A new way to explore ventricular-arterial coupling in young patients with untreated hypertension

Introduction

Commonly assessed as arterial elastance (Ea) to ventricular end-systolic elastance (Ees) ratio, ventricular-arterial coupling (VAC) has independent prognostic value in hypertension.

Aim

To investigate whether new coupling indices may be able to identify left ventricular (LV) performance changes induced by blood pressure (BP) overload earlier than conventional ones.

Materials and methods

50 young individuals were prospectively enrolled: 25 (40±8 years) newly diagnosed untreated hypertensives and 25 controls (38±9 yrs). All underwent at the same time carotid-femoral pulse wave velocity (PWV) measurement through a tonometer and an echocardiogram to calculate global longitudinal strain (GLS) and myocardial work efficiency (GWE). Two new indices of VAC were derived: PWV/GLS, previously validated and PWV/GWE, still unknown.

Results

ESV/SV ratio was lower in hypertensive (0.48±0.17) than in controls (0.57±0.14) but without any significant difference (p=0.18), whereas PWV/GLS was significantly lower in hypertensives than in controls (−0.45±0.19 vs −0.35±0.09 m/sec%; p=0.02). PWV/GLS ratio correlated with Ea/Ees (r=0.52; p<0.01), diastolic dysfunction degree (r=−0.59; p<0.001), age (r=−0.64; p<0.001), systolic BP (r=−0.41; p=0.002), diastolic BP (r=−0.39; p=0.005) and mean arterial pressure (MAP) (r=−0.40; p=0.004). PWV/GWE was higher in hypertensives than in controls (0.10±0.02 vs 0.08±0.01 m/sec%; p=0.001) and it was associated with Ea/Ees (r=−0.55; p=0.006), age (r=0.59; p<0.001), diastolic dysfunction degree (r=0.55; p<0.001), systolic BP (r=0.8; p<0.001), diastolic BP (r=0.5; p<0.001) and MAP (r=0.52; p<0.001).

Conclusions

Innovative indices of ventricular-arterial coupling could be more sensitive for investigating the impact of hypertension on LV performance.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): G. Martino University Hospital, Department of Clinical and Experimental Medicine - Cardiology Unit, University of Messina, Messina, Italy

Relationship between Pulse Wave Velocity and Myocardial Work in untreated hypertensive patients with preserved LVEF

Introduction

Hemodynamic interaction between left ventricular (LV) and arterial system is a key determinant of cardiovascular performance. The non-invasive carotid-femoral Pulse Wave Velocity (PWV), obtained with applanation tonometry, is considered the most precise way of estimating arterial stiffness. The LV myocardial work (MW), based on non-invasive LV pressure-strain loop (PSL), is a new promising tool to assess LV function.

Purpose

The aim of the study was to evaluate the correlation between PWV and MW parameters in a population of non-hypertensive and newly diagnosed untreated hypertensive people.

Material and methods

50 people (M=30), divided in hypertensive (group 1: n=25, 40±8 years) and non-hypertensive (group 2: n=25, 38±9 years), were prospectively enrolled. All underwent conventional transthoracic echocardiography and at the same day carotid femoral PWV was calculated with applanation tonometry (SphygmoCor® XCEL). MW parameters were obtained using 2D Speckle-tracking technique.

Results

Comparing the two groups, PWV and Global Work Wasted (GWW) were significantly higher in the hypertensives group (9.44±2.4 vs 7.56±1.1; p=0.001 and 130±2.5 vs 80.60±1.5, p=0.002), as shown in Figure 1, whereas Global Work Efficiency (GWE) and Global Work Constructive (GWC) were significantly lower (94±2.5 vs 95.8±1.2, p=0.003 and 2393±20 vs 2166±18, p=0.02). We found a linear and positive correlation of PWV with GWW (r=0.315, p=0.026), as seen in Figure 2, and a linear and negative correlation of PWV with GWE (r=−0.315, p=0.026).

