Interpretation of drug concentrations in an alternative matrix: the case of meprobamate in bile.

Investigating toxicological causes of death may require alternative matrices when the usual ones are lacking. Whereas forensic toxicology uses bile almost only for xenobiotic screening, a diagnostic test interpreting postmortem bile concentrations of meprobamate is reported. Based on 128 sets of autopsy data, its intrinsic qualities were good, with 0.95 sensitivity and 0.93 specificity. In a French forensic population, the positive and negative predictive factors were 0.90 and 0.97, respectively. It is a useful means of revealing overdoses where blood samples are not available or of confirming blood tests when postmortem redistribution is suspected.

Noninvasive exploration of cardiac autonomic neuropathy. Four reliable methods for diabetes?

OBJECTIVE: The purpose of this work was to assess relevant information that could be provided by various mathematical analyses of spontaneous blood pressure (BP) and heart rate (HR) variabilities in diabetic cardiovascular neuropathy. RESEARCH DESIGN AND METHODS: There were 10 healthy volunteers and 11 diabetic subjects included in the study. Diabetic patients were selected for nonsymptomatic orthostatic hypotension in an assessment of their cardiovascular autonomic impairment. Cardiac autonomic function was scored according to Ewing's methodology adapted to the use of a Finapres device. The spontaneous beat-to-beat BP and HR variabilities were then analyzed on a 1-h recording in supine subjects. The global variabilities were assessed by standard deviation, fractal dimension, and spectral power. The cardiac baroreflex function was estimated by cross-spectral sequences and Z analyses. RESULTS: In diabetic patients, Ewing's scores ranged from 1 to 4.5, confirming cardiovascular autonomic dysfunction. In these diabetic patients, global indices of variabilities were consistently lower than in healthy subjects. Furthermore, some of them (standard deviation and fractal dimension of HR, spectral power of systolic blood pressure and HR) were significantly correlated with the Ewing's scores. The Z methods and the spectral analysis found that the cardiac baroreflex was less effective in diabetic subjects. However, the baroreflex sensitivity could not be reliably assessed in all the patients. The sequence method pointed out a decreased number of baroreflex sequences in diabetic subjects that was correlated to the Ewing's score. CONCLUSIONS: Indices of HR spontaneous beat-to-beat variability are consistently related to the degree of cardiac autonomic dysfunction, according to Ewing's methodology. The Z method and spectral analysis confirmed that the cardiac baroreflex was impaired in diabetic patients. These methods might be clinically relevant for use in detecting incipient neuropathy in diabetic patients.

Mental stress-induced increase in blood pressure is not related to baroreflex sensitivity in middle-aged healthy men.

The baroreflex that acts to blunt blood pressure (BP) variations through opposite variations in heart rate should limit the BP increase produced by an emotional challenge. However, relations between baroreflex sensitivity and BP reactivity induced by a psychological stress in a large group of adults have never been firmly established. In 280 healthy men, rest (10 minutes) and stress (5 minutes) BP and heart rate were recorded beat to beat by a blood pressure monitor. The mental stress was elicited by a well-standardized computerized version of a word color conflict stress test (Stroop Color Test). Rest and stress baroreflex sensitivity was assessed by the cross-spectral analysis of BP and heart rate and by the sequence method. The stress-induced increase in systolic BP (22.4+/-0.1 mm Hg) was not correlated with resting baroreflex sensitivity but was slightly correlated (r=0.2, P<0.001) with BP variability assessed either by standard deviation or by mid-frequency band spectral power. Our results suggested that a centrally mediated sympathetic stimulation overcame cardiac autonomic regulation and emphasized the role of the sympathetic vasoconstriction in the pressure response at the onset of the stressing stimulation. During the sustained sympathoexcitatory phase, the cardiac baroreflex blunts BP variations but at a lower sensitivity.

Spontaneous cardiac baroreceptor reflex and regional circulations in conscious rats.

