[Analysis on the household secondary attack rates of the SARS-CoV-2 Delta variant and the associated factors]

Objective: To evaluate the household secondary attack rates of the SARS-CoV-2 Delta variant and the associated factors. Methods: A COVID-19 outbreak caused by the Delta variant occurred in Nanjing in July 2021. A total of 235 cases with current addresses in Nanjing were reported from 171 households. The subjects in this study were selected from household close contact(s) of infected cases. The information on household index cases and their contacts were collected, and the household secondary attack rate (HSAR) and the risk factors were analyzed by the multi-factor logistic regression model. Results: A total of 234 cases of household close contacts and 64 household secondary cases were reported from 103 households, and the HSAR was 27.4% (64/234, 95%CI:22.0% to 33.4%). The proportions of household size for 2 to 3, 4 to 5, and 6 to 9 were 64.1% (66), 26.2% (27) and 9.7% (10), respectively. A total of 35 cases of household cluster outbreaks were reported (35/103, 34.0%). The number of the first case in the household (FCH) was 103 and males accounted for 27.2% (28 cases), with the median age (Q₁, Q₃) of 49 (9, 56). The number of household close contacts was 234 and males accounted for 59.0% (138 cases), with the median age (Q₁, Q₃) of 42 (20, 55) and the median exposure period (Q₁, Q₃) of 3 (1, 3) days. The multi-factor logistic regression model showed that the higher HSAR was observed in the FCH with the features of airport staff (OR=2.913, 95%CI:1.469-5.774), detection from home quarantine screening (OR=6.795, 95%CI:1.761-26.219) and detection from mass screening (OR=4.239, 95%CI:1.098-16.368). Meanwhile, higher HSAR was observed in cases with longer household exposure (OR=1.221, 95%CI:1.040-1.432), non-vaccination (OR=2.963, 95%CI:1.288-6.813) and incomplete vaccinations (OR=2.842, 95%CI:0.925-8.731). Conclusion: The generation interval of the Delta variant is shortened, and the ability of transmission within the household is enhanced. In the outbreak in Nanjing, the associated factors of HSAR are occupation, detection route, vaccination and exposure period.

Early memory impairment is accompanied by changes in GluA1/p-GluA1 in APP/PS1 mice

AIMS

Exploring the neurobiological mechanisms of early AD damage Background: The early diagnosis of Alzheimer's disease (AD) has a very important impact on the prognosis of AD. However, the early symptoms of AD are not obvious and difficult to diagnose. Existing studies have rarely explored the mechanism of early AD. AMPARs are early important learning memory-related receptors. However, it is not clear how the expression levels of AMPARs change in early AD.

OBJECTIVE

We explored learning memory abilities and AMPAR expression changes in APP/PS1 mice at 4 months, 8 months, and 12 months.

METHOD

We used the classic Morris water maze to explore the learning and memory impairment of APP/PS1 mice and used western blotting to explore the changes in AMPARs in APP/PS1 mice.

RESULT

We found that memory impairment occurred in APP/PS1 mice as early as 4 months of age, and the impairment of learning and memory gradually became serious with age. The changes in GluA1 and p-GluA1 were most pronounced in the early stages of AD in APP/PS1 mice.

CONCLUSION

Our study found that memory impairment in APP/PS1 mice could be detected as early as 4 months of age, and this early injury may be related to GluA1.

[Reoperation rate and related factors in patients with Crohn's disease]

Objective: To analyze the cumulative reoperation rate of postoperative Crohn's disease (CD) patients and investigate the operation reasons and the effects of drugs on surgical recurrence. Method: Patients with Crohn's disease who had undergone intestinal resection from January 2000 to March 2020 in Peking Union Medical College Hospital were enrolled. Patients were divided into reoperation and non-reoperation group according to whether they had a second operation. And the basic characteristics and the reasons for the primary and second operation were retrospectively analyzed. Meanwhile, patients were divided into low-risk reoperation group and high-risk group based on risk stratification. Kaplan-Meier methods were performed to analyze the cumulative surgical recurrence rate and to compare the recurrence rate in different risk stratification and chi-square tests was used to analyze the effects of different maintenance drugs on reoperation. Result: A total of 160 patients were enrolled in the study. There were 110 males and 50 females, and the age at first operation was (35.6±14.1) years old. There were 40 patients in the reoperation group and 120 patients in the non-reoperation group. According to univariate analysis, the proportion of male gender(P=0.030), penetrating phenotype(P<0.001), history of appendectomy before the primary surgery(P=0.035) and no postoperative maintenance therapy (P<0.001) were higher in surgical recurrence group. In terms of the operation reasons, intestinal obstruction accounted for the highest proportion in the primary operation (26.9%, 43/160), while the intestinal fistula was the most common reason for reoperation (42.5%, 17/40). After the primary surgery, the cumulative reoperation rates at 1, 3, 5 and 10 years were 5.9% (9 cases), 12.3% (17 cases), 21.8% (25 cases) and 37.6% (34 cases), respectively. The ten years cumulative reoperation rate of the high-risk group was 42.8% (31 cases), which was much higher than that of low-risk group (19.8%, 3 cases), and the difference was statistically significant (P=0.006). There was no statistically significant difference in the surgical recurrence rate of low-risk group patients(P=0.076)whether maintenance therapies were added or not, while the recurrence rate of high-risk group patients who did not receive maintenance therapy was higher than those who received immunosuppressant with or without (±) 5-aminosalicylic acid (ASA) (P=0.001) and biological agent±5-ASA (P=0.001), and the difference was statistically significant. Conclusion: Patients with CD are still at risk of reoperation after surgery. Immunosuppressive agents and biologics can prevent patients from reoperation in high-risk groups.

Ultrasensitive Multiplex Detection of Single Nucleotide Polymorphisms Based on Short-Chain Hybridization Combined with Online Preconcentration of Capillary Electrophoresis

Reliable multiple single nucleotide polymorphisms (SNPs) detection at low abundance is of great significance for disease diagnosis and biomedical research. Herein, we have developed a novel and simple method for multiple SNPs detection combining solid-phase capture by specific hybridization with online preconcentration of capillary gel electrophoresis-laser-induced fluorescence (CGE-LIF). The method presents an excellent performance due to its favorable traits: the solid-phase short-chain hybridization ensures the high specificity of SNP detection; the effective separation ability of CGE can easily achieve multiplex detection; the simple online preconcentration significantly improves the detection sensitivity of fluorescent probe by nearly 100-fold. For a single SNP target, the assay achieves a limit of detection as low as 0.01-0.02% for three different NRAS mutations in the same codon. For multiple SNP targets, as low as 0.05% abundance can be easily realized. Our method is simple, efficient, ultrasensitive, and universal for multiple SNPs detection without complex enzymatic or chemical ligation reaction, which shows great potential in early clinical diagnosis.

