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Biomedical subjects

M Fredrikson

Publications and source records attributed to M Fredrikson.

At least 109 records · Page 6Linked to original sources
PubMed1990

Classical conditioning of vascular responses in mild hypertensives and normotensives.

Using a discriminative classical conditioning paradigm, this study addresses the question of whether vascular responses are more easily acquired or slower to extinguish in mild hypertensives than in normotensive controls. We subjected 18 mild hypertensives, with a resting systolic/diastolic blood pressure of 141/100 mmHg, and 17 normotensive controls similar in age, with resting systolic/diastolic blood pressure 122/80 mmHg, to a discriminative Pavlovian conditioning paradigm with tones of 8 s duration serving as conditioned stimuli (CS) and a mild electric shock as an unconditioned stimulus (UCS). Digital finger pulse volume (FPV) responses were recorded during an acquisition phase, where CS+, but not CS-, was repeatedly paired with the UCS (12 trials), and an extinction phase where shocks were withheld (12 trials). During the acquisition phase, mild hypertensives displayed greater anticipatory vasoconstrictive responses both to CS+ and CS- compared with normotensive controls. In addition, unconditioned FPV responses were enhanced in mild hypertensives. During the extinction phase, mild hypertensives evidenced increased resistance to extinction since conditioned vasoconstriction was more frequently observed in response to CS+ than to CS- in mild hypertensives only. Thus, vascular dysregulation in mild hypertensives was evident both for unconditioned and conditioned vasoconstriction. Data are compatible both with a centrally determined increased conditionability in mild hypertensive compared with normotensive and with a decreased threshold for peripheral vascular responsiveness among mild hypertensives.

Adult↗
PubMed1990

Do instructions modify effects of beta-adrenoceptor blockade on anxiety?

To study the interaction between physiological and cognitive factors in anxiety, 44 subjects with public speaking anxiety were allocated to four different groups. Two groups received either beta-adrenoceptor blockade (100 mg of atenolol) or placebo orthogonally crossed with an instruction that heart rate would decrease or an instruction that did not mention cardiovascular effects. During the delivery of a speech, measures of heart rate, systolic and diastolic blood pressures, and self-reported anxiety were obtained. All variables increased during an anticipation period before speech, and heart rate, systolic blood pressure, and self-reported anxiety increased further during speech. Regardless of instructions, atenolol decreased heart rate and systolic blood pressure during both anticipation and speech, whereas no differences were found in self-reported anxiety. This lack of a relationship was seen in spite of the correctly perceived heart rate reduction in the atenolol-treated group receiving an instruction that heart rate would decrease. Cardiac aware subjects, according to the Autonomic Perception Questionnaire, showed higher levels of heart rate and self-reported anxiety at rest than did cardiac unaware subjects. During speech, even though heart rate was similar in atenolol treated groups, self-reported anxiety was higher in cardiac aware than in cardiac unaware subjects. The lack of a relationship between heart rate and self-reported anxiety is discussed in terms of primary and secondary emotions. It is suggested that the perception of external rather than internal cues determines situationally elicited anxiety.

Adult↗
PubMed1990

Electrodermal responsivity in young hypotensive and hypertensive men.

Electrodermal responses were recorded during the presentation of 16 moderately intense (1000 Hz, 90dB) tones in three groups of young men: borderline hypertensives (138/79 mmHg), normotensives (112/65 mmHg), and hypotensives (104/63 mmHg). Electrodermal response habituation was measured as a decline in response over trials, number of trials to a response criterion of three successive nonresponses, and number of inversions of response amplitude (larger responses following smaller responses) in the stimulus sequence. Habituation was fastest in hypotensives. Nonspecific electrodermal responses at rest and during tone presentations were most frequent in borderline hypertensives, least frequent in the hypotensive group, with the normotensive group falling in between. There were no significant differences in electrodermal level. The rapid habituation rate in hypotensives is discussed in terms of cursory information processing associated with impulsive behaviour. The higher nonspecific electrodermal activity in borderline hypertensives is interpreted to indicate increased sympathetic nervous system activity.

Adolescent↗
PubMed1989

Cardiovascular responses in the laboratory and in the natural environment: is blood pressure reactivity to laboratory-induced mental stress related to ambulatory blood pressure during everyday life?

