Evaluation of a two-site immunoradiometric assay for measuring noncomplexed (free) prostate-specific antigen

Serum prostate-specific antigen (PSA) in men is present as two different molecular forms separable by gel-filtration chromatography (GFC). We have evaluated a two-site IRMA that measures only the noncomplexed (free) form of PSA (F-PSA). Verification that the F-PSA assay measures solely F-PSA was obtained by assaying GFC-fractionated serum samples with both the F-PSA IRMA and a commercial PSA assay that measures total PSA (T-PSA: F-PSA plus alpha 1-antichymotrypsin-complexed PSA). The F-PSA assay detected only the 30-kDa peak corresponding to the free form of PSA, whereas the T-PSA assay detected two peaks: complexed PSA at approximately 90 kDa and F-PSA at approximately 30 kDa. The F-PSA assay had an analytical detection limit of 0.03 microgram/L and a measuring range up to 50 micrograms/L. The intraassay CV was 1.7-10% in the concentration range of 0.2-30 micrograms/L. The interassay CV was 3.4-12.5% in the same concentration range. Dilution and recovery studies showed no significant deviation from linearity across the assay range. The assay was insensitive to interference from hemoglobin, bilirubin, and total lipids up to concentrations of 5, 0.2, and 10 g/L, respectively. No significant loss of immunological activity (analyte stability) was seen day-to-day ( < or = 5) or after repeated freeze/thaw ( < or = 5) cycles. We conclude that the F-PSA IRMA is an accurate, precise, and reliable tool for measuring F-PSA in human serum.

Evaluation of a two-site immunoradiometric assay for measuring noncomplexed (free) prostate-specific antigen

Serum prostate-specific antigen (PSA) in men is present as two different molecular forms separable by gel-filtration chromatography (GFC). We have evaluated a two-site IRMA that measures only the noncomplexed (free) form of PSA (F-PSA). Verification that the F-PSA assay measures solely F-PSA was obtained by assaying GFC-fractionated serum samples with both the F-PSA IRMA and a commercial PSA assay that measures total PSA (T-PSA: F-PSA plus alpha 1-antichymotrypsin-complexed PSA). The F-PSA assay detected only the 30-kDa peak corresponding to the free form of PSA, whereas the T-PSA assay detected two peaks: complexed PSA at approximately 90 kDa and F-PSA at approximately 30 kDa. The F-PSA assay had an analytical detection limit of 0.03 microgram/L and a measuring range up to 50 micrograms/L. The intraassay CV was 1.7-10% in the concentration range of 0.2-30 micrograms/L. The interassay CV was 3.4-12.5% in the same concentration range. Dilution and recovery studies showed no significant deviation from linearity across the assay range. The assay was insensitive to interference from hemoglobin, bilirubin, and total lipids up to concentrations of 5, 0.2, and 10 g/L, respectively. No significant loss of immunological activity (analyte stability) was seen day-to-day ( &lt; or = 5) or after repeated freeze/thaw ( &lt; or = 5) cycles. We conclude that the F-PSA IRMA is an accurate, precise, and reliable tool for measuring F-PSA in human serum.

The role of 5-HT1A autoreceptors and alpha 1-adrenoceptors in the inhibition of 5-HT release--II NAN-190 and SDZ 216-525

Novel 5-HT1A receptor antagonists, WAY 100135 and WAY 100635, were used to test the involvement of 5-HT1A receptors in the decrease of hippocampal extracellular 5-HT induced by the 5-HT1A/alpha 1 ligands, NAN-190 and SDZ 216-525. Using microdialysis in anaesthetized rats, it was found that WAY 100135 (3 mg/kg s.c.) and WAY 100635 (0.3 mg/kg s.c.) antagonised the decrease of 5-HT induced by the 5-HT1A receptor agonist 8-OH-DPAT (0.025 mg/kg s.c.) but did not alter 5-HT when administered alone. Both NAN-190 (0.03 and 0.3 mg/kg s.c.) and SDZ 216-525 (1 mg/kg s.c.) decreased 5-HT. The effect of 0.03 mg/kg s.c. NAN-190 was antagonised by WAY 100135 (3 mg/kg s.c.) and WAY 100635 (0.3 mg/kg s.c.). The effect of SDZ 216-525 (1 mg/kg s.c.) was also blocked by WAY 100635 (0.3 mg/kg s.c.). However, the 5-HT response to a high dose of NAN-190 (0.3 mg/kg s.c.) was not antagonised by WAY 100635 (0.3 or 3 mg/kg s.c.). Our experiments using WAY 100635 and WAY 100135 provide clear evidence that NAN-190 and SDZ 216-525 act as agonists at the 5-HT1A autoreceptor, supporting our earlier studies using the non-selective 5-HT1A antagonist, pindolol. However, our data reveal that, at least in the case of NAN-190, non-5-HT1A receptor mechanisms mediate the decrease of 5-HT induced by higher doses. A lack of specificity of NAN-190 (and possibly SDZ 216-525) at high doses may explain the failure of previous studies to detect a 5-HT1A receptor agonist action.

