A pilot in vivo proton magnetic resonance spectroscopy study of amino acid neurotransmitter response to ketamine treatment of major depressive disorder.

The N-methyl-D-aspartate receptor antagonist ketamine can improve major depressive disorder (MDD) within hours. To evaluate the putative role of glutamatergic and GABAergic systems in ketamine's antidepressant action, medial prefrontal cortical (mPFC) levels of glutamate+glutamine (Glx) and γ-aminobutyric acid (GABA) were measured before, during, and after ketamine administration using proton magnetic resonance spectroscopy. Ketamine (0.5 mg kg(-1) intravenously) was administered to 11 depressed patients with MDD. Glx and GABA mPFC responses were measured as ratios relative to unsuppressed voxel tissue water (W) successfully in 8/11 patients. Ten of 11 patients remitted (50% reduction in 24-item Hamilton Depression Rating Scale and total score ⩽10) within 230 min of commencing ketamine. mPFC Glx/W and GABA/W peaked at 37.8%±7.5% and 38.0%±9.1% above baseline in ~26 min. Mean areas under the curve for Glx/W (P=0.025) and GABA/W (P=0.005) increased and correlated (r=0.796; P=0.018). Clinical improvement correlated with 90-min norketamine concentration (df=6, r=-0.78, P=0.023), but no other measures.

Antipsychotic-induced vacuous chewing movements and extrapyramidal side effects are highly heritable in mice.

Pharmacogenomics is yet to fulfill its promise of manifestly altering clinical medicine. As one example, a predictive test for tardive dyskinesia (TD) (an adverse drug reaction consequent to antipsychotic exposure) could greatly improve the clinical treatment of schizophrenia but human studies are equivocal. A complementary approach is the mouse-then-human design in which a valid mouse model is used to identify susceptibility loci, which are subsequently tested in human samples. We used inbred mouse strains from the Mouse Phenome Project to estimate the heritability of haloperidol-induced activity and orofacial phenotypes. In all, 159 mice from 27 inbred strains were chronically treated with haloperidol (3 mg kg(-1) per day via subdermal slow-release pellets) and monitored for the development of vacuous chewing movements (VCMs; the mouse analog of TD) and other movement phenotypes derived from open-field activity and the inclined screen test. The test battery was assessed at 0, 30, 60, 90 and 120 days in relation to haloperidol exposure. As expected, haloperidol caused marked changes in VCMs, activity in the open field and extrapyramidal symptoms (EPS). Unexpectedly, factor analysis demonstrated that these measures were imprecise assessments of a latent construct rather than discrete constructs. The heritability of a composite phenotype was ∼0.9 after incorporation of the longitudinal nature of the design. Murine VCMs are a face valid animal model of antipsychotic-induced TD, and heritability estimates from this study support the feasibility of mapping of susceptibility loci for VCMs.

Magnesium and bupivacaine-induced convulsions in awake pregnant rats.

BACKGROUND: Magnesium sulfate (MgSO(4)) is widely used for the treatment and prevention of convulsions associated with preeclampsia. The aim of this study was to determine whether it alters the dose of bupivacaine required to produce convulsions in awake pregnant rats. METHOD: Twelve pregnant rats were pretreated with an intravenous infusion of either MgSO(4) or saline. Following 2 h of the pretreatment, bupivacaine was concomitantly infused in all animals until the onset of convulsions. Mean arterial pressure (MAP) and heart rate (HR) were monitored throughout. Serial arterial samples were obtained during the infusion. At the onset of convulsions, fetuses were delivered and maternal and fetal blood, as well as various tissue samples, were obtained. All samples were assayed for bupivacaine and magnesium concentrations. RESULTS: Maternal MAP and HR decreased significantly shortly after the initiation of MgSO(4), while saline did not affect these measurements. Baseline concentrations of magnesium in plasma were similar in both MgSO(4) and saline groups; magnesium increased significantly during the infusion of MgSO(4). The dose (mean+/-SD) of bupivacaine required to produce convulsions in the animals receiving MgSO(4) was significantly larger (10.2+/-1.9 mg/kg) than that in the saline group (5.9+/-1.0 mg/kg) (P<0.05). As a consequence, bupivacaine concentrations in the brain and liver at the onset of convulsions were greater in animals receiving MgSO(4) (16.0+/-8.4 and 18.2+/-4.3 microg/g wet weight, respectively) than in those given saline (12.1+/-2.2 and 9.9+/-2.0 microg/g wet weight, respectively). Fetal bupivacaine concentrations at the onset of convulsions in the MgSO(4) group were also higher than those in saline group. However, the rate of placental transfer of this drug was similar between MgSO(4) and saline animals. CONCLUSION: This study demonstrates that the clinically used concentration of magnesium sulfate increased the threshold of bupivacaine-induced convulsions in awake rats.