Conclusion

This study highlights the role of PWV and MW evaluation in hypertensives. Higher PWV and GWW could be considered as red flags of myocardial damage suggesting the need of an early appropriate antihypertensive therapy.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): University Ospital G. Martino - Messina

Ceftibuten stability to active-site serine and metallo-beta-lactamases

Ceftibuten is an oral third-generation cephalosporin active against a wide range of bacteria and shows an improved stability to hydrolysis by several beta-lactamases because of the carboxyethilidine moiety at position 7 of the ss-acyl side chain. The kinetic interactions between ceftibuten and active-site serine and metallo-ss-lactamases were investigated. The activity of several TEM-derived extended spectrum beta-lactamases (ESbetaLs) against ceftibuten, cefotaxime and ceftazidime was compared using K(m), K(cat) and K(cat)/K(m). Ceftibuten behaved as a poor substrate for class A and B beta-lactamases compared with cefotaxime. The chromosomal class C beta-lactamase from Enterobacter cloacae 908R gave a high K(cat) value (21 s(-1)), whereas there was poor activity with enzymes from Acinetobacter baumannii and Morganella morganii and ceftibuten. Ceftibuten resists hydrolysis in the presence of typical respiratory or urogenital-tract pathogens producing beta-lactamases.

Excretion and metabolism of propionyl-L-carnitine in the isolated perfused rat kidney

Propionyl-L-carnitine (PLC) is an ester of L-carnitine (LC) under evaluation for the treatment of cardiovascular disorders. The renal disposition of PLC was studied in the isolated perfused rat kidney with deuterium-labeled derivative (PLC-CD3). Kidneys of male Sprague-Dawley rats were perfused at initial PLC-CD3 concentrations of 10 (n = 4) and 200 microM (n = 5). High-performance liquid chromatography/mass spectrometry was used to quantify PLC-CD3, deuterated L-carnitine (LC-CD3) and acetyl-L-carnitine (ALC-CD3) in perfusate and urine. PLC-CD3 in perfusate decreased in a monoexponential manner with a half-life of 90 +/- 24 min (S.D.) (10 microM) and 94 +/- 11 min (200 microM). The renal excretory clearance of PLC-CD3 was significantly lower (P < .05, unpaired t test) at an initial concentration of 10 microM (45 +/- 23 microl/min) than at 200 microM (85 +/- 28 microl/min), but in both cases it was substantially less than the glomerular filtration rate, which indicates extensive tubular reabsorption. The renal excretory clearance of PLC-CD3 represented less than 6% of the total clearance, which suggests that metabolism is the major renal elimination route for this compound. The appearance in perfusate and urine of LC-CD3 and ALC-CD3 provided additional evidence for a metabolic role of the kidney. The apparent renal excretory clearance values for these metabolites were always significantly higher than the values obtained for the corresponding endogenous compounds, which suggests that LC-CD3 and ALC-CD3, as formed metabolites, underwent passive or carrier-mediated movement directly into urine.

Determination of L-carnitine, acetyl-L-carnitine and propionyl-L-carnitine in human plasma by high-performance liquid chromatography after pre-column derivatization with 1-aminoanthracene

A new sensitive high-performance liquid chromatographic procedure for the determination of L-carnitine (LC), acetyl-L-carnitine (ALC) and propionyl-L-carnitine (PLC) in human plasma has been developed. Precolumn derivatization with 1-aminoanthracene (1AA), performed in phosphate buffer in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) as catalyst, is involved. The fluorescent derivatives were isocratically separated on a reversed-phase column (C18). The eluate was monitored with a fluorimetric detector set at 248 nm (excitation wavelength) and 418 nm (emission wavelength). Because of the presence of endogenous carnitines, the validation was performed using dialyzed plasma. The identity of the derivatized compounds was assessed by mass spectrometry and the purity of the chromatographic peaks was confirmed by HPLC-tandem mass spectrometry. The limits of quantitation were 5 nmol/ml for LC, 1 nmol/ml for ALC and 0.25 nmol/ml for PLC. The recovery of the extraction procedure was in the range 82.6%-95.4% for all 3 compounds. Good linearity (R approximately 0.99) was observed within the calibration ranges studied: 5-160 nmol/ml for LC, 1-32 nmol/ml for ALC and 0.25-8 nmol/ml for PLC. Precision was in the range 0.3-16.8% and accuracy was always lower than 10.6%.

