Pulsatile Features of Major Arteries in Rats during Hypotension Caused by Acute Blood Loss.

The study examined the modes of pulsations of the femoral and carotid arteries of rats in situ (n=14) during acute blood loss, which sequentially caused a deep BP drop, cardiac and respiration arrest, and termination of ECG signals. When BP dropped to 19 (13; 26) mm Hg, the mechanosensitivity of passively pulsing arteries determined by the ratio of the swing range of electroimpedance oscillations of arterial segment to pulse pressure increased by 3.2 (2 ; 4) times (p<0.05). During the decrease of BP to the threshold value of 13 (8; 15) mm Hg, the arterial pulsing mode changed from passive to intermediate and then to the active one characterized by constriction of arterial segment in response to systolic elevation of BP. After cardiac arrest and BP drop almost to zero, the arterial pulsing switched to autonomic rhythmical vasomotions with the rate, which was greater than the frequency of still sustained QRS pulses of ECG. The observed phenomena are explained by transarterial hypotensive transition hypothesis, which argues that peculiarities of pulsations and vasomotions of major arteries during deep BP drop are typical of arterioles under normal or diminished BP. The study refined the hypothesis of "peripheral heart" and its role in hypo- and hypertension.

Chronic Effects of Modeled Myocardial Infarction, Thoracic Trauma, and Denervation of Hind Limb on Rheographic Parameters of Rat Femoral Arteries In Situ.

In experiments on narcotized male rats (n=85), the mean electroimpedance Z and peak-to-peak magnitudes (the swing ranges) of passive (ΔZp) and active (ΔZa) pulsatile electroimpedance oscillations of isolated segment of femoral arteries were determined in situ. These rheographic parameters (RP) were measured in intact animals and in those with modeled chronic myocardial infarction, chronic denervation of the right hind leg, as well as in rats subjected to sham operations to mimic denervation or infarction (with thoracic trauma). The rats with modeled myocardial infarction demonstrated decreasing trends of all RP. In sham-operated rats with thoracic trauma, ΔZp increased significantly on postsurgery months 2-4 by 4.3 times in comparison with the control. No essential correlation was found in denervated rats between RP of any femoral artery and severity of neuropathic pain syndrome assessed by autotomy of the operated leg. In these rats, the mean electroimpedance Z of any femoral artery was significantly greater than the control level. They demonstrated especially high values of ΔZp with significant difference between ΔZp of innervated and denervated hind leg. In denervated rats, ΔZa was significantly greater than the control value without significant difference between ΔZa of both femoral arteries. The paradoxically great increase of ΔZp (100- and 50-fold for innervated and denervated legs, respectively) and a significant 3-fold increment of ΔZa in both hind legs provoked by denervation of one of them are discussed in relation to searching for the ways of systemic influences on vascular network in clinics and experiments.

Hydrodynamic model of blood flow in major arteries pulsing in various modes.

