Behavioral Functioning of the Fetus after Prenatal Toxin Exposure and Neural Insult

Recent advances in methods for direct observation of the rodent fetus permit behavioral assessment prior to birth. Combined with sensitive quantitative measures of behavior, these techniques have revealed dose-dependent functional deficits in fetal rats after prenatal exposure to methylazoxymethanol (MAM). Pregnant rats were injected i.p. with 10 mg/kg MAM on day 17 (E17) of a 22 day gestation. The fetal offspring were then observed on one of seven prenatal or postnatal ages (E18–E21 and P1, P5, and P10). Dependent measures included interlimb movement synchrony during spontaneous movement, facial wiping (defensive) response to lemon solution, oral grasping and suckling response to a non-nutritive nipple, and hindlimb stepping after mechanical tail stimulation. Collectively, these experiments revealed deficits that emerged in waves across development at the peak expression of each newly emerging behavior. This variability in the timing and expression of behavioral deficits revealed a possible pattern of prenatal behavioral development likely to be observed prior to the delayed emergence of developmental disabilities such as autism, adult onset psychiatric disorders such as schizophrenia, or even late onset neurological disease such as Parkinson\u27s. Because deficits were transient, revealed only at time points early in the peak expression of each behavior, traditional outcome measures are unlikely to detect this type of neural insult. Such results also emphasize the need to elucidate mechanisms that underlie changes in fetal behavior, not only during typical development, but also those that may be differentially altered after exposure to neurotoxins and other prenatal insults

Behavioral Functioning of the Fetus after Prenatal Toxin Exposure and Neural Insult

Recent advances in methods for direct observation of the rodent fetus permit behavioral assessment prior to birth. Combined with sensitive quantitative measures of behavior, these techniques have revealed dose-dependent functional deficits in fetal rats after prenatal exposure to methylazoxymethanol (MAM). Pregnant rats were injected i.p. with 10 mg/kg MAM on day 17 (E17) of a 22 day gestation. The fetal offspring were then observed on one of seven prenatal or postnatal ages (E18–E21 and P1, P5, and P10). Dependent measures included interlimb movement synchrony during spontaneous movement, facial wiping (defensive) response to lemon solution, oral grasping and suckling response to a non-nutritive nipple, and hindlimb stepping after mechanical tail stimulation. Collectively, these experiments revealed deficits that emerged in waves across development at the peak expression of each newly emerging behavior. This variability in the timing and expression of behavioral deficits revealed a possible pattern of prenatal behavioral development likely to be observed prior to the delayed emergence of developmental disabilities such as autism, adult onset psychiatric disorders such as schizophrenia, or even late onset neurological disease such as Parkinson\u27s. Because deficits were transient, revealed only at time points early in the peak expression of each behavior, traditional outcome measures are unlikely to detect this type of neural insult. Such results also emphasize the need to elucidate mechanisms that underlie changes in fetal behavior, not only during typical development, but also those that may be differentially altered after exposure to neurotoxins and other prenatal insults

Temperature Preference in IAF Hairless and Hartley Guinea Pigs (Cavia porcellus)

The Hairless strain of guinea pigs (Cavia porcellus) is the result of a spontaneous recessive mutation first identified at the Institute Armand Frappier (IAF) in 1978. Despite the longstanding availability of this strain, little is known about its thermoregulatory behavior. The aim of this study was to determine temperature preference in Hartley and Hairless guinea pigs by observing each strain in a ring-shaped apparatus containing a nonlinear temperature gradient. Temperatures were maintained by separately controlled heating mats lining the apparatus. Set point temperatures ranged from 24 to 38 °C. Guinea pigs (Hartley female, Hairless female, and Hairless male guinea pigs; n = 8 each group) were placed either singly or in pairs at 1 of the 8 randomized starting points within the apparatus. Subjects were observed for 30 min and coded for location within the temperature gradient by both frequency and duration. When placed singly in the apparatus, all 3 groups spent more time in the 30 °C zones. However, when placed as pairs with a cagemate, Hartley female guinea pigs spent more time in the cooler range of temperatures from 24 to 30 °C, whereas Hairless guinea pigs preferred a range of 30 to 38 °C. These results confirm a temperature preference of 30 ± 2 °C for both Hartley and Hairless guinea pigs when singly housed. However, data from the paired housing condition suggest that context plays an important role in thermoregulatory behavior

