Development of extended pharmacokinetic models for propofol based on measured blood and brain concentrations.

Propofol's pharmacokinetics have been extensively studied using human blood samples and applied to target-controlled infusion systems; however, information on its concentration in the brain remains scarce. Therefore, this study aimed to simultaneously measure propofol plasma and brain concentrations in patients who underwent awake craniotomy and establish new pharmacokinetic model. Fifty-seven patients with brain tumors or brain lesions who underwent awake craniotomy were sequentially assigned to model-building and validating groups. Plasma and brain (lobectomy or uncapping margins) samples were collected at five time-points. The concentration of propofol was measured using high-performance liquid chromatography. Population pharmacokinetic analysis was conducted through a nonlinear mixed-effects modeling program using a first-order conditional estimation method with interactions. Propofol's brain concentrations were higher than its plasma concentrations. The measured brain concentrations were higher than the effect site concentrations using the previous models. Extended models were constructed based on measured concentrations by incorporating the brain/plasma partition coefficient (Kp value). Extended models showed good predictive accuracy for brain concentrations in the validating group. The Kp value functioned as a factor explaining retention in the brain. Our new pharmacokinetic models and Kp value can predict propofol's brain and plasma concentrations, contributing to safer and more stable anesthesia.

Association between intraoperative end-tidal carbon dioxide and postoperative organ dysfunction in major abdominal surgery: A cohort study.

BACKGROUND: Data on the effects of intraoperative end-tidal carbon dioxide (EtCO2) levels on postoperative organ dysfunction are limited. Thus, this study was designed to investigate the relationship between the intraoperative EtCO2 level and postoperative organ dysfunction in patients who underwent major abdominal surgery under general anesthesia. METHODS: We conducted a cohort study involving patients who underwent major abdominal surgery under general anesthesia at Kyoto University Hospital. We classified those with a mean EtCO2 of less than 35 mmHg as low EtCO2. The time effect was determined as the minutes when the EtCO2 value was below 35 mmHg, whereas the cumulative effect was evaluated by measuring the area below the 35-mmHg threshold. The outcome was postoperative organ dysfunction, defined as a composite of at least one organ dysfunction among acute renal injury, circulatory dysfunction, respiratory dysfunction, coagulation dysfunction, and liver dysfunction within 7 days after surgery. RESULTS: Of the 4,171 patients, 1,195 (28%) had low EtCO2, and 1,428 (34%) had postoperative organ dysfunction. An association was found between low EtCO2 and increased postoperative organ dysfunction (adjusted risk ratio, 1.11; 95% confidence interval [CI], 1.03-1.20; p = 0.006). Additionally, long-term exposure to EtCO2 values of less than 35 mmHg (≥224 min) was associated with postoperative organ dysfunction (adjusted risk ratio, 1.18; 95% CI, 1.06-1.32; p = 0.003) and low EtCO2 severity (area under the threshold) (adjusted risk ratio, 1.13; 95% CI, 1.02-1.26; p = 0.018). CONCLUSIONS: Intraoperative low EtCO2 of below 35 mmHg was associated with increased postoperative organ dysfunction.

Relationship between the Use of Fentanyl-Based Intravenous Patient-Controlled Analgesia and Clinically Significant Events in Laparoscopic Gynecological Surgery: A Single-Center Retrospective Cohort Study.

Background: This study examined the relationship between the use of fentanyl-based intravenous patient-controlled analgesia (ivPCA) and the incidence of a clinically significant event (CSE), while considering both the analgesic effects and side effects in laparoscopic gynecological surgery. Methods: This study included 816 patients undergoing laparoscopic gynecological surgery under general anesthesia at Kyoto University Hospital between 2012 and 2018. The primary exposure was the use of fentanyl-based ivPCA. We defined an outcome measure­CSE­that integrates severe wound pain and vomiting assumed to negatively affect patient recovery. We performed multivariable logistic regression analysis to assess the independent relationship between ivPCA use and CSE. Results: Multivariable logistic regression analysis revealed that fentanyl-based ivPCA was independently associated with increased CSE (adjusted odds ratio (95% confidence interval): 1.80 (1.24−2.61), p = 0.002). Use of ivPCA was associated with a reduced incidence of postoperative severe wound pain (adjusted odds ratio (95% confidence interval): 0.50 (0.27−0.90), p = 0.022), but was also associated with an increased incidence of vomiting (adjusted odds ratio (95% confidence interval): 2.65 (1.79−3.92), p < 0.001). Conclusion: The use of fentanyl-based ivPCA in laparoscopic gynecological surgery is associated with increased CSE.