Traditionally, the arteries in mammals are viewed as the tubes with elastic wall, whose elasticity could be slowly (during a minute) tuned to change its diameter thereby regulating regional blood supply. Recent findings showed that an artery is a much more sophisticated organ, which can change elasticity of vascular wall within a fraction of a second during a cardiac cycle due to activation of its smooth muscles manifested by generation of arterial action potentials. The rapid variations in elasticity of vascular wall resulted in three basic modes of arterial pulsing: passive, active, and intermediate. The latter is characterized by counteraction of dilation force of arterial pressure and the contractile one of smooth muscle in arterial wall, which can result in seemingly "rigid" artery of constant diameter. The prevalence of any of these forces results in active or passive pulsing modes. Existence of various pulsing modes raises the question of their effect on the main function of blood vessels, i.e., the transport of blood. The aim of this study is to assess the effect of various modes of arterial pulsing on hydraulic impedance of major arteries. The linearized Navier-Stokes equation was employed to develop a model of pulsatile flow of viscous incompressible fluid at small velocity via a conduit artery with the walls of variable or constant elasticity. An essential feature of the developed model is the shape of variable pressure drop applied to the ends of arterial segment, which simulates the real changes in arterial pressure during the heartbeat. Here, it is modeled by periodic (systolic) positive bell-shaped impulses with maxima corresponding to systolic arterial pressure, while the minimal plateau level refers to diastolic arterial pressure. The model assesses the changes in arterial hydraulic impedance during a cardiac cycle relatively to the stable level corresponding to constant blood flow driven by persistent pressure drop. Within intermediate variety of pulsing modes between the active and passive ones, the approximation of rigid arterial segment with infinite elasticity of arterial wall showed that hydraulic impedance in rigid artery is not constant due to inertial properties of the flowing blood. In passive pulsing mode characterized with constant elasticity of arterial wall, the diameter of artery changes in parallel with systolic pressure applied to the ends of arterial segment. At this, the overall change of hydraulic resistance is negative. In active pulsing mode, elasticity of arterial wall varies at different phase shifts relative to arterial pressure due to periodic contractions and relaxation of the smooth muscles in arterial wall. An important feature of active mode is possibility to decrease the hydraulic impedance during the front of arterial pressure. Various experimental modes of artery pulsing can be mathematically simulated. The passive and active modes of pulsing as well as a broad variety of intermediate pulsing modes with various phase shifts between arterial pressure and its diameter result in potency of the arteries to tune its performance in order to meet the regional circulatory requirements. The model showed that active arterial pulsing can diminish the arterial hydraulic impedance and contribute to the work needed for circulation thereby helping the pumping action of the heart.

Relationship between Passive and Active Pulsations of Rat Artery as Vascular Extension of Frank-Starling Law.

The experiments on narcotized male rats (n=30) determined the parameters of passive and active pulsatile modes of isolated segment of femoral artery in situ. Rheographic elasticity (RE) and reactivity (RR) were correspondingly determined as the ratios of peak-to-peak (p2p) magnitudes of passive and active pulsatile oscillations of arterial electroimpedance (AEI) to p2p magnitude of BP undulations. The medians and interquartile ranges of RE and RR were 6 (3; 11) and 70 (40; 110) mΩ/mm Hg, respectively. The maximal and minimal values of RE and RR in various rats differed by 50 and 80 times, respectively, and were bimodally distributed: in major group (n=23), the values were RE<15 and RR<200 mΩ/mm Hg, whereas in minor group (n=7), these parameters were RE>20 and RR>300 mΩ/mm Hg. The above ranges of RE and RR parameters were considered as the diagnostic signs of normal and pseudo-healthy rats with pathologically augmented AEI oscillations, respectively. Statistical analysis of all rats (n=30) revealed the positive correlation between RE and RR (r=0.76) with linear regression RR=31+7.6×RE. It is hypothesized that this correlation is underlain by a mechanism similar to that described by the Frank-Starling law for myocardium.

Effect of Alternating Electric Current on Pulsation Mode of Rat Major Arteries In Situ.