Upregulation of CB1 receptors and agonist-stimulated [35S]GTPgammaS binding in the prefrontal cortex of depressed suicide victims.

Endogenous and exogenous cannabinoids (CBs) acting through the CB(1) receptors have been implicated in the regulation of several behavioral and neuroendocrine functions. Modulation of endocannabinoidergic system by ethanol in mouse brain, and the association of suicide and mood disorders with alcoholism suggest possible involvement of the cannabinoidergic system in the pathophysiology of depression and suicide. Therefore, the present study was undertaken to examine the levels of CB(1) receptors and mediated signaling in the dorsolateral prefrontal cortex (DLPFC) of subjects with major depression who had died by suicides (depressed suicides, DS). [(3)H]CP-55,940 and CB(1) receptor-stimulated [(35)S]GTPgammaS binding sites were analyzed in membranes obtained from DLPFC of DS (10) and matched normal controls (10). Upregulation (24%, P<0.0001) of CB(1) receptor density (B(max)) was observed in DS (644.6+/-48.8 fmol/mg protein) compared with matched controls (493.3+/-52.7 fmol/mg protein). However, there was no significant alteration in the affinity of receptor (DS; 1.14+/-0.08 vs control; 1.12+/-0.10 nM). Higher density of CB(1) receptors in DS (38%, P<0.001) was also demonstrated by Western blot analysis. The CB(1) receptor-stimulated [(35)S]GTPgammaS binding was significantly greater (45%, P<0.001) in the DLPFC of DS compared with matched controls. The observed upregulation of CB(1) receptors with concomitant increase in the CB(1) receptor-mediated [(35)S]GTPgammaS binding suggests a role for enhanced cannabinoidergic signaling in the prefrontal cortex of DS. The cannabinoidergic system may be a novel therapeutic target in the treatment of depression and/or suicidal behavior.

Lower cortisol levels in depressed patients with comorbid post-traumatic stress disorder.

Post-traumatic stress disorder (PTSD) is often comorbid with major depressive episodes (MDEs) and both conditions carry a higher rate of suicidal behavior. Hypothalamic-pituitary-adrenal (HPA) axis and serotonin abnormalities are associated with both conditions and suicidal behavior, but their inter-relation is not known. We determined cortisol response to placebo or fenfluramine in MDE, MDE and PTSD (MDE+PTSD), and healthy volunteers (HVs) and examined the relation of cortisol responses to suicidal behavior. A total of 58 medication-free patients with MDE (13 had MDE+PTSD) and 24 HVs were studied. They received placebo on the first day and fenfluramine on the second day. Cortisol levels were drawn before challenge and for 5 h thereafter. The MDE+PTSD group had the lowest plasma cortisol, the MDE group had the highest, and HVs had intermediate levels. There were no group differences in cortisol response to fenfluramine. Suicidal behavior, sex, and childhood history of abuse were not predictors of baseline or postchallenge plasma cortisol. Cortisol levels increased with age. This study finds elevated cortisol levels in MDE and is the first report of lower cortisol levels in MDE+PTSD. The findings underscore the impact of comorbidity of PTSD with MDE and highlight the importance of considering comorbidity in psychobiology.

Proliferation of glial cells induced by lithium in the neural lobe of the rat pituitary is enhanced by dehydration.