Disposition of L-carnitine and acetyl-L-carnitine in the isolated perfused rat kidney

The isolated perfused rat kidney was used to investigate the regulation, specificity and concentration-dependence of the renal tubular disposition of L-carnitine (LC) and its ester, acetyl-L-carnitine (ALC). Tritiated markers were used to study the renal disposition of LC and ALC and HPLC was used to purify 3H-LC and 3H-ALC before radiochemical analysis. At perfusate concentrations comparable to those found in plasma in vivo (50 microM for LC and 5 microM for ALC), the renal clearance of both analogues was substantially less than GFR (P < .05) which, in view of their negligible binding to perfusate proteins, is indicative of extensive reabsorption. During the first 20 min of perfusion, the percent tubular reabsorption (%TR) of LC and ALC was 94 +/- (SD) 2.6% and 97 +/- 0.6%, respectively. The extent of 3H-ALC and 3H-LC enrichment of perfusate in experiments with 3H-LC and 3H-ALC, respectively, provided evidence for the capability of the rat kidney to acetylate LC and deacetylate ALC. In addition, a portion of renally generated 3H-ALC and 3H-LC was found to undergo leakage into renal tubules and escape subsequent reabsorption. It was also found that the %TR of both compounds decreased substantially when the perfusate concentration was increased above endogenous levels; each compound was capable of decreasing the %TR of the other; and trimethylamine-N-oxide, a metabolite of LC, had no significant effect on the renal handling of the carnitine derivatives.

Determination of pentoxifylline and its metabolites in human plasma by high-performance liquid chromatography with solid-phase extraction

A simple and reliable method for the determination of pentoxifylline and its main metabolites in human plasma has been developed using high-performance liquid chromatography. After selective solid-phase extraction, pentoxifylline, its metabolites and an internal standard, 7-(2'-chloroethyl)theophylline, were separated on a 5-micron LiChrospher 100 RP-18 column using water-dioxan-acetonitrile (87:6.5:6.5, v/v/v) acidified with acetic acid (0.5%, v/v) as the mobile phase. The analytes were detected at 275 nm. The lowest detectable concentration for all analytes was 25 ng/ml; the recovery was 85%. The assay has been successfully applied to analysis of these compounds in human plasma after administration of an oral dose of 400 mg of pentoxifylline to healthy volunteers.

Determination of the tricyclic compound adosupine and its three metabolites in plasma and brain of rat using high-performance liquid chromatography

An analytical method for the detection in biological samples of the novel tricyclic compound adosupine (10-acetoamido-5-methyl-5,6-dihydro-11H-dibenzo[b,e]azepin-6 ,11-dione), which is capable of influencing various forms of urinary bladder hyperreflexia has been developed using high-performance liquid chromatography with UV detection. Liquid-liquid extraction was used to isolate the parent compound, three metabolites and an analogue (added as internal standard) from plasma and brain of rat. Adosupine was well separated from its three metabolites with 0.01 M disodium hydrogenphosphate-acetonitrile-methanol-nonylamine (59.986:38:2:0.014) at pH 4.5 as mobile phase using a C18 reversed-phase column. The standard curves were linear in the range 50-5000 ng/ml (or ng/g) for adosupine and metabolites in both plasma and brain. The between- and within-assay variations for high and low concentrations of the parent compound and the three metabolites were 8.2-14%. In the range 50-5000 ng/ml (or ng/g) the accuracy of the method was satisfactory, with the relative error always lower than 10%. Analytical recoveries of added adosupine and the three metabolites were higher than 82%. The method has been applied successfully, to investigate the pharmacokinetics of the drug and its distribution in the central nervous system of rats.

High-performance liquid chromatographic evaluation of Med 15 and its metabolites Med 5 and tolmetin in rat plasma

A simple and reliable high-performance liquid chromatographic method is described for the quantitative analysis of the new non-steroidal anti-inflammatory agent Med 15 and its metabolites Med 5 and tolmetin in rat plasma. After selective extraction the three analytes and an internal standard (p-phenyl-phenol) were separated on a reversed-phase Ultrasphere 5 micron column using potassium dihydrogenphosphate (0.05 M)-acetonitrile (52:48) (pH 4.7) as the mobile phase. The analytes were detected at 313 nm; the sensitivity of the method proved to be 0.05 microgram/ml for all three compounds. The method has been applied to investigate Med 15 pharmacokinetics in rats.