In experiments on narcotized rats, the electrical potential and impedance of isolated segment of the right femoral and/or carotid artery were simultaneously recorded in situ via two extracellular nonpolarizable Ag/AgCl electrodes mounted along the arteries at the interelectrode distance of 4 mm. The active, passive, and intermediate pulsing modes of arterial segment were determined according to the phase relations between its electrical impedance and BP, which was simultaneously measured in the symmetrical part of the respective left artery and used to assess pressure in the examined segment. The study assessed the effect of amplitude (0.2-2.0 mA) of alternating probe current (100 kHz), which was used to measure the electrical impedance of arterial segment, on its pulsing mode. The pulsing mode determined at the initial minimal probe current of 0.2 mA was passive with out-of-phase pulsatile oscillations of electrical impedance and BP. After elevation of the probe current amplitude to maximal level of 2 mA, these oscillations became in-phase indicating transition of the arterial segment to active pulsing mode. This transition was accompanied by appearance of arterial voltage impulses synchronized with BP upstrokes and an 11-fold median increase in the peak-to-peak value of electrical impedance oscillations with the interdecile range of 7-15 (N=28). Under moderate amplitude of probe current (0.3-0.5 mA), the intermediate mode of arterial pulsing was observed featured by a delayed, weak, and short active constriction during BP front, which was insufficient to resist and counterbalance the dilating effect of rising BP. In this case, the pulsatile oscillations of electrical impedance were smaller than those observed in active or passive pulsing modes indicating a possibility to stabilize the arterial diameter during pulsatile oscillations of BP. The effect of alternating electric current on the mode of arterial pulsation is explained with electrical model of smooth muscle cell membrane reflecting the rectifying features of potassium channels and predicting membrane hyperpolarization in response to external alternating current passing across the cell. The visibilities of therapeutic neurotropic and angiotropic stimulation with alternating electric current are discussed.

Pelvic Electric Potential as a Marker of Autonomic Dysfunctions and Risk Factor of Neurogenic Arrhythmias in Humans.

Differential high-resolution ECG (V1-V2) and pelvic electric potential measured between the coccyx and perineum were recorded simultaneously in resting supine position in men with autonomic nervous system disorders (N=37). In healthy volunteers (N=23), the effective (rms) value of PEP presented by median and interdecile range was 30 (20-80) µV within the frequency band of 0.03-80 Hz. In patients, the corresponding value was significantly higher: 140 (80-280) µV. In both groups, the amplitude harmonic spectrum of pelvic electric potential decreased monotonically with frequency according to 1/f1.6 law. In some patients (N=16), rare single or grouped high-amplitude impulses (up to 1 mV) of pelvic electric potential with total duration of about 1 sec were observed; of them, some persons (N=7) demonstrated practically one-to-one synchronous relations between these impulses and arrhythmia episodes indicating abnormal activity of the autonomic nervous system as their most probable common cause. The high-amplitude pelvic electric potential impulses were also observed in ECG records as interference signals with an amplitude attaining 50 µV. Thus, high-resolution ECG and pelvic electric potential can reveal the risk of abnormal neurogenic influences on the heart. The data obtained are discussed in relation to diagnostics of the autonomic nervous system disorders, neurogenic arrhythmias, and risk of sudden cardiac death.

Bimodal Electrical Properties of Rat Major Artery Segment In Situ.

In experiments on narcotized rats, BP in the left femoral artery as well as local electrical potential and electrical impedance of the symmetric segment of the right femoral artery were simultaneously recorded in situ with two extracellular nonpolarizable Ag/AgCl electrodes located along the artery at a distance of 3 mm from each other. The pulsatile arterial electrical potentials with amplitude of 100-200 µV and duration of about 50 msec were recorded, which coincided with the front of BP wave corrected for a 10-msec delay of the pressure transducer. Under normal conditions, the pulsatile oscillations of arterial electroimpedance were in-phase with BP oscillations, so the rising phase of BP was paralleled by elevation of electroimpedance reflecting constriction of the arterial segment. This finding is viewed as indicative of periodic myogenic Ostroumov-Bayliss effect triggered by arterial pulse. After local application of tetrodotoxin (3×10-7 М), procaine (0.5%), or lidocaine (spray 10%) to isolated arterial segment, its electroimpedance oscillated out-of-phase with BP, so the changes of electroimpedance were similar to the response of a passive elastic tube to pulsatile BP. The applied agents completely (tetrodotoxin) or pronouncedly (procaine, lidocaine) inhibited the pulsatile arterial electrical potential. The present data indicate the possibility of passive and active modes of arterial pulsing, which differ by the amplitude of pulsatile arterial electrical potential as well as by phasic relations between BP and electroimpedance. The possible physiological role of various modes of pulsing in major arteries is discussed.