Association between intraoperative end-tidal carbon dioxide and postoperative nausea and vomiting in gynecologic laparoscopic surgery.

Gynecologic laparoscopic surgery has a high incidence of postoperative nausea and vomiting (PONV). Studies suggest that low intraoperative end-tidal carbon dioxide (EtCO2) is associated with an increased incidence of PONV, but the results have not been consistent among studies. This study investigated the association between intraoperative EtCO2 and PONV in patients undergoing gynecologic laparoscopic surgeries under general anesthesia. This retrospective cohort study involved patients who underwent gynecologic laparoscopic surgeries under general anesthesia at Kyoto University Hospital. We defined low EtCO2 as a mean EtCO2 of < 35 mmHg. Multivariable modified Poisson regression analysis examined the association between low EtCO2 and PONV during postoperative two days and the postoperative length of hospital stay (PLOS). Of the 739 patients, 120 (16%) had low EtCO2, and 430 (58%) developed PONV during postoperative two days. There was no substantial association between low EtCO2 and increased incidence of PONV (adjusted risk ratio: 0.96; 95% confidence interval [CI] 0.80-1.14; p = 0.658). Furthermore, there was no substantial association between low EtCO2 and prolonged PLOS (adjusted difference in PLOS: 0.13; 95% CI - 1.00 to 1.28; p = 0.816). Intraoperative low EtCO2, specifically a mean intraoperative EtCO2 below 35 mmHg, was not substantially associated with either increased incidence of PONV or prolonged PLOS.

Incidence, clinical characteristics and long-term prognosis of postoperative symptomatic venous thromboembolism: a retrospective cohort study.

OBJECTIVES: The purpose of this study was to evaluate the incidence, clinical characteristics and prognosis of postoperative symptomatic venous thromboembolism (VTE) in Japan. DESIGN: Retrospective observational study. Two data sets, Contemporary ManageMent AND outcomes in patients with Venous ThromboEmbolism (COMMAND VTE) Registry and Japanese Society of Anesthesiologists (JSA) annual report, were used for current analyses. SETTING: Eighteen of 29 centres participated in the COMMAND VTE Registry. PARTICIPANTS: Acute symptomatic patients with VTE who had undergone surgery 2 months prior to the diagnosis at 18 centres from January 2010 to December 2013 were identified in the COMMAND VTE Registry. From each centre's JSA annual report, the overall population that had received anaesthetic management during this period was retrieved. INTERVENTIONS: None. PRIMARY AND SECONDARY OUTCOME MEASURES: The primary outcome was the incidences and clinical characteristics of postoperative symptomatic VTE. The secondary outcomes were recurrent VTE, major bleeding and all-cause death. RESULTS: We identified 137 patients with postoperative symptomatic VTE, including 57 patients with pulmonary embolism. The incidences of postoperative symptomatic VTE and pulmonary embolism were 0.067% and 0.028%, respectively, based on data from 2 03 943 patients who underwent surgery, managed by anaesthesiologists, during the study period. The incidences of postoperative symptomatic VTE varied widely, depending on surgical and anaesthetic characteristics. Postoperative symptomatic VTE occurred at a median of 8 days after surgery, with 58 patients (42%) diagnosed within 7 days. The cumulative incidence, 30 days after VTE, of recurrent VTE, major bleeding, and all-cause death was 3.0%, 5.2%, and 3.7%, respectively. CONCLUSION: This study, combining the large real-world VTE and anaesthesiology databases in Japan revealed the incidence, clinical features and prognosis of postoperative symptomatic VTE, providing useful insights for all healthcare providers involved in various surgeries. TRIAL REGISTRATION: Not applicable.

Intraoperative end-tidal carbon dioxide and postoperative mortality in major abdominal surgery: a historical cohort study.