High-throughput ultra-sensitive discrimination of single nucleotide polymorphism via click chemical ligation

Single nucleotide polymorphisms (SNPs) have been proven to be important biomarkers for disease diagnosis, prognosis and disease pathogenesis. Here, taking the advantages of a self-assembled oligonucleotide sandwich structure and robust chemical reactions, we have developed a simple, high-throughput and effective colorimetric analytical technique termed CuAAC-based ligation-assisted assays (CuAAC-LA) for SNP detection using a DNA-BIND 96-well plate. With the 5'-azide and 3'-alkyne groups labelled on two oligonucleotide probes, the target DNA can direct a Cu(i)-catalyzed alkyne-azide cycloaddition (CuAAC) click reaction. Since the small difference in duplex stability caused by a single-nucleotide mismatch was amplified by the steric effects of these reactive groups for the ligation reaction of an unstable duplex, CuAAC-LA exhibited an ultra-sensitive discrimination ability for a mutant type target in the presence of large amounts of wild type targets. As low as 0.05% SNP could be clearly detected, which was better than most previously reported methods by various DNA ligases, indicating that a simple and rapid synthetic method i.e., the DNA template-directed click reaction held the potential to replace the ligase for SNP detection.

[Analysis on clinical features of patients with ulcerative colitis associated colorectal cancer]

Objective: To analyze the clinical features of ulcerative colitis associated colorectal cancer (UC-CRC). Methods: A total of 869 inpatients with Ulcerative Colitis (UC) in Peking Union Medical Hospital from January 1998 to January 2018 were continuously enrolled. Clinical data and the outcome of colorectal cancer (CRC) were collected via medical records and telephone follow-up. Chi-square test and logistic regression model were used to analyze the data. Results: There were 16 patients in 869 UC inpatients who were diagnosed with CRC during a period of 7 548 person years and the incidence rate of UC-CRC was 1.84%. Compared to UC inpatients without CRC, a longer course of disease (OR=1.087, 95% CI:1.046-1.129) , a lower usage rate of 5-Aminosalicylic Acid(5-ASA) (OR=0.218, 95% CI:0.052-0.915) and a higher incidence rate of intestinal stenosis (OR=16.533, 95% CI:3.824-71.478) were found in UC inpatients with CRC. Conclusions: A long disease course is a risk factor for UC patients developing CRC, while 5-ASA therapy can reduce the risk of suffering from CRC. For UC patients with intestinal stenosis, CRC should be warned for occurring.

Inequity in inpatient services utilization: a longitudinal comparative analysis of middle-aged and elderly patients with the chronic non-communicable diseases in China

Background

Aging and the chronic non-communicable diseases (NCDs) challenge the Chinese government in the process of providing hospitalization services fairly and reasonably. The Chinese government has developed the basic medical insurance system to solve the problem of “expensive medical cost and difficult medical services” for vulnerable groups and alleviate the unfair phenomenon. However, few studies have confirmed its effect through longitudinal comparison. This study aimed to explore the trend in the inequity of inpatient use among middle-aged and elderly individuals with NCDs in China.

Methods

This longitudinal comparative study was based on CHARLS data in 2011, 2013 and 2015. Concentration index (CI) was used to measure the variation trend of inequity of inpatient services utilization, while the decomposition method of the CI was applied to measure the factors contributing to inequity in inpatient services utilization. The effect of each factor on the change of inequity in inpatient services utilization was divided into the change of the elasticity and the change of inequality using the Oaxaca-type decomposition method.

Results

The affluent middle-aged and elderly patients with NCDs used more inpatient services than poor groups. The per capita household consumption expenditure (PCE) and Urban Employee Basic Medical Insurance (UEBMI) contributed to the decline in pro-rich inequality of inpatient use, while the New Rural Cooperative Medical Scheme (NRCMS) contributed to the decline in pro-poor inequality of inpatient use.

Conclusions

There was a certain degree of pro-rich unfairness in the probability and frequency of inpatient services utilization for middle-aged and elderly individuals with NCDs in China. The decrease of pro-wealth contribution of PCE and UEBMI offset the decrease of pro-poor contribution of NRCMS, and improved the equity of inpatient services utilization, favoring poor people.

[Analysis of chyle leakage after central lymph node dissection for thyroid carcinoma]

Objective: To analyze the clinical characteristics, treatment and prognosis of chyle leakage after central lymph node dissection for thyroid cancer. Methods: A retrospective analysis was made of 985 patients who underwent surgical for thyroid carcinoma plus central lymph node dissection from January 2017 to June 2018 in Renji Hospital Affiliated to Medical College of Shanghai Jiaotong University. Patients were divided into those without (group A, n=973) and with (group B, n=12) chyle leakage. Patients with chyle leakage who underwent left central lymph node dissection were divided into group B1 (n=5) and right central lymph node dissection into group B2 (n=7). Patients with chyle leakage were treated with fat-free diet and negative pressure drainage. SPSS 20.0 software was used to analyze the general condition, surgical pathology, postoperative drainage, hospitalization days, treatment and prognosis of patients in B1 and B2 groups. Results: The incidence of chyle leakage after central lymph node dissection for thyroid cancer was 1.2% (12/985). There were no significant differences in age, sex, size of primary lesion, number of lymph node dissection in central area and number of lymph node metastasis in central area between group A and group B (all P>0.05). The drainage volume on the first day after operation [((51.7±26.7)) ml] and the average hospitalization days [(3.4±0.8) d] in group A were significantly lower than those in group B ([131.3±56.0)]ml, [10.4±2.6)]d). The differences were statistically significant (t value was -5.442, -11.238, respectively, both P<0.001). There were no significant differences in age, size of primary lesion, number of lymph node dissection, number of lymph node metastasis, drainage volume on the first day after operation and average hospitalization days between group B1 and group B2 (all P>0.05). All chyle leakages in group B stopped after conservative management without surgical intervention. Conclusion: The occurrence of chyle leakage after central lymph node dissection is a rare complication. It can be cured by conservative treatment such as diet control, pressure bandaging and negative pressure drainage, and generally does not require secondary surgery.

[Nested case-control study on risk factors of postoperative hyperactive-type delirium in geriatric orthopedic patients]

Objective: To investigate the risk factors of postoperative hyperactive-type delirium(PHTD) in geriatric orthopedic patients using nested case-control study. Methods: Seventy-four patients who underwent orthopedic surgeries in the Second Affiliated Hospital of Wenzhou Medical University from January 2008 to December 2013, aged 65 or above, American Society of Anesthesiologists (ASA) physical status Ⅰ-Ⅳ, with complete medical records and confirmed diagnosis of PHTD were selected as case group. A control group of 444 patients, on the basis of 1∶6 versus nested case group, from the same cohort but without PHTD was established. Data patterns such as patient age, gender, ASA classification, status of preoperative/postoperative electrolytes, preoperative blood glucose, preoperative/postoperative plasma albumin and preoperative/postoperative hematocrit(Hct), uses of non-steroidal analgesics, anticholinergic drugs and benzodiazepines drugs, type of anesthesia, anesthesia duration, difference in postoperative analgesia were collected and analyzed. Results: Univariate Logistic regression analysis showed that gender, age, ASA grade, preoperative electrolytes, anesthesia duration, operative duration, intraoperative hypotension and the difference of postoperative analgesia were risk factors for PHTD. Multiple Logistic regression analysis showed that gender (OR=2.562, 95%CI: 1.438-4.564, P=0.001), age (OR=3.929, 95%CI: 1.788-8.633, P=0.001), preoperative electrolytes(OR=3.714, 95%CI: 2.068-6.670, P<0.001)were the independent risk factors for PHTD. Conclusion: Male, elderly patients and abnormalities of preoperative electrolyte are the independent risk factors for PHTD in geriatric orthopedic patients.