The effect of prolonged pneumoperitoneum on renal function in an animal model

BACKGROUND

Prolonged, increased intra-abdominal pressure (IAP) during laparoscopic surgery has been associated with oliguria and anuria.

STUDY DESIGN

The objective of this study was to evaluate the effects of various levels of IAP on renal function. Ten groups of three adult female farm pigs were given a general anesthetic, followed by establishment of an IAP of 0, 5, 10, 15, or 20 mm Hg with CO2, 20 mm Hg with argon gas, abdominal wall lift device, renal vein occlusion (RVO), 15 mm Hg with CO2 plus dopamine administration at 2 microgram/kg/minute, or 20 mm Hg retroperitoneal CO2 insufflation. The following studies were recorded: baseline central venous pressure (CVP), pulmonary wedge pressure (PWP), cardiac output (CO), renal vein flow (RVF), renal artery pressure (RAP), selective urine output (UO), urinary osmolarity, and creatinine clearance; the parameters were repeated every 30 minutes for the four hours of the IAP study and two hours after release of the IAP.

RESULTS

The results were analyzed within two main IAP groups: less than 15 mm Hg and greater than or equal to 15 mm Hg. There was no clinically significant variation in the CVP, PWP, and RAP. The CO decreased slightly and this was more significant in the greater than or equal to 15 mm Hg group. The RVF and UO decreased concomitantly and significantly in the greater than or equal to 15 mm Hg group. Even after two hours of desufflation, the RVF did not return to baseline, although the UO improved. Creatinine clearance decreased significantly in the greater than or equal to 15 mm Hg group. The RVO group exhibited similar changes in the study parameters as those seen in the greater than or equal to 15 mm Hg group, although the RVF did not improve on release of the renal vein in the RVO group. Changes were the same with an argon or CO2 IAP of 20 mm Hg. The abdominal wall lift device had an associated decrease in RVF at 15 KG force but no alteration in UO. Retroperitoneal insufflation resulted in the same decrease in RVF and UO as seen with the same IAP. Dopamine did not afford a protective effect on UO during an IAP of 15 mm Hg.

CONCLUSIONS

The decreased UO during prolonged IAP greater than or equal to 15 mm Hg in the animal model is associated with a corresponding decrease in RVF, but does not appear to be associated with any permanent renal derangement nor any transient histologic changes.

A 5-hydroxytryptamine lesion markedly reduces the incidence of burst-firing dorsal raphe neurones in the rat

Recently, we described neurones in the rat dorsal raphe nucleus (DRN) with electrophysiological characteristics typical of 5-hydroxytryptamine (5-HT) neurones except that the neurones fired brief bursts. Here we report the effect of 5-HT lesions on the incidence of these burst-firing neurones. In vivo extracellular recordings revealed that in rats pretreated with the selective 5-HT neurotoxin, 5,7-dihydroxytryptamine, the occurrence of typical 5-HT neurones was significantly decreased (80%) compared to controls. In these 5-HT lesioned animals, the number of the burst-firing DRN neurones was also significantly reduced (91%). Neurones previously characterised as not containing 5-HT, were not altered by the lesion. These data are further evidence to support our hypothesis that burst-firing neurones in the DRN contain 5-HT.

Evidence for a repetitive (burst) firing pattern in a sub-population of 5-hydroxytryptamine neurons in the dorsal and median raphe nuclei of the rat