Developmental Pathways of Motor Dysfunction

Recent evidence has revealed unique patterns of behavioral development after prenatal insult similar to those outlined in studies of adult metabolic dysfunction after prenatal malnutrition. The hallmark features of this Developmental Pathway include a prenatal insult to the nervous system (environmental or genetic) followed by a period of Silent Vulnerability, where no or few functional deficits are observed, and finally emergence of later dysfunction. Possible mechanisms leading to later dysfunction from prenatal insult may include secondary or cascade effects due to the timing of prenatal insults relative to later developing structures in the brain. Methods best employed to study the mechanisms of these pathways are microgenetic and longitudinal designs that include behavioral assessment during the prenatal period of development, and animal models such as the guinea pig

Temperature Preference in IAF Hairless and Hartley Guinea Pigs (Cavia porcellus)

The Hairless strain of guinea pigs (Cavia porcellus) is the result of a spontaneous recessive mutation first identified at the Institute Armand Frappier (IAF) in 1978. Despite the longstanding availability of this strain, little is known about its thermoregulatory behavior. The aim of this study was to determine temperature preference in Hartley and Hairless guinea pigs by observing each strain in a ring-shaped apparatus containing a nonlinear temperature gradient. Temperatures were maintained by separately controlled heating mats lining the apparatus. Set point temperatures ranged from 24 to 38 °C. Guinea pigs (Hartley female, Hairless female, and Hairless male guinea pigs; n = 8 each group) were placed either singly or in pairs at 1 of the 8 randomized starting points within the apparatus. Subjects were observed for 30 min and coded for location within the temperature gradient by both frequency and duration. When placed singly in the apparatus, all 3 groups spent more time in the 30 °C zones. However, when placed as pairs with a cagemate, Hartley female guinea pigs spent more time in the cooler range of temperatures from 24 to 30 °C, whereas Hairless guinea pigs preferred a range of 30 to 38 °C. These results confirm a temperature preference of 30 ± 2 °C for both Hartley and Hairless guinea pigs when singly housed. However, data from the paired housing condition suggest that context plays an important role in thermoregulatory behavior

Developmental Pathways of Motor Dysfunction

Recent evidence has revealed unique patterns of behavioral development after prenatal insult similar to those outlined in studies of adult metabolic dysfunction after prenatal malnutrition. The hallmark features of this Developmental Pathway include a prenatal insult to the nervous system (environmental or genetic) followed by a period of Silent Vulnerability, where no or few functional deficits are observed, and finally emergence of later dysfunction. Possible mechanisms leading to later dysfunction from prenatal insult may include secondary or cascade effects due to the timing of prenatal insults relative to later developing structures in the brain. Methods best employed to study the mechanisms of these pathways are microgenetic and longitudinal designs that include behavioral assessment during the prenatal period of development, and animal models such as the guinea pig

Developmental Changes in Infant Rat Motor Learning after Mid-Thoracic Spinal Transection

Prior work in this lab has demonstrated developmental trends in motor learning, both in the rat fetus and neonate. This learning alters the pattern of hindlimb coordination in response to an interlimb yoke, which links the two limbs together. After training, both older fetuses and young neonates not only acquire conjugate movements (simultaneous movements with parallel trajectories), but retain these movements for a substantial amount of time after the yoke has been removed. This motor learning also can be demonstrated in fetuses with mid-thoracic spinal transections, suggesting that spinal circuitry alone is sufficient for these adaptive changes in interlimb coordination. In contrast, postnatal day 10 (P10) rat pups do not show this type of learning. It is possible that this interlimb motor learning depends on spinal plasticity, which is diminished by descending inhibitory circuitry by P10. In this study, infant rats were prepared with either a mid-thoracic spinal transection or sham treatment on the day of birth (P0). Subsequently, on either P1 or P10, these two groups were tested in a 65-min session (5-min baseline, 30-min training period with an interlimb yoke, and 30-min testing period after the yoke is cut). Sham treated pups on P10 did not exhibit motor learning. However, transected pups on P10 showed substantial increases in conjugate limb movements. Shams and transected pups also differed on P10 in the spontaneous activity they exhibited (e.g. high amplitude movements and myoclonic twitching), suggesting that the type and amount of movements exhibited may play a role in this type of spinally mediated motor learning

Temporal Organization of Spontaneous Movement in Fetal Mice across Uterine Environmental Conditions using Direct Observational Techniques and High Resolution Ultrasound Imaging

