Expression Of Dopamine Receptor Subtypes Research Articles

Probiotics (Bacillus clausii and Lactobacillus fermentum NMCC-14) Ameliorate Stress Behavior in Mice by Increasing Monoamine Levels and mRNA Expression of Dopamine Receptors (D1 and D2) and Synaptophysin.

Stress is a physiological consequence of the body to adversity. The gut–brain axis and probiotics are gaining interest to provide better treatment for stress and other neurological disorders. Probiotic (Lactobacillus fermentum NMCC-14 and Bacillus clausii, 1010 colony-forming unit/day/animal, per oral) effects were investigated in acute (up to day 7) and subacute (days 8–14) restraint-stressed and normal mice through behavioral paradigms (elevated plus maze: EPM, light dark box/dark light box: LDB, and open field test: OFT). Time spent in the open arms of the EPM, time spent in the light compartment of the LDB, and movable time and time spent in the center of the OFT were significantly (p ≤ 0.05, n = 5) increased in probiotic-treated restraint-stressed mice. Enzyme-linked immunoassay determined blood cortisol and adrenocorticotropic hormone (ACTH) levels, which were reduced significantly (p < 0.05, n = 5) in probiotic-treated restraint-stressed mice. Hematoxylin and eosin-stained hippocampal slides also showed less or no neurodegeneration in the probiotic-treated animals. High-performance liquid chromatography and quantitative polymerase chain reaction were performed to determine the monoamine levels and mRNA expression of dopamine receptor subtypes (D1 and D2) and synaptophysin in the mice hippocampus (HC) and prefrontal cortex (PFC). The dopamine, serotonin, and norepinephrine levels were also significantly (p < 0.05, n = 5) increased in the HC and PFC of probiotic-treated animal brains. Fold expression of mRNA of D1 and D2 (except HC, LF-S, day 14) receptors and synaptophysin was also significantly (p < 0.05, n = 5) increased in the same brain parts of probiotic-treated restraint-stressed mice. Comparing mice in the Lactobacillus fermentum NMCC-14 and Bacillus clausii groups to mice in the normal group, only a significant (p < 0.05, n = 5) decrease was observed in the serum ACTH and cortisol levels on day 14 in Bacillus clausii-treated mice, where all other parameters also showed improvement. In comparison, Bacillus clausii showed greater stress suppressant activity than Lactobacillus fermentum NMCC-14. However, both probiotic bacteria can be a better and safer therapeutic alternative for ailments than currently available drugs.

The sodium salicylate affects the expression of NMDA receptor and GABAa receptor subunits in spiral ganglion neurons of the cochlea through DA receptor

Objective:To investigate mRNA expression of dopamine receptor subtypes in the rat cochlear spiral ganglion neurons (SGN) following exposure to the sodium salicylate. In addition, we observed the effect of sodium salicylate on N methyl-D-aspartic acid (NMDA) receptor subunit NR1 and gamma aminobutyric acid (GABA)a receptor subunit GABRα2 mRNA under the circumstance of DR activation or blocking. Moreover, we also focused on the the interaction between receptors mediated by SS.Method:Immunofluorescence techniques were applied to detect DR (DR1 and DR2) expression in cultured rat SGN. Moreover, RT-PCR was performed to assess NR1 and GABRα2 subunit mRNA.Result:Immunofluorescence images showed co-localization of DR1/DR2 and βⅢ-tubulin protein in SGN bodies and axons. RT-PCR results illustrated that ①DR subtypes of DRd1-5 were detected in the SGN. ②The mRNA expression of all subtypes of DR and GABRα2, NR1 subunits were obviously upregulated except DRd3 after treatment with sodium salicylate. Among them, DRd1 expression increased 34.64%(t=-5.123,P=0.007),DRd2 expression increased 34.60%(t=-5.206,P=0.006),DRd4 expression increased 20.87%(t=-3.337,P=0.029),DRd5 expression increased 26.42%(t=-6.054,P=0.004),GABRα2 expression increased 30.41%(t=-2.839,P=0.047),NR1 expression increased 39.22%(t=-6.243,P=0.003).③After exposure to sodium salicylate (5 mmol/L), dopamine (100 μmol/L), DR1 agonist (SKF38393,20 μmol/L), DR2 agonist (Quinpirole,20 μmol/L), GABRα2 expression increased 21.78%,27.45%,33.02%,33.42% respectively (F=12.399,P=0.001),and NR1 expression increased 28.70%,26.82%,29.03%,35.05%(F=50.395,P=0.000) respectively.④Compared with the group of sodium salicylate treatment alone, both sodium salicylate + DR1 antagonist (SCH23390,20 μmol/L) group and sodium salicylate + DR2 antagonists (Eticlopride,20 μmol/L) group had a suppression on GABRα2 and NR1 mRNA expression.GABRα2 mRNA reduced 29.56%,37.10%(F=22.101,P=0.000) and NR1 mRNA expression decreased 37.62%,32.83% respectively(F=72.933,P=0.000).Conclusion:Most of the DR subtypes mRNA expression in SGN were increased following exposure to sodium salicylate. DR may be involved in the effect of sodium salicylate on GABAaR and NMDAR mRNA expression.