PURPOSE: There is a paucity of data on the effect of intraoperative end-tidal carbon dioxide (EtCO2) levels on postoperative mortality. The purpose of this study was to investigate the relationship between intraoperative EtCO2 and 90-day mortality in patients undergoing major abdominal surgery under general anesthesia. METHODS: We conducted a historical cohort study of patients undergoing major abdominal surgery under general anesthesia at Kyoto University Hospital. We measured the intraoperative EtCO2, and patients with a mean EtCO2 value < 35 mm Hg were classified as low EtCO2. The time effect was determined based on minutes below an EtCO2 of 35 mm Hg, and cumulative effects were evaluated by measuring the area under the threshold of 35 mm Hg for each patient. RESULTS: Of 4,710 patients, 1,374 (29%) had low EtCO2 and 55 (1.2%) died within 90 days of surgery. Multivariable Cox regression analysis-adjusted for age, American Society of Anesthesiologists Physical Status classification, sex, laparoscopic surgery, emergency surgery, blood loss, mean arterial pressure, duration of surgery, type of surgery, and chronic obstructive pulmonary disease-revealed an association between low EtCO2 and 90-day mortality (adjusted hazard ratio, 2.2; 95% confidence interval [CI], 1.2 to 3.8; P = 0.006). In addition, severity of low EtCO2 was associated with an increased 90-day mortality (area under the threshold; adjusted hazard ratio; 2.9, 95% CI, 1.2 to 7.4; P =0.02); for long-term exposure to an EtCO2 < 35 mm Hg (≥ 226 min), the adjusted hazard ratio for increased 90-day mortality was 2.3 (95% CI, 0.9 to 6.0; P = 0.08). CONCLUSION: A mean intraoperative EtCO2 < 35 mm Hg was associated with increased postoperative 90-day mortality.

RéSUMé: OBJECTIF: Il n'existe que très peu de données s'intéressant à l'effet du niveau peropératoire télé-expiratoire du dioxyde de carbone (EtCO2) sur la mortalité postopératoire. L'objectif de cette étude était d'examiner la relation entre l'EtCO2 peropératoire et la mortalité à 90 jours chez des patients subissant une chirurgie abdominale majeure sous anesthésie générale. MéTHODE: Nous avons réalisé une étude de cohorte historique portant sur des patients subissant une chirurgie abdominale majeure sous anesthésie générale à l'Hôpital universitaire de Kyoto. Nous avons mesuré l'EtCO2 peropératoire, et les patients avec une valeur moyenne d'EtCO2 < 35 mmHg ont été catégorisés comme EtCO2 faible. L'effet temps a été déterminé en fonction de la durée, en minutes, avec une EtCO2 inférieure à 35 mmHg, et les effets cumulatifs ont été évalués en mesurant l'aire sous le seuil de 35 mmHg pour chaque patient. RéSULTATS: Sur 4710 patients, 1374 (29 %) avaient une EtCO2 faible et 55 (1,2 %) sont décédés dans les 90 jours suivant la chirurgie. Une analyse de régression multivariée de Cox, ajustée pour tenir compte des facteurs suivants : âge, statut physique selon l'American Society of Anesthesiologists, sexe, chirurgie par laparoscopie, chirurgie d'urgence, pertes de sang, tension artérielle moyenne, durée de la chirurgie, type de chirurgie et maladie pulmonaire obstructive chronique, a révélé une association entre une EtCO2 faible et la mortalité à 90 jours (rapport de risque ajusté, 2,2; intervalle de confiance [IC] à 95 %, 1,2 à 3,8; P = 0,006). De plus, la sévérité de l'EtCO2 basse était associée à une augmentation de la mortalité à 90 jours (aire sous le seuil; rapport de risque ajusté; 2,9, IC 95 %, 1,2 à 7,4; P =0,02); pour une exposition à long terme à une EtCO2 < 35 mmHg (≥ 226 minutes), le rapport de risque ajusté pour une mortalité accrue à 90 jours était de 2,3 (IC 95 %, 0,9 à 6,0 ; P = 0,08). CONCLUSION: Une EtCO2 peropératoire moyenne < 35 mmHg était associée à une augmentation de la mortalité postopératoire à 90 jours.

Factors associated with somnolence during brain function mapping in awake craniotomy.