Potential antidepressant activity and enhancement of serotonin uptake of a new dibenzothiadiazepine derivative

A molecule, 6-methyl-6,11-dihydro-11-[(N,N-dimethylamino) acetyl]dibenzo[c,fl-[1,2,5]thiadiazepine 5,5-dioxide, (IM/P/3/4, CAS 128377-70-8), was identified in a screening program, which had the scope of finding compounds with antidepressive potential without the common sideeffects of existing antidepressive medication. IM/P/3/4 was found active a) in antagonizing apomorphine (16 mg/kg) and reserpine-induced hypothermia in mice; b) in potentiating yohimbine-induced lethality in mice; c) in reducing immobility of rats forced to swim and of mice suspended by the tail. IM/P/3/4 does not affect a) apomorphine-induced stereotypy; b) amphetamine-induced hypermotility; c) haloperidol-induced catalepsy and water-induced grooming and d) does not induce stereotypy or alter motor activity. The compound also a) reduced the beating of rat right heart atria only at a concentration of 3 x 10-4 mol/l; b) had weak anticholinergic activity; c) antagonized electroshock-induced convulsions and d) prevented indometacin-induced duodenal ulcers. IM/P/3/4 does not have good affinity for noradrenergic, serotonergic, dopaminergic, histaminergic or muscarinic receptors and does not displace imipramine, desipramine and mianserine from their binding sites. IM/P/3/4 increases 5-hydroxyindolacetic acid content and 3H-serotonin uptake in the hypothalamus. The present results suggest that IM/P/3/4 is a potential antidepressant with reduced side effects and with a mechanism of action which is different from that of other antidepressants.

Effect of enantiomers of propranolol on desipramine-induced anti-immobility in the forced swimming test in the rat

The effect of d- and l-enantiomers of propranolol on desipramine-induced anti-immobility effects and on brain desipramine levels was studied in the rat. Intraperitoneal propranolol and desipramine were administered three times, 25, 6, 2 and 24, 5, 1 h respectively, before the test. It was found that l-propranolol but not d-propranolol, at the same doses (2.5 and 5 mg/kg), antagonized 20 mg/kg desipramine without altering desipramine brain levels. It is suggested that blockade of beta-adrenergic receptors rather than membrane-stabilizing or pharmacokinetic effects is responsible for the antagonism of propranolol toward desipramine.

Effect of serotoninergic drugs on stress-induced hyperthermia (SIH) in mice

8-OH-DPAT (2.5-10 mg/kg) and buspirone (10 mg/kg) but not 5,7-DHT (200 micrograms/mouse), pCPA (75 and 150 mg/kg, three times), ritanserin (0.1 and 0.2 mg/kg), LY 53857 (1.5 and 3 mg/kg), GR 38032 F (0.1-100 micrograms/kg), TFMPP (5 and 20 mg/kg) and mCPP (2.5 and 5 mg/kg) antagonized the rise in body temperature that occurs to the last mice removed from their group housing, which was termed as stress-induced hyperthermia (SIH). Ro 15-1788, at a dose which blocked the effect of diazepam on SIH, did not reverse the anxiolytic effect of buspirione. Instead, when cerebral 5-HT content was reduced to 50% by 5,7-DHT-induced lesion, the effect of buspirone on SIH was decreased. TFMPP 5 mg/kg did not shorten significantly the onset of SIH as could have been expected by an anxiogenic drug, while the dose of 20 mg/kg did not modify the pattern of SIH at all. The lower dose of TFMPP evoked a hyperthermic and the higher a hypothermic response.

Cholinergic drug effects on antidepressant-induced behaviour in the forced swimming test

The contribution of anticholinergic effects to the action of desipramine and nomifensine was investigated in the forced swimming test in rats. The immobility time was reduced by high doses of atropine (10-25 mg/kg i.p.) and scopolamine (1.5 mg/kg i.p., 1 and 0.5 h before the test, respectively) and was unaffected by physostigmine (0.25-0.5 mg/kg i.p., 1 h before the test). Unlike atropine (25 mg/kg), scopolamine (1.5 mg/kg) increased motor activity (open-field). The anti-immobility effect of i.p. desipramine (20 or 30 mg/kg) and nomifensine (2.5 or 5 mg/kg), administered 24, 5 and 1 h before the test, was potentiated by scopolamine (0.5-1.0 mg/kg) and antagonized by physostigmine (0.25-0.5 mg/kg). The brain levels of desipramine and nomifensine were unaffected by scopolamine or physostigmine. Motor performance was impaired in rats treated with physostigmine and desipramine whereas hypermotility was observed in rats treated with scopolamine and nomifensine. The anti-immobility effect of atropine (25 mg/kg) and scopolamine (1.5 mg/kg) was not antagonized by physostigmine (0.5 mg/kg). These results indicate that anticholinergic mechanisms alone are not sufficient to influence immobility time and suggest that the cholinergic system may control, the neural circuitry upon which desipramine and nomifensine act to reduce immobility time.