Simultaneous multiple single nucleotide polymorphism detection based on click chemistry combined with DNA-encoded probes

A novel strategy utilizing a DNA template-directed CuAAC click reaction to mimic a ligation reaction based on DNA ligase was successfully established for multiple SNP detection with high sensitivity and specificity.

Single nucleotide polymorphisms (SNPs) are emerging as important biomarkers for disease diagnosis, prognostics and disease pathogenesis. As one type of disease is always connected to several SNP sites, there is great demand for a reliable multiple SNP detection method. Herein, we mimicked a ligation reaction based on DNA ligase and originally utilized an enzyme-free DNA template-directed click reaction for SNP detection. With 5′-alkyne and 3′-azide groups labelled on two oligonucleotide probes, the target DNA-directed Cu(i)-catalyzed alkyne–azide cycloaddition (CuAAC) click reaction produced a new DNA strand with a triazole backbone, as a mimic of a DNA phosphodiester linkage. Trace amounts of the target (as low as 25 fmol in 50 μL) could be sensitively detected using capillary gel electrophoresis with laser-induced fluorescence (CGE-LIF). Meanwhile, SNP caused an obvious difference in the efficiency of the click reaction, and 0.5% SNP could be easily detected. More importantly, multiplexed SNP detection in a one tube reaction was successfully achieved only by encoding different lengths of the DNA probes for the different SNP sites.

[Clinical observation and related factors analysis of neonatal asphyxia complicated with retinal hemorrhage]

Objective: To observe and analyze related factors of neonatal asphyxia complicated with retinal hemorrhage. Methods: It was a retrospective case series. Seven hundred and twenty-one cases with neonatal asphyxia after 72 hours of birth were enrolled in this study. Fundus examination was performed on these newborns using the third generation wide-angle digital retina imaging system (RetCamⅢ), and the bleeding level was divided into level I, level Ⅱ and level Ⅲ. The conditions of the newborn and the mother during pregnancy were correlatively analyzed. The other factors were also analyzed including delivery mode, birth weight, gestational age, gender, grade of neonatal asphyxia, scalp hematoma, intracranial hemorrhage, fetal intrauterine distress, mother's age and antenatal complications. Single factor χ(2) test and multivariate logistic regression analysis were used to screen and judge risk factors causing retinal hemorrhage related to neonatal asphyxia. Results: In 721 cases of neonatal asphyxia, retinal hemorrhage was found in 204 newborns (28.29%). The hemorrhage was at level Ⅰ in 77 cases (37.75%) , at level Ⅱ in 38 cases (18.63%) and at level Ⅲ in 89 cases (43.63%) . Four cases also had vitreous hemorrhage. Asphyxia was mild in 673 infants (93.34%) and severe in 48 infants (6.66%). The difference in the degree of retinal hemorrhage between the patients with mild and severe asphyxia was significant (χ(2)=22.336, P=0.000). When asphyxia was aggravated, the degree of retinal hemorrhage increased. Relative factors analysis showed that delivery mode (χ(2)=158.643, P<0.05), gestational age (χ(2)=24.522, P<0.05), birth weight (χ(2)=11.916, P<0.05) and grade of neonatal asphyxia (χ(2)=19.809, P<0.05) had correlations with retinal hemorrhage. Logistic regression analysis indicated that grade of neonatal asphyxia and delivery mode were risk factors of retinal hemorrhage in neonatal asphyxia (OR=0.304, 0.085). Conclusion: The incidence of retinal hemorrhage in neonatal asphyxia was 28.29%. The degree of neonatal asphyxia and delivery mode may play roles in the occurrence of retinal hemorrhage in newborns with asphyxia. With aggravation of asphyxia, the degree of retinal hemorrhage may increase. (Chin J Ophthalmol, 2017, 53: 358-362).

[Assessment for pain control efficiency of ultrasound guided adductor canal block in total knee arthroplasty: a report of 28 continuous cases]

Objective: To assess the pain control efficiency of continuous adductor canal block in total knee arthroplasty. Methods: From October to December 2015, patients with severe knee osteoarthritis undergoing primary unilateral TKA were observed clinically.All of the patients received ultrasound-guided continuous adductor canal block after surgery.NPRS Pain score in rest and activity at 2, 6, 12, 24, 48 h after surgery were collected, preoperative and postoperative quadriceps strength at 24, 48 h were analyzed. Opioids consumption and anesthesia related adverse effects were also recorded. Results: All of the patients were enrolled. Rest pain control was fairly good(1.8±1.5), (2.4±1.5), (2.7±1.3), (2.7±1.7), (2.3±1.4) score, but the patients were not satisfied with activity pain control(3.1±2.1), (3.1±2.1), (4.2±2.2), (4.7±2.5), (6.2±2.4) score. There were statistically differences comparing the NPRS in rest pain with the score in activity, except for the results between each other at 6 hours (P=0.252>0.05)after surgery.The results showed no significant differences comparing quadriceps strengthpreoperatively with 24, 48 h postoperatively by repeated measurements variance analysis.Eight patients acquired additional use of dolantin once (100 mg/per time) within 24 h and among them three patients acquired once dolantin during 24 to 48 h. Eleven patients complained nausea postoperatively, one reported vomiting and one experienced xerostomia. Conclusion: Ultrasound-guided continuous adductor canal block can reduce resting pain after TKA, but has a limited effect in activity pain control.Quadriceps strength had been spared after ACB, which might performearly benefits in rehabilitation. ACB-related complications need further observation to be defined.