Somnolence during brain function mapping is one of the factors that inhibit the accomplishment of the goals of awake craniotomy. We examined the effect of anesthesia depth measured by bispectral index (BIS) during pre-awake phase on somnolence during brain function mapping and also explored the factors associated with somnolence. We examined the association between BIS values during pre-awake phase and somnolence during the first 30 min of brain function mapping in 55 patients who underwent awake craniotomy at Kyoto University Hospital from 2015 to 2018. The pre-awake BIS value was defined as the mean BIS value for 60 min before the removal of the airway. Somnolence during brain function mapping was the primary outcome, defined as either of the following conditions: inability to follow up, disorientation, or inability to assess speech function. Additionally, we compared patient or perioperative variables between patients with/without somnolence. Somnolence occurred in 14 patients (25.5%), of which 6 patients (10.9%) were unable to complete brain function mapping. There was no significant difference in the pre-awake BIS value between patients with/without somnolence (median: 46 vs. 49, P = 0.192). Somnolence was not significantly associated with age, gender, and the number of preoperative anticonvulsive drugs, but patients with somnolence had a significantly lower preoperative Western Aphasia Battery (WAB) aphasia quotient score (median 93.8 vs. 98.6, P = 0.011). We did not find an association between pre-awake BIS value and somnolence during brain function mapping. Somnolence likely occurs in patients with a low preoperative WAB aphasia quotient score.

Acute kidney injury after pediatric liver transplantation: incidence, risk factors, and association with outcome.

PURPOSE: Data on the incidence of, risk factors for, and association with outcomes of acute kidney injury (AKI) after pediatric liver transplantation are scarce. We conducted a retrospective cohort study to determine the incidence of AKI after pediatric liver transplantation. In addition, we examined risk factors for AKI and association of AKI with outcomes. METHODS: This study included 156 children aged between 3 months and 18 years undergoing liver transplantation at Kyoto University Hospital. AKI was defined according to the Kidney Disease: Improving Global Outcomes guidelines based on serum creatinine and urine output. We used multivariable logistic regression with stepwise variable selection to identify independent risk factors for AKI. RESULTS: AKI occurred in 72 patients (46.2%); 34 (21.8%) had stage 1, 32 (20.5%) had stage 2, and 6 (3.8%) had stage 3 AKI. Factors independently associated with the development of AKI were increased preoperative total bilirubin level (adjusted odds ratio, 1.04 per 1 mg/dl; 95% confidence interval, 1.01-1.09; P = 0.026) and increased intraoperative blood loss (adjusted odds ratio, 1.03 per 10 ml/kg; 95% confidence interval, 1.00-1.06; P = 0.022). AKI was significantly associated with prolonged hospitalization (median, 61 vs. 46 days; P = 0.028). In-hospital mortality rate was 4.2% in patients with AKI and 3.6% in those without AKI (P = 1.000). CONCLUSION: The incidence of AKI after pediatric liver transplantation was 46.2%. Increased preoperative total bilirubin level and increased intraoperative blood loss were independently associated with the development of AKI. AKI was associated with prolonged hospitalization.

Relationship Between Intraoperative Hypotension and Acute Kidney Injury After Living Donor Liver Transplantation: A Retrospective Analysis.

OBJECTIVE: Acute kidney injury (AKI) is common after liver transplantation (LT) and has a significant impact on outcomes. Although several risk factors for post-LT AKI have been identified, the effect of intraoperative hemodynamic status on post-LT AKI remains unknown. Therefore, the authors aimed to investigate the relationship between hemodynamic parameters during LT and postoperative AKI. DESIGN: A retrospective observational study. SETTING: University hospital. PARTICIPANTS: Patients who underwent living donor LT (n = 231). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Severe AKI (stages 2-3 according to recent guidelines) was the primary outcome. Multivariable logistic regression analysis was used to control for confounding variables to obtain the independent relationship between intraoperative hemodynamic parameters (mean arterial pressure [MAP] and cardiac index) and severe AKI. The prevalence of severe AKI was 30.7%. Nadir MAP during the surgery was independently predictive of severe AKI (adjusted odds ratio, 2.11 [95% confidence interval, 1.32-3.47] per 10-mmHg decrease; p = 0.002). Subgroup analyses based on various patient or operative variables and extensive sensitivity analyses showed substantially similar results. Severe hypotension (MAP<40 mmHg), even for fewer than 10 minutes, was related significantly to severe AKI (adjusted odds ratio, 3.80 [95% confidence interval, 1.17-12.30]; p = 0.026). In contrast, nadir cardiac index was not related significantly to severe AKI. CONCLUSIONS: The authors found an independent relationship between degree of intraoperative hypotension and risk of severe AKI in living donor LT recipients. Severe hypotension, even for a short duration, was related significantly to severe AKI.