Expression of dopamine and adrenergic receptors in mouse embryonic stem cells and preimplantation embryos

Abstract Using RT-PCR we examined expression of dopamine and adrenergic receptors in undifferentiated and spontaneously differentiating mouse embryonic stem (ES) cells. We also examined expression of dopamine receptor subtypes in mouse ovulated oocytes and preimplantation embryos. Comparing the expression of catecholamine receptors in undifferentiated mouse ES cells and in blastocysts (from which ES cells are derived), we found that transcripts of all five dopamine receptors were expressed in both cell types. In contrast, we detected eight adrenergic receptor subtypes in undifferentiated mouse ES cells, but only three subtypes were found in mouse blastocysts. In three adrenergic receptors (α1D, α2B, β1), we found higher expression in the spontaneously differentiating ES cells than in undifferentiated ES cells, and the α1B adrenoceptor was not even detectable in the undifferentiated cells. These results indicate that genes encoding all types of catecholamine receptors are transcribed in mouse ES cells, and some of them are differentially expressed during ES cell differentiation. We found several profiles of dopamine receptor mRNA expression during the preimplantation period. The DR3 transcript was present in all examined stages (oocytes, 4-cell embryos, 8- to 16-cell embryos, blastocysts). DR1 and DR4 transcripts were not found in oocytes, but we detected them in preimplantation embryos. The DR2 receptor transcript was found in all examined stages except for the 4-cell embryos, and the DR5 receptor transcript was found in all examined stages except for the 8- to 16-cell embryos. The expression profiles of dopamine receptor transcripts suggest different roles of some receptor subtypes in particular preimplantation developmental stages.

The dopamine D2receptor is expressed and sensitizes adenylyl cyclase activity in airway smooth muscle