Cardiovascular activity recorded at rest and during mental stress in the laboratory was studied in relation to ambulatory recorded cardiovascular activity at work and at home. Fifty-five Type A men (M = 42.4 years) underwent a standardized laboratory mental stress protocol in which systolic blood pressure, diastolic blood pressure, and heart rate were recorded at baseline and during a 15 min mental arithmetic task (MAT). On a subsequent day, ambulatory blood pressure and heart rate were recorded at 20 minute intervals for 12-14 hr during normal activities at home and at work. Subjects completed a behavioral diary concurrently with each cuff inflation. High and Low groups were identified based upon a median split of their cardiovascular response levels at baseline and during the MAT. Subjects with high systolic blood pressure levels during the MAT had high systolic blood pressure at home, at work, during physical activity, and when they reported being 'stressed'. Baseline systolic blood pressure in the laboratory was less consistently related to ambulatory systolic pressure across ambulatory conditions. Diastolic blood pressure at baseline was related to ambulatory diastolic blood pressure at work, at home, and when resting. Diastolic blood pressure during the MAT was associated with higher diastolic pressure at work and at home. Heart rate at baseline and during the MAT was related to heart rate at work and during physical activity. Change scores derived by subtracting mean values during the MAT from baseline resting levels were not associated with ambulatory blood pressures or heart rates under any daily conditions. In the best case, systolic blood pressure measured during the MAT was related to systolic blood pressure during physical activity, to systolic blood pressure and heart rate during mental stress, to systolic and diastolic blood pressure at rest, and to systolic blood pressure and heart rate at work but not at home. We conclude that levels of blood pressure and heart rate measured in the laboratory, but not reactivity (i.e, change scores) during the MAT, are related to blood pressure and heart rate levels recorded in the natural environment, especially in the work setting.

Activities of Daily Living↗
PubMed1989

Blood lipids as related to cardiovascular and neuroendocrine functions under different conditions in healthy males and females.

Correlations were calculated between, on the one hand, total serum cholesterol, low-density (LDL) and high-density (HDL) lipoprotein cholesterol, and triglycerides, and, on the other hand, systolic (SBP) and diastolic blood pressure (DBP), heart rate (HR), urinary epinephrine, norepinephrine, and cortisol in 30 healthy males and 30 healthy females, aged 30-50. The cardiovascular and neuroendocrine measurements were obtained under different real-life and laboratory conditions. The most striking finding was that, in men, but not in women, total serum cholesterol was significantly positively correlated with SBP in all conditions (LDL and HDL cholesterol followed the same pattern). In women, but not in men, epinephrine and norepinephrine during laboratory-induced mental stress were significantly positively correlated with total cholesterol, LDL and triglycerides.

Adult↗
PubMed1988

Plasma catecholamines and production of thromboxane B2 by platelets after psychological and physical tests in normotensive and mild hypertensive subjects.

In our previous studies strenuous exercise, adrenaline infusion and surgical stress have been shown to evoke increased plasma thromboxane B2 (TxB2) concentrations and production by platelets. Here we report the effects of acute psychological and physical tests, during 24 h direct monitoring of blood pressure and heart rate, on plasma catecholamine levels and TxB2 production by platelets in normotensive, borderline and mild hypertensive subjects. After psychological tests plasma noradrenaline and adrenaline values in the whole material were slightly elevated as compared to the basal levels measured 24 h after the attachment of the cannula. TxB2 production remained unaltered. After physical tests both plasma noradrenaline and adrenaline were clearly increased as was also the TxB2 production by platelets. When the subjects were divided into normotensive and hypertensive ones, unexpectedly, basal plasma values of catecholamines were higher in normotensive volunteers but TxB2 production was more marked in hypertensive subjects.

Blood Platelets↗
PubMed1986

Autonomic reactions to social and neutral stimuli in subjects high and low in public speaking fear.