Previous electrophysiological studies have shown that spontaneously active mesencephalic 5-hydroxytryptaminergic neurons of anaesthetized or freely moving animals fire solitary spikes in a slow, regular pattern. In the present study, using extracellular single unit recordings from dorsal and median raphe neurons of the anaesthetized rat, an additional electrophysiological property of a sub-population of presumed 5-hydroxytryptaminergic neurons was observed. These neurons, during their otherwise regular firing pattern, repeatedly fired two (or occasionally three or even four) spikes where only one was expected. Spikes in this burst-like repetitive firing mode (spikes in doublets or triplets) occurred in a short time interval (range: 2.4-11.5 ms), and with a diminishing spike amplitude. Cross-correlation analysis of spikes in doublets revealed a very high interdependency between them. The proportion of spikes in doublets to solitary spikes showed great variation between different neurons, ranging from 5 to 95% of the total spikes displayed. However, for each neuron the proportion of spikes in doublets to solitary spikes, and the time interval between the spikes in doublets, remained constant during control recordings. All these features are characteristic of single neurons firing in a repetitive firing pattern rather than simultaneous recordings of two separate 5-hydroxytryptaminergic neurons. Repetitive firing neurons were recorded with a similar frequency in both chloral hydrate and Saffan anaesthetized rats, and were detected using both glass and metal electrodes. Furthermore, neurons with a repetitive firing pattern were inhibited by intravenous administration of a selective 5-hydroxytryptamine1A receptor agonist and a 5-hydroxytryptamine reuptake inhibitor, thus displaying responses typical of 5-hydroxytryptaminergic neurons. Repetitive firing neurons occurred in both the dorsal and median raphe nuclei, although they were much more frequent in the dorsal raphe nucleus (91 of 332 neurons). The occurrence of repetitive firing neurons in the midbrain raphe nuclei is a newly described phenomenon which may indicate unique properties of a sub-population of 5-hydroxytryptaminergic neurons. In functional terms, it could modify both axonal and dendritic 5-hydroxytryptamine release, and provide an additional option for neuronal information signalling.

Release of cerebral 5-hydroxytryptamine evoked by electrical stimulation of the dorsal and median raphe nuclei: effect of a neurotoxic amphetamine

Recent neuroanatomical data suggest that the axons and terminals of serotonergic neurons of the dorsal and median raphe nuclei are morphologically and pharmacologically distinct. Here we attempted to establish a functional in vivo model of serotonergic terminals derived from these nuclei, and then carry out a preliminary comparison of their physiological and pharmacological properties. Brain microdialysis was used to monitor extracellular 5-hydroxytryptamine in the hippocampus (dorsal and median raphe innervation) and frontal cortex (preferential dorsal raphe innervation) of the anaesthetized rat. To distinguish 5-hydroxytryptamine released by terminals of dorsal raphe neurons from that released by median raphe neurons, one or other of these nuclei was stimulated electrically. Electrical stimulation of either the dorsal or median raphe nucleus evoked a release of 5-hydroxytryptamine in the hippocampus. Whereas stimulation of the dorsal raphe nucleus also released 5-hydroxytryptamine in the frontal cortex, stimulation of the median raphe nucleus did not. No release of 5-hydroxytryptamine was evoked when electrodes were located in regions bordering the dorsal raphe nucleus and the median raphe nucleus. The amounts of hippocampal 5-HT released by stimulation of the dorsal or median raphe nucleus were found to be similarly altered by a 5-hydroxytryptamine uptake inhibitor (citalopram) and calcium-free perfusion medium, and also by increasing stimulation frequency (2-10 Hz). Furthermore, the amount of 5-hydroxytryptamine released by electrical stimulation of either the dorsal raphe nucleus or median raphe nucleus was markedly reduced in rats pretreated with p-chloroamphetamine. In summary, our data show that electrical stimulation of the dorsal or median raphe nucleus releases 5-hydroxytryptamine in a regionally specific manner (hippocampus versus frontal cortex), suggesting that serotonergic nerve terminals of the dorsal and median raphe pathways were being activated selectively. Using this model, we found no differences in the responsiveness of dorsal and median raphe pathways to a specific set of physiological and pharmacological manipulations. In particular, our data suggest that the neurotoxic action of p-chloroamphetamine may not be targeted solely on serotonergic axons and terminals of the dorsal raphe nucleus but includes those of the median raphe nucleus.

Measurement of the proportion of free to total prostate-specific antigen improves diagnostic performance of prostate-specific antigen in the diagnostic gray zone of total prostate-specific antigen

OBJECTIVES

This study examined the clinical significance of non-complexed (free) prostate-specific antigen (PSA) in the differential diagnosis of prostate cancer with an emphasis on patients with total PSA values between 4.0 and 10.0 ng/mL (the diagnostic gray zone).

METHODS

Serum samples were obtained from three specimen banks. Patient samples consisted of 55 untreated histologically confirmed primary cancer, 62 men with untreated benign prostatic disease histologically confirmed by 6 negative sextant biopsies, and 64 asymptomatic healthy male controls with normal digital rectal examinations and PSA values less than 4.0 ng/mL. All patients were between the ages of 50 and 75 years. Total PSA levels were determined using the PA immunoassay performed on the TOSOH AIA-1200 automated immunoassay instrument. Free PSA levels were determined using a monoclonal-polyclonal antibody sandwich radioimmunoassay. The proportion of free to total PSA was calculated by dividing the patient's free PSA value by the total PSA value.