Low preoperative regional cerebral oxygen saturation in hemodialysis patients.

BACKGROUND: Regional cerebral oxygen saturation (rSO2) monitoring by near-infrared spectroscopy provides valuable information regarding cerebral oxygen delivery, and it has been increasingly used in cardiovascular surgery. Although it has been shown that dialysis-dependent patients [hemodialysis (HD) patients] suffer from low cerebral perfusion, limited information is available on cerebral tissue oxygenation levels in HD patients. FINDINGS: In this retrospective study, the preoperative rSO2 values in 9 HD patients undergoing coronary artery bypass graft surgery were compared with those in 40 non-HD patients. HD patients had lower preoperative rSO2 values than non-HD patients (median: 46 vs. 68%, respectively, P < 0.001). Despite adjusting for age, hemoglobin concentration, and left ventricular ejection fraction using multivariable linear regression, HD showed a strong association with low rSO2 (estimated coefficient: -20.4, P < 0.001). CONCLUSIONS: HD showed a strong association with low preoperative rSO2 values in patients undergoing coronary artery bypass graft surgery, even after adjusting for known factors that affect rSO2 values, including age, hemoglobin concentration, and cardiac systolic function. Further research is required to elucidate the mechanisms decreasing rSO2 values in HD patients.

Effect of arginine vasopressin on systemic and pulmonary arterial pressure in a patient with pulmonary hypertension secondary to pulmonary emphysema: a case report.

Although data from several studies support the use of arginine vasopressin (AVP) for the treatment of hypotension concomitant with pulmonary hypertension (PH) in the cardiac surgery setting, to our knowledge, no previous studies have reported the effect of AVP on the systemic and pulmonary circulation of patients with PH secondary to lung diseases. In this report, we present the hemodynamic responses to bolus administrations of AVP and noradrenaline in a patient with PH secondary to pulmonary emphysema. The patient showed low systemic vascular resistance hypotension during off-pump single-lung transplantation. The bolus administration of AVP (0.5 U) increased systemic arterial pressure by 35.2%, with a minimal change in pulmonary arterial pressure, resulting in a significant decrease in the pulmonary arterial pressure/systemic arterial pressure ratio. In contrast, the bolus administration of noradrenaline (10 or 20 µg) increased both systemic and pulmonary arterial pressures by 14.8 and 6.7%, respectively. In summary, the bolus administration of AVP effectively increased systemic arterial pressure with a minimal effect on pulmonary arterial pressure in a patient with PH secondary to pulmonary emphysema. This case highlights the potential utility of AVP to treat low systemic vascular resistance hypotension in patients with PH secondary to lung diseases.

Muscarinic receptors acting at pre- and post-synaptic sites differentially regulate dopamine/DARPP-32 signaling in striatonigral and striatopallidal neurons.

Muscarinic receptors, activated by acetylcholine, play critical roles in the functional regulation of medium spiny neurons in the striatum. However, the muscarinic receptor signaling pathways are not fully elucidated due to their complexity. In this study, we investigated the function of muscarinic receptors in the striatum by monitoring DARPP-32 (dopamine- and cAMP-regulated phosphoprotein of M(r) 32 kDa) phosphorylation at Thr34 (the PKA-site) using mouse striatal slices. Treatment of slices with a non-selective muscarinic receptor agonist, oxotremorine (10 µM), rapidly and transiently increased DARPP-32 phosphorylation. The increase in DARPP-32 phosphorylation was completely abolished either by a dopamine D(1) receptor antagonist (SCH23390), tetrodotoxin, genetic deletion of M5 receptors, muscarinic toxins for M1 and M4 receptors, or 6-hydroxydopamine lesioning of dopaminergic neurons, whereas it was enhanced by nicotine. Analysis in D(1)-DARPP-32-Flag/D(2)-DARPP-32-Myc transgenic mice revealed that oxotremorine increases DARPP-32 phosphorylation selectively in D(1)-type/striatonigral, but not in D(2)-type/striatopallidal, neurons. When D(1) and D(2) receptors were blocked by selective antagonists to exclude the effects of released dopamine, oxotremorine increased DARPP-32 Thr34 phosphorylation only in D(2)-type/striatopallidal neurons. This increase required activation of M1 receptors and was dependent upon adenosine A(2A) receptor activity. The results demonstrate that muscarinic receptors, especially M5 receptors, act at presynaptic dopaminergic terminals, regulate the release of dopamine in cooperation with nicotinic receptors, and activate D(1) receptor/DARPP-32 signaling in the striatonigral neurons. Muscarinic M1 receptors expressed in striatopallidal neurons interact with adenosine A(2A) receptors and activate DARPP-32 signaling.

