIN TISSUE OF THE NEWBORN RAT

—Dexamethasone administration to newborn rats resulted in an increase in phenylethanolamine N-methyltransferase activity in superior cervical ganglia. The same treatment resulted in a decrease in tyrosine hydroxylase and choline acetyltransferase activities. The decline in choline acetyltransferase activity after dexamethasone treatment was only seen when the drug was given before 5 days of age. When dexamethasone was given to pregnant rats it caused an age-dependent decrease in choline acetyltransferase in the adrenals, superior cervical ganglia and para-aortic chromaffin tissue of the offspring. These results suggest that dexamethasone administration may delay the development of the preganglionic neurons of sympathetic ganglia. This in turn would delay the development of tyrosine hydroxylase but not phenylethanolamine N-methyltransferase.

Regional development of catecholamine biosynthesis in rat brain.

Abstract— The ontogenetic development of norepinephrine and dopamine and their associated biosynthetic and degradative enzymes was investigated in five anatomical regions of the rat brain. Clear regional differences were found in the development of both norepinephrine and tyrosine hydroxylase (EC 1.14.3.1). In the case of both norepinephrine and tyrosine hydroxylase, brainstem structures achieved adult levels well before forebrain structures. The development of DOPA decarboxylase (EC 4.1.1.26), monoamine oxidase (EC 1.4.3.4) and catechol‐0‐methyl transferase (EC 2.1.1.6) did not appear to differmarkedly from area to area. Further analysis of the data revealed that in forebrain structures both the amines and the biosynthetic enzymes developed concurrently. By contrast, in the brainstem structures, there was a dissociation of amine and enzyme development with development of tyrosine hydroxylase, in particular, markedly preceding that of norepinephrine and of DOPA decarboxylase. The bases for both the lower amine levels in the infant brain and the regional developmental differences are discussed in relation to the anatomical organization of the central catecholamine‐containing neurons.

Tyrosine hydroxylase in rat brain: developmental characteristics.

Abstract— The development of tyrosine hydroxylase (tyrosine 3‐hydroxylase, EC 1.14.3.a) activity has been examined in whole rat brain and in various regions and subcellular fractions thereof. The specific activity of tyrosine hydroxylase increased almost 15‐fold from 15 days of gestation to adulthood. With maturation, those regions of the brain that contain only terminals of the catecholaminergic neurons showed the greatest increases in enzyme activity. There was a shift in the subcellular distribution of tyrosine hydroxylase from the soluble fraction in the fetal brain to the synaptosomal fraction in the adult brain. Tyrosine hydroxylase, dopamine hydroxylase (EC 1.14.2.1) and the specific uptake mechanism for norepinephrine appear to develop in a coordinated fashion.