RESULTS

When all subjects were included, both total PSA and the proportion of free to total PSA significantly differentiated between patients with prostate cancer and patients with benign histologic conditions (P < 0.0001). However, in men with total PSA values between 4.0 and 10.0 ng/mL, the proportion of free to total PSA significantly differentiated between patients with benign and malignant histologic conditions (P = 0.0004), whereas the total PSA did not (P = 0.13). Among this subgroup of patients, the analysis of sensitivity and specificity showed that the proportion of free to total PSA had a clearly higher specificity compared with that of the total PSA at the same level of sensitivity.

CONCLUSIONS

Measurement of the free PSA level in a patient's serum and calculation of the proportion of free to total PSA enhances the ability to distinguish benign histologic conditions from cancer while retaining high sensitivity for detecting cancer in men who present with total PSA levels between 4.0 and 10.0 ng/mL. A large-scale population-based study is currently in progress to confirm this preliminary finding.

Electroconvulsive shock increases dopamine D1 and D2 receptor mRNA in the nucleus accumbens of the rat

The present study examined the effects of acute and repeated administration of electroconvulsive shock (ECS) on levels of D1 and D2 receptor mRNAs in the nucleus accumbens and striatum (caudate-putamen) of the rat. Quantitative in situ hybridisation with 35S-labelled oligonucleotide probes specific for D1 and D2 receptor mRNAs was utilised. Compared to controls, rats receiving a single ECS showed higher levels of both D1 and D2 receptor mRNAs in the nucleus accumbens 4 h, but not 24 h, after treatment. Similarly, rats receiving ECS repeatedly (five ECS in 10 days) also exhibited higher levels of D1 and D2 receptor mRNAs in the nucleus accumbens 4 h, but not 24 h, after the last treatment. The effects of single and repeated ECS treatment on dopamine receptor mRNA levels were localised to the caudal region of the nucleus accumbens. No statistically significant changes in mRNA levels were detected in the striatum of rats treated with either acute or repeated ECS. We discuss the possibility that increased expression of D1 and D2 receptors in the nucleus accumbens may be involved in the dopamine-enhancing properties of ECS detected in behavioural studies.

Interaction between a selective 5-HT1A receptor antagonist and an SSRI in vivo: effects on 5-HT cell firing and extracellular 5-HT

1. The acute inhibitory effect of selective 5-hydroxytryptamine (serotonin) reuptake inhibitors (SSRIs) on 5-HT neuronal activity may offset their ability to increase synaptic 5-HT in the forebrain. 2. Here, we determined the effects of the SSRI, paroxetine, and a novel selective 5-HT1A receptor antagonist, WAY 100635, on 5-HT cell firing in the dorsal raphé nucleus (DRN), and on extracellular 5-HT in both the DRN and the frontal cortex (FCx). Extracellular electrophysiological recording and brain microdialysis were used in parallel experiments, in anaesthetized rats. 3. Paroxetine dose-dependently inhibited the firing of 5-HT neurones in the DRN, with a maximally effective dose of approximately 0.8 mg kg-1, i.v. WAY 100635 (0.1 mg kg-1, i.v.) both reversed the inhibitory effect of paroxetine and, when used as a pretreatment, caused a pronounced shift to the right of the paroxetine dose-response curve. 4. Paroxetine (0.8 mg kg-1, i.v.), doubled extracellular 5-HT in the DRN, but did not alter extracellular 5-HT in the FCx. A higher dose of paroxetine (2.4 mg kg-1, i.v.) did increase extracellular 5-HT in the FCx, but to a lesser extent than in the DRN. Whereas 0.8 mg kg-1, i.v. paroxetine alone had no effect on extracellular 5-HT in the FCx, in rats pretreated with WAY 100635 (0.1 mg kg-1), paroxetine (0.8 mg kg-1, i.v.) markedly increased extracellular 5-HT in the FCx. 5. In conclusion, pretreatment with the selective 5-HT1A receptor antagonist, WAY 100635, blocked the inhibitory effect of paroxetine on 5-HT neuronal activity in the DRN and, at the same time, markedly enhanced the effect of paroxetine on extracellular 5-HT in the FCx. These results may be relevant to recent clinical observations that 5-HT1A receptor antagonists in combination with SSRIs have a rapid onset of antidepressant effect.