Dopamine receptors are G protein-coupled receptors that are divided into two subgroups, "D(1)-like" receptors (D(1) and D(5)) that couple to the G(s) protein and "D(2)-like" receptors (D(2), D(3), and D(4)) that couple to G(i). Although inhaled dopamine has been reported to induce bronchodilation in patients with asthma, functional expression of dopamine receptor subtypes has never been described on airway smooth muscle (ASM) cells. Acute activation of G(i)-coupled receptors inhibits adenylyl cyclase activity and cAMP synthesis, which classically impairs ASM relaxation. In contrast, chronic activation of G(i)-coupled receptors produces a paradoxical enhancement of adenylyl cyclase activity referred to as heterologous sensitization. We questioned whether the dopamine D(2)-like receptor is expressed on ASM, whether it exhibits classical G(i)-coupling, and whether it modulates ASM function. We detected the mRNA encoding the dopamine D(2) receptor in total RNA isolated from native human ASM and from cultured human airway smooth muscle (HASM) cells. Immunoblots identified the dopamine D(2) receptor protein in both native human and guinea pig ASM and cultured HASM cells. The dopamine D(2) receptor protein was immunohistochemically localized to both human and guinea pig ASM. Acute activation of the dopamine D(2) receptor by quinpirole inhibited forskolin-stimulated adenylyl cyclase activity in HASM cells, which was blocked by the dopamine D(2) receptor antagonist L-741626. In contrast, the chronic pretreatment (1 h) with quinpirole potentiated forskolin-stimulated adenylyl cyclase activity, which was inhibited by L-741626, the phospholipase C inhibitor U73122, or the protein kinase C inhibitor GF109203X. Quinpirole also stimulated inositol phosphate synthesis, which was inhibited by L-741626 or U73122. Chronic pretreatment (1 h) of the guinea pig tracheal rings with quinpirole significantly potentiated forskolin-induced airway relaxation, which was inhibited by L-741626. These results demonstrate that functional dopamine D(2) receptors are expressed on ASM and could be a novel therapeutic target for the relaxation of ASM.

Effectiveness of cabergoline in monotherapy and combined with ketoconazole in the management of Cushing’s disease

The expression of dopamine receptor subtypes has been reported in corticotroph adenomas, and this finding support the possibility for medical treatment of Cushing's disease (CD) with dopamine agonists when conventional treatment has failed. The aim of this study was to evaluate the effectiveness of cabergoline (at doses of up 3 mg/week), alone or combined with relatively low doses of ketoconazole (up to 400 mg/day), in 12 patients with CD unsuccessfully treated by transsphenoidal surgery. After 6 months of cabergoline therapy, normalization of 24 h urinary free cortisol (UFC) levels occurred in three patients (25%) at doses ranging from 2-3 mg/week, whereas reductions ranging from 15.0 to 48.4% were found in the remaining. The addition of ketonocazole to the nine patients without an adequate response to cabergoline was able to normalize UFC excretion in six patients (66.7%) at doses of 200 mg/day (three patients), 300 mg/day (two patients) and 400 mg/day (one patient). In the remaining patients UFC levels did not normalize but a significant reduction ranging from to 44.4 to 51.7% was achieved. In two of the six responsive patients to combination therapy, the weekly dose of cabergoline could be later reduced from 3 to 2 mg. Our findings demonstrated that cabergoline monotherapy was able to reverse hypercortisolism in 25% of patients with CD unsuccessfully treated by surgery. Moreover, the addition of relatively low doses of ketoconazole led to normalization of UFC in about two-thirds of patients not achieving a full response to cabergoline.

Dopamine D3 receptor and schizophrenia: A widened scope for the immune hypothesis

Schizophrenia may be related to immunity as is suggested by many findings of altered immune parameters in schizophrenic patients. How immune alterations might be involved in the emergence of psychosis is still unclear. Clearly, however, the dopamine hypothesis has been confirmed in recent studies, which implies a crucial role for dopamine and the dopamine D2 receptor (D2R) within the pathogenesis of schizophrenia. The Dopamine D3 receptor (D3R) is considered to have autoreceptor properties modulating the synthesis and release of dopamine, thereby possibly antagonizing the dopamine D2-receptor-mediated effects of dopamine and has been found reduced in schizophrenic patients during acute psychosis and increasing in the advent of negative schizophrenic symptoms. Immune parameters apparently influence the expression of dopamine receptors by means of their capability to induce regulatory factors involved in the expression of dopamine receptor subtypes, such as the neurotrophins, associations of which with psychosis have been reported repeatedly. Here, we propose a hypothesis of immune alterations that influence the production of distinct neurotrophins such as BDNF and NGF that, as animal studies suggest, influence the expression of dopamine receptor subtypes. This mechanism could result in a decrease of D3R and a consecutive relative preponderance of D2R and thereby connect immune alterations and schizophrenia.

