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A Coury

Publications and source records attributed to A Coury.

16 recordsLinked to original sources
PubMed1997

Dynamic changes in nucleus accumbens dopamine efflux during the Coolidge effect in male rats.

The Coolidge effect describes the reinitiation of sexual behavior in a "sexually satiated" animal in response to a novel receptive mate. Given the role of the mesolimbic dopamine (DA) system in the initiation and maintenance of motivated behavior, microdialysis was used to monitor nucleus accumbens (NAC) DA transmission during copulation, sexual satiety, and the reinitiation of sexual behavior. In agreement with earlier reports, the presentation of an estrous female behind a screen and copulation were associated with significant increases in NAC DA efflux. Return of NAC DA concentrations to baseline values coincided with a period of sexual satiety, although concentrations of the DA metabolites, dihydroxyphenylacetic acid and homovanillic acid, remained elevated. The presentation of a novel receptive female behind a screen resulted in a slight increase in NAC DA, which was augmented significantly during renewed copulation with the novel female. The present data suggest that the stimulus properties of a novel receptive female may serve to increase NAC DA transmission in a sexually satiated male rat, and this, in turn, may be related to the reinitiation of sexual behavior.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1997

Correlation of fetal frontal lobe and transcerebellar diameter measurements: the utility of a new prenatal sonographic technique.

Several authors have reported the value of the sonographic assessment of both the fetal frontal lobe and the cerebellum. Both frontal lobe shortening and cerebellar hypoplasia have been associated with fetal aneuploidy. We anecdotally observed that the distance between the calvarium and the posterior cavum septum pellucidum (frontal lobe) closely approximated the transcerebellar diameter. This study was undertaken to investigate this relationship. Between 1 July 1994 and 1 January 1996, the frontal lobe (posterior cavum septum pellucidum to the inner calvarium) and transcerebellar diameter were measured in patients referred to two prenatal ultrasound laboratories in Denver, Colorado, USA. All pregnancies had certain dates and were uncomplicated. Statistical comparison was completed using interval polynomial regression analysis. During the study period, we performed 221 detailed ultrasound examinations in which the frontal lobe and the transcerebellar diameter were measured. We found a correlation coefficient of 0.950 when comparing the two variables (p < 0.0001). Some conditions (Down's syndrome, lethal trisomies and pathological microcephaly) have differential effects on the frontal lobe and the transcerebellar diameter. Our preliminary judgement is that this new technique may prove to be a useful tool in assessing the relative effect of these conditions on structural neuroanatomy.

Adult↗
PubMed1996

Does monoamine oxidase inhibition by pargyline increase extracellular dopamine concentrations in the striatum?

The present study examined the possibility that pargyline-induced stimulation of dopamine neurotransmission in the striatum measured by intracerebral microdialysis may be related to alterations in the function of dopamine nerve terminals in close proximity to the implanted microdialysis probe. Changes in extracellular concentrations of dopamine were determined bilaterally in the striata of awake rats by microdialysis with concentric dialysis probes and by chronoamperometry with electrochemical (stearate-graphite paste) recording electrodes, after inhibition of monoamine oxidase by pargyline and subsequent blockade of dopamine uptake by nomifensine. Pargyline (75 mg/kg, i.p.) increased dopamine overflow by 14 nM from a mean basal value of 9 nM as determined from dialysis probes implanted in the right striatum. Pargyline failed, however, to increase basal concentrations of dopamine measured by electrochemical electrodes implanted alone in the contralateral striatum. In contrast, 3 h following pargyline, administration of nomifensine (10 mg/kg, i.p.) increased extracellular dopamine concentrations to a similar magnitude above baseline levels in both right and left striata (135 and 127 nM, respectively). In a separate group of rats, electrochemical electrodes were implanted in the left striatum with the tip of the electrode placed directly adjacent to the lumen of a dialysis probe. In contrast to pargyline's inability to increase basal extracellular dopamine measured at individually implanted electrochemical electrodes in the striatum, pargyline administration increased dopamine concentrations measured at electrodes implanted adjacent to non-perfused dialysis probes to an extent similar to that observed by dialysis alone (25 vs 14 nM, respectively). The present study indicates that pargyline increases dopamine concentrations in the region of striatal tissue immediately adjacent to the shaft of a permanently implanted dialysis probe, but not at the tip of an electrochemical electrode. The former effect appears to reflect an interaction between monoamine oxidase inhibition and the effects elicited by the physical presence of the dialysis probe in tissue.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1993

Electrical stimulation of reward sites in the ventral tegmental area increases dopamine transmission in the nucleus accumbens of the rat.