Studies on the role of 5-HT1A autoreceptors and alpha 1-adrenoceptors in the inhibition of 5-HT release--I. BMY7378 and prazosin

The present study utilized in vivo microdialysis to investigate the importance of 5-HT1A autoreceptors and alpha 1-adrenoceptors in the decreased 5-HT release obtained following administration of the mixed 5-HT1A autoreceptor partial agonist/alpha 1-adrenoceptor antagonist BMY7378, the selective 5-HT1A receptor agonist 8-OH-DPAT and the alpha 1-adrenoceptor antagonist prazosin. BMY7378 (0.25 mg/kg, s.c.), 8-OH-DPAT (0.025 mg/kg, s.c.) and prazosin (0.1-1.0 mg/kg, s.c.) all suppressed ventral hippocampal 5-HT efflux. The BMY7378- and 8-OH-DPAT-induced inhibition of 5-HT release were reversed by a 40 min pre-treatment with either (+/-)pindolol (8 mg/kg, s.c.) or WAY-100635 (0.3 mg/kg, s.c.), to block 5-HT1A autoreceptors. Neitehr of these antagonists altered the prazosin-induced (0.3 mg/kg, s.c.) 5-HT disease.

THE RESULTS

(i) confirm that both an alpha 1-adrenoceptor antagonist (prazosin) and 5-HT1A autoreceptor stimulants (BMY7378 and 8-OH-DPAT) may reduce cerebral 5-HT release; (ii) support that the BMY7378-induced decrease in 5-HT release results from 5-HT1A autoreceptor agonism, rather than alpha 1-adrenoceptor blockade; and (iii) argue against "physiological" antagonism (i.e. via blockade of beta-adrenoceptors, 5-HT1B receptors or some other mechanism) as an explanation for the reversal by pindolol of 5-HT1A autoreceptor agonist-induced suppression of 5-HT release. These data support the usefulness of pindolol, as well as the more specific compound WAY-100635, to block 5-HT1A autoreceptors.

Inhibition of median and dorsal raphe neurones following administration of the selective serotonin reuptake inhibitor paroxetine

Acute systemic injection of selective serotonin reuptake inhibitors (SSRIs) decreases 5-HT neuronal firing in the dorsal raphe nucleus (DRN). Recent data, however, question whether these drugs also inhibit the firing of 5-HT neurones in the median raphe nucleus (MRN). Using in vivo extracellular electrophysiological recording techniques in the chloral hydrate anaesthetised rat, we have tested the effect of acute administration of the SSRI, paroxetine, on 5-HT neuronal activity in the MRN and DRN. Presumed 5-HT neurones in the MRN displayed the same electrophysiological characteristics as those in the DRN, the only detectable difference being that MRN neurones showed a significantly (p < 0.001) slower mean (+/- SEM(n)) spontaneous firing rate (MRN, 5.6 +/- 0.9 (14) spikes/10 s; DRN, 13.5 +/- 1.6 (24) spikes/10 s). Paroxetine caused a dose-related (0.1-0.8 mg/kg i.v.) inhibition of all MRN neurons tested (n = 8), producing a complete cessation of cell-firing at the highest doses. DRN neurones (n = 9) responded in a similar fashion. Furthermore, paroxetine inhibited MRN and DRN neurones with almost identical potency (MRN ED50 259 +/- 57 micrograms/kg i.v.: DRN ED50 243 +/- 49 micrograms/kg i.v.). In the majority of cells tested, the effect of paroxetine was reversed by the 5-HT1A receptor antagonists spiperone or (+)WAY100135, implicating the involvement of the 5-HT1A autoreceptor. The selective 5-HT1A receptor agonist 8-OH-DPAT also inhibited the firing of MRN (n = 5) and DRN (n = 12) neurones and with equal potency (MRN ED50, 1.32 +/- 0.40 microgram/kg i.v.: DRN ED50, 1.19 +/- 0.23 microgram/kg i.v.).(ABSTRACT TRUNCATED AT 250 WORDS)

Repeated ECS differentially affects rat brain 5-HT1A and 5-HT2A receptor expression

We investigated the effect of electroconvulsive shock (ECS), administered five times over 10 days, on 5-HT1A and 5-HT2A receptor mRNA and binding site densities in the rat brain using in situ hybridization histochemistry and quantitative autoradiography. ECS treatment increased 5-HT1A receptor mRNA abundance and binding site densities in the dentate gyrus, but decreased these parameters in the CA3c layer of the hippocampus. No changes in 5-HT1A receptor mRNA and binding sites occurred in other hippocampal subfields, neocortex or raphe nuclei. Repeated ECS was also found to increase 5-HT2A receptor binding site densities in the neocortex and this was accompanied by a non-significant increase in cortical 5-HT2A receptor mRNA abundance. Our study demonstrates that in the rat, repeated ECS produces anatomically and molecularly discrete effects on 5-HT1A and 5-HT2A receptor gene expression. These changes may be relevant to the therapeutic effect of repeated ECS in depression.