Nicotine regulates DARPP-32 (dopamine- and cAMP-regulated phosphoprotein of 32 kDa) phosphorylation at multiple sites in neostriatal neurons.

Nicotinic acetylcholine receptors (nAChRs) regulate dopaminergic signaling in the striatum by modulating the release of neurotransmitters. We have recently reported that nicotine stimulates the release of dopamine via alpha4beta2(*) nAChRs and/or alpha7 nAChRs, leading to the regulation of DARPP-32 at Thr34, the site involved in regulation of protein phosphatase-1 (PP-1). In this study, we investigated the regulation of DARPP-32 phosphorylation at its other sites, Thr75 [cyclin-dependent kinase-5 (Cdk5) site], Ser97 (CK2 site), and Ser130 (CK1 site), that serve to modulate Thr34 phosphorylation and dephosphorylation. In neostriatal slices, nicotine (100 microM) increased phosphorylation of DARPP-32 at Ser97 and Ser130 at an early time point (30 s) and decreased phosphorylation of DARPP-32 at Thr75 at a late time point (3 min). The increase in Ser97 and Ser130 phosphorylation was mediated through the release of dopamine via activation of alpha4beta2(*) nAChRs and alpha7 nAChRs and the subsequent activation of dopamine D1 and D2 receptors. The decrease in Thr75 phosphorylation was mediated through the release of dopamine via activation of alpha4beta2(*) nAChRs and the subsequent activation of dopamine D1 receptors. These various actions of nicotine on modulatory sites of phosphorylation would be predicted to result in a synergistic increase in the state of phosphorylation of DARPP-32 at Thr34 and thus would contribute to increased dopamine D1 receptor/DARPP-32 Thr34/PP-1 signaling.

Protective actions of various local anesthetics against the membrane dysfunction produced by in vitro ischemia in rat hippocampal CA1 neurons.

Local anesthetics block not only the Na(+) but also the K(+) and Ca(2+) channels in the mammalian neurons. It is well known that lidocaine has neuroprotective actions against the ischemic insult of neurons in the central nervous system. In order to elucidate how other local anesthetics as well as lidocaine show the neuroprotective effects against in vitro ischemic insult, intracellular recordings were made from CA1 pyramidal neurons in rat hippocampal slices. Superfusion with the medium deprived of oxygen and glucose (in vitro ischemia) produced a rapid depolarization after 5 min of exposure. When the normal medium was immediately reintroduced after the rapid depolarization, the membrane depolarized further (persistent depolarization), the neurons showed no functional recovery. Pretreatment with tetracaine, bupivacaine, procaine, lidocaine, mepivacaine, or dibucaine (10 or 300 microM) prolonged the latency of the rapid depolarization, and most of the drugs partially restored the membrane potential toward the pre-exposure level after the reintroduction. Judging from the neuroprotective actions such as the prolongation and the potential recovery by these drugs, lidocaine, bupivacaine, and dibucaine are candidates for the therapeutic use against the ischemic insult. Suppression of the regenerative Na(+) conductance is somehow involved in the neuroprotective actions of local anesthetics.

Differential regulation of dopamine D1 and D2 signaling by nicotine in neostriatal neurons.

