Lizard heart rate and motor activity relationships in the circadian and ultradian ranges

• 1.1. The heart rate and motor activity of lizards (Gallotia galloti) maintained in a light-dark cycle (12:12 hr) and with changing cyclic temperature were recorded. Both variables showed a circadian pattern, motor activity variations leading heart rate by approximately 110 min.
• 2.2. Results from cross spectral analysis showed that heart rate was highly correlated with temperature and both variables were changing practically in phase. However, motor activity and temperature were less correlated and in this case motor activity led temperature by approximately 100 min.
• 3.3. In the ultradian range, two periodicities could be distinguished in the power spectra of motor activity and heart rate variations during the day: one between 0.019 and 3.9 × 10⁻³ cycles/min (central peak around 85 min period) and another, of lower power, between 0.05 and 0.02 cycles/min (central peak around 34 min period). During the night, only the heart rate showed both periodicities but with a lower amplitude.
• 4.4. The presence of ultradian oscillations in heart rate during the night suggested that they do not depend on motor activity which was almost absent during that daily period.
• 5.5. Motor activity and heart rate were also highly correlated in the ultradian range, motor activity leading heart rate by around 5 min at the 85 min main peak.

     

Circadian and Ultradian Rhythms in Heart Rate and Motor Activity of Smokers, Abstinent Smokers, and Nonsmokers

In a field study, heart rate and motor activity were assessed continuously in 12 male smokers during 2 smoking and 2 abstinence days and in 12 male nonsmokers during 4 days. A circadian analysis revealed earlier activity acrophases in smokers than nonsmokers and earlier heart rate acrophases in abstinent than smoking smokers. Furthermore, heart rate acrophases of smoking smokers significantly anticipated activity acrophases;, whereas in abstinent smokers and nonsmokers the two parameters oscillated in phase. With the use, in smoking smokers, of the individual average smoking interval as a hypothetical ultradian period length, significant periodicities were found for heart rates in 16 and for activity in 15 of 24 observation days. These rhythms were nicotine independent and based on heart rate and activity increases prior to lighting up the cigarettes. Individual frequency spectra for the 16 h after getting up and the 7 h after going to bed did not reveal single dominant frequencies but rather complex frequency distributions. Power spectra of the daytime data revealed no group differences for activity and no heart rate differences between smoking smokers and nonsmokers. In abstinent smokers, however, a significant reduction of heart rate frequencies slower than 1 cycle/135 min and a significant increase of heart rate frequencies faster than 1 cycle/20 min were observed as compared with all other groups. This effect persisted over the 2 abstinence days, suggesting an activity-independent change in the frequency distribution of heart rates after quitting smoking.     

Circadian and Ultradian Rhythms in Heart Rate and Motor Activity of Smokers,Abstinent Smokers,and Nonsmokers

In a field study, heart rate and motor activity were assessed continuously in 12 male smokers during 2 smoking and 2 abstinence days and in 12 male nonsmokers during 4 days. A circadian analysis revealed earlier activity acrophases in smokers than nonsmokers and earlier heart rate acrophases in abstinent than smoking smokers. Furthermore, heart rate acrophases of smoking smokers significantly anticipated activity acrophases;, whereas in abstinent smokers and nonsmokers the two parameters oscillated in phase. With the use, in smoking smokers, of the individual average smoking interval as a hypothetical ultradian period length, significant periodicities were found for heart rates in 16 and for activity in 15 of 24 observation days. These rhythms were nicotine independent and based on heart rate and activity increases prior to lighting up the cigarettes. Individual frequency spectra for the 16 h after getting up and the 7 h after going to bed did not reveal single dominant frequencies but rather complex frequency distributions. Power spectra of the daytime data revealed no group differences for activity and no heart rate differences between smoking smokers and nonsmokers. In abstinent smokers, however, a significant reduction of heart rate frequencies slower than 1 cycle/135 min and a significant increase of heart rate frequencies faster than 1 cycle/20 min were observed as compared with all other groups. This effect persisted over the 2 abstinence days, suggesting an activity-independent change in the frequency distribution of heart rates after quitting smoking.     