Effect of Doxazosin on Autonomic Nervous Control and Urodynamics of Rat Urinary Bladder during Modeled Infravesical Obstruction.

The therapeutic effect of doxazosin (40 µg/kg/day over one month) on urinary bladder was examined in female rats with modeled chronic infravesical obstruction (IVO) produced by graduated mechanical constriction of the proximal urethral segment. In one month, IVO induced a pronounced vesical hypertrophy both in treated and untreated rats that manifested in increased bladder weight and capacity, the latter increment being pronouncedly greater in treated rats. In untreated IVO rats, infusion cystometry revealed elevated basal intravesical pressure of void bladder P0, markedly increased maximal (premicturitional) pressure Pmax, and increased amplitude of spontaneous oscillations of intravesical pressure ΔPdet in filled bladder. Doxazosin produced no significant effect on Pmax rise during IVO, but prevented elevation of P0 and increment of ΔPdet in filled bladder. During gradual filling of urinary bladder in control (intact) rats, the parasympathetic vesical influences increased progressively, while in untreated IVO rats, the adrenergic influences prevailed even at maximal filling of the bladder. In IVO rats, doxazosin prevented the bias of the sympathetic-parasympathetic balance in the filled bladder in favor of sympathetic influences, but did not prevent this bias in a void bladder. It is hypothesized that α-adrenoblockers improve micturition during IVO caused by benign prostatic hyperplasia not only by decreasing the urethral resistance to urine flow due to down-regulation of prostate smooth muscle tone, but also by a direct action of these blockers on detrusor adrenergic receptors and central structures involved in urinary bladder control.

Electrical Rhythms Revealed by Harmonic Analysis of a High-Resolution Cardiogram.

The front-end low-noise electronic amplifiers and high-throughput computing systems made it possible to record ECG with a high resolution in the low-frequency range including the respiration and Mayer frequencies and to analyze ECG with digital filtering technique and harmonic analysis. These tools yielded ECG spectra of narcotized rats, which contained the characteristic pulsatile triplets and pentaplets with splitting constant equal to respiration rate, as well as the peaks at respiration and Mayer frequencies. The harmonic analysis of ECG determined the frequency parameters employed to tune the software bandpass filters, which revealed the respiratory (R) and Mayer (M) waves in the time domain with the amplitudes of 20-30 µV amounting to 5% ECG amplitude. The depolarizing myorelaxant succinylcholine chloride capable to trigger various types of arrhythmias, transiently increased R-wave, inhibited M-wave, and provoked a negative U-wave within a heartbeat ECG cycle synchronously with inspiration. It is hypothesized that M-, R-, and U-waves in ECG reflect cardiotropic activity of autonomic nervous system. The respective spectral peaks in ECG can be employed to assess intensity of sympathetic and parasympathetic cardiotropic influences, their balance, and the risk of arrhythmias.

Ischemia in pelvic organs as an independent pathogenic factor in the development of benign prostatic hyperplasia and urinary bladder dysfunction.

Blood supply to the pelvic organs of outbred male rats was diminished by graduated constriction of the distal part of the inferior vena cava. Deficiency of intramural blood supply in prostate and urinary bladder was revealed by bioimpedance harmonic analysis according to the magnitude of first cardiac peak in the bioimpedance spectrogram. In 1-1.5 months, the histological examination revealed the glandular-stromal form of progressive benign prostatic hyperplasia in all ischemic rats. The development of hyperplasia was not accompanied by the changes in testosterone, dihydrotestosterone, or estradiol in blood and prostatic tissue. Assessment of vesical functional status by recording the intravesical pressure during infusion cystometry revealed an increase in the amplitude of spontaneous fluctuations of detrusor tone and intravesical pressure during bladder filling, which can be considered as indicator of detrusor hyperactivity. The data conclude that chronic ischemia of pelvic organs is an individual pathogenic factor in the development of benign prostatic hyperplasia and associated urinary disorders.