Rats dehydrated by 6 days of water deprivation had a low level of mitotic activity in the astrocytes ('pituicytes') of the neural lobe of the pituitary. Mitotic activity in the pituicytes was greatly increased when isotonic lithium was administered in the last 3 days of water deprivation. Rehydration on the last day of the experiment produced a further increase in mitoses. Isotonic solutions of sodium, potassium or rubidium chloride did not increase mitoses. This model of cell proliferation is of interest because the mitotic activity is related to a physiological attempt to maintain homeostasis rather than a response to injury or the development of neoplasia.

Pharmacokinetics of betamethasone in twin and singleton pregnancy.

OBJECTIVE: The aims of the study were to compare the pharmacokinetics of betamethasone in singleton pregnancy with the pharmacokinetics in twin pregnancy and to assess the adrenal suppression produced by betamethasone. STUDY DESIGN: We measured serial betamethasone and cortisol levels in 30 singleton and 21 twin pregnancies after the first dose of betamethasone and calculated the pharmacokinetic parameters for betamethasone including volume of distribution, half-life, and clearance. We also measured cord and maternal blood levels of betamethasone at the birth of infants of 13 singleton and 9 twin pregnancies. RESULTS: The half-life of betamethasone in mothers with twin pregnancies was significantly shorter than that in mothers with singleton pregnancies (7.2 +/-2.4 versus 9.0 +/- 2.7 hours; P <.017). Clearance of betamethasone in the twin pregnancies appeared greater than in singleton pregnancies (8.4 +/- 6.4 versus 5.7+/- 3.1 L/h; P =.06) but did not reach statistical significance. Volume of distribution was similar in the two groups. Because the time between the last dose of betamethasone and birth varied widely (range, 2-158 hours), mothers with a longer interval after treatment tended to have a higher cord-to-maternal betamethasone ratio than did mothers with a shorter interval in both twin and singleton pregnancies. This finding indicated delayed fetal clearance, but the correlation was weak (R (2) = 0.29 for twins and 0.08 for singletons). CONCLUSION: The shorter half-life of betamethasone in twin pregnancy than in singleton pregnancy may cause the level of betamethasone to be subtherapeutic for lung maturation in twin pregnancy.

Effects of clozapine, olanzapine, risperidone, and haloperidol on hostility among patients with schizophrenia.

OBJECTIVE: This study compared the specific antiaggressive effects of clozapine with those of olanzapine, risperidone, and haloperidol. METHODS: A total of 157 inpatients with schizophrenia or schizoaffective disorder and a history of suboptimal treatment response were randomly assigned to receive clozapine, olanzapine, risperidone, or haloperidol in a double-blind 14-week trial. The trial was divided into two periods: eight weeks during which the dosage was escalated and then fixed, and six weeks during which variable dosages were used. The hostility item of the Positive and Negative Syndrome Scale (PANSS) was the principal outcome measure. Covariates included the items that reflect positive symptoms of schizophrenia (delusions, suspiciousness or feelings of persecution, grandiosity, unusual thought content, conceptual disorganization, and hallucinations) and the sedation item of the Nurses Observation Scale for Inpatient Evaluation (NOSIE). RESULTS: Patients differed in their treatment response as measured by the hostility item of the PANSS. The scores of patients taking clozapine indicated significantly greater improvement than those of patients taking haloperidol or risperidone. The effect on hostility appeared to be independent of the antipsychotic effect of clozapine on other PANSS items that reflect delusional thinking, a formal thought disorder, or hallucinations and independent of sedation as measured by the NOSIE. Neither risperidone nor olanzapine showed superiority to haloperidol. CONCLUSION: Clozapine has a relative advantage over other antipsychotics as a specific antihostility agent.

Dopamine D(2) receptor availability and amphetamine-induced dopamine release in unipolar depression.