People with specific animal phobias react with increased autonomic activity when exposed to fear-relevant stimuli. The present study examined whether individuals having a less circumscribed fear (public speaking fear) also react with increased autonomic responses when exposed to fear-relevant i.e. social stimuli. A High-fear and a Low-fear group, as indicated by the PRCS questionnaire, were exposed to pictures of faces (social stimuli) and mushrooms (neutral stimuli) while heart rate (HR) and skin conductance responses (SCRs) were measured. It was found that: Social stimuli evoked larger SCRs as compared to neutral stimuli only in the High-fear group; SCR magnitude to social stimuli was positively correlated with self-reported fear in the High-fear group; the High-fear group showed larger overall SCRs compared with the Low-fear group; the High-fear group showed slower SCR habituation to social stimuli as compared to the Low-fear group; the High-fear group displayed more nonspecific electrodermal fluctuations than did the Low-fear group. Both the High-fear and the Low-fear group displayed HR deceleration to social but not to neutral stimuli. Thus, subjects high in public speaking fear reacted with increased skin conductance activity when exposed to social stimuli compared to low-fear subjects. The two groups did not differ in heart rate responses. These results are discussed in terms of orienting, defense and species-specific response patterns.

Adult↗
PubMed1986

Personal control over work pace--circulatory, neuroendocrine and subjective responses in borderline hypertension.

Cardiovascular and neuroendocrine reactivity during arithmetic task performance were studied in 24 patients with borderline hypertension and normotensive controls. Personal control (self-paced versus externally paced performance) resulted in an attenuated blood pressure (BP) response to task performance in normotensives but not in borderline hypertensives. In response to self-paced work, systolic blood blood pressure (SBP) reactivity was significantly greater in borderline hypertensives, but the heart rate (HR) reactivity was similar in borderline hypertensives and normotensives under the different pacing conditions. Task difficulty (pace variation during external pacing) did not differentially affect reactivity in borderline hypertensives and normotensives. Venous plasma noradrenaline and adrenaline were unaffected by task performance. At rest after the task performance plasma noradrenaline was elevated in both normotensives and borderline hypertensives. The latter group also showed a persistent elevation of diastolic blood pressure after task performance, suggesting a prolonged vasoconstrictor response. The present findings indicate that, in terms of circulatory responses, borderline hypertensives may profit less than normotensives from personal control over environmental demands.

Adult↗
PubMed1986

Racial differences in cardiovascular reactivity to mental stress in essential hypertension.

Racial differences in cardiovascular and non-cardiovascular sympathetic nervous system (SNS) activity were studied at rest and during an aversive reaction-time task in established hypertensives, borderline hypertensives and normotensive controls. White and black subjects of each group were subjected to 16 signalled reaction time tasks where a 110 decibel (dB) white noise was delivered contingent upon poor performance. During 16 signalled foreperiods (35 s) the following measurements were taken: systolic and diastolic blood pressures, heart rate, respiration-rate and muscle and skin blood flow. Muscle and skin vascular resistances were calculated. Skin conductance activity was recorded as an index of non-cardiovascular SNS-activation. Resting cardiovascular activity was similar in black and white hypertensives and controls, whereas skin conductance activity was greater in white compared to black hypertensives and controls. During the reaction-time task both quantitative and qualitative differences between the races tended to emerge. Heart rate and systolic blood pressure increased less in black patients and controls than in whites. Muscle and skin vascular resistance increased in blacks but was unaffected by behavioural demands in whites. Skin conductance reactivity was attenuated in black patients and controls. Thus, blacks compared to whites show lesser cardiac sympathomimetic responses but enhanced vascular responses to mental stress.

Adult↗
PubMed1985

Learned control of heart rate during exercise in patients with borderline hypertension.

Twelve patients with borderline hypertension [less than or equal to 21 X 33/12.6, greater than or equal to 18 X 6/12.0 kPa (less than or equal to 160/95; greater than or equal to 140/90 mm Hg)] participated in an experiment aimed at testing whether they could learn to attenuate heart rate while exercising on a cycle ergometer. Six experimental (E) subjects received beat-to-beat heart-rate feedback and were asked to slow heart rate while exercising; six control (C) subjects received no feedback. Averaged over 5 days (25 training trials) the exercise heart-rate of the E group was 97.8 bt min-1, whereas the C group averaged 107 bt min-1 (P = 0.03). Systolic blood pressure was unaffected by feedback training. Generally, changes in rate-pressure product reflected changes in heart-rate. Oxygen consumption was lower in the E than in the C group late in training. We conclude that neurally mediated changes associated with exercise in patients with borderline hypertension can be brought under behavioral control through feedback training.