Daily form of rest in the catfish Ictalurus nebulosus and the frog Rana temporaria]

By means of recording the cardiac rhythm, respiration rate and motor activity in unrestrained animals, studies have been made on the dynamics of formation of cataleptic-like immobilization in the teleost I. nebulosus. Rhythmic illumination at a rate 3/min. (10 sec light on - 10 sec light off) in the daytime gradually caused the onset of immobilization in the fish. This immobilization is characterized by the specific heart rate, type of respiration and the degree of plastic tone. Under the same experimental conditions, the formation of photogenic catalepsy in the frog Rana temporaria was confirmed. Typical heart rate, respiration pattern and the degree of plastic tone were determined as well. The role of illumination rhythm in the onset of all conditions which are characteristic for the "awakefulness-rest" cycle is discussed.     

Individual differences in motor skills ability affect the self-regulation of heart rate

Twenty males who scored relatively high on the rotor-pursuit motor skills task (High performance group) were given seven 2-minute trials to increase heart rate and seven 2-minute trials to decrease heart rate, as were 20 males who scored relatively low on the rotor-pursuit task (Low performance group). Visual analogue feedback was not provided during the first and last acceleration and deceleration trials but was presented during all other trials. Both groups of subjects were able to decrease heart rate significantly with and without feedback. Subjects in the High performance group were able to increase heart rate significantly with feedback and could generalize this increase to a no-feedback trial following feedback trials. Subjects in the Low performance group could not increase heart rate with or without feedback. Changes in respiration rate paralleled those noted for heart rate, but changes in chin electromyographic activity generally did not parallel the heart rate results. The heart rate data are discussed in terms of motor skills theories of self-regulation of heart rate.     

Study of ECG, parameters of external respiration and motor activity of rats of different ages during acute poisoning with fluoroacetamide

Acute poisoning with fluoroacetamide (FAA), an efficient blocker of the tricarboxylic acid cycle, was studied in newborn and adult Wistar rats. FAA was administered once: to adult rats at a dose of 11 mg/kg peros, to the 7-day old rat pups at doses of 3 and 50 mg/kg subcutaneously. For 7 days after the poisoning, ECG, respiration, and motor activity were recorded. Based on the obtained data, clinical analysis of ECG and analysis of the heart rate variability (HRV) were performed to evaluate the state of the autonomic nervous system. Administration of FAA to adult rats leads to pronounced disturbances in activities of cardiovascular and respiratory systems. The most dangerous is development of acute pulmonary heart and of respiratory disorder. Characteristic is development of diffuse myocardial alterations. In newborn rat pups, statistically significant disturbances of cardiac activity and respiration are absent. The rat pup death occurs due to the total organism exhaustion accompanied by arrest of development. In adult rats, during intoxication, the appearance of bursts of combined cardiac and respiratory tachyarrhythmias can be observed, as well as of regular high-amplitude convulsive inhalations following in the decasecond rhythm. In rats of all age groups, injection of FAA, after a brief increase of role of humoral-metabolic and sympathetic activity, leads to the gradual steady predominance of parasympathetic effects on HRV. These data can serve as a confirmation of that under conditions of inhibition of the Kreps cycle enzymatic reactions there occurs activation of physiological processes resulted from activity of alternative metabolic pathways. This statement is also confirmed by the absence of the ontogenetically fixed inhibition of the spontaneous motor activity in the FAA-poisoned rat pups. This also confirms our earlier statement about importance of pentose phosphate cycle reactions for realization of the decasecond and minute rhythms and about the absence of rigid dependence of these rhythms on activity of neuronal structures.     

Individual differences in motor skills ability affect the self-regulation of heart rate

Twenty males who scored relatively high on the rotor-pursuit motor skills task (High performance group) were given seven 2-minute trials to increase heart rate and seven 2-minute trials to decrease heart rate, as were 20 males who scored relatively low on the rotor-pursuit task (Low performance group). Visual analogue feedback was not provided during the first and last acceleration and deceleration trials but was presented during all other trials. Both groups of subjects were able to decrease heart rate significantly with and without feedback. Subjects in the High performance group were able to increase heart rate significantly with feedback and could generalize this increase to a no-feedback trial following feedback trials. Subjects in the Low performance group could not increase heart rate with or without feedback. Changes in respiration rate paralleled those noted for heart rate, but changes in chin electromyographic activity generally did not parallel the heart rate results. The heart rate data are discussed in terms of motor skills theories of self-regulation of heart rate.Some of the results reported in this article are based on a doctoral dissertation submitted to the Graduate School of Northern Illinois University by the second author. The heart rate data were presented at the Convention of the American Psychological Association, Anaheim, 1983.     

