Persisting subsensitivity of the striatal dopamine system after fetal exposure to beta-endorphin

Fetal exposure to placental corticotropin-releasing hormone (pCRH) programs developmental trajectories

The maternal endocrine stress system is profoundly altered during the course of human pregnancy. The human placenta expresses the genes for CRH as early as the seventh week of gestation and it is the expotential increase in placental CRH (pCRH) over the course of human gestation that is responsible for the greatest modification in the maternal stress system. The bi-directional placental release of hormones into the maternal and fetal compartments has profound influences for both. The influential Fetal Programming model predicted that early or fetal exposures to maternal signals of threat or adverse conditions have lifelong consequences for health outcomes. A basic assumption of this model was that developing organisms play a dynamic role in their own construction. Data are reviewed and new data are presented that elevated pCRH over the course of human gestation plays a fundamental role in the organization of the fetal nervous system, modifies birth phenotype (the timing of the onset of spontaneous labor and delivery), and influences developmental, temperamental and metabolic trajectories. Evidence for sex differences and conserved function across species is presented. Finally, a model is presented that proposes several pathways that pCRH can program risk for health and disease.

Neurobehavioral risk is associated with gestational exposure to stress hormones

The developmental origins of disease or fetal programming model predict that early exposures to threat or adverse conditions have lifelong consequences that result in harmful outcomes for health. The maternal endocrine 'fight or flight' system is a source of programming information for the human fetus to detect threats and adjust their developmental trajectory for survival. Fetal exposures to intrauterine conditions including elevated stress hormones increase the risk for a spectrum of health outcomes depending on the timing of exposure, the timetable of organogenesis and the developmental milestones assessed. Recent prospective studies, reviewed here, have documented the neurodevelopmental consequences of fetal exposures to the trajectory of stress hormones over the course of gestation. These studies have shown that fetal exposures to biological markers of adversity have significant and largely negative consequences for fetal, infant and child emotional and cognitive regulation and reduced volume in specific brain structures.

Maternal hypothalamic-pituitary-adrenal disregulation during the third trimester influences human fetal responses

Maternal peptides from the hypothalamic-pituitary-adrenal (HPA) axis rise during human pregnancy. The effects of circulating maternal adrenocorticotropin (ACTH) and beta-endorphin (BE) on human fetal behavior was determined in 135 women during their 32nd week of gestation. Fetal behavior was measured by assessing heart rate habituation to a series of repeated vibroacoustic stimuli. Individual differences in habituation were determined by computing the number of consecutive responses above the standard deviation during a control period. There was no significant relation between levels of ACTH, BE and the rate of fetal heart rate habituation. However, an index of HPA disregulation (uncoupling of ACTH and BE) was related significantly to fetal behavior. Fetal exposure to high levels of maternal BE relative to ACTH was associated with significantly lower rates of habituation. Results indicate that maternal stress and stress-related peptides influence fetal response patterns. It is possible that this influence persists over the life span.

Disregulation of proopiomelanocortin and contagious maladaptive behavior

Self-injurious behavior (SIB) is an untreatable and often life-threatening problem among individuals with developmental disorders, especially those diagnosed with autism. Functioning, relationships and processing of the proopiomelanocortin (POMC) system are "uncoupled" in subgroups of self-injuring individuals resulting in different ratios of ACTH and opioids in the bloodstream, particularly under conditions of stress. In this study, relations between SIB and POMC were evaluated in a multi-year study of the largest prospective sample studied to date. Observations were collected on palmtop computers for 45 treatment-resistant patients who exhibited chronic SIB. Behavior of each subject was observed in natural settings without disruption or intrusion, for continuous, 2.5-h periods, two times a day (morning and afternoon), 4 days a week for two consecutive weeks, for a total of 40 h/subject. Blood was collected in the morning, late afternoon and immediately after an SIB episode on two separate occasions separated by at least 6 months. Levels of beta-endorphin (beta E) and ACTH were assayed by RIA. We discovered that the SIB was the best predictor of subsequent SIB. Moreover, the majority of subjects exhibited this contagious pattern of SIB. Levels of POMC fragments were reliable over a 6- to 9-month period. Subjects exhibiting POMC disregulation characterized by high morning levels of beta E had the highest transitional probabilities of SIB (i.e. contagious patterns; F=8.17, P<0.01). These findings suggest that subjects with "contagious" SIB may represent a behavioral phenotype associated with disregulated expression of the POMC gene.

A novel pharmacological concept in an animal model of psychosis

OBJECTIVE

We have analysed pharmacologically induced perturbation of functional and structural neurogenesis in the prefrontal cortex (PFC) and hippocampus.

METHOD

Juvenile gerbils received a single dose of methamphetamine (METH, 50 mg/kg, i.p.). In adults the following parameters were quantitatively investigated: prefrontal dopaminergic and GABAergic innervation densities (immunocytochemistry), morphogenesis of pyramidal cells (Golgi), dentate granule cell proliferation (BrdU-labelling), working memory and behavioural inhibition (delayed response, open-field).