Phytochrome-Mediated Control of Diamine Oxidase Level in the Epicotyl of Etiolated Lentil (Lens culinaris Medicus) Seedlings

Diamine oxidase (DAO; EC 1.4.3.6) levels are strongly reduced in epicotyls of 3-day-old etiolated lentil (Lens culinaris Medicus) seedlings upon exposure to continuous red and blue light, as compared to etiolated controls. Far-red light inhibits DAO activity to a lesser extent. A less marked effect can also be obtained by short (5-10 min) daily exposures. Phytochrome involvement in this light-mediated response has been demonstrated by red/far-red reversibility experiments. These findings provide the first evidence that mechanisms underlying the photoregulation of DAO level in the Leguminosae are related to photomorphogenesis and are essentially unrelated to the photosynthetic capacity of the seedling.

Stimulation of dopamine D-2 but not D-1 receptors reduces immobility time of rats in the forced swimming test: implication for antidepressant activity

The involvement of dopamine D-1 and D-2 receptor mechanisms was investigated in the forced swimming test with rats. d,1-Sulpiride, a D-2 receptor antagonist, reported to reduce desipramine-induced anti-immobility, did not alter the brain levels of desipramine. In addition, the anti-immobility effect of desipramine was not antagonized by SCH 23390, a D-1 receptor antagonist. Amineptine (20 mg/kg i.p., 60 min before testing), a dopamine uptake blocker, and LY171555 (0.2 mg/kg i.p., 60 min before testing), a dopaminergic D-2 stimulant reduced immobility time in the forced swimming test, but benserazide + 1-DOPA (200 mg/kg p.o., 45 min before testing), which increases dopamine release, or SKF 38393A (20 mg/kg s.c., 60 min before testing), a D-1 agent, did not. The anti-immobility effect but not the stereotypy was increased following chronic (21 days) LY171555 (0.1 and 0.2 mg/kg i.p.) treatment. The effect of acute or repeated (7 days) LY171555 (0.2 mg/kg i.p.) treatment was antagonized by 1-sulpiride (50 mg/kg i.p., 90 min before testing), a D-2 receptor antagonist. Neither SKF 38393A (20 mg/kg s.c., 60 min before testing) nor SCH 23390 (0.05 mg/kg s.c., 30 min before testing) modified the acute anti-immobility effect of LY171555 (0.2 mg/kg i.p.) SCH 23390 (0.025 and 0.05 mg/kg) increased the immobility time at doses which decreased motor activity. The increase in immobility time brought about by SCH 23390 was not antagonized by SKF 38393A (20 mg/kg). The findings indicate that activation of dopamine D-2 receptors could reduce immobility time.

New method for recording cystometrograms in conscious, freely moving rats

A new cystometric technique has been developed that is suitable for quantitative studies on physiopharmacology of micturition in conscious, freely moving rats. The method involves the transvesical infusion of warm saline at various filling rates through a catheter chronically implanted into the bladder dome. The various parameters of the collecting and voiding phase of the cystometrogram were recorded. Results obtained indicate that characteristics of the bladder voiding cycle of conscious, freely moving rats are qualitatively similar but quantitatively different from those described previously in anesthetized animals.

On the role of endogenous GABA in the forced swimming test in rats

GABA content was reduced in the nucleus accumbens, cortex and brainstem of rats after 5 but not after 45, 120 min or 24 hr, from the termination of the pretest session. This reduction was not observed in rats performing on rotarod. Intraperitoneal AOAA (25 mg/kg; 24, 5 and 1 hr before the test), reduced at the same extent immobility time regardless whether the animals had been exposed to a pretest session. In pretested animals, reduction in immobility time produced by AOAA (25 mg/kg X 3 times) was similar to that observed following 50 mg/kg, 5 hr before testing. This reduction was not antagonized by GABA antagonists bicuculline (2 mg/kg) or picrotoxin (2 mg/kg), given intraperitoneally 30 and 20 min before the test respectively. Intraperitoneal sodium valproate (200 or 400 mg/kg; 24, 5 and 1 hr before the test) and isoniazide (200 mg/kg) or 4-deoxypyridoxine (400 mg/kg), administered 1 or 1.5 hr before the test, were ineffective. AOAA (25 mg/kg X 3 times) gave a similar increase in GABA levels to 50 mg/kg only once in the brainstem, nucleus accumbens and hypothalamus and a greater increase in the other brain areas. After 5 hr from single dosing, 25 mg/kg AOAA increased GABA levels less than 50 mg/kg AOAA in the brainstem, nucleus accumbens, frontal cortex and striatum, and increased it to same extent in the other areas. Sodium valproate (400 mg/kg X 3 times) increased GABA levels in all brain areas, except hippocampus, although to a lesser extent than AOAA.