BACKGROUND: Reduced dopaminergic transmission has been implicated in the pathophysiology of major depression. The aim of the present study was to measure striatal D(2) receptor availability and amphetamine-induced dopamine release in nonpsychotic, unmedicated, unipolar patients during an episode of major depression. METHODS: The striatal equilibrium specific to nonspecific partition coefficient (V(3)") of the D(2) receptor antagonist [(123)I]IBZM was measured with single photon emission computerized tomography before and after amphetamine administration in 9 depressed subjects and 10 matched healthy control subjects. RESULTS: No significant differences were observed in preamphetamine D(2) receptor availability between depressed patients (0.73 +/- 0.08) and control subjects (0.78 +/- 0.10, p =.23). Amphetamine-induced reduction in [(123)I]IBZM V(3)" (DeltaV(3)") was similar in depressed patients (-9.8 +/- 5.5%) and control subjects (-7.8 +/- 2.5%, p =.32). Amphetamine induced a transient improvement in symptomatology in depressed patients, but this improvement did not correlate with [(123)I]IBZM DeltaV(3)". CONCLUSIONS: This study did not replicate previously reported alterations in striatal D(2) receptor density in depressed patients and suggests that stimulant-induced dopamine release is not altered in major depression.

Haloperidol blood levels in acute mania with psychosis.

In this study, the authors examined the relationship between steady-state haloperidol blood levels and clinical response in patients with acute psychotic mania. Fifty-four inpatients with acute mania were randomly assigned to receive either haloperidol 25 mg/day or haloperidol 5 mg/day. Each subject also received a concomitant medication: lorazepam 4 mg/day, lithium, or placebo. The relationship between steady-state haloperidol blood levels and clinical improvement was studied using analysis of covariance. There was wide interindividual variation in the haloperidol blood level-dose ratio. Haloperidol blood levels (log-transformed) were found to significantly correlate with clinical response in acute mania. Low-dose haloperidol with concomitant lithium may produce an optimal response in acute mania. Haloperidol blood levels may be clinically useful in identifying patients who are nonresponsive because of low drug levels and, hence, in enhancing optimal haloperidol dosing for acute mania with psychosis.

Gender differences in autoantibodies to oxidative DNA base damage in cigarette smokers.

Oxidative DNA damage and antibodies to that damage have been implicated in lung, breast, and colorectal cancer. In this observational validation study, the relationship between anti-5-hydroxymethyl-2'-deoxyuridine (HMdU) autoantibody (aAb) and plasma micronutrients was assessed in 140 heavy smokers by ELISA. Anti-HMdU aAbs were 50% higher in women after adjustment for cigarettes/day (CPD; P = 0.002), although men smoked more and had higher plasma cotinine levels. The women reported taking more vitamin C (P < 0.005) and had higher plasma levels of alpha-carotene and beta-carotene (P < 0.001) and cryptoxanthin (P < 0.01) than men. Neither CPD nor cotinine was associated with aAb titers. Anti-HMdU aAbs were associated inversely with alpha-tocopherol (P = 0.10), retinol (P = 0.06), and age (P = 0.04) in women but not in men. In contrast to the men, women 50 years of age (P = 0.05). Given the same duration of exposure, women had higher anti-HMdU aAbs and also reached peak levels at a lower cumulative smoking exposure (30 years) compared with male smokers (40 years). Subjects smoked an average of 28.9 +/- 0.81 CPD and initiated smoking at 17.2 +/- 0.33 (SE) years of age. Therefore, smokers who reported smoking for 30 years were typically <50 years old. Women

The disposition of benzoylecgonine in maternal and fetal rats.

