Blood pressure and heart rate response to apomorphine in urethane anesthetized rats

The mechanisms involved in the hypotensive effect of apomorphine were studied in urethane anesthetized rats. The intravenous injection of apomorphine (0.01-0.75 mg/kg) produced a dose dependent fall in mean blood pressure. At the higher doses used (0.5-0.75 mg/kg) a marked bradycardia accompanied the hypotensive effect. These cardiovascular effects were prevented by pretreating the animals with pimozide (0.01-0.1 mg/kg). Low doses of haloperidol (0.03-0.3 mg/kg) did not antagonize the hypotensive action of apomorphine. Higher doses of haloperidol (1-3 mg/kg) reduced markedly the mean blood pressure. Atropine (1 mg/kg) partially antagonized the decrease in mean blood pressure induced by apomorphine and prevented completely the bradycardia. Hexamethonium (10 mg/kg) reduced the mean blood pressure and when apomorphine was administered, a residual hypotensive effect and no bradycardia was observed. It is concluded that the cardiovascular actions of apomorphine are central in origin and mainly due to the stimulation of a dopamine receptor. A probable peripheral effect could not be discarded.     

Awareness of the response after feedback training for changes in heart rate and sudomotor laterality.

Examined the relation between (a) the ability to control visceral responding on a biofeedback (BFB) task and (b) the ability to report behaviors actually contributing to this performance in 4 experiments with 97 male Ss. Ss received BFB training for unidentified visceral responses and then gave written reports about what they had done to control BFB displays. Independent judges were given these reports and, on the basis of knowledge about activities known to contribute to visceral activity, were asked to determine the visceral responses for which Ss had been trained. The reports of Ss who succeeded at bidirectional control of heart rate (Exp I) or sudomotor laterality (Exp II) showed awareness of behaviors related to BFB as assessed by this procedure, whereas the reports of Ss who failed at bidirectional control did not. Subsequent experiments indicated that these results did not depend on a learning strategy that might have been specific to the initial studies. Findings question the view that people are unaware of what they have done to produce the response after training on BFB tasks. (81 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phenylbutazone increases right atrial pressure and heart rate of running horses

The effect of inhibition of cyclooxygenase activity on the hemodynamic response to exertion was examined in 6 horses. Rates of O2 consumption and CO2 production and carotid, pulmonary arterial, and right atrial pressures were measured while the horses performed a standardized exercise test on a treadmill after treatment with phenylbutazone or a placebo. Phenylbutazone (8.8 mg/kg p.o. for 2 days and 4.4 mg/kg i.v. 60 min before exertion) abolished the exertion-induced increases in plasma 6-ketoprostaglandin F1 alpha and thromboxane B2 concentrations, confirming inhibition of cyclooxygenase activity. Phenylbutazone treatment resulted in significantly (P < 0.05) higher heart rates and right atrial pressures during exertion than did treatment with placebo, which may have been due to increased myocardial sensitivity to sympathetic stimulation and/or decreased venous compliance. There was not a detectable effect of phenylbutazone on carotid or pulmonary arterial pressures, O2 consumption, CO2 production, or blood lactate concentration. Changes in plasma volume during exertion were not influenced by phenylbutazone. These results demonstrate that cyclooxygenase products likely mediate or modulate some of the systemic hemodynamic responses to exertion in horses.     

Intoxicated behavioral disinhibition and the heart rate response to alcohol.

This study examined the association between the heart rate (HR) response to alcohol intoxication, which is thought to reflect sensitivity to alcohol-induced reward and alcohol-induced behavioral disinhibition. High- and low-HR responders to alcohol participated in a go/no-go task, under sober and intoxicated conditions. Errors of commission on this task have previously been related to behavioral disinhibition. High-HR responders made more intoxicated commission errors as compared with low-HR responders. High-HR responders also reported increased alcohol consumption, and controlling for the latter did not alter the significant association between high-HR responders and increased intoxicated errors of commission. These results are consistent with previous findings of an increased risk for addictive and disinhibited behavioral propensities in individuals with a high-HR response to alcohol intoxication. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Blood pressure and heart rate variability in autonomic disorders: a critical review