OBJECTIVE: To determine the relationships between the activity of the spontaneous cardiac baroreceptor reflex (BRX) and regional vascular dynamics in conscious unrestrained rats. DESIGN: Simultaneous beat-to-beat recordings of blood pressure and measurements of indices of mesenteric and hindquarters blood flows were performed in seven male normotensive conscious rats under baseline conditions during 1 h. METHODS: The relationships between systolic blood pressure (SBP) and heart rate were examined using a computerized method, giving the degree of statistical dependence between values of the two parameters with the Z coefficient. This analysis permitted detection of cardiac beats related to cardiac BRX activity. Z analysis was also applied to SBP and to mesenteric or hindquarters blood flow or vascular resistance. Time-series representations were used to describe the chronological patterns corresponding to BRX spontaneous activity. RESULTS: In these rats, which presented spontaneous BRX-like patterns manifested by the Z analysis, BRX was active during approximately 15% of the time. For 80% of these patterns, cardiac BRX acted to buffer falls in SBP. These depressor events were preceded by muscular vasodilations whereas vasodilations in the mesentery were delayed. Z analysis of these spontaneous haemodynamic patterns confirmed that muscular vasodilations were strongly associated with falls in SBP, whereas vasodilations lagged behind SBP by about seven beats and were not dependent on simultaneous SBP values. CONCLUSIONS: The Z method showed that spontaneous hindquarters vasodilations were associated with cardiac BRX patterns and that mesenteric vasodilations were not concomitant with falls in SBP and may be the consequence either of a delayed central response or of a local mechanism such as myogenic autoregulation.

Heterogeneous computer network for real-time hemodynamic signal processing.

A computer network is described that allows real-time processing, graphical monitoring and off-line analysis of blood pressure, nervous activity and Doppler signals recorded in conscious rats. Real-time processing is performed by an acquisition station using a powerful microprocessor, allowing extraction and storage of several characteristic parameters from each cardiac cycle and real-time graphical monitoring. The experimenter can thereby follow the time evolution of the hemodynamic parameters. Experimental data are sent through the local network to a workstation that ensures off-line processing such as chronograms, histograms and statistical analyses.

[Role of sympathetic nerve fibers in hemodynamic responses to stress in rats]. / Rôle des fibres nerveuses sympathiques dans les réponses hémodynamiques au stress chez le rat.

Hemodynamic responses to acute stress exposure were studied in normotensive control (C) and chronically sympathectomized (S) rats. Male Sprague-Dawley rats received daily sc injections of either saline (C) or guanethidine (S) from 1 to 13 weeks of age. Doppler flow probes were then implanted for the measurement of blood velocity in the sub-diaphragmatic aorta, superior mesenteric artery and distal aorta (hindquarters). After 10 days of recovery and 24 hours before the study, the caudal artery was cannulated. In the conscious freely moving rats, mean arterial pressure (MAP), heart rate (HR) and indices of regional blood flows and vascular conductances (G as blood flow/MAP ratio) were recorded beat to beat, before and during emotional stress (jet of air for 2 min). In basal conditions, mean values of MAP and HR were similar in C (107 +/- 2 mmHg; 399 +/- 8 bpm, n = 9) and S (106 +/- 3 mmHg; 384 +/- 12 bpm, n = 7) rats. The effects of stress on MAP, HR, aortic (AoG), mesenteric (MeG) and hindquarters (HqG) vascular conductances are expressed as percentage changes from baseline (delta): [table: see text] These results highlight the role of vascular sympathetic nerves in pressor responses and systemic and mesenteric vasoconstrictions induced by stress in the rat. They also indicate that vasodilatation in the hindquarters vascular bed is not secondary to withdrawal of sympathetic vasoconstrictor tone but rather to active phenomena which do not involve the stimulation of vascular beta 2-adrenoceptors by neuronal catecholamines nor the release of vasodilator cotransmitters from the sympathetic nerve endings.

[Role of sympathetic nervous system on blood pressure and heart rate variabilities in the rat: spectral analysis]. / Rôle du système nerveux sympathique dans la variabilité de la pression artérielle et de la fréquence cardiaque chez le rat: étude par analyse spectrale.