Adult↗
PubMed1985

Cardiovascular and electrodermal adjustments during a vigilance task in patients with borderline and established hypertension.

We studied cardiovascular and noncardiovascular sympathetic nervous system (SNS) responses to a vigilance task in patients with borderline (BT) or established hypertension (HT). Twelve patients in each group and twelve normotensive controls (NT) were subjected to a signalled reaction-time (RT) task which included the presentation of a noxious 110 dB white noise contingent upon RT-performance at the end of a 30 sec foreperiod. During this foreperiod recordings were made of: systolic and diastolic blood pressures, heart rate, skin- and muscle-blood flows. Skin and muscle vascular resistances were calculated from mean blood pressure and regional blood flows. Skin conductance level, fluctuations and responses were recorded as noncardiovascular SNS-responses. Compared to NT both HT and BT had higher resting blood pressures, heart rate, skin- and muscle-vascular resistances. BT showed higher resting skin conductance levels than HT and NT who were not different from one another. During stimulation HT and BT evidenced pressor hyperreactivity compared to NT. The electrodermal effects did not parallel the cardiovascular ones. Skin conductance and cardiovascular variables were more closely related in NT than HT or BT. The presence of cardiovascular hyperreactivity together with the absence of noncardiovascular hyperreactivity in HT indicates heightened SNS-activity specific to the cardiovascular system and not part of generalized SNS-arousal. The similarity between HT and BT is consistent with the notion that the differences between BT and HT are quantitative rather than qualitative.

Adult↗
PubMed1985

Arterial blood pressure and general sympathetic activation in essential hypertension during stimulation.

We asked whether exaggerated blood pressure (BP) reactivity in patients with essential hypertension (HT) is a sign of specific activation of the cardiovascular system or of generalized sympathetic activation. Fourteen patients with essential hypertension and 14 matched normotensive (NT) controls were subjected to tasks involving attentional demands, mental arithmetic, a cold pressor test and isometric muscular contraction. Systolic and diastolic BPs, skin and muscle blood flows, heart rate, skin conductance level and fluctuations during each task were recorded. Urine samples for determination of epinephrine and norepinephrine excretion were collected after task completion. All tasks caused BP increases in both groups. HT showed greater absolute and percentage BP reactivity than NT during isometric muscle contraction. Variables for which reactivity differences were observed were poorly correlated across tasks both in HT and NT, whereas resting values prior to each task were highly correlated in both groups. Skin conductance activity, epinephrine and norepinephrine excretion rates being examples of non-cardiovascular sympathetic nervous system (SNS) indicators did not separate HT from NT. Thus, the exaggerated pressor response in HT is not accompanied by signs of generalized SNS activation.

Blood Pressure↗
PubMed1983

Muscle fibre composition in relation to blood pressure response to isometric exercise in normotensive and hypertensive subjects.

A positive relationship was demonstrated between the blood pressure and the fibre composition of the vastus muscle at rest in 17 hypertensive and 17 age- and sex-matched normotensive subjects. The hypertensive group had a higher proportion of fast twitch (FT) fibres (p less than 0.1). The circulatory response was measured during isometric exercise (IE) and cold pressor test (CPT). During IE the blood pressure increase was positively related to the percentage of FT fibres. No such relationship was demonstrated during CPT. It was thus found, particularly in hypertensive subjects, that an individual's muscle fibre profile is of importance for the blood pressure response during IE.

Adult↗
PubMed1981

Arterial blood pressure and electrodermal activity in hypertensive and normotensive subjects during inner- and outer-directed attention.

Arterial blood pressure (BP), skin conductance level (SCL) and spontaneous fluctuations in skin conductance (SFs) were monitored in 14 subjects with essential hypertension (HT), and 14 matched normotensive (NT) controls during a letter identification task (L) and mental arithmetic (MA). During both tasks, the groups displayed different response patterns such that SFs and BP tended to be negatively correlated in the HT group but were positively correlated in the NT group. No correlation between BT and SCL was obtained in any group during either task. SFs and SCL were positively correlated in the NT group during both tasks whereas no correlation was found in the HT group. The results are consistent with the hypothesis that an increased BP is associated with the rejection of the environment.

Adult↗