Leydig neuron activity modulates heartbeat in the medicinal leech

1. Leydig neurons fire spontaneously at low rates (less than 4 Hz), but their activity increases with mechanical stimulation or electrical stimulation of mechanosensory neurons. These conditions also cause acceleration of bursting in heart motor neurons. 2. The firing rate of Leydig cells was found to regulate heart rate in chains of isolated ganglia. When Leydig neurons were made to fire action potentials at relatively high frequencies (ca. 5-10 Hz), however, heart motor neurons ceased bursting and were either silenced or fired erratically. 3. Firing of Leydig neurons at high rates caused bilateral heart interneurons of ganglia 3 or 4 to fire tonically rather than in their normal alternating bursts Tonic firing of these heart interneurons accounts for the prolonged barrages of ipsps recorded in heart motor neurons and the disruption of their normal cyclic activity. 4. Preventing spontaneous activity of Leydig neurons with injected currents in isolated ganglia caused deceleration of the heartbeat rhythm but did not halt oscillation. 5. Electrical stimulation of peripheral nerve roots with Leydig neuron activity suppressed in isolated ganglia caused acceleration of heart rate.     

Circadian rhythms of body temperature and motor activity in rodents their relationships with the light-dark cycle

In rodents, the alternation of light and dark is the main synchronizer of circadian rhythms. The entrainment abilities of the LD cycle could be estimated by experimental modifications of the photoperiod and by following the subsequent temporal distribution of a circadian rhythm. The rate of reentrainment of a rhythm is determined by the nature of the studied variable, by the direction (advance or delay) and the magnitude (or value) of the phase shift. In rodents, core body temperature and motor activity are known to be well synchronized with each other under L:D 12:12 and under constant conditions (LL or DD). There are clear evidences that the circadian pattern of motor activity is generated by two oscillators, one from dusk signal and the other from dawn signal. Whether the circadian rhythms of body temperature and motor activity are generated by a common circadian mechanism or controlled by separate ones still remains unknown. The purpose of this review is to summarize the results obtained on the circadian rhythms of body temperature and motor activity throughout the daily cycle in order to clarify the relationships between these two functions.     

Change in the rate of shell deposition and shell microstructure in response to shell borers in the abalone haliotis rubra

Variations in heart rate under social interactions in unrestrained hermit crabs were studied. Two insulated Stainless Steel hook wires were inserted into the pericardiac cavity and connected simultaneously to a graphic recorder and to an oscilloscope used as control of the preparations.

Cardiac arrest is shown when another hermit appears into the visual field of the recording subject, coincident with the characteristic Alert Pattern. This arrest is followed by bradycardia (Hesitation Pattern). When motor activity is displayed or perceived from the other crab, cardiac arrest occurs again, and the heart rate is irregular during agonistic motor activity. When the conflict is resolved, a weak tachycardia is observed.     

Features of cardiovascular functioning during different phases of the menstrual cycle

The purpose of the present study was to determine whether there is a menstrual cycle effect on heart rate, blood pressure and heart rate variability. 10 healthy regularly cycling females (age 19-23 years) were studied during the follicular phase and luteal phase over two month. We found significant changes in heart rate, AMo and stress index during the menstrual cycle with a minimum in the follicular phase and maximum in the luteal phase. The HF and LF components decreased more during the luteal phase than during the follicular phase (p < 0.05), whereas a tendency for increase LF/HF was observed in the luteal phase. In the follicular phase SDNN, pNN50, Mo, MxDMn were significantly higher than in the luteal phase. Furthermore, the VIK was higher in the luteal phase compared to the follicular phase (p = 0.003). Blood pressure did not show any significant change during both these phases of the menstrual cycle. These findings indicate that sympathetic nervous activity in the luteal phase is greater than in the follicular phase, whereas parasympathetic nervous activity is predominant in the follicular phase. A difference of the balance of ovarian hormones may be responsible for these changes of autonomic functions during the menstrual cycle.     

Characteristics of the formation of conditioned defense reactions in monkeys in a primatological chair

Rate of reactions in motor conditioned electro-defensive reflexes and different kinds of internal inhibition, such as acute extinction, differentiation and delay with different retardations, were studied on monkeys in primatological chair. Specificity in formation of conditioned reactions was studied with simultaneous recording of vegetative (respiration and heart rate) and motor conditioned reactions. It has been established, that forming of vegetative and motor components of defensive reflex does not proceed synchronously. At first (2-4 trials) vegetative reactions appear, such as increase of heart and respiration rates. Conditioned motor reactions (legs' jerks) appear later, after 4-9 trials. It has been shown that in monkeys in the primatological chair we have a possibility to form all kinds of negative conditioned defensive reactions: acute extinction, differentiation, delay. Formation of delay inhibition with retardation of 90 s leads to neurotic disorders. But they last only for short periods and disappear after breaks in work. The obtained data are discussed from evolutionary point of view, with a comparative study of specificity of higher nervous activity formation among lower organized vertebrates and with consideration of processes of excitation and inhibition in evolution.     