The role of the sympathetic nervous system (SNS) in the genesis of the beat-to-beat variability of blood pressure (BP) and heart rate (HR) was studied using spectral analysis. The SNS activity of genetically normotensive rats of the Lyon strain (LN) was abolished in 2 ways: 1) adrenergic blockade with administrations of phentolamine (PHE, 5 mg/kg i.v.) or propranolol (PRO, 5 mg/kg i.v.) or both drugs (PHEPRO) or 2) destruction of the sympathetic fibers with an early chronic treatment with guanethidine (LNSx). HR and systolic (SBP) and diastolic (DBP) BP spectra were computed using 50 to 100 stationary sequences from 1 h beat-to-beat recordings and covered the 0.015-3.85 Hz frequency band. In LN rats, spectra obtained in baseline conditions exhibited a high-frequency peak (HF, 1.04-1.13 Hz) related to the respiratory frequency and a mid-frequency peak (MF, 0.38-0.45 Hz). Concerning BP, the alterations of the SNS induced significant decreases of the total modulus (mmHg/Hz1/2) of the MF band (0.27-0.74 Hz): [formula: see text] In addition, the MF peak of SBP and DBP spectra was abolished in LNSx and PHEPRO rats. Concerning HR spectra, the moduli of all the frequency components were decreased in PHEPRO rats only. In conclusion, the similarity of the results observed in LNSx and PHEPRO rats shows that the MF oscillations of BP depend in a large extent (65%) on the action of the sympathetic fibers and involve the activation of both alpha- and beta-adrenoceptors. Concerning DBP, this effect is especially mediated by the activation of alpha-adrenoceptors.(ABSTRACT TRUNCATED AT 250 WORDS)

[Computerized analysis of cardiovascular activity in the conscious unrestrained rat. Application to the study of a new antihypertensive agent]. / Analyse informatisée de l'activité cardiovasculaire chez le rat conscient et non restreint. Application à l'étude d'un nouvel antihypertenseur.

A more precise knowledge of cardiovascular activity in rats needs its direct recording for long periods of time, in conscious unrestrained animals. A system has been developed, which allows direct recording of blood pressure (BP) in freely moving rats, by means of a floating catheter chronically inserted in the abdominal aorta, connected to a rotating swivel, and then to a pressure transducer. A mini-computer performs on-line processing of BP curves, and stores the values of 5 cardiovascular parameters on hard disk: systolic, diastolic and mean arterial pressures, heart rate and dp/dt max. Off line processing allows graphic and statistical analysis of the data. Simultaneously recording from two rats is very useful in pharmacology because a treated animal and a control one are studied at the same time and in the same conditions. This methodology was used to evaluate the effects of a chronic treatment (2 mg/kg, ip, during 8 days) and of single injections (0.5 and 3 mg/kg, iv) of a new antihypertensive substance, CM 40441a, in 15 W old males SHR.

[Comparison of three methods for the estimation of spontaneous cardiac baroreflex sensitivity in normotensive and hypertensive subjects]. / Comparaison de trois méthodes d'estimation de la sensibilité du baroréflexe cardiaque spontané chez l'homme normotendu et hypertendu.

This study aimed at comparing estimations of spontaneous cardiac baroreflex sensitivity (BRS) obtained with 3 different methods from continuous non-invasive blood pressure recordings in humans. A new method, allowing the quantification of the statistical dependence between values of 2 parameters (Z coefficient), was applied to beat-to-beat systolic blood pressure (SBP) and heart period (HP) values. SBP and HP values with positive Z coefficient and corresponding to baroreflex activity (SBP and HP values both lower or higher than the modal values) were submitted to a linear regression and the regression coefficient (Zgain) was taken as an index of BRS. Second, cross-spectral analysis of SBP and HP gave a BRS value (Csgain) computed as the average value of transfer function moduli for frequencies between 0.07 and 0.14 Hz, with coherence between SBP and HP greater than 0.5. The third method relies on the analysis of linear sequences (r > 0.97) containing at least 3 values of SBP and HP varying in the same direction. The average regression coefficient obtained from all selected SBP and HP sequences is the index of BRS (Seqgain). SBP and HR were recorded during 1 hour with a Finapres in 10 healthy male volunteers (NT), 23 to 32 year-old (SBP: 123 +/- 2 mmHg) and 10 recent and untreated hypertensive subjects (HT) (SBP: 152 +/- 6 mmHg). [table: see text] These results show that, in both groups, Zgain and Seqgain correlated with Csgain. No correlation was found between Zgain and Seqgain in healthy volunteers whereas the correlation was strong in hypertensives probably due to more heterogeneous SBP levels and BRS values in these subjects. This suggests that these methods are sensitive to different ways of response of the baroreflex.

[The sympathetic and renin-angiotensin systems are complementary in blood pressure regulation]. / Les systèmes sympathique et rénine angiotensine se complètent pour contrôler la pression artérielle.

The consequences of a chronic destruction of sympathetic nerves or of the blockade of the renin angiotensin system (RAS) on the blood pressure (BP) level and its spontaneous variability were studied using a computerized method which allows a continuous monitoring of BP in conscious unrestrained rats. Guanethidine, used to lesion the sympathetic fibres did not alter the BP level but significantly enhanced its variability. On the opposite, angiotensin converting enzyme inhibition decreased the BP level without changing its variability. It is concluded that both systems play a complementary role as the RAS determines the long-term BP level while the sympathetic nerves control its short-term variability in conscious animals.