Efficiency assessment of shock wave therapy in patients with pelvic pain employing harmonic analysis of penile bioimpedance.

In searching for novel objective methods to diagnosticate pelvic pain and assess efficiency of analgesic therapy, 37 male patients were examined prior to and after the course of extracorporeal shock wave therapy (5-10 sessions) with the waves directed to projections of prostate and/or crura and shaft of the penis. The repetition rate of mechanical pulses was 3-5 Hz. The range of energy pulse density was 0.09-0.45 mJ/mm(2). The overall number of pulses in a session was 1500-3000 in any treated zone with total energy smaller than 60 J. The applicator was relocated every other series of 300-500 pulses. Effect of the shock wave therapy was assessed according to subjective symptomatic scales: International Prostate Symptom Score, International Index of Erectile Function, Quality of Life, and nociceptive Visual Analog Scale. The objective assessment of shock wave therapy was performed with harmonic analysis of penile bioimpedance variability, which quantitatively evaluated the low-frequency rhythmic and asynchronous activities at rest as well as the total pulsatile activity of the penis. The magnitude of spectrum components of bioimpedance variations was assessed with a novel parameter, the effective impedance. The spectral parameters were measured in 16 patients prior to and after the treatment course. The corresponding control values were measured in the group of healthy patients. Prior to the shock wave therapy course, all spectrum parameters of penile bioimpedance significantly differed from the control (p<0.05). After this course, low-frequency rhythmic and the total pulsatile activity decreased to normal, while asynchronous activity remained significantly different from the normal. The novel objective physiological criteria of pelvic pain diagnostics and efficiency of its treatment reflecting the regional features of circulation and neural activity corresponded to the clinical symptom scaling prior to and after the shock wave course, and on the whole, these criteria corroborated improvement of the patient state after this therapy.

Assessment of intramural blood flow and neurogenic control in intact and hypertrophic urinary bladder with harmonic analysis of bioimpedance in rats.

High-resolution impedancometry and harmonic (Fourier) analysis of variable component of bioimpedance revealed rhythmic oscillations of urinary bladder bioimpedance at the Mayer wave, respiration, and heartbeat frequencies. The power values of the corresponding Mayer, respiratory, and cardiac peaks were calculated to assess circulation in the urinary bladder wall and its autonomic nervous control at various stages of infusion cystometry in intact rats and in the rats with preliminary formed infravesical obstruction (IVO). In intact rats, filling of the bladder with physiological saline diminished the power of the first (fundamental) cardiac peak attesting to a decrease of the blood flow in the bladder wall. Simultaneously, the power of low-frequency Mayer peak reflecting sympathetic activity increased, while the power of respiratory peak decreased supposedly reflecting abatement of the parasympathetic influences. Bladder voiding was accompanied by a decrease of Mayer peak and increase of the respiratory one. Prior to infusion cystometry, the intravesical pressure in IVO rats was elevated while the power of fundamental cardiac peak was below the control value. Filling the bladder in these rats was accompanied by further decrease of the cardiac peak reflecting still greater drop in blood supply. In control rats, voiding the bladder normalized the vesical circulation assessed by the cardiac peak, while in IVO rats this peak remained decreased. The reciprocal changes of Mayer and respiratory peaks observed during infusion cystometry in the norm were replaced by unidirectional decrease in the power of both peaks in IVO rats, which probably attest to disturbance of autonomic nervous control in the hypertrophic urinary bladder in these rats.

Bioimpedance harmonic analysis as a tool to simultaneously assess circulation and nervous control.