RESULT

A single challenge of METH continuously suppresses granule cell proliferation in adult gerbils and initiates rewiring of neuronal networks in the PFC which run concurrently with the development of severe deficits in PFC-related behaviours.

CONCLUSION

It appears that a continuous remodelling of neuronal circuits is an inherent property of the brain, the biological significance of which seems to be to ascertain adaptive interaction between brain and environment. Learning more about drug-induced neuronal reorganization might be basic for understanding the genesis of psychotic conditions in the brain. This presentation is based both on own research and on a review of the literature.

Opioid receptor blockade during prenatal life modifies postnatal behavioral development

The ontogeny of physical characteristics, spontaneous motor, and sensorimotor behaviors of preweaning rats, as well as ambulation and emotionality at weaning (day 21) were studied in rats exposed to 50 mg/kg naltrexone (NTX) or saline (controls) daily throughout gestation by maternal administration; all animals were cross-fostered to untreated mothers at birth. Morphine challenge tests and nociceptive measures revealed that this dosage of opioid antagonist blocked opioid receptors for 24 h. At birth and weaning, animals in the NTX group weighed 12 and 20%, respectively, more than control offspring. The age at which a specific physical characteristic, spontaneous motor behavior, or reflex initially appeared and the age at which 100% of the animals demonstrated a particular characteristic/behavior often were accelerated in animals prenatally exposed to NTX. The frequency of ambulation was subnormal in the NTX group, and the frequency and/or incidence of rearing, grooming, wet-dog shakes, and defecation were reduced from normal levels in these opioid antagonist-exposed rats. These results imply that interactions of endogenous opioid systems during embryogenesis are determinants of somatic, physical, and behavioral development in postnatal life.

Maternal stress, HPA activity, and fetal/infant outcome

Preliminary conclusions from our research include the possibility that each of the HPA products evaluated, even though correlated (e.g., ACTH and beta E), may be linked to unique and specific outcomes. Maternal stress during the 28-30 weeks of gestation is associated with birth outcome. Increased levels of psychosocial stress were significantly related to gestational age at birth and infant birth weight. Maternal stress during the third trimester was associated with increased maternal plasma levels of ACTH and cortisol. This finding is consistent with possible mechanisms whereby psychosocial stress influences birth outcome. CRH controls the timing of labor and delivery. Precocious elevation of CRH is related to the risk of preterm delivery. This system may be "stress-sensitive." Even though pregnant women may be immunized from stress, the stress signal that is transmitted (release of ACTH and cortisol) is amplified by the placental release of CRH. This possibility has at least two consequences: (1) influencing the timing of delivery and (2) desensitization of hypophyseal corticotrophs and further "protection" of the pregnant women from the results of stress (i.e., release of ACTH and beta E). Beta E appears to influence fetal learning and perhaps the developing nervous system.

Prenatal exposure to morphine alters analgesic responses and preference for sweet solutions in adult rats

In the present study, we examined long-term effects of prenatal morphine on pain response and on preference for sweet solutions. Pregnant Fischer 344 rats were given increasing doses of morphine (0.75-12.0 mg/day) in slow-release emulsion, during gestational days 12-18. Control rats were injected with vehicle and were either pair-fed to morphine rats, or ad libitum fed. At birth, all litters were culled to 8-10 pups (half males and half females) and cross-fostered to naive, surrogate dams. Testing began when rats were 10-12 week old. Rats prenatally exposed to morphine exhibited higher analgesia in response to a morphine challenge, and a greater preference for saccharin solution as compared with both control groups. These findings indicate that prenatal morphine induces long-lasting alterations of systems involved in reward processes and in opiate analgesia, perhaps by modulating endogenous opiate systems.

Prenatal psychosocial factors and the neuroendocrine axis in human pregnancy

OBJECTIVE

Physiological processes including neuroendocrine function have been proposed as mediators of the relationship between prenatal psychological state and pregnancy outcome; however, there are virtually no human studies that have systematically assessed such mechanisms. Neuroendocrine processes are significantly altered during pregnancy, and are characterized by the evolution of a transient neuroendocrine system, the placenta, and modifications in endocrine control mechanisms. Because these alterations have implications for neuroendocrine responsivity to exogenous conditions, the aim of the present study was to examine the cross-sectional association between prenatal psychosocial factors and stress-related neuroendocrine parameters during human pregnancy.

METHOD

Fifty-four adult women with a singleton, intrauterine pregnancy were recruited before 28 weeks of gestation. Maternal antecubital venous blood samples were withdrawn at 28 weeks of gestation for bioassays of adrenocorticotropin hormone (ACTH), beta-endorphin (beta E), and cortisol. Measures of prenatal stress, social support, and personality were collected using a two-part, self-report questionnaire administered at 28 and 30 weeks of gestation. Biomedical data were obtained from the medical record. Factors known to influence neuropeptide and hormone levels during pregnancy were controlled, including gestational age, circadian variation, and obstetric risk.