[Research for intraoperative localization of parathyroid gland usingnanocarbon imaging combined with 99m Tc-MIBI]

Objective:To explore the clinical application of nanocarbon(NC) suspension liquid combined with low dose of 99m Tc-MIBI for parathyroid localization in the hyperparathyroidism surgery.Method:Forty-four patients with secondary hyperparathyroidism(SHPT) in the department of head-neck surgery of Renji Hospital, affiliated to Shanghai Jiaotong University, School of Medicine, were enrolled and randomized into 3 groups including low-dose 99m Tc-MIBI+NC groupⅠ, high dose99m Tc-MIBI+NC group Ⅱ,and control group Ⅲ.We compared the level of PTH,serum calcium before and after operation,and the intraoperative amount of radioactive isotopes of parathyroid gland, etc.Use t-test and Anova for statistical processing. Result:After operation,the PTH levels in group Ⅰ,Ⅱ,Ⅲ were(23.8±32.4)ng/L,(15.8±18.2)ng/L,(90.1±139.4)ng/L,respectively(groupⅠvs Ⅲ,P<0.05;groupⅡvs Ⅲ,P<0.05,groupⅠvsⅡ,P>0.05).The intraoperative amount of radioactive isotopes of parathyroid gland had no significant difference among group Ⅰ,group Ⅱ and group Ⅲ. Conclusion:Nanocarbon combined with 99m Tc-MIBI for SHPT surgery has important localization value.And low dose of 99m Tc MIBI can reduce the cost and radiation, which can achieve the same outcome for patients..

The influence of caecectomy on amino acid availability of three feedstuffs for ganders

1. Experiments were conducted to assess the influence of caecectomy on amino acid availability (AAA) of three feedstuffs for goose. 2. Nine caecectomised and 9 intact Yangzhou ganders, 24 weeks old, were used in these experiments. Fish meal, soybean meal and cottonseed meal were used as the sole source of protein. The endogenous amino acid (AA) losses were evaluated by a nitrogen (N)-free diet method. The influence of caecectomy on apparent amino acid availability (AAAA) in fish meal, soybean meal and cottonseed meal was assessed in experiment 1 and true amino acid availability (TAAA) of three protein diets was determined in experiment 2. 3. Results showed that, in the soybean meal and cottonseed meal, the AAAA and TAAA of most AA determined by the intact ganders were higher than in the caecectomised ganders; in the fish meal, the AAAA and TAAA of most AA determined by the intact ganders were lower than in the caecectomised ganders. 4. Results of the present study suggest that the effect of caecectomy on AAA in geese was dependent on the feedstuff assayed, and it was better to use caecectomised poultry for AAA assessment.

[Surgical exploration of the sentinel lymph nodes in the papillary thyroid carcinoma]

OBJECTIVE

To study the technique of sentinel lymph node mapping in the papillary thyroid carcinoma and its evaluation in the search for cervical metastases.

METHOD

Exploration of the sentinel lymph nodes of the papillary thyroid carcinoma by injection of methylene blue around the tumour among 25 patients during surgery. The nodes which stained blue and the other nodes removed by functional neck dissection were examined histologically after staining with hematoxylin-eosin-saffron (HES). We have evaluated the predictive value of the technique in mapping the cervical metastases in the sentinel lymph node.

RESULTS

Among the 25 patients, 22 patients presented sentinel lymph nodes (blue-stained), that is to say a rate of identification of 88%. At histological examination, 19 of the 22 patients had positive sentinel lymph nodes, of which 13 had also positive nodes not coloured with blue. The histological examination of patients without sentinel lymph node was negative.

CONCLUSION

The technique of the sentinel lymph node has a strong positive predictive value in the search for cervical node metastases in the papillary thyroid carcinoma.

Accessory proteins in the biogenesis of G protein-coupled receptors

Intracellular accessory proteins can be critical for G protein-coupled receptor (GPCR) biogenesis, including aspects of GPCR trafficking. Recent discoveries include the identification of multiple membrane-associated proteins that dictate not only the intracellular sequestration and/or transport of GPCRs, but also modulate-quite dramatically-GPCR ligand specificity subsequent to delivery to the cell surface. These exciting discoveries have shifted earlier paradigms of GPCR functionality.

Sensitization of adenylate cyclase induced by a dopamine D2 receptor mutant: inverse agonism by D2 receptor antagonists

Mutations of residues in the third intracellular loops of several G-protein coupled receptors have been shown to confer constitutive activation. The authors investigated the effects of one such mutation in the dopamine D2 receptor. Compared to the wild type D2, the mutant D2 receptor (D2T344K) showed a substantial increase in agonist affinity with affinity for antagonists unchanged. The increased agonist affinity was unaffected by pertussis toxin treatment, indicating it is an intrinsic property of the mutant receptor. The potency of dopamine for acute inhibition of forskolin-stimulated cAMP production in stably expressing Chinese Hamster Ovary (CHO) cells was higher for the mutant than the wild type receptor. CHO cells stably expressing D2T344K displayed enhanced responses to forskolin-stimulated adenylate cyclase activity compared with cells stably expressing the wild type D2 receptor. The increased forskolin responsiveness of adenylate cyclase is similar to the sensitization previously observed with wild type D2 receptor after agonist treatment. Adenylate cyclase responsiveness of CHO cells stably expressing D2T344K receptor was not further increased by agonist treatment. Sensitization was blocked by pertussis toxin and D2 receptor antagonists haloperidol, butaclamol, and clozapine, indicating inverse agonist activity of these compounds at D2T344K. Inverse agonist activity was further demonstrated by the finding that overnight treatment with these compounds drastically increased the density of the mutant receptor but had minimal effect on the density of the wild type receptor. Taken together, these results suggest the authors have generated a constitutively active dopamine D2 receptor capable of sensitizing adenylate cyclase in the absence of agonist activation.

Regulation of transport of the dopamine D1 receptor by a new membrane-associated ER protein

Many structural determinants for G protein-coupled receptor (GPCR) functions have been defined, but little is known concerning the regulation of their transport from the endoplasmic reticulum (ER) to the cell surface. Here we show that a carboxy-terminal hydrophobic motif, FxxxFxxxF, which is highly conserved among GPCRs, functions independently as an ER-export signal for the dopamine D1 receptor. A newly identified ER-membrane-associated protein, DRiP78, binds to this motif. Overexpression or sequestration of DRiP78 leads to retention of D1 receptors in the ER, reduced ligand binding, and a slowdown in the kinetics of receptor glycosylation. Our results indicate that DRiP78 may regulate the transport of a GPCR by binding to a specific ER-export signal.

Protection of intracellular dopamine cytotoxicity by dopamine disposition and metabolism factors

Dopamine has been hypothesized as a contributing factor for the selective degeneration of dopaminergic neurons in Parkinson's disease. However, the cytotoxic mechanisms of dopamine and its metabolites remain poorly understood. Using a stable aromatic amino acid decarboxylase (AADC) expressing a fibroblast cell line, we previously demonstrated a novel, non-oxidative cytotoxicity of intracellular dopamine. In this study, we further investigate the roles of dopamine metabolism and disposition proteins against intracellular dopamine cytotoxicity by co-expressing these factors in AADC-expressing cells. Our results indicate that overexpression of the vesicular monoamine transporter and monoamine oxidase A-induced protection against intracellular dopamine toxicity, and conversely that pharmacological inhibition of these pathways potentiated L-DOPA toxicity in catecholaminergic PC12 cells. Macrophage migration inhibitory factor and glutathione S-transferase (GST), factors that have recently been shown to be involved in dopamine metabolism, also exhibited a strong protective role against intracellular dopamine cytotoxicity. Our results support a potential role for non-oxidative cytoplasmic dopamine toxicity, and imply that disruption in dopamine disposition and/or metabolism could underlie the progressive degeneration of dopaminergic neurons in Parkinson's disease.