Cardiovascular effects of S 9490-3, a new converting enzyme inhibitor: a computerized study in conscious spontaneously hypertensive rats.

The acute cardiovascular effects of S 9490-3, a new angiotensin converting enzyme (ACE) inhibitor, were studied by means of a computerized analysis of the intra-aortic blood pressure (BP), recorded continuously for 48 h in conscious, unrestrained, adult spontaneously hypertensive rats (SHR). The first 24-h recording period was used as a control. On the second day, the rats received a single intravenous (i.v.) injection of S 9490-3 (0.2 mg/kg) at 11 a.m. followed by another 2 mg/kg i.v. injection at 3 p.m. Cardiovascular activity was studied up to 8 a.m. the next day. No significant cardiovascular effects appeared after the 0.2 mg/kg dose, whereas the 2 mg/kg dose induced a rapid fall in systolic and diastolic BP, which remained significant for about 11 h. This BP decrease was not associated with any elevation in heart rate, but with a short lasting increase in dP/dt max. These results are in good agreement with those already obtained with S 9490-3 in various experimental conditions. They suggest that long-term recordings of intra-arterial BP in freely moving rats is of value in the study of drugs which act on the cardiovascular system.

Baroreflex modulation of blood pressure and heart rate variabilities in rats: assessment by spectral analysis.

The role of the baroreflex in the spectral characteristics of mean arterial pressure (MAP) and heart rate (HR) was investigated in 12 control rats and 9 rats with chronic sinoaortic baroreceptor denervation (SAD) during 1) basal conditions and 2) ganglionic blockade with chlorisondamine and restoration of the basal MAP level. In SAD rats, power spectral density of MAP, estimated by a fast Fourier transform, was reduced in the low-frequency (LF, 0.27- to 0.74-Hz) band. Ganglionic blockade highly decreased LF power spectral density of MAP in control rats. No relationship was found between the MAP response to chlorisondamine, taken as an index of the sympathetic vasomotor tone, and the basal LF power spectral density. Transfer function analysis between MAP and HR showed that, in control rats, coherence was high for frequencies surrounding the LF and high-frequency peaks. In SAD rats, coherence was abolished in the LF band but maintained in the high-frequency band. In conclusion, approximately 80% of the LF power spectral density of MAP depends on the sympathetic nervous system activity, and the baroreflex accounts for one-half of this power and for the coherence between MAP and HR oscillations in the LF band.

Antihypertensive effects of S9490-3, a new converting enzyme inhibitor, in the conscious spontaneously hypertensive rat.

The acute and chronic cardiovascular effects of S9490-3, a new converting enzyme inhibitor, were studied by means of a computerized analysis of the intra-aortic blood pressure recorded for 48 consecutive hours, in the conscious, unrestrained adult spontaneously hypertensive rat (SHR). The software used allowed the simultaneous study of one control and one treated animal. A single intravenous dose of S9490-3 (2 mg/kg) induced a rapid fall in systolic and diastolic blood pressure, which remained significant for 11 h. This decrease was not associated with an elevation in heart rate. A chronic oral treatment with S9490-3 (1 mg/kg/24 h for 12 days) significantly lowered systolic and diastolic blood pressure and reduced the variability of systolic blood pressure. The heart rate was slightly increased at rest (day time) but significantly elevated in the freely exercising SHR (night time). However, it must be noted that this increase remained moderate. The baroreflex sensitivity of chronically treated animals was enhanced when measured after phenylephrine but not after nitroglycerine bolus. Chronically given S9490-3 significantly reduced the pressor effect of phenylephrine and decreased the left ventricle weight.

Computer analysis of intraarterially recorded blood pressure in conscious unrestrained rats.

A precise knowledge of cardiovascular activity and its pharmacological modifications in the conscious unrestrained animal requires intraarterial blood pressure recording for long periods of time. For that purpose, a technique was developed involving chronic catheterization of the rat abdominal aorta and the use of a computer system to perform the digitization of the blood pressure signal and the on-line calculation of five cardiovascular parameters. By means of duplexing, two rats (one treated and one control) can be studied simultaneously. Off-line processing is devoted to the graphic treatment and statistical analysis of the data. The effects of a single intravenous administration of dihydralazine are presented in order to show the usefulness of the technique.