We tested our hypothesis that pregnancy alters the pharmacokinetic profile of benzoylecgonine, and that this metabolite accumulates in the fetus longer than in the mother. Chronically catheterized near-term pregnant and nonpregnant female Sprague-Dawley rats received an intravenous infusion of benzoylecgonine over a period of 30 min. Adult or fetal blood and tissue samples were obtained either at the end of the infusion or 6 h postinfusion for analysis of benzoylecgonine and other cocaine metabolite concentrations via gas chromatography/mass spectrometry (GC/MS). Pregnancy altered benzoylecgonine pharmacokinetics. At the end of the infusion, benzoylecgonine concentration in the fetal plasma was markedly lower than in the maternal plasma with a fetal/maternal ratio of 0.14+/-0.01. A significantly lower concentration of benzoylecgonine was found in both maternal and fetal brain at 0 h postinfusion, with tissue/plasma concentration ratios of 0.04 and 0.24, respectively, suggesting that benzoylecgonine does not readily penetrate into the brain. At 6 h, the fetal concentration of benzoylecgonine was significantly higher than in the corresponding maternal blood and tissues. Ecgonine methyl ester, a metabolite of benzoylecgonine was found in the maternal liver, but not in the fetus. In addition, the amniotic fluid concentration of benzoylecgonine became significantly higher in the 6-h postinfusion samples as compared to the end of infusion value, suggesting that repeated intrauterine exposure to cocaine may cause an accumulation of benzoylecgonine in the fetus.

Continuation pharmacotherapy in the prevention of relapse following electroconvulsive therapy: a randomized controlled trial.

CONTEXT: Electroconvulsive therapy (ECT) is highly effective for treatment of major depression, but naturalistic studies show a high rate of relapse after discontinuation of ECT. OBJECTIVE: To determine the efficacy of continuation pharmacotherapy with nortriptyline hydrochloride or combination nortriptyline and lithium carbonate in preventing post-ECT relapse. DESIGN: Randomized, double-blind, placebo-controlled trial conducted from 1993 to 1998, stratified by medication resistance or presence of psychotic depression in the index episode. SETTING: Two university-based hospitals and 1 private psychiatric hospital. PATIENTS: Of 290 patients with unipolar major depression recruited through clinical referral who completed an open ECT treatment phase, 159 patients met remitter criteria; 84 remitting patients were eligible and agreed to participate in the continuation study. INTERVENTIONS: Patients were randomly assigned to receive continuation treatment for 24 weeks with placebo (n = 29), nortriptyline (target steady-state level, 75-125 ng/mL) (n = 27), or combination nortriptyline and lithium (target steady-state level, 0.5-0.9 mEq/L) (n = 28). MAIN OUTCOME MEASURE: Relapse of major depressive episode, compared among the 3 continuation groups. RESULTS: Nortriptyline-lithium combination therapy had a marked advantage in time to relapse, superior to both placebo and nortriptyline alone. Over the 24-week trial, the relapse rate for placebo was 84% (95% confidence interval [CI], 70%-99%); for nortriptyline, 60% (95% CI, 41%-79%); and for nortriptyline-lithium, 39% (95% CI, 19%-59%). All but 1 instance of relapse with nortriptyline-lithium occurred within 5 weeks of ECT termination, while relapse continued throughout treatment with placebo or nortriptyline alone. Medication-resistant patients, female patients, and those with more severe depressive symptoms following ECT had more rapid relapse. CONCLUSIONS: Our study indicates that without active treatment, virtually all remitted patients relapse within 6 months of stopping ECT. Monotherapy with nortriptyline has limited efficacy. The combination of nortriptyline and lithium is more effective, but the relapse rate is still high, particularly during the first month of continuation therapy.

Circadian time of morning light administration and therapeutic response in winter depression.

BACKGROUND: We investigated a possible mechanism of action for the antidepressant response to light-phase advances of the circadian clock-by measuring the onset of melatonin secretion before and after light treatment in the morning or evening. METHODS: Plasma melatonin was sampled in 42 patients with seasonal affective disorder, in the evening or overnight while depressed and after 10 to 14 days of light therapy (10 000 lux for 30 minutes) when symptoms were reassessed. RESULTS: Morning light produced phase advances of the melatonin rhythm, while evening light produced delays, the magnitude depending on the interval between melatonin onset and light exposure, or circadian time (morning, 7.5 to 11 hours; evening, 1.5 to 3 hours). Delays were larger the later the evening light (r = 0.40), while advances were larger the earlier the morning light (r = 0.50). Although depression ratings were similar with light at either time of day, response to morning light increased with the size of phase advances up to 2.7 hours (r = 0.44) regardless of baseline phase position, while there was no such correlation for evening light. In an expanded sample (N = 80) with the sleep midpoint used as a reference anchor for circadian time, early morning light exposure was superior to late morning and to evening exposure. CONCLUSION: The antidepressant effect of light is potentiated by early-morning administration in circadian time, optimally about 8.5 hours after melatonin onset or 2.5 hours after the sleep midpoint.