Identification of two prokineticin cDNAs: recombinant proteins potently contract gastrointestinal smooth muscle

The motility of gastrointestinal tract is regulated by classical neurotransmitters, neuropeptides, and humoral agents. Two novel human cDNAs have been cloned based on their sequence similarity to a frog skin secretion protein, Bv8, and a nontoxic protein of mamba snake venom. These human cDNAs encode two secreted proteins of 86 and 81 amino acids. Northern blot hybridization has revealed that these cDNAs are expressed in gastrointestinal tract, particularly the stomach. Recombinant proteins with authentic N-terminal sequences have been produced in Escherichia coli and refolded into functional proteins by careful control of protein aggregation. Mass spectrometry has confirmed the formation of five pairs of disulfide bonds. The refolded recombinant proteins potently contract gastrointestinal smooth muscle with EC(50) values in the subnanomolar range. The contractile effects of the recombinant proteins are specific for gastrointestinal smooth muscle, because they have no effect on vascular or respiratory smooth muscle. To reflect their potent and specific effects on gastrointestinal smooth muscle cells, we have named these recombinant proteins prokineticins. Ligand binding studies with iodinated prokineticin revealed the presence of a high-affinity site in ileal smooth muscle. The displacement of specific binding by GTP gamma S suggests that the prokineticin receptor may belong to the family of G protein-coupled receptors. Experiments with verapamil and nifedipine revealed that calcium influx is essential for the contractile activity of prokineticins on gastrointestinal smooth muscle. In summary, we have identified two novel endogenous regulators of gastrointestinal motility. The availability of recombinant prokineticins should provide novel therapeutic agents for disorders involving impaired gastrointestinal motility.

Evidence for non-oxidative dopamine cytotoxicity: potent activation of NF-kappa B and lack of protection by anti-oxidants

A stable aromatic acid decarboxylase expressing the Chinese hamster ovary cell line was developed to study the cytotoxic properties of intracellular and extracellular dopamine. The relative impermeability of cells to dopamine, but not to L-DOPA, allows the differentiation of extracellular and intracellular dopamine cytotoxicity. In contrast to extracellular dopamine, intracellular dopamine toxicity was resistant to antioxidant protection, and did not require melanin formation for its toxicity. Furthermore, we demonstrated a rapid and potent activation of the stress-inducible transcription factor NF-kappa B by intracellular dopamine, which was also largely insensitive to antioxidant inhibition. A distinctly slower and less potent NF-kappa B activation by extracellular dopamine was blocked by antioxidants and acetylsalicylic acid. Our results indicate the existence of a non-oxidative mechanism of dopamine cytotoxicity. Mitigating intracellular dopamine toxicity could be a novel strategy of slowing the progressive degeneration of dopaminergic neurons in Parkinson's disease.

Modulation of dopamine D(2) receptor signaling by actin-binding protein (ABP-280)

Proteins that bind to G protein-coupled receptors have recently been identified as regulators of receptor anchoring and signaling. In this study, actin-binding protein 280 (ABP-280), a widely expressed cytoskeleton-associated protein that plays an important role in regulating cell morphology and motility, was found to associate with the third cytoplasmic loop of dopamine D(2) receptors. The specificity of this interaction was originally identified in a yeast two-hybrid screen and confirmed by protein binding. The functional significance of the D(2) receptor-ABP-280 association was evaluated in human melanoma cells lacking ABP-280. D(2) receptor agonists were less potent in inhibiting forskolin-stimulated cAMP production in these cells. Maximal inhibitory responses of D(2) receptor activation were also reduced. Further yeast two-hybrid experiments showed that ABP-280 association is critically dependent on the carboxyl domain of the D(2) receptor third cytoplasmic loop, where there is a potential serine phosphorylation site (S358). Serine 358 was replaced with aspartic acid to mimic the effects of receptor phosphorylation. This mutant (D(2)S358D) displayed compromised binding to ABP-280 and coupling to adenylate cyclase. PKC activation also generated D(2) receptor signaling attenuation, but only in ABP-containing cells, suggesting a PKC regulatory role in D(2)-ABP association. A mechanism for these results may be derived from a role of ABP-280 in the clustering of D(2) receptors, as determined by immunocytochemical analysis in ABP-deficient and replete cells. Our results suggest a new molecular mechanism of modulating D(2) receptor signaling by cytoskeletal protein interaction.

Dopamine-stimulated sexual behavior is testosterone dependent in mice

Mice unable to synthesize dopamine (DA) in dopaminergic neurons were generated by gene-targeting techniques (Q.-Y. Zhou & R. D. Palmiter, 1995). These dopamine-deficient (DA-/-) mice required daily administration of 3,4-dihydroxyphenylalanine (L-DOPA) for survival beyond 2 to 3 weeks of age. This treatment stimulated mounting and aggressive behavior of adult DA-/- males toward both male and female mice. Both a nonspecific DA agonist (apomorphine) and a specific D1 agonist (SKF81297) stimulated aggression and mounting behavior; however, a D2 agonist (quinpirole) was less effective. Castration of male DA-/- mice demonstrated that these L-DOPA-stimulated behaviors depend on testosterone. In addition, replacement of testosterone to castrated males showed that the testosterone-responsive pathways of DA-/- males were more sensitive to testosterone than wild-type mice.

Dopamine-stimulated sexual behavior is testosterone dependent in mice

Mice unable to synthesize dopamine (DA) in dopaminergic neurons were generated by gene-targeting techniques (Q.-Y. Zhou & R. D. Palmiter, 1995). These dopamine-deficient (DA-/-) mice required daily administration of 3,4-dihydroxyphenylalanine (L-DOPA) for survival beyond 2 to 3 weeks of age. This treatment stimulated mounting and aggressive behavior of adult DA-/- males toward both male and female mice. Both a nonspecific DA agonist (apomorphine) and a specific D1 agonist (SKF81297) stimulated aggression and mounting behavior; however, a D2 agonist (quinpirole) was less effective. Castration of male DA-/- mice demonstrated that these L-DOPA-stimulated behaviors depend on testosterone. In addition, replacement of testosterone to castrated males showed that the testosterone-responsive pathways of DA-/- males were more sensitive to testosterone than wild-type mice.

Dopamine-deficient mice are severely hypoactive, adipsic, and aphagic

Mice unable to synthesize dopamine (DA) specifically in dopaminergic neurons were created by inactivating the tyrosine hydroxylase (TH) gene then by restoring TH function in noradrenergic cells. These DA-deficient (DA-/-) mice were born at expected frequency but became hypoactive and stopped feeding a few weeks after birth. Midbrain dopaminergic neurons, their projections, and most characteristics of their target neurons in the striatum appeared normal. Within a few minutes of being injected with L-dihdroxyphenylalanine (L-DOPA), the product of TH, the DA-/- mice became more active and consumed more food than control mice. With continued administration of L-DOPA, nearly normal growth was achieved. These studies indicate that DA is essential for movement and feeding, but is not required for the development of neural circuits that control these behaviors.