Multicycle harmonic (Fourier) analysis of bioimpedance was employed to simultaneously assess circulation and neural activity in visceral (rat urinary bladder) and somatic (human finger) organs. The informative value of the first cardiac harmonic of the bladder impedance as an index of bladder circulation is demonstrated. The individual reactions of normal and obstructive bladders in response to infusion cystometry were recorded. The potency of multicycle harmonic analysis of bioimpedance to assess sympathetic and parasympathetic neural control in urinary bladder is discussed. In the human finger, bioimpedance harmonic analysis revealed three periodic components at the rate of the heart beat, respiration and Mayer wave (0.1 Hz), which were observed under normal conditions and during blood flow arrest in the hand. The revealed spectrum peaks were explained by the changes in systemic blood pressure and in regional vascular tone resulting from neural vasomotor control. During normal respiration and circulation, two side cardiac peaks were revealed in a bioimpedance amplitude spectrum, whose amplitude reflected the depth of amplitude respiratory modulation of the cardiac output. During normal breathing, the peaks corresponding to the second and third cardiac harmonics were split, reflecting frequency respiratory modulation of the heart rate. Multicycle harmonic analysis of bioimpedance is a novel potent tool to examine the interaction between the respiratory and cardiovascular system and to simultaneously assess regional circulation and neural influences in visceral and somatic organs.

Rhythmic oscillations of human penile bioimpedance in healthy individuals and in patients with vascular erectile dysfunction.

Small variations of electric impedance (bioimpedance) of human penis were examined in healthy volunteers and in patients with vascular erectile dysfunction (ED). The harmonic analysis revealed rhythmic oscillations of penile bioimpedance at frequencies corresponding to the heart and respiration rates and Mayer wave (0.1 Hz) and to multiple frequencies (harmonics) of the respiratory and cardiac oscillations. In normal penile bioimpedance spectrum, the Mayer and respiratory peaks were several times higher than the first cardiac (pulsatile) harmonic indicating neurogenic origin of rhythmic bioimpedance variations in the whole penis. The most of healthy individuals (78%) demonstrated the cardiac harmonics at the frequency range of 4-7 Hz that violated the monotone decrement of the pulsatile harmonic series suggesting the resonant character of oscillations of the penile arteries at this "near" frequency range. In contrast to stable 1-4 cardiac harmonics, the amplitudes of the near-range resonant harmonics could vary during few minutes suggesting a causal relation of the corresponding bioimpedance oscillations with the varying vascular tone in penile arteries. The most patients (89%) with vascular ED demonstrated not only the first 1-4 monotonically decrementing harmonics and the near-resonant ones, but also the stable cardiac harmonics at the "far" frequency range of 8-14 Hz that also disturbed the monotonic character of the cardiac harmonic series indicating the sclerotic alterations in regional arteries. In ED patients, insignificant decrease of the initial cardiac harmonics C1-C3 in comparison with the norm was accompanied by pronounced and significant decrease of the respiratory R1 and Mayer M1 peaks. The study showed that the far-frequency bioimpedance resonances at the range of 8-14 Hz and dramatic drop of Mayer and respiratory peaks are the diagnostic signs of vascular ED independent on the accompanying hormonal or neurogenic disorders.

Fourier analysis of human finger bioimpedance variances.

Fourier analysis was employed to determine the amplitudes of spectrum components of small variations of electrical resistance (bioimpedance) in human finger recorded using an original hardware-software complex. It revealed periodic bioimpedance oscillations at the frequencies of heartbeats, respiration, and Mayer wave (0.1 Hz). These periodic variations were observed under normal conditions and during circulation arrest in the arm. It is concluded that the spectrum peaks of bioimpedance variations in the phalanx of human finger reflect periodic blood pressure changes in the major vessels and rhythmic neural control of the regional vascular tone. During normal blood flow, the greatest amplitude of rhythmic changes in bioimpedance was observed at the heart rate; it surpassed by an order of magnitude the amplitudes of respiratory oscillations and Mayer wave. In contrast, the largest amplitude of rhythmical changes of the impedance during circulation arrest corresponded to the oscillations at respiration rate, while the amplitude of variations at the heart rate was the smallest. Under circulation arrest, the maximum frequency of bioimpedance variations was approximately 1.4 Hz (the third respiratory harmonic), which indicates the upper limit of frequency range of neural modulation of vascular tone in human finger. During normal respiration and circulation, two side cardiac peaks were revealed in bioimpedance amplitude spectrum, whose amplitude reflected the depth of the respiratory amplitude modulation of pumping action of the heart. During normal breathing, the second and the third harmonics of the cardiac bioimpedance variations were split reflecting respiratory frequency modulation of the heart rate.