Sulfhydryl compounds can protect DNA against free-radical-induced DNA damages not only by scavenging of radicals, but also by chemical non-enzymatic repair or modification of such damages by hydrogen-donation. To investigate the influence of chemical repair and modification on mutations, induced by gamma-radiation-generated free radicals (.OH, .H), phosphate-buffered aqueous solutions of double-stranded (ds) M13 DNA were exposed to gamma-rays under N2 in the presence of 5 mM cysteamine. The exposed DNA was subsequently transfected to wild-type E. coli and mutations in the mutational target were characterized. This target in fact contains three different target sequences, i.e., the lac promoter/operator, the lacZ alpha gene and a 144 bp inframe insert. The mutation spectrum obtained was compared with those in the absence of cysteamine under N2 and N2O. In the latter case, the ratio of .OH and .H available for reacting with DNA is about the same as under N2 + cysteamine. The results show that chemical repair and/or modification by cysteamine of potentially lethal lesions takes place, leading to a much higher survival of ds M13 DNA in the presence of cysteamine than could be expected on basis of scavenging of .OH and .H alone. This higher survival appeared to be accompanied with a higher mutation induction. However, the N2 + cysteamine mutation spectrum shows a remarkable resemblance with the N2O-spectrum. This holds for the total mutation target, as well as each of the three targets, although the mutations obtained in each of the three targets under the same irradiation conditions are quite different. Thus, it can be concluded that cysteamine is mainly effective on radiation-induced potentially lethal DNA lesions, and not so much on (pre)mutagenic damages. Moreover, the type of mutation appeared to be strongly dependent on the mutational target sequence.     

Exercise studies in horses: 2. The cardiac response to exercise in normal horses and in horses with chronic obstructive pulmonary disease

The relationship of velocity (v) to heart rate (HR)and of kinetic energy (KE) to heart rate, were investigated in 6 normal horses and in 6 horses with chronic obstructive pulmonary, disease (COPD). Radiotelemetry was used to determine the heart rate while subjects were ridden on a 400m track. Velocity was measured by stop-watch between 2 markers 50 m apart at the end of the track. Kinetic energy was calculated from the formula KE =1/2 Mv2, where M = mass of horse, rider, saddle and bridle (KG) and V = velocity (metres per second). In all subjects, the relationship of velocity to heart rate was a linear one at each individual pace (i.e. walk, trot and gallop). There were however significant differences between the v/HR regression curves of each pace. These differences indicated that the increase in velocity per unit increase in heart rate was greater at the trot than at the walk, and greater at the gallop than at the trot. When data for all paces were combined, the relationship log v/log HR was a linear one. The above findings were also true of the relationship of kinetic energy to the heart rate. In horses, which reached maximal heart rate at a relatively low velocity, the v/HR curve became asymptotic. At comparable submaximal velocities, the heart rate of COPD subjects was approximately 20 beats per minute higher than that of normal subjects. This was also true when the term "kinetic energy per units mass" was substituted for velocity.     

Circadian pattern of heart rate variability in chronic heart failure patients. Effects of physical training

The effect of physical training on the circadian pattern of heart rate variability (recorded over 24 h in relation to both time and frequency) was assessed in 12 chronic heart failure patients randomized, in a cross-over design, to 8 weeks training or detraining, and compared with 12 age-matched normals. Training improved heart rate variability indices: all R-R interval 5 min standard deviations increased by 17.6%, the root mean square of the differences of successive R-R intervals by 34.9%, the percentage difference between adjacent normal R-R intervals > 50 ms by 112.5%, total power by 58.3%, high frequency by 128.5% and low frequency by 65.0%. Compared with controls, circadian variations in autonomic parameters were maintained in chronic heart failure. Training-induced changes were observed at different time intervals throughout the day: the highest values were at 0100 h-0700 h (detraining: low frequency 361 +/- 83 ms2, high frequency 126 +/- 47 ms2; training: low frequency 535 +/- 202 ms2, high frequency 227 +/- 115 ms2, P < 0.01) and the lowest at 1300 h-1900 h (detraining: low frequency 91 +/- 23 ms2, high frequency 39 +/- 14 ms2; training: low frequency 154 +/- 42 ms2, high frequency 133 +/- 67 ms2, P < 0.05). In chronic heart failure, training maintains and improves circadian variations in heart rate variability measures.     

The response of the fetal heart rate of amniocentesis

Fetal heart rate monitoring during 107 amniocenteses suggested that acceleration of the fetal heart rate indicated fetal well-being. Eight out of the 19 fetuses who did not show this response (as against 2 out of the 88 others) had a low Apgar score at birth.     

Development and habituation of the heart rate orienting response to auditory and visual stimuli in the rat.