Lack of relationship between effect of desipramine on forced swimming test and brain levels of desipramine or its demethylated metabolite in rats

Animals were injected with 20 mg/kg desipramine (DMI) 1 h (acute) or 24, 5 and 1 h (subchronic) or once daily for 7 consecutive days (chronic) before the forced swimming test (FST). DMI was also injected at a dose of 40 mg/kg acutely. Animals were killed immediately after test for evaluation of brain concentrations of DMI and its demethylated metabolite desmethyldesipramine (DDMI). Acute and chronic DMI 20 mg/kg gave rise to similar brain concentrations but only chronic DMI was active on FST. Acute DMI 20 mg/kg and 40 mg/kg gave rise to different brain concentrations but similar effects on FST. DDMI concentrations were similar after the various DMI treatments. Results seem to indicate that no relationship exists between effect of DMI on FST and brain concentrations of either DMI or DDMI.

Disposition and metabolism of minaprine in the rat

After iv. injection (5 mg/kg) to rats, minaprine is cleared rapidly from plasma with an elimination t 1/2 of 34 min. After the same dose but given orally the drug is rapidly absorbed from the rat gastrointestinal tract. The ratio of the area under the curves (AUC) of the parent drug indicates low bioavailability (5%). Two metabolites of minaprine (M3 and M5) appeared rapidly in rat plasma and far exceed minaprine concentrations. Other known urinary metabolites of the drug were undetectable in rat plasma and brain within the limits of the sensitivity of the method. Minaprine rapidly enters the central nervous system and then distributes almost evenly in various regions beyond the blood/brain barrier. It concentrates in brain tissue reaching concentrations two-three times those in plasma. It metabolites enter the brain less rapidly and their brain AUC never reached 50% of the plasma AUC.

Kinetic and pharmacological studies on estazolam in mice and man

After i.v. and oral doses of estazolam (5 mg/kg) to mice, the drug was rapidly cleared with a beta half-life (t1/2 beta) of 0.7 h. The active metabolite, 1-oxo-estazolam, was present in traces in mouse plasma and brain. Its elimination t1/2 (beta), determined after i.v. injection of 1-oxo-estazolam (5 mg/kg) to mice, was similar to that of the parent drug in both plasma and brain. After a single oral dose of estazolam (4 mg) to four human volunteers the drug was rapidly absorbed and reached maximum plasma concentrations in one to three hours. Elimination t1/2 of estazolam in humans was 19 h. The metabolite was undetectable in human plasma after either single or multiple doses of estazolam. These results, together with the finding that 1-oxo-estazolam was less effective than estazolam, in terms of ED50 and brain concentrations necessary to antagonize leptazol convulsions and disrupt rota-rod performance in mice, indicate that the metabolite does not contribute significantly to the pharmacological effects of its parent drug.

Disposition and metabolism of buspirone and its metabolite 1-(2-pyrimidinyl)-piperazine in the rat

After i.v. injection (10 mg/kg) to rats, buspirone is rapidly cleared from blood with a t1/2 (beta) or 30 min. After the same dose is given orally, the drug is not detectable in blood or brain within the limits of sensitivity of the method. The metabolite 1-(2-pyrimidinyl)-piperazine (1-PP) has a longer t1/2 than buspirone. It is present to about the same extent in rat plasma and brain after either i.v. or p.o. buspirone. Unlike buspirone, 1-PP accumulates in the brain reaching concentrations between four-and five times those in plasma. Its brain AUC is higher than that of buspirone even when buspirone is given i.v. The results suggest that 1-PP may contribute to the pharmacological effect of the parent drug.