Multiple laboratory comparison of the doubly labeled water technique

A double-blind study was conducted to determine between-laboratory variability in the doubly labeled water method for measurement of total energy expenditure in humans, and to compare the accuracy and precision of three widely-used procedures for calculating rates of carbon dioxide production from the original isotope data. Eighteen laboratories from five countries participated in the study. All laboratories were provided with five water standards containing varying amounts of 2H and 18O, and in addition 11 laboratories were provided with urine and dose specimens from one (six laboratories) or two (five laboratories) healthy elderly subjects of normal height and weight undergoing a calorimetric validation of the doubly labeled water method. The data from the five water standards were analyzed to predict between-laboratory variability in the doubly labeled water technique in all laboratories. In addition, data from the subjects were analyzed using the "slope-intercept", "2-point" and "modified" methods of calculation. The results confirm that the doubly labeled water method can be an accurate technique for the measurement of energy expenditure in adult human subjects in some laboratories. However, there was substantial between-laboratory variability in the results and some laboratories returned physiologically impossible results. There was no significant effect of calculation procedure on the accuracy of the technique in this limited comparison, although the slope-intercept procedure appeared to be more susceptible to analytical error than the other procedures. The isotope standards analyzed by participants in this study will be made available to other investigators on request.

Behavioural and neuroendocrine responses to D-fenfluramine in rats treated with neurotoxic amphetamines

The amphetamine derivatives p-chloroamphetamine (pCA), 3,4-methylenedioxymethamphetamine (MDMA, 'Ecstasy') and D-fenfluramine can, if given repeatedly in high doses to rats, produce a degeneration of serotonergic nerve terminals which we have previously shown to result in a reduction in D-fenfluramine-evoked release of 5-HT in vivo. It is therefore possible that fenfluramine-evoked responses may have value as a probe of 5-HT neurodegeneration in man. The present study examined the effect of pre-treatment with these three agents (pCA 12 mg/kg×2; MDMA 20 mg/kg×8; D-fenfluramine 12.5 mg/kg×8, 14 days prior to testing) on behavioural (5-HT syndrome) and neuroendocrine [prolactin and adrenocorticotrophin (ACTH)] responses in rats to acute administration of D-fenfluramine and other serotonergic agonists. All three pre-treatments attenuated the D-fenfluramine-evoked behavioural syndrome, but did not affect the prolactin or ACTH responses to acute challenge with D-fenfluramine (apart from a small effect of pre-treatment with pCA on the ACTH response to D-fenfluramine). For comparison, the effect of pCA pre-treatment on the behavioural responses to acute administration of pCA and the 5-HT(1A) and 5-HT(2) receptor agonists 8-hydroxy-2-(di- n- propylamino)tetralin (8-OH-DPAT) and 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), respectively, were also examined. pCA pre-treatment attenuated all components of the behavioural response to pCA but had little or no effect on the behavioural responses to 8-OH-DPAT or DOI, suggesting that there was no alteration in post-synaptic 5-HT(1A) or 5-HT(2) receptor function. While the loss of behavioural effect of D-fenfluramine on rats pre-treated with neurotoxic amphetamines can be understood in terms of the loss of D-fenfluramine's 5-HT-releasing action following 5-HT neurodegeneration, the lack of change in the neuroendocrine responses to D-fenfluramine is not easily explicable in this way. These results emphasise the need for further research into the actions of D-fenfluramine before carrying it forward as a probe of neurodegeneration in man.

p-Chloroamphetamine (PCA), 3,4-methylenedioxy-methamphetamine (MDMA) and d-fenfluramine pretreatment attenuates d-fenfluramine-evoked release of 5-HT in vivo