Prenatal insult to the developing nervous system is one of the leading causes of developmental disabilities such as cerebral palsy, autism, or mental retardation. Current animal models of prenatal neural insult hold promise for the development of assessment tools for these disorders, using methods of direct observation of the rodent fetus and detailed quantification of limb movements. Despite this promise, the environment of the rodent fetus under direct observation is not equivalent to that of the human fetus typically observed with ultrasound. Additionally, current methods using ultrasound to observe the rodent fetus in utero greatly impact the behavior of the fetal subject, particularly when general anesthesia is used. In order to determine how these changes in observational condition and prenatal environment impact spontaneous movement of the fetus, pregnant C57BL/6J mice were prepared with spinal anesthesia for fetal observation free from general anesthesia. On the day before birth, a single fetus from each pregnancy was observed under one of three environmental or observational conditions: (a) simultaneous direct observation and ultrasound imaging, in order to compare these two observational techniques, (b) ultrasound visualization of the fetus under uterine externalization, in order to assess the impact of the uterine environment on movement visible with sonography and (c) intra-abdominal ultrasound observation of fetal movement, creating a translational model more equivalent to methods used with the human fetus. Ultrasound was collected using a 40 MHz transducer probe and VisualSonics Vevo 770 system. Movement was scored from play back of DV recordings, and analyzed with a measure called Interlimb Movement Synchrony, which quantifies the temporal patterning between limb pairs. This measure has been observed to produce clear developmental patterns in a number of species, including preterm human infants, and has been found sensitive in detecting prenatal toxin exposure in fetal rats. Analysis of the direct and ultrasound observations revealed no differences in synchrony profiles, with a mean kappa adjusted reliability of 85%. Although lower rates of movement were observed in both the externalized uterine and intra-abdominal conditions, only minor differences in Interlimb Synchrony profiles were observed. Taken together these results suggest the observational techniques employing direct and ultrasound observations hold promise as tools in developing and assessing translational models of human fetal neural functioning and developmental disabilities

Temporal Organization of Spontaneous Movement in Fetal Mice across Uterine Environmental Conditions using Direct Observational Techniques and High Resolution Ultrasound Imaging

Prenatal insult to the developing nervous system is one of the leading causes of developmental disabilities such as cerebral palsy, autism, or mental retardation. Current animal models of prenatal neural insult hold promise for the development of assessment tools for these disorders, using methods of direct observation of the rodent fetus and detailed quantification of limb movements. Despite this promise, the environment of the rodent fetus under direct observation is not equivalent to that of the human fetus typically observed with ultrasound. Additionally, current methods using ultrasound to observe the rodent fetus in utero greatly impact the behavior of the fetal subject, particularly when general anesthesia is used. In order to determine how these changes in observational condition and prenatal environment impact spontaneous movement of the fetus, pregnant C57BL/6J mice were prepared with spinal anesthesia for fetal observation free from general anesthesia. On the day before birth, a single fetus from each pregnancy was observed under one of three environmental or observational conditions: (a) simultaneous direct observation and ultrasound imaging, in order to compare these two observational techniques, (b) ultrasound visualization of the fetus under uterine externalization, in order to assess the impact of the uterine environment on movement visible with sonography and (c) intra-abdominal ultrasound observation of fetal movement, creating a translational model more equivalent to methods used with the human fetus. Ultrasound was collected using a 40 MHz transducer probe and VisualSonics Vevo 770 system. Movement was scored from play back of DV recordings, and analyzed with a measure called Interlimb Movement Synchrony, which quantifies the temporal patterning between limb pairs. This measure has been observed to produce clear developmental patterns in a number of species, including preterm human infants, and has been found sensitive in detecting prenatal toxin exposure in fetal rats. Analysis of the direct and ultrasound observations revealed no differences in synchrony profiles, with a mean kappa adjusted reliability of 85%. Although lower rates of movement were observed in both the externalized uterine and intra-abdominal conditions, only minor differences in Interlimb Synchrony profiles were observed. Taken together these results suggest the observational techniques employing direct and ultrasound observations hold promise as tools in developing and assessing translational models of human fetal neural functioning and developmental disabilities

Prenatal Behavior of the C57BL/6J Mouse: A Promising Model for Human Fetal Movement during Early to Mid-Gestation

The study of fetal neurobehavioral development in genetically altered mice promises a significant advance in our understanding of the prenatal origins of developmental disabilities in humans. Despite their importance, little is known about fetal neurobehavioral development in mice. In this study, we observed prenatal behavioral patterns of the C57BL/6J mouse, a common background strain for genetically altered mice, and report their similarity to those observed in the early to mid-gestation human fetus. Fetal offspring from pregnant C57BL/6J dams were observed on the day before birth (E18 of a 19-day gestation). Scoring and analysis of fetal movement included Prechtl\u27s Method for Qualitative Assessment, Interlimb Movement Synchrony, a measure of the temporal relationship between movements of limb pairs, and Behavioral State, quantified through detailed analysis of high and low amplitude limb movements. With the exception of fetal breathing movements, all categories and patterns of behavior typically reported in the early to mid-gestation human fetus were observed in the C57BL/6J mouse fetus. Our results suggest that behavioral analysis of fetal C57BL/6J mice may yield important new insights into early to mid-gestation human behavioral development