In vivo microdialysis with HPLC-ED was used to measure dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the nucleus accumbens of the rat, prior, during, and after 15-min periods of electrical brain stimulation at sites in the ventral tegmental area (VTA) that supported intracranial self-stimulation (ICSS). In the first experiment, both ICSS and yoked stimulation of the VTA evoked significant increases in extracellular concentrations of DA, its metabolites, and 5-HIAA. Comparable results from ICSS and yoked groups were interpreted as evidence that the rewarding properties of VTA stimulation were a causal factor in the elevated DA transmission in the nucleus accumbens, rather than intense operant behavior. Further evidence for this hypothesis came from a second set of data in which changes in extracellular DA levels during the measurement of rate/intensity functions for ICSS were positively correlated. 5-HIAA concentrations also increased during ICSS but these changes were not correlated with either ICSS rate or current intensity, suggesting that changes in serotonin metabolism were unlikely to subserve brain stimulation reward in the VTA. These results add to the growing body of evidence linking changes in extracellular DA in the mesolimbic DA system with both brain stimulation reward and the conditioned and unconditioned rewarding effects of biologically relevant stimuli.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Extracellular dopamine in the rat striatum during ischemia and reperfusion as measured by in vivo electrochemistry and in vivo microdialysis.

The effects of transient global forebrain ischemia and reperfusion on striatal extracellular dopamine levels were analyzed using both in vivo electrochemistry and in vivo microdialysis in urethane-anesthetized rats. Electrochemical records showed that extracellular dopamine levels increased once during the period of ischemia, and a second time during reperfusion. This biphasic pattern was not detected by microdialysis, probably because of the relatively low time resolution of this technique. Microdialysis provided evidence that the voltammetric signal was a measure of dopamine, and also allowed measurement of the metabolites dihydroxyphenylacetic acid and homovanillic acid, both of which decreased during ischemia. The biphasic dopamine pattern seen in rats is similar to that reported previously in gerbils, suggesting that it is a phenomenon common to transient ischemia and reperfusion across different species and models of transient global ischemia. This phenomenon may have important implications for therapeutic intervention in cerebral ischemia.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Uterine-umbilical artery Doppler velocimetry in pregnant women with systemic lupus erythematosus.

We evaluated continuous wave uterine-umbilical artery Doppler velocimetry for predicting pregnancy outcome in women with systemic lupus erythematosus (SLE). Lupus anticoagulant (LAC) and anticardiolipin (ACL) antibody status also were correlated with Doppler results and outcome. Three Doppler vascular patterns were identified in 27 pregnancies of 26 women with SLE. Patients with normal flow velocity in both vessels had normal outcomes (n = 18). Reduced flow velocity of the umbilical artery only was present in five women, whose newborn infants were of lesser gestational age and birthweight, two being small for gestational age. In four pregnancies reduced flow velocity was noted in both vessels. These cases had the poorest outcome, with three perinatal losses and all fetuses being small for gestational age. Doppler velocimetry showed 100% sensitivity and negative predictive value in the detection of the small for gestational age fetus and abnormal antepartum fetal heart rate tracing. Fourteen of 18 women with normal Doppler studies did not have preeclampsia or SLE flare-ups, whereas all nine women with abnormal Doppler studies had such complications. In all 27 pregnancies the women were screened for LAC, and 21 women also were tested for the ACL antibody. Poor correlation was found between antiphospholipid antibody status and Doppler results in three of the six pregnancies with positive antibody testing the patients had normal Doppler studies and outcomes. Thus, Doppler velocimetry may help determine when these substances will affect the outcome adversely. In this study the umbilical-placental vascular system was affected more often. Uterine-umbilical arterial Doppler velocimetry uniquely identified the fetus at risk for adverse perinatal outcome in pregnancies complicated by SLE. Thus, it is a potentially valuable tool in clarifying the pathophysiology and in the management of SLE in pregnancy.