Studied development and habituation of responsivity to sound and visual stimuli in 120 8–19 day old Sprague-Dawley pups by using a change in heart rate (HR) as the indicant response (Exp I). A change in HR to sound (white noise) first occurred around 14–25 days of age and was acceleratory in nature. Within 3 days, the direction of the HR response shifted to bradycardia. The HR response to light was also characterized by tachycardia in young pups (14 days), which shifted to bradycardia as the pups matured (16 days and older). In Exp II, the HR response of 15- and 19-day-old Ss was studied at 3 auditory stimulus intensities (60, 70, and 90 db, B scale). Stimulus intensity influenced the magnitude of the cardiac response in the 19-day-old pups. Data suggest that even weak sensory stimuli elicited a defensive reaction (HR acceleration) during the 1st few days that followed onset of function in each sensory system; later in development, the same stimulus elicited an orienting response (cardiac deceleration). (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aggressiveness, family history of alcoholism, and the heart rate response to alcohol intoxication.

Some sons of male alcoholics (SOMAS) are characterized by an increased heart rate (HR) response to alcohol intoxication, which is thought to reflect increased sensitivity to alcohol-induced reward. Such a response has also been related to increased physical aggression. However, the confounding effect of aggression in SOMAS may be obscuring the interpretation of these findings. The HR response to alcohol was therefore assessed in 4 groups: high/low aggressive SOMAS and high/low aggressive non-SOMAS. Results indicate that aggressive SOMAS had the highest intoxicated HR response and that they reported the most alcohol consumption. This suggests that in some cases the high comorbidity between alcohol misuse and aggression is related to an increased sensitivity to alcohol-induced reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Blood pressure, renin activity and heart rate changes during propranolol therapy of hypertension

Seven boys with fracture(s) of the bony pelvis and associated partial or complete rupture of the posterior urethra were managed by the time-honored technique of early suprapubic cystostomy and concomitant primary realignment of the urethra over a catheter. Of the 4 children who had a functionally significant urethral stricture 3 were cured within a few months by 1 or 2 simple urethral dilatations and 1 by subsequent transperineal lysis of the angulated urethra from its surrounding fibrous tissue. Followup data for 8 to 22 years (mean 14 years) indicate that all 7 patients void with an excellent stream and are continent, free of infection and potent. In fact, 3 of the 4 married boys have fathered children.     

Metaiodobenzylguanidine and heart rate variability in heart failure

It is assumed that the low-frequency power (LF) of heart rate variability (HRV) increases with progress of congestive heart failure (CHF), therefore positively correlating with cardiac 123I-metaiodobenzylguanidine (MIBG) washout. It is demonstrated here that HRV, including normalized LF, correlated inversely with MIBG washout and positively with the ratio of heart-to-mediastinum MIBG activity in controls and CHF patients, whereas these correlations were not observed within CHF patients. Thus MIBG washout may increase and HRV including normalized LF may decrease with CHF, although the HRV and MIBG measures may not similarly change in proportion to the severity of the cardiac autonomic dysfunction in CHF.     

Pulsatile release of somatotropin related to meal feeding and somatotropin response to secretagogues in horses

Our goal was to establish a time of day and(or) interval from feeding that would avoid the refractory period after a somatotropin (ST) surge and optimize the responsiveness of horses to ST secretagogues. Two experiments were conducted with eight geldings conditioned to consume grain at 0800 and 1600 daily. In Exp. 1, during a 24-h period, these geldings averaged 3.2 +/- .3 pulses of ST with peak amplitude of 4.2 +/- .4 ng/mL, pulse duration of 55 +/- 6 min, and interpeak interval of 400 +/- 57 min. No ST peaks occurred within 2 h after either grain feeding. In Exp. 2, eight geldings were given 50 micrograms of ST-releasing factor (STRF) at 0800. Two geldings that had a pulse of ST between 0700 and 0800 failed to respond to STRF, but the other six responded with a pulse of ST at 37 +/- 3 min; peak amplitude was 4.6 +/- 2.2 ng/mL and duration was 123 +/- 25 min. Experiments 3 and 4 were with mares aged 20 to 26 yr and conditioned to be fed grain at 0800 daily. In Exp. 3, blood was sampled for 8 h beginning at 0500. Seven of the eight mares had a ST pulse in progress at 0500. Five additional pulses were detected, all from 0740 to 0940, but none from 0600 to 0700 or from 1000 to 1300. In Exp. 4, four of the same eight mares were given 50 micrograms of STRF at 0700 and the other four at 1300. Three of the four treated at 0700 and all four treated at 1300 responded to STRF with ST peaks at 20 +/- 5 min; peak amplitude was 12.7 +/- 9.5 ng/mL and duration was 69 +/- 6 min. In Exp. 5, nine mares aged 20 to 26 yr were fed grain at 0800 and 1600 as in Exp. 1 and 2 and given a nonpeptidal ST secretagogue (STS, Merck L-163,255) i.v. at 0, 1, or 5 mg/kg (n = 3 mares/dose) at 1300. No mare had a pulse of ST during the 1 h before treatment. All six mares given STS responded with ST pulses. The ST responses to STS at 1 and 5 mg/kg did not differ (P > .05); time to ST peak was 35 +/- 4 min, pulse amplitude was 24.0 +/- 6.3 ng/mL, and pulse duration was 100 +/- 9 min. We conclude that mares and geldings fed grain once or twice daily usually have a period of 2 to 5 h after feeding with no ST pulses. When horses are fed grain at 0800, one may give a ST secretagogue at 1300 to avoid a refractory period and improve the probability of an ST response.     