Previous work has suggested that repeated treatment with substituted amphetamines including PCA, MDMA and d-fenfluramine produces a persistent neurodegeneration which is relatively selective for the fine serotoninergic terminals arising from the dorsal raphe nucleus. The aim of the present study was to investigate whether the acute releasing effect of d-fenfluramine might also be sensitive to lesions produced by PCA, MDMA and d-fenfluramine itself. Basal and 5-HT release evoked by d-fenfluramine or 100 mM KCl was measured by microdialysis in frontal or parietal cortex of rats 2 weeks after they had been treated with a neurodegenerative regime of PCA, MDMA, d-fenfluramine, or vehicle. In frontal cortex of vehicle controls, d-fenfluramine (10 mg/kg IP) and KCl (100 mM via microdialysis probe) evoked an increase in 5-HT of 1740% and 779% of basal, respectively. PCA pretreatment reduced d-fenfluramine-evoked 5-HT release by 90.9% while potassium-evoked release was reduced by only 66.8%. Similar results were obtained in parietal cortex. MDMA (20 mg/kg x 8) and d-fenfluramine (1.25 mg/kg x 8) pretreatment reduced d-fenfluramine-evoked release of 5-HT in frontal cortex by 45.2% and 72.0%, respectively. Overall, the present data are consistent with the hypothesis that the acute release of 5-HT evoked by d-fenfluramine occurs via those terminals destroyed by pretreatment with PCA, MDMA and d-fenfluramine, while KCl evokes release from both PCA-sensitive and PCA-insensitive terminals. The significance of these results for the interpretation of neuroendocrine data from d-fenfluramine challenge tests is discussed.

Highly resistant bacterial osteomyelitis in Somalia

Chronic osteomyelitis is a major health problem in the aftermath of the conflict in Somalia. We studied the microbiology of chronic osteomyelitis among 30 patients in a large hospital in Mogadishu. Gram-negative bacteria were isolated from 77% of patients; most of these isolates were highly resistant to standard antibiotic agents but all were sensitive to ciprofloxacin, an oral fluoroquinolone antibiotic. Ciprofloxacin may prove useful in the management of chronic osteomyelitis due to highly resistant gram-negative bacteria.

The effect of kainic acid on the release of GABA in rat neostriatum and substantia nigra

In order to test the hypotheses that stimulation of non-N-methyl-D-aspartate (NMDA) receptors in the neostriatum causes the release of gamma-aminobutyric acid (GABA) from nigrostriatal neurones, dual microdialysis was carried out in the neostriatum and substantia nigra of freely moving rats. Application of kainic acid to the neostriatum caused a dose-dependent release of GABA both locally and, at the same time, from the ipsilateral substantia nigra. These effects were blocked by the non-NMDA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX). Direct application of kainic acid to the substantia nigra caused a DNQX-sensitive local release of GABA. It is concluded that excitatory amino acid receptor stimulation of the neostriatum releases GABA from striatonigral neurones and that stimulation of the substantia nigra causes the release from striatonigral terminals and/or the collaterals of nigrofugal neurones.

An investigation of the origin of extracellular GABA in rat nucleus accumbens measured in vivo by microdialysis

GABA transmission in the nucleus accumbens is believed to play a central role in motivational processes and the expression of psychostimulant drug action. Here we report measurements of extracellular GABA in nucleus accumbens of the rat and investigate its origin. Extracellular GABA was detected using microdialysis in combination with a novel HPLC-based assay. In the awake rat, GABA in the microdialysates (1) increased 10-fold following perfusion with 0.5 mM nipecotic acid, a GABA releasing agent and uptake blocker, (2) increased 7-fold following local perfusion with 50 mM KCl, (3) decreased 50% following perfusion with tetrodotoxin, (4) decreased 50% following perfusion with a Ca(2+(-free medium and (5) decreased 40% following perfusion with high (12.5 mM) MgCl. Finally, in the anaesthetized rat, GABA in the microdialysates decreased 50% following i.p. injection of 100 mg/kg 3-mercaptoproprionic acid, a GABA synthesis inhibitor. We conclude that GABA in microdialysates from nucleus accumbens of the rat (awake) responds appropriately to selected pharmacological agents and derives at least in part (50%) from neurones.

Biochemical evidence for the regulation of central noradrenergic activity by 5-HT1A and 5-HT2 receptors: microdialysis studies in the awake and anaesthetized rat

