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Previous studies in anesthetized normotensive rats demonstrated that a single mouth opening for 10 min obtained by an ad hoc dilator (mandibular extension [ME]) produced a blood pressure reduction by about 20 mmHg lasting for about 2 h and that once-repeated ME prolonged this effect. We here describe these effects in hypertensive rats. Mean (intra) arterial blood pressure (MABP) and heart rate (HR) was followed for up to a maximum of 470 min after single or repeated 10 min-lasting ME in two groups of anesthetized, male, 6-9 months old hypertensive rats. In one group, hypertension was induced by dexamethasone (20 μg/kg/day, subcutaneously for 7 days; Dex-HT); the other group was spontaneously hypertensive rats (SHR). Studies were done, in Dex-HT rats, after only surgical procedures (no ME, sham-operated rats), single ME, early repeated (after 10 min) ME (ER-ME) and late repeated (after 160 min) ME (LR-ME) and, in SHR, after only surgical procedures and ER-ME. One-way ANOVA for repeated measures revealed no significant effect on MABP and HR in sham-operated groups. In Dex-HT rats, single ME was followed by a significant MABP decline by 25 mmHg, lasting for 100 min; ER-ME and LR-ME were followed by an even greater significant MABP decline by 40 mmHg, which outlasted the experimental observation period. In SHR, ER-ME gave similar results as in Dex-HT rats. HR significantly declined in all, except sham-operated groups. In conclusions, ME is followed by a prolonged MABP decline also in hypertensive rats. This effect is even more pronounced, in length and magnitude, after repeated ME., (© 2018 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.)

Purpose: We have recently shown that in humans submaximal mouth opening associated with partial masticatory movements for 10 min is followed by a small but significant and prolonged reduction of blood pressure and heart rate. We here report the effects of a fixed mouth opener., Methods: In 22 seated normotensive volunteers the effect on blood pressure and heart rate was studied in randomized order after fixed mandibular extension and after a control procedure consisting in keeping a stick between the incisor teeth (both for 10 min). Automated recordings every 10 min were done for 40 min before and 120 min following the procedure., Results: Two-way ANOVA for repeated measures on absolute values (actual recordings) and on changes from baseline revealed that, compared to controls, systolic, diastolic and mean blood pressure and heart rate were significantly lower after mandibular extension. Compared to controls, mandibular extension induced an average blood pressure drop of 2.88 mmHg (systolic), 2.55 mmHg (diastolic) and 2.42 mmHg (mean) over the entire observation period. The average decline over the central part of the observation period (30th to 80th min) was, respectively, of 3.62, 3.70 and 3.61 mmHg. The decrements of heart rate were of 2.11 and 2.66 beats per min. All these differences were statistically significant. The hypotensive and bradycardic responses persisted for 70-120 min., Conclusions: This study shows that, in normotensives, a single fixed submaximal mouth opening for 10 min is followed by prolonged albeit small reductions of blood pressure and heart rate.

The trigemino-cardiac reflex is a brainstem reflex known to lead to a decrement in heart rate and blood pressure, whereas few data have been collected about its effects on the cerebral hemodynamic. In this study we assess the in vivo effects of trigeminal nerve peripheral stimulation by mandibular extension on pial microcirculation and systemic arterial blood pressure in rats. Experiments were performed in male Wistar rats subjected to mandibular extension obtained inserting an ad hoc developed retractor between the dental arches. Mean arterial blood pressure and heart rate were recorded and the pial arterioles were visualized by fluorescence microscopy to measure the vessel diameters before (15 minutes) during (5-15 minutes) and after (80 minutes) mandibular extension. While in control rats (sham-operated rats) and in rats subjected to the dissection of the trigeminal peripheral branches mean arterial blood pressure, heart rate and pial microcirculation did not change during the whole observation period (110 minutes), in rats submitted to mandibular extension, mean arterial blood pressure, heart rate and arteriolar diameter significantly decreased during stimulation. Afterward mean arterial blood pressure remained reduced as well as heart rate, while arteriolar diameter significantly increased evidencing a vasodilatation persisting for the whole remaining observation time. Therefore, trigeminal nerve proprioceptive stimulation appears to trigger specific mechanisms regulating systemic arterial blood pressure and pial microcirculation.