Chronic infusion of a melanocortin receptor agonist modulates dopamine receptor binding in the rat brain

Previous studies have shown that melanocortin peptides have facilitatory effects on dopaminergic neurotransmission. In the present study we tested the hypothesis that chronic exposure to melanocortin receptor agonists causes a prolonged release of dopamine resulting in changes in the expression of dopamine receptor subtypes. Using an autoradiographic approach we found that a 2 week intracerebroventricular infusion of the melanocortin receptor agonist melanotan-II induced changes in dopamine D1-like and D2-like receptor binding in several regions of the rat brain. D1-like receptor binding was increased in the nucleus accumbens and the caudate putamen, but reduced in the substantia nigra (reticular part), whereas D2-like receptor binding was reduced in the caudate putamen, but increased in the periaqueductal grey, substantia nigra (compact part) and the ventral tegmental area. These data suggest that chronic infusion of a melanocortin receptor agonist alters the activity of dopaminergic neurons in the ventral tegmental area and substantia nigra, and support the hypothesis that melanocortin peptides may regulate the activity of central dopamine neurons.

Expression of dopamine receptors in the subthalamic nucleus of the rat: characterization using reverse transcriptase–polymerase chain reaction and autoradiography

We analysed the expression of dopamine receptor subtypes in the subthalamic nucleus by means of reverse transcriptase–polymerase chain reaction. We also studied, using autoradiography, all pharmacologically characterized dopamine receptors in four subregions of the subthalamic nucleus. For comparison, dopamine receptor subtypes were also evaluated in brain regions where they are more abundant and well characterized. The radioligands used were: [ 3H]SCH-23390, [ 3H]emonapride and [ 3H]2-dipropylamino-7-hydroxy-1,2,3,4-tetrahydronaphthalene for dopamine D 1, D 2 and D 3 receptors, respectively; and [ 3H]YM-09151-2 in the presence of raclopride for dopamine D 4 receptors. Finally, we also evaluated the effect of unilateral 6-hydroxydopamine injection into the medial forebrain bundle on dopamine receptor levels expressed in the ipsilateral subthalamic nucleus. The lesion was estimated by decrease in the binding of [ 3H]WIN-35428, a specific dopamine transporter label. D 1, D 2 and D 3 receptor messenger RNAs and binding sites were present in the subthalamic nucleus, but no messenger RNA for D 4 receptors was found, although specific binding sites for these receptors were observed. As compared to the intact side, the 6-hydroxydopamine lesion did not change D 1 receptors, increased D 2 receptors, and decreased D 3 receptors and the dopamine transporter. The results suggest that postsynaptic D 1, D 2 or D 3 receptors can mediate the effect of dopamine on subthalamic nucleus neuronal activity. D 4 receptors would mediate exclusively presynaptic effects. These results reinforce the idea that dopamine receptors in the subthalamic nucleus may play an important role in the physiology of the basal ganglia and in the pathophysiology of Parkinson's disease.

Maternal Cocaine Treatment Alters Dynorphin and Enkephalin mRNA Expression in Brains of Fetal Rhesus Macaques

Cocaine exposure in utero is known to cause a variety of behavioral and motor deficits that may be attributable to alterations in the dopamine neurocircuitry. To ascertain cocaine effects in the fetus, we developed a nonhuman primate model in which pregnant monkeys were administered cocaine from day 20 through day 60 or 70 of gestation. Fetuses from these pregnancies develop a repertoire of neural deficiencies, including decreased mRNA expression of tyrosine hydroxylase in the midbrain and increased mRNA expression of dopamine receptor subtypes in the rostral forebrain. Presently, we studied the effects of maternal cocaine treatment on the mRNA expression of the endogenous opioids preprodynorphin (PPD) and preproenkephalin (PPE) in fetal monkey brains. Fetuses exposed to saline (0.9%) or cocaine (3 mg/kg) were delivered by Caesarean section, the fetal brains were dissected, and tissue RNA was extracted and quantified using ribonuclease protection assay analysis. The opioid peptides PPD and PPE were expressed in the fetal monkey brain by day 60, and even higher levels were found in day 70 fetuses. Maternal exposure to cocaine increased gene expression of PPD and PPE in the fetus at both day 60 and day 70 of gestation. Dynorphin mRNA levels were significantly elevated in the striatum, whereas enkephalin mRNA was elevated in both the frontal cortex and the striatal area of fetuses whose mothers received cocaine. Changes in the expression of these opioid peptides in presumed dopamine target neurons, which mediate motivation and reward, as well as motor control, provide further evidence for profound consequences of in utero cocaine exposure on the developing dopamine neurocircuitry.

