Heart rate response of the rat fetus and neonate to a chemosensory stimulus (original) (raw)
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Autonomic drug effects on the heart rate of early rat embryos
Teratology, 1974
We examined the effect of cardioactive drugs on the heart rate of intact rat embryos at day 11 (25 somites) of gestation, the stage of development prior to cardiac innervation. Tested were the autonomic drugs methoxamine and isoproterenol, the P-adrenergic receptor blocker propranolol, and the phosphodiesterase inhibitor theophylline. Our observations indicated that (1) methoxamine had no effect; (2) isoproterenol and theophylline caused increases in the heart rate; and (3) propranolol inhibited the effect of isoproterenol but did not affect the response to theophylline. We concluded that our results are consistent with (1) Ahlquist's ('48) original concept of a and @ adrenergic receptors and the observation that the heart has no a receptors, (2) with the role of cyclic-AMP in the model of the adrenergic receptor proposed by Sutherland ('68), and (3) with the observations that the embryonic heart at this stage of development is not yet innervated and so is without the vagal reflex arc (Hogg, '57; Gomez, '58).
Development and pH sensitivity of the respiratory rhythm of fetal mice in vitro
Neuroscience, 2006
In newborn and adult mammals, chemosensory drive exerted by CO 2 and H ؉ provides an essential tonic input: without it the rhythm of respiration is abolished. It is not known, however, whether this chemosensory drive and the respiratory rhythm appear simultaneously during development. In isolated brainstem-spinal cord preparations from fetal mice, we determined at what stage of fetal life the respiratory rhythm appeared in third to fifth cervical ventral roots (phrenic motoneurons) and whether this fetal rhythm was sensitive to chemosensory inputs. A respiratory-like rhythm consisting of short duration bursts of discharges recurring at 2-16 min ؊1 was detected in two of nine embryonic day 13 fetuses; it was abolished by transection of the spinal cord between the first to second cervical segments and was phase-related to rhythmic activity from medullary units of the ventral respiratory group. At embryonic day 13, it coexisted with a slow rhythm (0.1-2.0 min ؊1) of long duration bursts of action potentials which was generated by the spinal cord. At later fetal stages, the respiratory-like rhythm became more robust and of higher frequency, while the spinal cord rhythm became less obvious. At all fetal stages, acidification of the superfusion medium from pH 7.5-7.2 or 7.4-7.3 or 7.4 to 7.2 increased the frequency of both the respiratory-like and the spinal cord rhythms. In addition, acidification reduced the amplitude of the integrated burst activity of the spinal cord rhythm of embryonic day 13-embryonic day 16 fetuses and the respiratory-like rhythm of embryonic day 17 and older fetuses. Our results indicate that the rhythms transmitted by phrenic motoneurons during fetal development are chemosensitive from early fetal stages. Through its effects on induction and patterning of the rhythm, chemosensory drive may play a role in activity-dependent formation of respiratory neural networks.
Behavior of rat fetuses following chemical or tactile stimulation
Behavioral Neuroscience, 1988
The behavior of fetal rats was examined on Day 19 of gestation with procedures that enabled chemical stimulation and direct observation of fetuses. Rat fetuses are sensitive to both tactile stroking and intraoral infusion of chemical solutions, but the pattern and amount of activity depend upon the modality of stimulation. Fetal responsiveness is affected by prior experience with chemical stimuli. Repeated exposure within a 10-min period results in a waning of response, and repeated exposure across a delay of 48 hr results in a different pattern of response than is seen to a novel stimulus. Reexposure to a stimulus experienced earlier in gestation also alters fetal responsiveness to other forms of tactile and chemical stimulation. These findings indicate that the rat fetus exhibits olfactory function in utero and suggest central processing of sensory information, including evidence of habituation, a fetal orienting reflex to novel stimuli, and the existence of prenatal behavioral states associated with different patterns of response.