Various procedures involving stimulations of facial regions are known to induce so-called trigemino-cardiac reflexes that entail a decrease of heart rate and blood pressure. We here report the effects of a specific stimulation that consists in a submaximal passive mandibular extension obtained by means of a dilatator applied for 10 minutes between the upper and lower incisor teeth, associated with partial active masticatory movements. Blood pressure and heart rate were determined in 18 young normal volunteers by Omron M4, before (20 minutes), during (10 minutes) and after mandibular extension (80 minutes) and under control conditions (same overall duration without stimulation). While control values remained stable, mandibular extension was followed by a progressive decline of both blood pressure (up to about 12/11 mmHg) and heart rate (up to about 13 bpm), statistically confirmed by ANOVA both on absolute values and on changes from basal values. The decline of systolic blood pressure and heart rate significantly correlated with basal values. The present findings indicate that submaximal opening of the mouth, associated to partial masticatory movements, induces a prolonged reduction of blood pressure and heart rate in normotensive volunteers.

There is evidence suggesting that exposure to an abnormal magnetic environment may produce psychophysiological effects related to abnormalities in responses to stress. This may be of relevance for space medicine where astronauts are exposed to a magnetic field different from that exerted by the Earth. Aim of this study was to assess how the exposure of the head to a magnetic field simulating the one encountered by the International Space Station (ISS) during a single orbit (90 min) around the Earth affects the cardiovascular and psychophysiological parameters. Twenty-four human volunteers were studied double blindly in random order under sham and magnetic exposure. During exposure, the persons were shown a set of pictures of different emotional content while subjective self-rating, skin conductance (SC), blood pressure (BP), and heart rate (HR) were measured. In addition, BP, HR, and tooth pain threshold were assessed before and after exposure. While subjects were under magnetic exposure, skin conductance was strongly differentiated (F(2,36)=22.927; p=0.0001), being high during emotionally involving (positive and negative) pictures and low during neutral pictures. Conversely, when subjects were under sham exposure, no significant differences were observed. There was, however, a trend for higher heart rate during picture viewing under magnetic exposure as compared to sham exposure. No effects were found for the other variables. These results suggest that an abnormal magnetic field that simulates the one encountered by ISS orbiting around the Earth may enhance autonomic response to emotional stimuli.

Previous studies have shown that exposure to an electromagnetic field (EMF) of 37 Hz at a flux density of 80 microT peak enhances nociceptive sensitivity in mice. Here we examined the effects on pain sensitivity and some indexes of cardiovascular regulation mechanisms in humans by measuring electrical cutaneous thresholds, arterial blood pressure, heart rate and its variability, and stress hormones. Pain and tolerance thresholds remained unchanged after sham exposure but significantly decreased after electromagnetic exposure. Systolic blood pressure was significantly higher during electromagnetic exposure and heart rate significantly decreased, both during sham and electromagnetic exposure, while the high frequency (150-400 mHz) component of heart rate variability, which is an index of parasympathetic activity, increased as expected during sham exposure but remained unchanged during electromagnetic exposure. Cortisol significantly decreased during sham exposure only. These results show that exposure to an EMF of 37 Hz also alters pain sensitivity in humans and suggest that these effects may be associated with abnormalities in cardiovascular regulation., (Copyright 2004 Wiley-Liss, Inc.)