Age-dependent changes in the expression of dopamine receptor subtypes in human peripheral blood lymphocytes

The pharmacological profile and the density of dopamine D 3 and D 5 receptor subtypes expressed by human peripheral blood lymphocytes of subjects of different ages (ranging from 20 to 75 years) were assessed using radioligand binding techniques. Dopamine D 3 receptor was assayed with [ 3H]7-hydroxy-N,N-di- n-propyl-2-aminotetraline ([ 3H]7-OH-DPAT) as a ligand. Dopamine D 5 receptor was assayed using [ 3H][R]-(+)-(-chloro-2,3,4,5,tetrahydro-5-phenyl-1H-3-benzazepin-al-hemimaleate) ([ 3H]SCH 23390) as a ligand. The affinity and the pharmacological profile of [ 3H]7-OH-DPAT and [ 3H]SCH 23390 at dopamine D 3 and D 5 receptor, respectively, were similar in subjects of different ages. The density of dopamine D 3 receptor binding sites was slightly decreased in subjects of 30–39 years in comparison with younger individuals. A remarkable loss of dopamine D 3 receptor was then found between 40 and 49 years of age in comparison with younger subjects. A further slight decrease was noticeable between 50 and 59 years of age. The number of [ 3H]7-OH-DPAT binding sites was then stabilized after 60 years of age. The density of dopamine D 5 receptor binding sites did not show age-dependent changes. The above findings indicate the occurrence of a decline in the density of lymphocyte dopamine D 3 but not D 5 receptor between adult and mature subjects. The possibility that dopamine D 3 receptor assay in peripheral blood lymphocytes may represent a tool for investigating dopamine receptor function in aging and age-related neurological disorders is discussed.

Enhanced Amphetamine Sensitivity and Increased Expression of Dopamine D2 Receptors in Postpubertal Rats after Neonatal Excitotoxic Lesions of the Medial Prefrontal Cortex

Functional and structural abnormalities in the medial prefrontal cortex (MPFC) and overactive dopamine (DA) neurotransmission are thought to be the key pathologies in schizophrenia. To understand the role of MPFC in the pre- and postpubertal development of the subcortical DA system, the effects of neonatal [postnatal day 7 (PD7)] MPFC excitotoxic lesions on locomotor behaviors and the expression of DA receptor subtypes and DA transporter were investigated in Sprague Dawley rats at PD35 and PD56, respectively. No significant differences in the novelty of d-amphetamine-induced locomotion were observed between sham-operated and ibotenic acid-lesioned rats at PD35. Postpubertally (at PD56), however, the locomotor activity of lesioned rats in the novel environment and after d-amphetamine administration was enhanced significantly compared with controls. The expressions of DA D1, D2, D3, and D4 receptors and DA transporter were then estimated in MPFC-lesioned and sham-operated rats at PD59 and PD60. The levels of DA D2 receptors, measured using [3H]-YM-09151-2 binding, and its mRNA by in situ hybridization, were observed to be significantly increased at PD60 in striatal and limbic areas of lesioned rats. Levels of other DA receptor subtypes were not significantly affected at any time points. Lesioned rats at PD39 show a small increase in DA transporter level in the shell of nucleus accumbens; however, this effect seems to wear off at PD60. The data suggest that neonatal MPFC lesions may alter the functional development and maturation of mesolimbic/nigrostriatal DA systems in that neonatally lesioned rats grow into a behavioral/neurochemical deficit.