Here we have studied the effect of various 5-HT1A and 5-HT2 receptor-selective drugs on noradrenaline release in the hippocampus on anaesthetized and awake rats using microdialysis. In the anaesthetized rat, administration of the 5-HT1A agonists buspirone, gepirone and ipsapirone increased noradrenaline levels in the microdialysates. However, the common metabolite of these compounds, 1-PP (an alpha-2 adrenoceptor antagonist with low affinity for 5-HT1A receptors), also increased noradrenaline efflux whilst the 5-HT1A receptor agonist 8-OH-DPAT and MDL 73005EF, which are not metabolized to 1-PP, did not. In the awake rat, buspirone but also 8-OH-DPAT increased noradrenaline efflux. A similar effect was observed in response to MDL 73005EF and the 5-HT1A ligand NAN-190. Since the latter two drugs have weak intrinsic activity at the post-versus presynaptic 5-HT1A receptor, a presynaptic mechanism (inhibition of 5-HT release) was implicated. The 5-HT2 receptor may be important to this mechanism as noradrenaline increased following administration of the 5-HT2 receptor antagonists, ritanserin and ICI 170,809. In conclusion, our data indicate that there are clear differences in the effects of 5-HT1A and 5-HT2 receptor-selective drugs on noradrenaline efflux in hippocampus of the anaesthetized versus awake rat. Our findings are reconcilable with the hypothesis that in the awake (but not anaesthetized) rat, release of noradrenaline in hippocampus is influenced by an inhibitory tone mediated via 5-HT2 receptors. If this inhibitory tone is removed, either by decreasing 5-HT release through activation 5-HT1A autoreceptors or by blocking postsynaptic 5-HT2 receptors, noradrenaline release increases.

Measurement of GABA in rat brain microdialysates using o-phthaldialdehyde-sulphite derivatization and high-performance liquid chromatography with electrochemical detection

A number of recent studies have detected gamma-aminobutyric acid (GABA) in brain microdialysates by measuring an electroactive o-phthaldialdehyde (OPA)-alkylthiol derivative using HPLC with electrochemical detection. A particular problem of this approach is the stench of the thiol reagents involved, and the poor stability of the electroactive GABA derivative. Here we report that these practical disadvantages can be overcome by substitution of the OPA-alkylthiol reaction with an OPA-sulphite reaction. This provides a simple, sensitive and reliable means for determination of GABA in microdialysates of rat brain.

Threat of hepatitis E virus infection in Somalia during Operation Restore Hope

In support of Operation Restore Hope, the United States military established a diagnostic laboratory for infectious diseases, the Joint Forward Laboratory, in Mogadishu, Somalia. Because sporadic hepatitis due to unknown causes was a frequent problem, staff members of the Joint Forward Laboratory evaluated 31 Somalis, five displaced Ethiopians, and three Western relief workers who had acute clinical hepatitis. Patients lived in multiple locations in Somalia--Mogadishu, Baidoa, and Merca--and became ill between December 1992 and February 1993. IgM antibody to hepatitis A virus was found in one English relief worker, and IgM antibody to hepatitis E virus was found in 20 (65%) of 31 Somalis, two (40%) of five Ethiopians, and two (67%) of three Western relief workers. No patient had evidence of acute hepatitis B, malaria, yellow fever, or other arbovirus infections. These data indicate that hepatitis E virus--the major cause of enterically transmitted non-A, non-B hepatitis--was a common cause of acute sporadic hepatitis in Somalia during the initial stages of Operation Restore Hope.

Effect of acute and repeated administration of 5-HT1A receptor agonists on 5-HT release in rat brain in vivo

1. Electrophysiological measurements of 5-HT neuronal activity report that repeated administration of 5-HT1A receptor agonists leads to desensitization of the 5-HT1A autoreceptor but this has not yet been detected in measurements of brain 5-HT synthesis or metabolism. Here we have determined the effect of repeated administration of 5-HT1A receptor agonists on brain 5-HT release using microdialysis. 2. Acute administration of the 5-HT1A receptor agonists buspirone (0.1-5 mg/kg s.c.) and ipsapirone (0.03-3 mg/kg s.c.) caused a dose-dependent decrease in 5-HT output in ventral hippocampus of the chloral hydrate anaesthetized rat. 3. The 5-HT response to buspirone (0.1 and 0.5 mg/kg s.c.) and ipsapirone (0.3 mg/kg s.c.) was significantly inhibited by pre-treatment with the 5-HT1/beta-adrenoceptor antagonist pindolol (8-16 mg/kg s.c.). The 5-HT response to buspirone (0.1 mg/kg s.c.) and ipsapirone (0.3 mg/kg s.c.) was not blocked by pretreatment with a combination of the beta 1 and beta 2-adrenoceptor antagonists metoprolol and ICI 118,551 (4 mg/kg s.c.). 4. The effect of an acute challenge of buspirone (0.5 mg/kg s.c.) on 5-HT output in ventral hippocampus was not attenuated in rats treated twice daily for 14 days with 0.5 or 5 mg/kg s.c. buspirone compared to saline-injected controls. Similarly, the decrease in 5-HT induced by an acute challenge of ipsapirone (0.5 mg/kg s.c.) was not attenuated in rats treated twice daily for 14 days with 5 mg/kg s.c. ipsapirone.(ABSTRACT TRUNCATED AT 250 WORDS)