[Antiarrhythmic properties of 2-(2'-hydroxy-2')-substituted ethyl-1,2,3,4-octahydropyrrolo[1,2-a]pyrazines]. / Antiaritmicheskie svoistva 2-(2'-gidroksi-2'-zameshchennykh)-étil-oktagidropirrolo[1,2-a]pirazinov.

The antiarrhythmic activity and acute toxicity of a series of 2-(2'-hydroxy-2')-substituted ethyloctahydropyrrolo[1,2-a]pyrazines were studied. Two most promising compound (PV-238) is characterized by high antiarrhythmic activity, broad spectrum of action, and low toxicity.

Discharge activity of single muscle vasoconstrictor efferents in cats during opposite changes in arterial pressure.

Signals of individual muscle vasoconstrictor efferents of gastrocnemius muscle were recorded in narcotized cat during rise and fall of systemic arterial pressure induced by phenylephrine and sodium nitroprusside, respectively. In control, mean discharge rate of these efferents was 2.0 0.4 Hz. Phenylephrine (45 microg/kg) increased arterial pressure from 120.3 4.2 to 170.7 8.2 mm Hg. This increase was accompanied by a short-term (5-10 sec) decrease in discharge rate of muscle vasoconstrictor efferents to 0.5 0.3 Hz followed by virtually complete recovery of muscle discharge rate against the background of increased arterial pressure. Sodium nitroprusside (30 microg/kg) decreased arterial pressure from 132.8 6.2 to 64.1 4.3 mm Hg. Under these conditions the discharge rate of vasoconstrictor efferents increased to 3.5 0.6 Hz and remained at this level throughout the hypotension period (2-3 min). Unloading of baroreceptors (occlusion of the carotid artery) increased the discharge rate of muscle vasoconstrictor efferents throughout the occlusion period (up to 30 sec). Thus, blood pressure rise and drop induced asymmetric by their duration changes in the discharge responses of muscle vasoconstrictor efferents. Phenylephrine increased asymmetry of the vasoconstrictor component of the baroreflex and induced cumulative rise of discharge rate of muscle vasoconstrictor efferents in response to a series of short-term reversible blood pressure jumps caused by repeated occlusions of the abdominal aorta. Our findings extend our knowledge on the efferent component of the baroreflex regulation and on possible mechanisms of hypertension.

Stimulus-dependent effects in the actions of sodium channel blockers on sensory C-units.

Stimulus-dependent inhibition of discharges from cutaneous C fibers from mechanothermo-sensitive (MTS) units (nociceptive sensors) can explain the paradoxical analgesic effect of local anesthetics at low concentrations, insufficient to block axonal conduction of nerve impulses. Three types of experiments are proposed which could detect the stimulus-dependent inhibition of the terminal section of sensory C units: a method involving repeated series of stimuli, the increasing stimulus method, and the spike encounter method. The applications of these methods to assessing the magnitudes of the neuroleptic effects of local anesthetics and cardiac antiarrhythmics is discussed.

[Stimulus-dependent effects of the sodium channel blockers in the C-fiber sensory units]. / Stimulozavisimye éffekty pri deistvii blokatorov natrievykh kanalov na sensornye C-edinitsy.

The data obtained suggest a use-dependent inhibition in the skin terminals of the C-fibre sensory units. The terminals are discussed in respect to search of efficient local anaesthetising agents as well as cardiac anti-arrhythmic agents with obvious neurotropic effects.