Objective: Episodic reports suggest that geomagnetic disturbances of solar origin are associated with biological and clinical events, including increased arterial blood pressure (BP). We reassessed this aspect by relating solar activity levels to ambulatory BP measured in our out-patient population., Patients and Methods: The ambulatory BP measurements of 447 consecutive untreated patients attending a hypertension out-patient clinic who did a monitoring for diagnostic purposes over 5 years were retrieved. The mean daytime, night-time and 24-h BP and heart rate values were related to the temporally corresponding geomagnetic index k-sum obtained by the nearest observatory. K-sum is a local measurement of the irregular disturbances of the geomagnetic field caused by solar particle radiation., Results: Significant to highly significant positive correlations were observed for k-sum with systolic (daytime and 24 h) and diastolic BP (daytime, night-time and 24 h), but not with heart rate. No correlations were found with the k-sum of 1 or 2 days before the monitorings. Multiple correlations which also included other potential confounding factors (date, age) confirmed a significant effect of k-sum on BP. Comparison made in season-matched subgroups of quiet and disturbed days (using three different criteria of definition), always showed significantly higher values in the disturbed days for all BP parameters except systolic night-time pressure. The difference between the quietest and the most disturbed days was of about 6 to 8 mm Hg for 24-h systolic and diastolic BP., Conclusion: These results are unlikely to be due to unrelated secular trends, but seem to reflect a real relation between magnetic field disturbances and BP.

An association between hypertension and decreased pain perception (hypoalgesia) has been shown in experimental hypertension and confirmed in humans by electrical tooth pulp stimulation. The aim of this study was to confirm, using two other techniques, whether hypertension is associated with hypoalgesia in humans. In 77 untreated essential hypertensive outpatients, 37 normotensive outpatients and 27 normotensive volunteers subjective cutaneous sensitivity was assessed by an electrical stimulator. Thirty-three measurements were repeated after one month. In addition, in eight normotensive volunteers and eight hypertensives the thresholds of the polysynaptic components R2 and R3 of the blink reflex to electrical stimulation of the supraorbitalis nerve were evaluated. Tooth pulp stimulation was done in 85 of the subjects who measured cutaneous sensitivity and in all of the blink reflex study. Cutaneous perceptive, pain and tolerance thresholds were significantly higher in the hypertensives compared with both normotensive groups, with no significant difference between these two. The results were identical when age and sex-matched subgroups were compared and a high reproducibility was found for all three parameters. Similar findings were obtained for the tooth pulp thresholds and highly statistically significant correlations were found between cutaneous and tooth pulp sensitivity and between these indices and blood pressure. The thresholds of R2 and R3 were also significantly higher in the hypertensives and a significant correlation was found between R3 threshold and diastolic pressure. These results confirm that hypertension is associated to hypoalgesia in humans.

In arterial hypertension, casual blood pressure seems to be weakly related to the level of cardiac involvement. The aim of the present study was to assess if blood pressure during ambulatory monitoring, and during different stress tests, is a stronger predictor of anatomical and functional changes observed in hypertensive heart disease. To this aim, 29 untreated patients with borderline-to-moderate essential hypertension underwent an echo-Doppler evaluation to determine left ventricular thickness and mass. From transmitral flow, the ratio between late and early filling velocities (A/E ratio) was used to assess left ventricular diastolic behaviour. On the same day that ultrasonic study was carried out, we also measured a set of casual blood pressures; conducted a mental arithmetic test (standardized series of mental subtractions); a handgrip test (30% of maximum voluntary contraction for 3 minutes); and performed noninvasive ambulatory monitoring of blood pressure (Spacelabs 5200). Significant relationships were observed between left ventricular mass and both night-time systolic blood pressure (r = 0.46, P less than 0.02) and peak systolic blood pressure during mental stress (r = 0.39, P less than 0.05). The A/E ratio was significantly associated with casual systolic and diastolic blood pressure (r = 0.45, P less than 0.02; r = 0.38, P less than 0.05, respectively); day-time diastolic blood pressure (r = 0.47, P less than 0.02); night-time systolic and diastolic blood pressure (r = 0.44, P less than 0.05; r = 0.42, P less than 0.05 respectively); and peak systolic blood pressure during the mental arithmetic test (r = 0.44, P less than 0.05). Our results seem to confirm the presence of a relationship between causal blood pressure and left ventricular filling. Moreover, the transmitral flow seems to be dependent on both mean levels of blood pressure on ambulatory monitoring and systolic blood pressure during mental stress. As concerns left ventricular mass, the correlations observed support the weakness of the links between blood pressure and left ventricular anatomy.