RESULTS

In the present sample, prenatal psychosocial stress, social support, and personality variables were associated with neuroendocrine parameters in two primary ways. First, certain psychosocial factors were significantly associated with plasma levels of ACTH, beta E, and cortisol, and second, psychosocial factors were associated with a measure of disregulation of the normal relationship between two pro-opiomelanocortin (POMC) derivatives, ACTH and beta E. Furthermore, a combination of the maternal psychosocial and sociodemographic factors during pregnancy accounted for 36% of the variance in ACTH, 22% of the variance in the ACTH-beta E disregulation index, 13% of the variance in cortisol, and 3% of the variance in beta E.

CONCLUSIONS

The present findings are consistent with the premise that maternal-placental-fetal neuroendocrine parameters are significantly associated, both in magnitude and specificity, with features of maternal psychosocial functioning in pregnancy despite the systemic alterations associated with the endocrinology of pregnancy. These findings provide a basis for further investigations of the role of the neuroendocrine system as a putative mediating pathway between prenatal psychosocial factors and birth outcome, and possibly also as a mechanism linking features of the maternal psychosocial environment to fetal/infant brain development.

Prenatal stress has long-term effects on brain opiate receptors

Prenatal stress has been associated with a number of behavioral consequences including altered sensitivity to exogenous opiates. In the present study, mu opiate receptors were compared in the 42-day-old offspring from females stressed on days 15-22 of gestation and from females who were unstressed controls. Membrane homogenates from the prenatal stress group showed less binding of the mu opiate receptor ligand, [3H]DAGO in striatum but not in several other brain regions. Saturation studies suggest this difference is due to fewer striatal mu opiate receptors in offspring of prenatally stressed females. Using in vitro receptor autoradiography, the decreased binding in striatum was found mostly in the rostral striatum, extending into the nucleus accumbens with conservation of the normal anatomic distribution of receptor rich patches.

Effects of prenatal morphine treatment of rats on mortality, bodyweight and analgesic response in the offspring

A method is presented for the maternal ingestion of morphine in rats in order to investigate morphine's prenatal effects. Effects on the offspring of the treatment throughout pregnancy were compared with effects of treatment during specific periods of the pregnancy. Morphine treatment (25 mg/kg per day) throughout pregnancy resulted in 0% survival of the offspring. Morphine treatment up to gestational day 21 resulted in 65.4 +/- 7.7% survival of the offspring, and up to gestational day 17 in 31.8 +/- 13% survival. Reduction in the neonatal birth weight was maximal in animals treated with 25 mg/kg of morphine per day from gestational day 4 throughout pregnancy. The analgesic effect of morphine in the offspring was tested with the hot plate method. Male offspring treated with morphine from gestational day 1 to day 17 showed an elevated thermal response after morphine injections on day 80-90 post partum. These findings indicate a long-lasting, post-partum alteration in that part of the opiate system involved in the perception of noxious stimuli.

Opioids and the developing organism: a comprehensive bibliography, 1984-1988

A comprehensive bibliography of the literature concerned with opioids and the developing organism for 1984-1988 is presented. Utilized with companion papers (Neurosci. Biobehav. Rev. 6:439-479; 1982; 8:387-403; 1984), these articles cover the clinical and laboratory references beginning in 1875. For the years 1984, 1985, 1986, 1987, and 1988, a total of 877 citations were recorded. A series of indexes accompanies the citations in order to make the literature more accessible. These indexes are divided into clinical and laboratory topics, and subdivided into such topics as the type of opioid explored and the general area of biological interest (e.g., physiology).

Beta-endorphin disregulation in autistic and self-injurious behavior: a neurodevelopmental hypothesis

Peptides derived from pro-opiomelanocortin (POMC) influence neurodevelopmental processes. Earlier studies indicated that MSH/ACTH compounds improved behavioral efficiency in retarded individuals. Recent studies have shown that opiate blockers reduce treatment-resistant self-injurious behavior (SIB), an autistic-like, developmental disorder. Although the exact mechanisms are unknown, prenatal POMC disregulation, addiction to endogenous opiates and elevated pain threshold have been proposed to account for this behavior. In study one, four SIB patients were given 0, 25, 50 or 100 mg of naltrexone on separate weeks in a double blind, Latin square design. A specific dose dependent reduction in SIB was observed in three patients. In study two, plasma b-endorphin was measured in 40 patients with SIB, a related behavior, stereotypy (ST) or controls. SIB and ST patients had higher levels of endorphin than controls. These data added new support for the role of b-endorphin in a treatment-resistant patient group.