Dose-related differences in the distribution of cocaine in the maternal-fetoplacental compartments in rats.

Our goals were to examine whether a high dose of cocaine to causing CNS toxic manifestations in the pregnant rats influences the delivery of cocaine to the fetus, and whether the non-placental compartments have a significant role in the distribution of cocaine to the fetal tissues. Either a low or high dose of cocaine was infused intravenously to near-term pregnant rats. Arterial blood pressure and heart rate were monitored. Cardiac output and uterine and placental blood flows were measured by using radiolabeled microspheres. Plasma and tissue samples were obtained from the mother, placenta, and fetus and analyzed for cocaine and its metabolites via capillary gas chromatography/mass spectrometry. A high dose of cocaine induced convulsions that were accompanied by increased arterial blood pressure and decreased uteroplacental blood flow. However, the distribution pattern of cocaine and metabolites in the mother and fetus were similar between the high and low dose groups. Considerable amounts of cocaine and its metabolites were in the placenta. Previously ignored non-placental tissues, such as the amnion and myometrium appear to be a significant source for cocaine accumulation in the fetus.

Stimulation of cannabinoid receptor agonist 2-arachidonylglycerol by chronic ethanol and its modulation by specific neuromodulators in cerebellar granule neurons.

In an earlier study, we reported that chronic ethanol (EtOH) stimulates the formation of anandamide in human SK-N-SH cells. In the present study, we investigated the effect of chronic EtOH on the formation of yet another cannabinoid receptor (CB1) agonist, 2-arachidonylglycerol (2-AG), in cerebellar granule neurons (CGNs). The formation of 2-[(3)H]AG without any stimulation was more pronounced in the older cultures than in younger cultures. Exposure of CGNs to EtOH led to a significant increase in the level of 2-[(3)H]AG (P<0.05). Incubation with the anandamidehydrolase inhibitor phenylmethylsulfonyl fluoride and EtOH did result in an additive increase in 2-[(3)H]AG, but did not with E-6-(bromomethylene)tetrahydro-3-(1-naphthelenyl)-2H-pyran-2-one. The formation of 2-[(3)H]AG was enhanced by ionomycin in both the control and EtOH-exposed CGNs, and the ionomycin-stimulated 2-[(3)H]AG synthesis was inhibited by the intracellular chelating agent 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. Further, glutamate increased the formation of 2-[(3)H]AG only in control CGNs. MK-801 inhibited the EtOH-induced 2-[(3)H]AG synthesis, suggesting the participation of intracellular Ca(2+) in EtOH-induced 2-[(3)H]AG synthesis. The dopamine receptor (D2) agonist did not modify the 2-AG synthesis in either the control or EtOH-exposed CGNs. However, the D2 receptor antagonist inhibited the EtOH-induced formation of 2-[(3)H]AG. The EtOH-induced 2-[(3)H]AG formation was inhibited by SR141716A and pertussis toxin, suggesting the CB1 receptor- and Gi/o-protein-mediated regulation of 2-AG. The observed increase in 2-AG level in CGNs is possibly a mechanism for neuronal adaptation to the continuous presence of EtOH. These findings indicate that some of the pharmacological actions of EtOH may involve alterations in the endocannabinoid signaling system.

Modulation of amphetamine-induced striatal dopamine release by ketamine in humans: implications for schizophrenia.