Heart rate variability and newborn heart rate responses to illumination changes.

Investigated heart rate (HR) response patterns to the onset and offset of a 30-sec increase in illumination in 16 human newborns. Ss were divided into 2 groups based on a measure of pretrial HR variability. Only Ss with the high pretrial HR variability responded significantly to the change in stimulation. The response to onset was characterized by a significant quartic trend containing both decelerative and accelerative components. The response to offset only approached significance and had a pattern similar to the onset response. Although the occurrence of systematic response patterns was related to the level of pretrial HR variability, this measure of autonomic lability may have been related to influences associated with delivery and not to stable individual differences. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Peripheral heat as a reward for heart rate response in the curarized rat

It is generally assumed that the mechanical perception of shivering is necessary for the perception of cold discomfort. Shivering of rats in a cool environment was eliminated by curarization. The rats were kept alive by artificial respiration. Heart rate was proportional to rectal temperature in a group of controls. One group of rats was conditioned to increase heart rate to trigger an infrared lamp; another group was conditioned to decrease heart rate to obtain heat. When compared with the results of the control group without infrared heat reward, the results obtained from the two heart-rate-modifying groups show that shivering is not a necessary signal to determine thermoregulatory behavior in rats and, presumably, cold discomfort in man.     

Effect of endurance exercise training on heart rate variability at rest in healthy young and older men

Heart rate variability (HRV) (SD of the RR interval), an index of parasympathetic tone, was measured at rest and during exercise in 13 healthy older men (age 60 to 82 years) and 11 healthy young men (age 24 to 32 years) before and after 6 months of aerobic exercise training. Before exercise training, the older subjects had a 47% lower HRV at rest compared with the young subjects (31 +/- 5 ms vs 58 +/- 4 ms, p = 0.0002). During peak exercise, the older subjects had less parasympathetic withdrawal than the young subjects (-45% vs -84%, p = 0.0001). Six months of intensive aerobic exercise training increased maximum oxygen consumption by 21% in the older group and 17% in the young group (analysis of variance: overall training effect, p = 0.0001; training effect in young vs old, p = NS). Training decreased the heart rate at rest in both the older (-9 beats/min) and the young groups (-5 beats/min, before vs after, p = 0.0001). Exercise training increased HRV at rest (p = 0.009) by 68% in the older subjects (31 +/- 5 ms to 52 +/- 8 ms) and by 17% in the young subjects (58 +/- 4 ms to 68 +/- 6 ms). Exercise training increases parasympathetic tone at rest in both the healthy older and young men, which may contribute to the reduction in mortality associated with regular exercise.     

Immune response to changes in training intensity and volume in runners

We examined the acute and chronic effects of changes in training volume and intensity on the blood lymphocyte percentages and immunoglobulin levels in runners. Twelve runners participated in four 10-d phases of low volume/low intensity (LV/LI), high volume/low intensity (HV/LI), or high volume/high intensity (HV/HI) running. Subjects were assigned to one of two different training group orders: 1) LV/LI, HV/LI, LV/LI, HV/HI; or 2) LV/LI, HV/HI, LV/LI, HV/LI. Venous blood was drawn at rest on days 1, 4, and 7; and 5 min post-exercise on days 1 and 7 of each 10-d phase. Lymphocyte subsets were determined by flow cytometry for CD3+, CD4+, CD8+, and HLA-DR+. IgG, and IgM levels were obtained by ELISA analysis. Immunoglobulin, CD8+ and HLA-DR+ levels, and pre-exercise plasma cortisol concentrations were not significantly affected by alterations in volume or intensity. A transient decrease (P < 0.05) was observed in CD4+ and the CD4/CD8 ratio 5 min post-exercise during the HV/LI and HV/HI phases. Results indicate that the exercise-induced lymphocyte subset reduction is transient and suggest that it is more dependent upon training intensity than volume, and the training order of exposure to the high-intensity stimulus may determine the magnitude of subsequent responses.