Nicotine, acting on nicotinic acetylcholine receptors (nAChRs) expressed at pre-synaptic dopaminergic terminals, has been shown to stimulate the release of dopamine in the neostriatum. However, the molecular consequences of pre-synaptic nAChR activation in post-synaptic neostriatal neurons are not clearly understood. Here, we investigated the effect of nAChR activation on dopaminergic signaling in medium spiny neurons by measuring phosphorylated DARPP-32 (dopamine- and cAMP-regulated phosphoprotein of Mr 32 kDa) at Thr34 (the PKA-site) in mouse neostriatal slices. Nicotine produced dose-dependent responses, with a low concentration (1 microm) causing a sustained decrease in DARPP-32 Thr34 phosphorylation and a high concentration (100 microm) causing a transient increase in DARPP-32 Thr34 phosphorylation. Depending on the concentration of nicotine, either dopamine D2 or D1 receptor signaling was predominantly activated. Nicotine at a low concentration (1 microm) activated dopamine D2 receptor signaling in striatopallidal/indirect pathway neurons, likely by activating alpha4beta2* nAChRs at dopaminergic terminals. Nicotine at a high concentration (100 microm) activated dopamine D1 receptor signaling in striatonigral/direct pathway neurons, likely by activating (i) alpha4beta2* nAChRs at dopaminergic terminals and (ii) alpha7 nAChRs at glutamatergic terminals, which, by stimulating the release of glutamate, activated NMDA/AMPA receptors at dopaminergic terminals. The differential effects of low and high nicotine concentrations on D2- and D1-dependent signaling pathways in striatal neurons may contribute to dose-dependent actions of this drug of abuse.

Metabotropic mGlu5 receptors regulate adenosine A2A receptor signaling.

Dopamine, by activating dopamine D1-type receptors, and adenosine, by activating adenosine A(2A) receptors, stimulate phosphorylation of DARPP-32 (dopamine- and cAMP-regulated phosphoprotein of M(r) 32,000) at Thr-34. In this study, we investigated the effect of metabotropic glutamate (mGlu) receptors on DARPP-32 phosphorylation at Thr-34 in neostriatal slices. A broad-spectrum mGlu receptor agonist, trans-ACPD, and a group I mGlu receptor agonist, DHPG, stimulated DARPP-32 phosphorylation at Thr-34. Studies with mGlu receptor antagonists revealed that the effects of trans-ACPD and DHPG were mediated through activation of mGlu5 receptors. The action of mGlu5 receptors required activation of adenosine A(2A) receptors by endogenous adenosine. Conversely, the action of adenosine A(2A) receptors required activation of mGlu5 receptors by endogenous glutamate. Coactivation of mGlu5 and adenosine A(2A) receptors by exogenous agonists synergistically increased DARPP-32 phosphorylation. mGlu5 receptors did not require activation of dopamine D1-type receptors by endogenous dopamine, nor did dopamine D1-type receptors require activation of mGlu5 receptors by endogenous glutamate. DHPG potentiated the effect of forskolin, but not that of 8-bromo-cAMP, and stimulated DARPP-32 phosphorylation in the presence of the phosphodiesterase inhibitor IBMX, suggesting that mGlu5 receptors stimulate the rate of cAMP formation coupled to adenosine A(2A) receptors. The action of mGlu5 receptors was attenuated by inhibitors of extracellular signal-regulated kinase, but not by inhibitors of phospholipase C, p38, casein kinase 1, or Cdk5. The results demonstrate that mGlu5 receptors potentiate adenosine A(2A)DARPP-32 signaling by stimulating the adenosine A(2A) receptor-mediated formation of cAMP in an extracellular signal-regulated kinase-dependent manner.

Regulation of DARPP-32 dephosphorylation at PKA- and Cdk5-sites by NMDA and AMPA receptors: distinct roles of calcineurin and protein phosphatase-2A.

Glutamatergic inputs from corticostriatal and thalamostriatal pathways have been shown to modulate dopaminergic signaling in neostriatal neurons. DARPP-32 (dopamine- and cAMP-regulated phosphoprotein of M (r) 32 kDa) is a signal transduction molecule that regulates the efficacy of dopamine signaling in neostriatal neurons. Dopamine signaling is mediated in part through phosphorylation of DARPP-32 at Thr34 by cAMP-dependent protein kinase, and antagonized by phosphorylation of DARPP-32 at Thr75 by cyclin-dependent protein kinase 5. We have now investigated the effects of the ionotropic glutamate NMDA and AMPA receptors on DARPP-32 phosphorylation in neostriatal slices. Activation of NMDA and AMPA receptors decreased the state of phosphorylation of DARPP-32 at Thr34 and Thr75. The decrease in Thr34 phosphorylation was mediated through Ca(2+) -dependent activation of the Ca(2+) -/calmodulin-dependent phosphatase, calcineurin. In contrast, the decrease in Thr75 phosphorylation was mediated through Ca(2+) -dependent activation of dephosphorylation by protein phosphatase-2A. The results provide support for a complex effect of glutamate on dopaminergic signaling through the regulation of dephosphorylation of different sites of DARPP-32 by different protein phosphatases.