Spare receptors and intrinsic activity: studies with D1 dopamine receptor agonists

The intrinsic activities of selected dopamine D1 receptor agonists were compared in three distinct molecular expression systems, C-6, Ltk, and GH4 cells transfected with primate D1A receptors. The influence of the cell expression system on intrinsic activity varied markedly among agonists. Dihydrexidine (DHX), a potent full agonist with dramatic antiparkinsonian actions, displayed intrinsic activity similar to dopamine in all three cell lines. In contrast, SKF82958 and SKF38393 (full and partial agonists, respectively, in rat striatum) had intrinsic activities equal to dopamine in GH4 cells that expressed a high density of D1 receptors, yet were of lower intrinsic activity in C-6 cells having 15-fold fewer receptors. The idea that spare receptors are one important determinant of observed intrinsic activity was explored directly by "receptor titration," in which ca. 90% of D1 receptors in Ltk cells were inactivated using EEDQ, an irreversible antagonist. Whereas EEDQ pretreatment decreased the potency of all agonists, it changed the intrinsic activity of some, but not all, drugs. A 40% decrease was seen with the partial agonist SKF38393, and, surprisingly, a 30% decrease was seen with the purported full agonist SKF82958. Conversely, the intrinsic activity of DHX and A68930 were unaffected by the EEDQ treatment. The data demonstrate that significant and biologically meaningful differences in intrinsic efficacy (e.g., DHX vs. SKF82958) may be obscured in test systems that have sufficient receptor reserve (e.g., the striatum). Such differences in intrinsic efficacy may be an important predictor of the clinical utility of D1 agonists.

Targeted disruption of the tyrosine hydroxylase gene reveals that catecholamines are required for mouse fetal development

Tyrosine hydroxylase catalyses the initial, rate-limiting step in the catecholamine biosynthetic pathway. Catecholamines, which include dopamine, noradrenaline, and adrenaline, are important neurotransmitters and hormones that regulate visceral functions, motor coordination and arousal in adults. The gene encoding tyrosine hydroxylase becomes transcriptionally active in developing neuroblasts during mid-gestation of rodent embryos, before the onset of neurotransmission. Here we show that inactivation of both tyrosine hydroxylase alleles results in mid-gestational lethality: about 90% of mutant embryos die between embryonic days 11.5 and 15.5, apparently of cardiovascular failure. Administration of L-DOPA (dihydroxyphenylalanine), the product of the tyrosine hydroxylase reaction, to pregnant females results in complete rescue of mutant mice in utero. Without further treatment, however, they die before weaning. We conclude that catecholamines are essential for mouse fetal development and postnatal survival.

Exclusion of close linkage of Tourette's syndrome to D1 dopamine receptor

OBJECTIVE

The authors' goal was to establish if a mutation in D1 dopamine receptor locus (DRD1), or one genetically close to it, could cause Gilles de la Tourette's syndrome.

METHOD

DRD1 and linked markers (D5S36, D5S61, and D5S62) were studied in a large Mennonite Tourette's syndrome kindred. Only individuals with the full Tourette's syndrome were considered to be affected in one series of analyses; in another series the diagnostic spectrum was broadened to include chronic multiple tics. Liability classes were defined to take into account age at onset and sex differences; dominant inheritance was assumed. The authors' version of the LINKMAP program of the LINKAGE package modified to run under distributed parallel processing (Linda LINKMAP) was used for the multipoint linkage analysis.

RESULTS

Complete (theta = 0.0) linkage of Tourette's syndrome with DRD1 was ruled out (lod score of -10.1) when the disease was defined narrowly. The area of exclusion of linkage (lod score between -2 and -10.5) extended from map position -0.10 to map position 0.50. The authors conducted an additional (centromeric) multipoint analysis with D5S36 as well as glucocorticoid receptor (GRL) and D5S22, resulting in an overlapping area of exclusion to map position -0.30 when the disease was defined narrowly.

CONCLUSIONS

This result provides strong evidence against linkage of the DRD1 D1 dopamine receptor locus with Tourette's syndrome. This exclusion extends the authors' earlier work with the dopamine system in Tourette's syndrome to exclude the two best characterized dopamine receptors from linkage with Tourette's syndrome.

Characterization of gene organization and promoter region of the rat dopamine D1 receptor gene

Genomic and cDNA clones encoding the rat D1 receptor were isolated and sequenced. Comparison of the D1 receptor cDNA and genomic sequences revealed that the rat D1 receptor gene is organized into two exons separated by a small intron in the 5' untranslated region of its mRNA. The transcription start site is located 864 bp upstream from the translational initiation site. The 5'-flanking sequences of the D1 receptor gene do not contain TATA and CAAT canonical sequences, but have a high G+C content, potential cyclic AMP and glucocorticoid response element sequences, and binding sites for transcription factors such as Sp1, Ap1, and Ap2. Transfection studies using the D1 5'-flanking sequence and CAT gene fusion constructs have demonstrated that (1) the D1 promoter is active in D1-expressing neuroblastoma NS20Y cells, but inactive in D1-deficient glioma C6 and kidney 293 cells, (2) the information contained within 735 bp of 5'-flanking sequence of the D1 gene appears to be sufficient to confer its cell-specific expression, and (3) the D1 gene promoter responds to cyclic AMP induction, suggesting the existence of an auto-regulation mechanism by which the stimulation of D1 receptor exerts a positive feedback on its own gene expression.

Cholera toxin-sensitive 3',5'-cyclic adenosine monophosphate and calcium signals of the human dopamine-D1 receptor: selective potentiation by protein kinase A

The signal transduction pathways of the dopamine-D1 receptor were investigated in two cell types stably transfected with the human D1 receptor cDNA, rat pituitary GH4C1 cells (GH4-hD1), and mouse Ltk-fibroblast cells (L-hD1). In both GH4-hD1 and L-hD1 cell lines, stimulation of the dopamine-D1 receptor induced a marked increase in cAMP accumulation. In addition, dopamine potentiated activation of L-type voltage-dependent calcium channels in a cAMP-dependent manner in GH4-hD1 cells. However, in L-hD1 cells, dopamine increased cytosolic free calcium concentrations ([Ca++]i) by mobilization of intracellular calcium rather than by calcium influx. This effect was correlated with a dopamine-induced enhancement of phospholipase C activity in L-hD1 cells. Pretreatment (24 h) with cholera toxin (CTX) was used to maximally activate the GTP-binding protein (G protein) Gs, causing a maximal elevation of cAMP levels and uncoupling the D1 receptor from Gs. The described actions of dopamine in both cell lines were abolished by pretreatment with CTX, indicating that CTX substrates (e.g. Gs) may mediate these actions. The blockade by CTX was not due to CTX-induced elevation of cAMP, since pretreatment with forskolin or 8-bromo-cAMP to activate cAMP-dependent protein kinase did not inhibit dopamine actions nor alter basal [Ca++]i. Pretreatment (1-3 h) of L-hD1 cells with forskolin (10 microM) or 8-bromo-cAMP (5 mM) altered neither the basal activity of phospholipase C nor basal [Ca++]i in L-hD1 cells but greatly enhanced the dopamine-induced increase of phosphatidyl inositol turnover and [Ca++]i. From these results we conclude that: 1) the dopamine-D1 receptor induces multiple and cell-specific signals, including elevation of cAMP levels in both GH and L cells, cAMP-dependent activation and potentiation of opening of L-type voltage-dependent calcium channel in GH cells, and a novel phosphatidyl inositol-linked mobilization of cellular calcium in L cells; 2) coupling of the D1 receptor to these responses involves CTX-sensitive proteins, possibly Gs; and 3) acute preactivation of cAMP-dependent protein kinase can markedly enhance, rather than attenuate, certain pathways of dopamine-D1 transmembrane signaling.