BACKGROUND: Recent brain imaging studies have indicated that schizophrenia is associated with increased amphetamine-induced dopamine release in the striatum. It has long been hypothesized that dysregulation of subcortical dopamine systems in schizophrenia might result from a failure of the prefrontal cortex (PFC) to adequately control subcortical dopaminergic function. The activity of midbrain dopaminergic neurons is regulated, in part, by glutamatergic projections from the PFC acting via glutamatergic N-methyl-D-aspartate (NMDA) receptors. The goal of this study was to test the hypothesis that a pharmacologically induced disruption of NMDA transmission leads to an increase in amphetamine-induced dopamine release in humans. METHODS: In eight healthy volunteers, we compared striatal amphetamine-induced (0.25 mg/kg) dopamine release under control conditions and under sustained disruption of NMDA transmission induced by infusion of the noncompetitive NMDA antagonist ketamine (0.2 mg/kg intravenous bolus followed by 0.4 mg/kg/hour intravenous infusion for 4 hours). Amphetamine-induced dopamine release was determined with single photon emission computed tomography, as the reduction in the binding potential (BP) of the radiolabeled D(2) receptor antagonist [(123)I]IBZM. RESULTS: Ketamine significantly enhanced the amphetamine-induced decrease in [(123)I]IBZM BP, from -5.5% +/- 3.5% under control conditions to -12. 8% +/- 8.8% under ketamine pretreatment (repeated-measures analysis of variance, p =.023). CONCLUSIONS: The increase in amphetamine-induced dopamine release induced by ketamine (greater than twofold) was comparable in magnitude to the exaggerated response seen in patients with schizophrenia. These data are consistent with the hypothesis that the alteration of dopamine release revealed by amphetamine challenge in schizophrenia results from a disruption of glutamatergic neuronal systems regulating dopaminergic cell activity.

Disposition of bupivacaine and its metabolites in the maternal, placental, and fetal compartments in rats.

BACKGROUND: This study was designed to determine the disposition of bupivacaine and its metabolites in the maternal, placental, and fetal compartments, using multiple sampling time points in chronically prepared awake pregnant rats. METHODS: All animals received an intravenous infusion of bupivacaine at a rate of 0.33 mg. kg-1. min-1 over a period of 15 min. The fetuses were delivered either at the end of infusion or at 2 or 4 h after dosing. Maternal and fetal blood and tissue samples were obtained for the assays of bupivacaine and its metabolites using capillary gas chromatography-mass spectrometry. RESULTS: The elimination half-life of bupivacaine was 37.7 min. The major metabolite was 3'-hydroxybupivacaine. Bupivacaine and 3'-hydroxybupivacaine were present in all samples at the end of administration. The fetal to maternal concentration ratio of bupivacaine in plasma was 0.29, and in the placenta was 0.63. The amnion contained the highest bupivacaine concentration: threefold higher in the maternal and 11-fold higher than in the fetal plasma. At 4 h after dosing, bupivacaine was no longer detectable in any maternal and fetal samples, whereas 3'-hydroxybupivacaine was still present in all tissues except the fetal plasma and heart. CONCLUSIONS: These data indicate that a considerable amount of bupivacaine is taken up by both sides of the placenta, as well as the amnion and myometrium. 3'-Hydroxybupivacaine was present in all tissues except the fetal plasma and heart samples, even after the parent compound became no longer detectable. Whether this slow elimination of 3'-hydroxybupivacaine causes any adverse effects on the fetus-newborn needs to be explored.

Increased baseline occupancy of D2 receptors by dopamine in schizophrenia.

The classical dopamine hypothesis of schizophrenia postulates a hyperactivity of dopaminergic transmission at the D(2) receptor. We measured in vivo occupancy of striatal D(2) receptors by dopamine in 18 untreated patients with schizophrenia and 18 matched controls, by comparing D(2) receptor availability before and during pharmacologically induced acute dopamine depletion. Acute depletion of intrasynaptic dopamine resulted in a larger increase in D(2) receptor availability in patients with schizophrenia (19% +/- 11%) compared with control subjects (9% +/- 7%, P = 0.003). The increased occupancy of D(2) receptors by dopamine occurred both in first-episode neuroleptic-naive patients and in previously treated chronic patients experiencing an episode of illness exacerbation. In addition, elevated synaptic dopamine was predictive of good treatment response of positive symptoms to antipsychotic drugs. This finding provides direct evidence of increased stimulation of D(2) receptors by dopamine in schizophrenia, consistent with increased phasic activity of dopaminergic neurons.