Several data suggest the possible involvement of serotonin (5HT) and of the serotoninergic (5HTergic) system in the pathophysiology of essential hypertension. Our study aim was thus to measure a peripheral 5HTergic marker, such as platelet 5HT uptake, in 8 hypertensive patients, as compared with healthy controls. All subjects included underwent evaluation of the pain threshold, in view of the possible relationship between mechanisms involved in pain modulation and those regulating blood pressure. The results showed a decrease of the maximal velocity (Vmax) of platelet 5HT uptake in the patients, who also exhibited an increase in the pain threshold. These data, although preliminary, are suggestive with regard to an increased concentration of extraplatelet 5HT, which might play a role in both hypertension and the change in pain threshold.

Ambulatory blood pressure (BP) monitoring has been extensively utilized, so far, for studying BP profile and hypotensive treatment in arterial hypertension. In this paper, preliminary data will be reported from a clinical study on the possible contribution of the combined ECG and BP monitoring in clarifying mechanisms of dizziness in patients with multiple or complex cardiovascular problems. Results are shown of three patients with ischaemia, arrhythmias and/or episodes of hypotension, and of three patients with borderline hypertension and marked fluctuations of BP.

Ambulatory monitoring of the intra arterial blood pressure (IBP), through the Selyg-Oxford System, has been used so far primarily for studies on hypertension. Aim of our study is to explore the possibility of obtaining from IBP indications useful to extend its field of application. The study will investigate: the usefulness of the continuous monitoring of the systolic time intervals (STI), measured from IBP as ventricular performance indicators, the increasing of specificity of the ECG allowed by the simultaneous beat by beat estimate of the STI's, the possibility of achieving the same information from non invasive peripheral pressure transducers. In this paper we are presenting the results obtained from the combined analysis of the STI's, ECG and IBP in a first series of 13 patients, selected out of 50 on the basis of the highest number of episodes of IBP variations, to allow the evaluation of the algorithms performances in severe conditions.

To investigate the seasonal influences on various arterial blood pressure measurements, 22 subjects in the high normal to mild hypertensive range were examined twice following the same protocol. In one group (13 subjects), measurements were first done in warm conditions and repeated 5-7 months later in cold conditions; in the second group (nine subjects) a reverse sequence was followed. Blood pressure was measured under casual conditions during a hand grip exercise test, mental arithmetic test, and submaximal multistage bicycle exercise test; during the following 24 hours, blood pressure was measured serially with a noninvasive ambulatory blood pressure recorder. Daily outdoor maximum and indoor laboratory temperatures were also obtained. In the cold season, significantly higher values (on the average by 5-10 mm Hg, p less than 0.01) were obtained in both groups for mean diastolic daytime blood pressure. For other measurements, a trend toward higher values in the cold season was observed in both groups, although statistical significance was not obtained in all instances. For nighttime measurements, irrespective of the seasonal sequence, lower values were observed in the second session. Significant correlations were found between the differences in the average daytime ambulatory blood pressures and the corresponding changes of daily maximum outdoor temperatures after 5-7 months. These observations indicate that arterial blood pressure may be strongly influenced by environmental temperature. This phenomenon should be taken into account both in the evaluation of the individual hypertensive patients and in the design and analysis of studies on arterial hypertension, especially when ambulatory blood pressure techniques are employed.

An association between increased blood pressure levels and hypoalgesia has been reported in the experimental animal and in man. The relation between pain perception and cardiovascular function is however still obscure. In order to gain some insight into this aspect, normotensive subjects with low and high tolerance to pain, as assessed by tooth pulp stimulation, were compared for blood pressure and heart rate during cold pressor test, 24 hr urinary catecholamines, supine and upright PRA and plasma beta-endorphin levels. No significant difference was observed between the two groups for casual blood pressure, heart rate and PRA. Compared to subjects with low tolerance to pain, those with high tolerance to pain were significantly older and had: 1) significantly higher levels of diastolic blood pressure and of beta endorphin levels during cold pressor test; 2) significantly higher beta-endorphin levels after cold pressor test; 3) a significantly higher excretion of noradrenaline (but not of adrenaline and dopamine).