Effect of Drugs on Chemoreceptor Responsiveness in Fetal Sheep
Pediatric Research, 1995
This study was designed to examine the effects of the drugs ketamine, morphine, pentobarbital, and propranolol on fetal chemoreceptor responsiveness. Eleven fetal lambs (gestational age 125-133 d) were chronically instrumented with a catheter in a hindlimb artery and vein and a forelimb artery; a carotid arterial oximeter catheter was placed in six of these fetuses. An inflatable cuff occluder was placed around the maternal hypogastric artery. Acute fetal hypoxemia was induced repeatedly by reducing uterine blood flow. Fetal heart rate, arterial pressure, and carotid arterial oxygen saturation were monitored continuously before and after administering ketamine, morphine, pentobarbital, or propranolol to the fetus. The ratio Aheart rate/AO, saturation has been shown previously to be a reproducible index of chemoreflex response. The differences in baseline values and changes with drugs were compared by multiple regression analysis coded by effects. Chemoreflex response was markedly attenuated by ketamine and morphine but not by pentobarbital or propranolol. Because the cardiovascular response to hypoxemia is blunted by some drugs, caution should be exercised in interpreting heart rate responses to hypoxemia in the fetus when these drugs have been administered to the mother. (Pediatr Res 38: 938-943, 1995) Abbreviation AHRIAsat = ratio of the decrease in heart rate to the decrease in 0, saturation Acute fetal hypoxemia causes a bradycardic response (I), sponse to acute hypoxemia that is quantitative and reproducible which we have previously shown is due to stimulation of (2). peripheral chemoreceptors. The sensitivity of fetal chemoreceptors determines the severity of the bradycardic response. Chemoreceptor sensitivity depends on baseline oxygenation;
2020 Computing in Cardiology, 2020
To evaluate and assess the cardiovascular system during fetal development in the utero of pregnant mouse, it is essential to understand the effect of mandatory anesthesia treatment on sympathetic and parasympathetic nervous system activities. The preliminary study presented in this paper explores the changes in fetal and maternal Heart Rate Variability (HRV) parameters as well as fetal-maternal Heart Rate (HR) coupling measures during anesthesia. ECG signals of 6 pregnant mice and 10 fetuses were recordedfor 15 min. The obtained ECG signals were segmented into three periods, each for a duration of 5 min. Maternal and fetal HRV parameters in addition to fetal-maternal coupling patterns were computed for each of the three segments of the ECG signals. During the first 10 min, results show that mean and root mean square of successive differences (RMSSD) of maternal HR did not change, but significantly decreased after the first 10 min. A similar result was observed for the mean, RMSSD an...
Cyclic variation in fetal heart rate and sympathetic activity
American journal of obstetrics and gynecology, 1987
The effects of alpha- and beta-adrenergic blockade on electrocortical activity-related cyclic variability in fetal heart rate and mean arterial pressure were investigated in eight fetal lambs between 119 and 138 days of gestation. In the absence of adrenergic blockade, fetal heart rate during high-voltage slow activity was significantly higher than that during low-voltage fast activity. Propranolol (2.0 mg/hr) produced a decrease in fetal heart rate, but the decrease was only statistically significant during high-voltage slow activity. Phentolamine (5.0 mg/hr) induced a significant increase in fetal heart rate with a small but statistically significant decrease in mean arterial pressure. The cyclic variability in fetal heart rate between low-voltage fast activity and high-voltage slow activity was abolished by propranolol and enhanced by phentolamine. These results indicate that the cyclic variability in the fetal heart rate associated with electrocortical activity can be accounted ...
Bulletin of Experimental Biology and Medicine, 2011
We studied changes in the autonomic balance of heart regulation (by the parameters of heart rate variability) in non-pregnant female rats and rats on the days 10-11 of pregnancy on the next day after stress provoked by acute hypobaric hypoxia, intermittent normobaric hypoxia, or immobilization. The same parameters were assessed in 36-day-old offspring. In nonpregnant rats, the intermittent hypoxia resulted in a shift of the autonomic balance of heart regulation towards activation of the parasympathetic nervous system; in pregnant females, immobilization led to a shift of the autonomic balance towards the sympathetic nervous system. In the offspring, the changes also depended on the type of stress.
Behavioral Neuroscience, 1985
With the pregnant rat under ether anesthesia, rat fetuses were exposed on Day 17 of gestation to a taste/odor stimulus {mint) injected into the amniotic fluid and/or lithium chloride injected into the peritoneum. Behavior of injected fetuses was directly observed on Day 19 of gestation following chemomyelotomy and laparotomy of the female and immersion of the uterus into a warm saline bath. With these procedures, a series of four experiments was conducted to assess the behavioral effects of (a) the mint taste/odor alone, (b) the LiC1 alone, (c) the pairing of mint and LiC1 on the day of conditioning, and (d) the reexposure to mint after an earlier pairing of mint and LiC1. These experiments provide clear evidence that rat fetuses are capable of forming conditioned taste/odor aversions as early as Day 17 of gestation and, further, that rat fetuses are capable of expressing these learned aversions in utero.
2010
Aims: Heart rate variability (HRV) reveals information on the functional state of the autonomic nervous system (ANS). This study was initiated to assess the physiological-and maturational development of the ANS by comparing HRV data of healthy prematures with term infants. Methods: Short-term recordings of HRV in 39 premature healthy infants (29-35 weeks' gestation) were performed and compared with normative data of term infants. Frequency domain HRV parameters are computed in three frequency bands. Results: Gestational age of newborn infants is correlated with HRV. Prematures showed significant lower HRV parameters than term infants. The most significant differences were discerned for HRV parameters reflecting parasympathetic activity, whereas the pulse of the baroreceptor reflex was similar for prematures and term infants at 0.07 Hz (0.1 Hz adults). A respiratory peak in the HF-band according to respiratory sinus arrhythmia (RSA), as is common in adults, was not detected for prematures as it is not detected in term infants. Conclusions: Maturation of the ANS is accompanied by increasing HRV with a pronounced increase of parasympathetic activity. These changes are measurable by shortterm recordings. The physiological pulses concerning baroreceptor reflex activity and respiratory modulation were similar in prematures and term infants.