Molecular cloning and characterization of an adenosine receptor: the A3 adenosine receptor

We have previously reported the selective amplification of several rat striatal cDNA sequences that encode guanine nucleotide-binding regulatory protein (G protein)-coupled receptors. One of these sequences (R226) exhibited high sequence identity (58%) with the two previously cloned adenosine receptors. A full-length cDNA clone for R226 has been isolated from a rat brain cDNA library. The cDNA clone encodes a protein of 320 amino acids that can be organized into seven transmembrane stretches. R226 has been expressed in COS-7 and CHO cells and membranes from the transfected cells were screened with adenosine receptor radioligands. R226 could bind the nonselective adenosine agonist tritiated N-ethyladenosine 5'-uronic acid ([3H]NECA) and A1-selective agonist radioiodinated N6-2-(4-amino-3-iodophenyl)-ethyladenosine ([125I]APNEA) but not A1-selective antagonists tritiated 1,3-dipropyl-8-cyclopentylxanthine ([3H]DPCPX) and 8-(4-[([[(2-aminoethyl)amino]carbonyl]methyl)oxy]-phenyl)-1, 3-dipropylxanthine ([3H]XAC) or the A2-selective agonist ligands tritiated 2-[4-(2-carboxyethyl)phenyl]ethyl-amino 5'-N-ethylcarboxamidoadenosine ([3H]CGS21680) and radioiodinated 2-[4-([2-[(4-aminophenyl)methylcarbonylamino] ethylaminocarbonyl]ethyl)phenyl]ethylamino 5'-N-ethylcarboxamidoadenosine. Extensive characterization with [125I]APNEA showed that R226 binds [125I]APNEA with high affinity (Kd = 15.5 +/- 2.4 nM) and the specific [125I]APNEA binding could be inhibited by adenosine ligands with a potency order of (R)-N6-phenyl-2-propyladenosine (R-PIA) = NECA greater than S-PIA greater than adenosine greater than ATP = ADP but not by antagonists XAC, isobutylmethylxanthine, and DPCPX. In R226 stably transfected CHO cells, adenosine agonists R-PIA, NECA, and CGS21680 inhibited by 40-50% the forskolin-stimulated cAMP accumulation through a pertussis toxin-sensitive G protein with an EC50 of 18 +/- 5.6 nM, 23 +/- 3.5 nM, and 144 +/- 34 nM, respectively. Based on these observations we conclude that R226 encodes an adenosine receptor with non-A1 and non-A2 specificity, and we thus name it the A3 adenosine receptor. mRNA analyses revealed that the highest expression of R226 was in the testis and low-level mRNAs were also found in the lung, kidneys, heart, and some parts of the central nervous system such as cortex, striatum, and olfactory bulb. The high-expression level of the A3 receptor in the testis suggests a possible role for adenosine in reproduction.

Linkage Analysis of the D1 Dopamine Receptor Gene and Manic Depression in Six Families

Disturbances in dopaminergic activity may play an important role in the pathogenesis of manic depression. The effects of dopamine are mediated by at least five G protein coupled receptors, D1, D2, D3, D4 and D5. Recently, three separate research groups have cloned and characterized the D1 dopamine receptor, which localizes to 5q35.1. We undertook a linkage analysis between the D1 receptor polymorphisms and manic depression in six families in which segregation of the disease was consistent with autosomal dominant inheritance. A highly polymorphic flanking DNA marker, CRI-L1200, was also analyzed as the D1 gene RFLPs were relatively uninformative in our families. Multipoint analyses of manic depression and these DNA markers resulted in lod scores of less than -3.0 at the D1 locus, indicating that the D1 dopamine receptor gene does not confer an inherited susceptibility to manic-depressive illness in the families studied.

Comparison of the distributions of D1 and D2 dopamine receptor mRNAs in rat brain

The distributions of messenger RNAs encoding both the D1 and D2 dopamine receptors have been determined in the rat brain by in situ hybridization. High levels of both mRNAs were found in the traditional dopaminoceptive regions of brain, including the caudate-putamen, nucleus accumbens, and olfactory tubercle; lower levels of both were found in a number of other neural structures, such as the lateral septum, olfactory bulb, hypothalamus, and cortex. High levels of D2 but not D1 receptor mRNA were identified in the midbrain dopamine cell groups, suggesting that the autoreceptors found in the substantia nigra and ventral tegmental area are exclusively D2. Other areas demonstrating differential distribution of these two mRNAs included the pituitary, amygdala, and hippocampus. Quantitative densitometric analysis revealed that in most of the brain regions studied in which both messages exist, the amounts of D1 and D2 receptor mRNAs were approximately equal. Finally, using thin (2.5-micron) sections through the caudate-putamen, about half of all cells were found to be positive for D1 receptor mRNA, and approximately 75% of cells contained D2 receptor mRNA. Subsequent analysis in sequential sections revealed that co-localization of D1 and D2 receptor mRNA occurred in 33% +/- 7% of all caudate-putamen cells: about half of all cells containing D1 receptor mRNA also contained D2 receptor mRNA, and approximately half of all D2 receptor mRNA-positive cells also contained D1 receptor mRNA. These results indicate that there is considerable overlap between D1 and D2 dopaminoceptive cells, and provide a basis for future regulatory studies of dopamine systems in brain within a defined anatomic context.

Multiple human D5 dopamine receptor genes: a functional receptor and two pseudogenes

Three genes closely related to the D1 dopamine receptor were identified in the human genome. One of the genes lacks introns and encodes a functional human dopamine receptor, D5, whose deduced amino acid sequence is 49% identical to that of the human D1 receptor. Compared with the human D1 dopamine receptor, the D5 receptor displayed a higher affinity for dopamine and was able to stimulate a biphasic rather than a monophasic intracellular accumulation of cAMP. Neither of the other two genes was able to direct the synthesis of a receptor. Nucleotide sequence analysis revealed that these two genes are 98% identical to each other and 95% identical to the D5 sequence. Relative to the D5 sequence, both contain insertions and deletions that result in several in-frame termination codons. Premature termination of translation is the most likely explanation for the failure of these genes to produce receptors in COS-7 and 293 cells even though their messages are transcribed. We conclude that the two are pseudogenes. Blot hybridization experiments performed on rat genomic DNA suggest that there is one D5 gene in this species and that the pseudogenes may be the result of a relatively recent evolutionary event.