Evidence has been provided on the increased presence, in essential hypertension, of endogenous digitalis-like factor(s) [DLIS, digoxin-like immunoreactive substance(s)] able to cross-react with antidigoxin antibodies and to inhibit the membrane-bound sodium-potassium pump. An inhibition of the sodium pump could lead, in smooth muscle cells, to an increase of intracellular calcium ions and to an increase of total peripheral resistances. In this study the relation between plasma levels of DLIS and the acute hypotensive effect of a calcium antagonist (nifedipine) has been evaluated in a group of borderline to severe hypertensive patients and in a control group of normotensive subjects. The results obtained confirm that the hypotensive effect of nifedipine is related to pretreatment blood pressure and show, only in hypertensive patients, a significant relation of DLIS with both pretreatment blood pressure and blood pressure decrement induced by nifedipine. These findings are compatible with a possible role of DLIS in modulating cellular calcium handling.

Blood pressure (BP) decreases significantly in patients with immune complex nephritis and hypertension in the course of therapeutic plasma exchange (TPE). To investigate possible underlying mechanisms of this effect, the variations of supine and upright BP and plasma renin activity (PRA) acutely induced by PE (performed by isovolumetric replacement of plasma with 4% albumin in saline solution) were analyzed in six patients. On the average, both supine and upright BP decreased after TPE; however, statistical significance was obtained only for upright systolic BP. Supine and upright PRA did not change significantly, although a clearly blunted response to posture was observed in three patients. The changes of BP induced by TPE were apparently not due to a functional depression of the renin-angiotensin system, since the more marked decrements in BP were observed in the patients with lower basal PRA.

The aim of this study was to evaluate the long-term reproducibility and the possible seasonal influences on casual blood pressure and ambulatory blood pressure monitoring in patients with borderline or mild arterial hypertension. Two sets of measurements were performed at 6-month intervals, one set in the warm and one in the cold season, using the same protocol, consisting of measurements of casual and ambulatory blood pressures, together with the recording of outdoor temperatures. Casual blood pressure was measured by an automatic recorder and 24-h ambulatory blood pressure monitoring was performed by a non-invasive device. For the selected intervals, the reproducibility of most pressure measurements was low; in addition, casual diastolic pressure and 24-h systolic and diastolic pressures were significantly higher in the cold than in the warm season. Taken together, these findings confirm and extend the results obtained in several large-scale studies and support the importance of taking environmental temperature into account, not only in epidemiological studies but also in small-scale studies and probably even in the individual patients, especially when using integrated evaluations by ambulatory monitoring.

The aim of the study was to evaluate the relationships between left ventricular (LV) filling and age, heart rate (HR), blood pressure (BP), and LV mass in three groups of subjects with different casual blood pressure. Twenty normotensive subjects (NT: age 39.2 +/- 7.2; BP 121.6 +/- 11.3/77.7 +/- 7.5 mm Hg), 16 borderline hypertensives (BH: age 38.6 +/- 9.2; BP 138.2 +/- 11.6/91.7 +/- 9.4 mm Hg), and 20 essential hypertensives (EH: age 44.5 +/- 8.3; BP 165.7 +/- 14.8/107.6 +/- 11.4 mm Hg) underwent 2D Echo evaluation and PW Doppler measurements of transmitral blood flow velocity. In NT, the Doppler indexes of LV filling showed significant correlations only with age and heart rate (age v E peak: r = .68 P less than .001; v A peak: r = .45, P less than .05; v A/E: r = .78, P less than .001. Heart rate v A peak: r = .78, P less than .001, v A/E: r = .74, P less than .001, respectively). Similar but weaker relationships were observed in BH. On the contrary, EH showed no significant correlations with age or heart rate, but with both systolic blood pressure (SBP), diastolic blood pressure (DBP), and LV mass (SBP v A peak: r = .49, P less than .05; v A/E: r = .68, P less than .001; DBP v E peak: r = 44, P less than .05; v A/E: r = .58, P less than .01. Left ventricular mass v E peak: r = .45, P less than .05; v A/E: r = .51, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)