Adult↗
PubMed1990

Effects of neurotensin on dopamine release and metabolism in the rat striatum and nucleus accumbens: cross-validation using in vivo voltammetry and microdialysis.

The effects of the neuropeptide neurotensin on dopamine release and metabolism in the posteromedial nucleus accumbens and anterior dorsomedial striatum of the anesthetized rat were investigated using in vivo chronoamperometry and intracerebral microdialysis techniques. A dose-dependent augmentation of dopamine efflux as evidenced by increases in the chronoamperometric signal was observed in the nucleus accumbens following intracerebroventricular injections of neurotensin. However, neurotensin failed to alter extracellular concentrations of dopamine in the striatum. The selective effects of neurotensin on mesolimbic dopamine neurons were confirmed using in vivo microdialysis. These results demonstrate that neurotensin can selectively enhance the release and metabolism of dopamine in neurons projecting from the ventral tegmental area to the nucleus accumbens.

Animals↗
PubMed1990

Doppler umbilical artery velocimetry in fetuses with polyhydramnios.

Polyhydramnios is a condition of multiple etiologies, many of a benign nature, but some of which are incompatible with life. To evaluate Doppler velocimetry results as a prognostic parameter in these fetuses, we reviewed all of our cases of polyhydramnios that underwent Doppler analysis in the third trimester. Fifty-four fetuses were studied. Eleven (20.4%) had abnormal waveforms and 43 (79.6%) had normal waveforms. An abnormal waveform was associated with a significantly higher incidence of congenital anomalies, perinatal mortality and intrauterine growth retardation. Six of the 11 fetuses had abnormal karyotypes. Macrosomia was present in 37.2% of fetuses with normal waveforms and in no fetus with an abnormal waveform. Doppler analysis may aid in the counseling and management of patients with polyhydramnios. In cases with an abnormal ratio, the physician and patients should be prepared for a poor outcome and third trimester genetic analysis should be strongly considered.

Chi-Square Distribution↗
PubMed1989

Pregnancy surveillance with Doppler velocimetry of uterine and umbilical arteries.

Previous studies with Doppler velocimetry have demonstrated a strong correlation between abnormal waveforms and fetal-maternal disease. This study was designed to evaluate the potential role of Doppler velocimetry as a screening test in routine prenatal care. Two hundred fifty-five pregnant women had routine monthly Doppler (systolic/end-diastolic ratio) studies on the uterine and umbilical arteries starting in the twentieth week of gestation. When a cutoff value of 3 was used at 30 weeks for the umbilical arteries, there were 35 (13%) positive tests. In 20 of these values fell to less than 3 in the ensuing weeks and were considered false positive. The remaining 15 babies demonstrated positive clinical pathologic correlates. When a value of 2.6 was used at 26 weeks for uterine arteries, there were nine positive results, seven of which had clinical pathologic correlates. This study suggested an overall positivity rate of 7%; therefore it provides encouragement for a larger venture in which screening and impact on decision making are evaluated.

Adult↗
PubMed1987

Autooxidative degradation of implanted polyether polyurethane devices.

While certain polyether polyurethanes have been shown to be biostable, undesirable interactions between polymer, the body environment and device can occur. For example, the corrosion products of metallic parts can cause relatively rapid autooxidation of polyether soft segments. This phenomenon was first demonstrated in our laboratories by immersing polyurethane test specimens in metal ion solutions of different oxidation potentials. Subsequently, the mechanism was reasonably duplicated by immersing Pellethane 2363-80A insulated cardiac pacing leads in 3%, 37 degrees C hydrogen peroxide. In vivo studies after 1 year show that corrosion products from pure Co and Fe produce the most rapid degradation of the polyurethane.

Animals↗