Molecular biology of the dopamine receptors

Because of their importance in pathophysiology, the dopamine receptors have been the subjects of intense pharmacological and physiological research. Their structures have remained mostly unknown until recently with the application of molecular biological approaches. The cloning of the first dopamine receptor, the D2 receptor opened a new era in dopamine receptor research. It has led not only to new studies of its own biology but also to the characterization of the other dopamine receptors. The most striking conclusion of this fast moving research is that the dopamine receptors are more diverse than expected from their pharmacological characterizations. We discuss here the history of the cloning of the dopamine receptors and the impact that this research had on our understanding of the dopamine system.

A comparison of D1 receptor binding and mRNA in rat brain using receptor autoradiographic and in situ hybridization techniques

D1, a subtype of the dopamine receptors, is widely distributed in the nervous system and has been shown to be positively coupled to adenylate cyclase. Using a combination of in vitro receptor autoradiographic and in situ hybridization techniques, the present study examines the co-distribution of D1 receptor binding sites and D1 receptor messenger RNA in adjacent rat brain sections. D1 receptor binding sites were labeled using the selective antagonist [3H]SCH23390 (4.6 nM) in the presence of 1 microM ketanserin, while the D1 receptor messenger RNA was visualized with a 35S-labeled riboprobe corresponding to a region between transmembrane domains III and VI of the rat D1 receptor (bp 383-843). Analysis of serial sections suggested a good agreement between D1 receptor binding and messenger RNA in several brain regions, including the paleocortex, caudate-putamen, nucleus accumbens, amygdala and suprachiasmatic nucleus. Marked discrepancies between D1 receptor binding and messenger RNA were observed in other brain regions including the entopeduncular and subthalamic nuclei, substantia nigra (pars reticulata), hippocampus and cerebellum. While technical considerations may contribute to these results, much of the discordance between the distributions is likely due to the differential localization D1 receptor messenger RNA in cell bodies and receptor binding sites on fibers and may provide insights into receptor synthesis, transport and membrane insertion. In the basal ganglia, for instance, D1 receptors are synthesized in the striatum and are either transported to efferent projections in areas such as the substantia nigra, or remain localized in striatal cells bodies. Ibotenic acid lesions in the striatum are consistent with these conclusions and demonstrate a coordinate loss of D1 receptor binding and messenger RNA in the caudate-putamen that is accompanied by a degeneration of fibers projecting to substantia nigra and a loss of D1 binding in the pars reticulata. Neurons in the dentate gyrus and in the granular layer of the cerebellum, on the other hand, synthesize D1 receptors and transport them entirely to either their dendritic or axonal fields, respectively, in the molecular layer. This analysis provides a better understanding of dopaminergic receptor systems in the CNS and their anatomical organization.

A human D1 dopamine receptor gene is located on chromosome 5 at q35.1 and identifies an EcoRI RFLP

Dopaminergic neurons have been shown to affect voluntary movement, hormone secretion, and emotional tone. Mediating these activities are two receptor subtypes, D1 and D2, which are biochemically and pharmacologically distinct. The D1 subtype, the most abundant form of dopamine receptor in the central nervous system, stimulates adenylate cyclase, modulates D2 receptor activity, regulates neuron growth and differentiation, and mediates several behavioral responses. Recently we reported the cloning of a human D1 dopamine receptor gene (DRD1). High-stringency hybridization of the DRD1 clone to human genomic blots suggests that DRD1 is single copy. When used to probe a Southern blot made with DNAs from a rodent-human somatic cell hybrid panel, DRD1 hybridized to a 6.5-kb EcoRI restriction fragment which was assigned to chromosome 5. Fluorescent in situ hybridization of this gene to human metaphase chromosomes refined the location of DRD1 to 5q35.1. A search for RFLPs associated with DRD1 identified a two-allele EcoRI RFLP, allowing confirmation of DRD1's localization by linkage analysis in Centre d'Etude du Polymorphisme Humain families.

Cloning and expression of human and rat D1 dopamine receptors

The importance of the dopaminergic system in brain function has been emphasized by its association with neurological and psychiatric disorders such as Parkinson's disease and schizophrenia. On the basis of their biochemical and pharmacological characteristics, dopamine receptors are classified into D1 and D2 subtypes. As the most abundant dopamine receptor in the central nervous system, D1 receptors seem to mediate some behavioural responses, modulate activity of D2 dopamine receptors, and regulate neuron growth and differentiation. The D dopamine receptor has been cloned by low-stringency screening. We report here the cloning of human and rat D1 dopamine receptors by applying an approach based on the polymerase chain reaction. The cloned human D1 dopamine receptor has been characterized on the basis of four criteria: the deduced amino-acid sequence, which reveals that it is a G protein-coupled receptor; the tissue distribution of its messenger RNA, which is compatible with that of the D1 dopamine receptor; its pharmacological profile when transfected into COS-7 cells; and its ability to stimulate the accumulation of cyclic AMP in human 293 cells.

Cloning, functional expression, and mRNA tissue distribution of the rat 5-hydroxytryptamine1A receptor gene

G protein-coupled receptors comprise a family of genes that share significant sequence similarity. We have screened a rat genomic library under low stringency hybridization conditions with the coding portion of the hamster beta 2-adrenergic receptor gene to isolate new members of this gene family. We show that one of these clones, clone D, codes for a 5-hydroxytryptamine1A (5-HT1A) binding site since: 1) it possesses an intronless open reading frame encoding a protein with seven putative transmembrane domains and 89% amino acid identity with the human 5-HT1A receptor (G21); 2) when transfected into Ltk- cells, it expresses a ligand-binding site with the pharmacology of the 5-HT1A receptor subtype, including 5-HT- and spiroxatrine-displaceable binding of 8-hydroxy-(2-(N,N-di[2,3-3H]propylamino)-1,2,3,4-tetrahydronaphthalene (KH = 0.8 nM). We further show that clone D encodes a functional receptor because its binding site interacts with G proteins and because it mediates agonist-induced inhibition of basal and stimulated cAMP accumulation in transfected GH4C1 pituitary cells. Finally, we have analyzed the tissue distribution of 5-HT1A receptor mRNA in rat brain and have found that 5-HT1A mRNA is present with the expected distribution of the 5-HT1A receptor (highest in septum and hippocampus) but is present as three RNA species (3.9, 3.6, and 3.3 kilobases). These studies represent the first characterization of receptor function and brain distribution of the cloned rat 5-HT1A receptor.