Effect of the epiphysis and hypophysis on the circadian organization of the wakefulness-primary sleep cycle in the frog Rana temporaria

Using continuous non-contact registration of the heart rate and motor activity in unrestrained frogs, studies have been made of the effects of hypophysectomy and epiphysectomy on functional state of the organism. It was shown that removal of the epiphysis alleviates the circadian physiological rhythm of natural changes of functional states in wakefulness-primary sleep cycle, whereas removal of the hypophysis results in additional cyclic rhythm of two functional states in the diurnal periodicity of the behaviour. The latter effect is considered to be the ultradian rhythm, which in the intact animals is masked by the circadian one modulated by natural diurnal illumination. It is suggested that removal of the epiphysis reveals endogenous rhythm of the activity typical of periodic regimes of the spontaneous excitation at early stages of ontogenesis.     

Effects of Amlodipine on Orcadian Rhythms in Blood Pressure, Heart Rate, and Motility: A Telemetric Study in Rats

In male Wistar rats [light (L): 07:00-19:00 h, dark (D): 19:00-07:00 h], the effects of the calcium channel blocker amlodipine (1, 3, 10 mg/kg i.p.) on blood pressure, heart rate, and motor activity were studied by telemetric monitoring. Amlodipine was injected either at 07:00 h or at 19:00 h. Systolic and diastolic blood pressure were dose-dependently decreased with more pronounced effects in the dark span, ED₅₀ values in D were about seven times lower than in L. In contrast, the dose-dependent increase in heart rate was more pronounced in L than in D. No significant effects of amlodipine were found on motor activity. The study gives evidence for a circadian phase-dependency in the cardiovascular effects amlodipine in rats.     

Aerobic capacity of forestry workers and physical demands of forestry operations.

The present study aimed at evaluating the aerobic capacities of forestry workers and the physical demands of their occupation. A submaximal cycle ergometer test was conducted on 22 male forestry workers and 15 male sedentary office workers aged 40-59 years. The slope of the regression line of heart rates on given exercise intensities was significantly smaller in the forestry workers than in the office workers. The mean heart rate of the forestry workers was 9 beats.min-1 less than that of the office workers at the initial exercise intensity of 50 W. This difference increased to 25 beats.min-1 at 175 W. For 6 of the 22 forestry workers, heart rates were recorded continuously during a usual workday. The metabolic rates, as multiples of basal metabolic rate (in met) of various forestry activities were estimated from the average heart rate during the activity of interest and a predicted maximal oxygen consumption of the subject obtained from a submaximal cycle ergometer test. The mean energy expenditure was 4.5 met with a range of 3.3-6.3 met for an average of 509 min at a worksite. These results indicated that the forestry workers had high aerobic capacities and this was ascribed to the high physical demands of their occupation.     

Interrelations of the Autogenic Somatomotor Excitation of the Cardiac Activity in Developing Rats

In developing rats aged from newborns to 1.5 months, regularities were studied of the heart rate fluctuations associated with periodic bursts of the endogenous somatomotor excitation characteristic of early stages of postnatal ontogenesis of immature born animals. It has been established that decelerations predominate on the background of the motor bursts for the first week of life, whereas accelerations, since the beginning of the 3rd week. The heart rhythm changes can precede or lag behind the beginning of the motor excitation, which allows judging about the existence of two mechanisms of the interaction: about the heart reaction to motor activity and about the central drivers acting simultaneously on the both systems. Experiments with chronic desympathization and block of -adrenoreceptors indicate a participation of the sympathetic nervous system in formation of the motor-cardiac interaction.     

The development of the activity-rest cycle in the rabbit fetus

On 25-30-day rabbit foetuses, in chronic experiments using constant synchronous recording of the motor activity and heart rate, studies have been made of temporal organization of the activity-rest cycle. Already in 25-day foetus, three functional conditions may be distinguished: active, intermediate and resting ones, the duration of the latter increasing to the end of gestation up to 8-10 min, whereas the duration of the intermediate phase decreases, reaching its minimum to the 30th day if not being completely reduced. Cyclic pattern of active and resting phases is observed in 28-day foetuses; to the 29th-30th day, these phases from a unique activity-rest cycle, its duration reaching 20-30 min to the end of intrauterine period. It is suggested that the resting phase in foetal rabbits serves as a basis for the development of polyphasic sleep in adult animals.     

Effects of Amlodipine on Orcadian Rhythms in Blood Pressure,Heart Rate,and Motility: A Telemetric Study in Rats

In male Wistar rats [light (L): 07:00–19:00 h, dark (D): 19:00–07:00 h], the effects of the calcium channel blocker amlodipine (1, 3, 10 mg/kg i.p.) on blood pressure, heart rate, and motor activity were studied by telemetric monitoring. Amlodipine was injected either at 07:00 h or at 19:00 h. Systolic and diastolic blood pressure were dose-dependently decreased with more pronounced effects in the dark span, ED₅₀ values in D were about seven times lower than in L. In contrast, the dose-dependent increase in heart rate was more pronounced in L than in D. No significant effects of amlodipine were found on motor activity. The study gives evidence for a circadian phase-dependency in the cardiovascular effects amlodipine in rats.     

Sprouting and connectivity of embryonic leech heart excitor (HE) motor neurons in the absence of their peripheral target

The rhythmic pumping of the hearts in the medicinal leech,Hirudo medicinalis, is neurogenic and mediated by a defined circuit involving identified interneurons in a central pattern generator (CPG) and segmentally iterated motor neurons that drive the heart muscle. During early embryogenesis, presumptive heart excitor (HE) motor neurons extend many axon branches into the body wall; they later innervate the heart while retracting the supernumerary peripheral axons, and only much later in development receive synaptic input from the central pattern generator (Jellies, Kopp and Bledsoe (1992)J. Exp. Biol., 170, 71–92.)- In this study, HE motor neurons were deprived of an early interaction with the heart by surgical ablation of a circumscribed portion of body wall including the heart primordium. Anatomical and electrophysiological data were obtained using intracellular techniques to examine the hypothesis that peripheral interactions with the developing heart provide instructive cues for the final differentiation of these neurons. Target-deprived HE motor neurons continued to extend multiple axons in ventral, lateral and dorsal body wall throughout late embryonic and into postembryonic stages and they extended anomalous axons within the CNS. This resembles the early embryonic growth of HE motor neurons before heart tube differentiation. Furthermore, HE motor neurons deprived of heart contact exhibited tonic activity similar to the situation during early development before they are contacted by the CPG interneurons. In contrast, sham-operated and contralateral HE motor neurons oscillated normally. These results suggest that heart tube contact is specifically required for at least some aspects of HE development and provide a framework in which to identify cell-cell interactions that are involved in matching neurons and targets to generate behaviorally relevant neural circuits.     

Circadian pacemaker function and entrainment during maturation of transgenic hypertensive TGR(mREN2)27 and Sprague-Dawley rats

TGR(mREN2)27 (TGR) transgenic rats develop hypertension due to the mouse mRen-2 gene inserted in their genome. At 5 weeks of age, the blood pressure of TGR rats starts rising, until a maximum is reached at 10 weeks of age. Adult TGR rats show peak values of blood pressure (BP) during the light phase, while heart rate (HR) and motor activity (MA) peak at night. In the present experiment, we evaluated the evolution of circadian rhythms in motor activity, heart rate, and blood pressure of TGR and Sprague-Dawley (SD) rats under 12h light-dark cycles (LD 12:12). Results confirmed that the blood pressure of TGR rats starts to increase at 5 weeks of age, reaching a plateau by the 11th week. Parallel to the increase in blood pressure levels, there was a decrease in the period length of the blood pressure rhythm, a delay in the onset of the alpha phase of the blood pressure rhythm with respect to that of motor activity and heart rate, and a decrease in heart rate levels. In all of the variables studied, the alpha phase of SD rats always started before darkness, whereas that of TGR rats started after lights off. In general, heart rate and motor activity levels of TGR rats were higher than those of SD rats. The amplitude of the circadian rhythms studied was greater in TGR rats than in SD rats. The present results suggest that the different evolution of circadian rhythms in TGR and SD rats might be due to differences in the functioning of the entrainment pathway or the circadian clock itself, which can be detected in young rats and that are probably caused by the expression of the mouse transgene. (Chronobiology International, 18(4), 627-640, 2001)