Tyrosine administration to pregnant rats induces persistent behavioral modifications in the male offspring

Developmental expression of catecholamine system in the human placenta and rat fetoplacental unit

Catecholamines norepinephrine and dopamine have been implicated in numerous physiological processes within the central nervous system. Emerging evidence has highlighted the importance of tightly regulated monoamine levels for placental functions and fetal development. However, the complexities of synthesis, release, and regulation of catecholamines in the fetoplacental unit have not been fully unraveled. In this study, we investigated the expression of enzymes and transporters involved in synthesis, degradation, and transport of norepinephrine and dopamine in the human placenta and rat fetoplacental unit. Quantitative PCR and Western blot analyses were performed in early-to-late gestation in humans (first trimester vs. term placenta) and mid-to-late gestation in rats (placenta and fetal brain, intestines, liver, lungs, and heart). In addition, we analyzed the gene expression patterns in isolated primary trophoblast cells from the human placenta and placenta-derived cell lines (HRP-1, BeWo, JEG-3). In both human and rat placentas, the study identifies the presence of only PNMT, COMT, and NET at the mRNA and protein levels, with the expression of PNMT and NET showing gestational age dependency. On the other hand, rat fetal tissues consistently express the catecholamine pathway genes, revealing distinct developmental expression patterns. Lastly, we report significant transcriptional profile variations in different placental cell models, emphasizing the importance of careful model selection for catecholamine metabolism/transport studies. Collectively, integrating findings from humans and rats enhances our understanding of the dynamic regulatory mechanisms that underlie catecholamine dynamics during pregnancy. We identified similar patterns in both species across gestation, suggesting conserved molecular mechanisms and potentially shedding light on shared biological processes influencing placental development.

Interaction between the circadian clocks of mother and fetus

In mammals, a unidirectional communication exists between the biological clocks of the mother and fetus. As a biological clock begins oscillating in the suprachiasmatic nuclei of the fetus, redundant circadian signals entrain the fetal clock to the prevailing light-dark cycle. Recent studies have revealed an activatable dopamine system within the fetal hypothalamus which may serve as a final common pathway by which maternal signals entrain the fetus. An entrained biological clock during fetal life makes the developing mammal better prepared for life in the outside world.

The nature of human hazards associated with excessive intake of amino acids

In recent years there has been a large increase in the consumption of individual amino acids as dietary supplements. This has resulted not only from the use of certain amino acids as flavoring agents, but other amino acids are taken for perceived health benefit, for enhancement of physical performance, as well as for psychological effects. Two reviews of the scientific literature exist that mainly deal with effects in animals, and three major reports consider the safety of amino acids for human consumption. This article is a brief summary of the available evidence regarding the safety of individual amino acids when taken in excess relative to the amounts absorbed from dietary protein.

Tryptophan ingestion by pregnant rats induces pituitary and mammary tumours in the adult female offspring

The present study was designed to evaluate the long-term consequences of tryptophan treatment on the central serotonergic activity in the female offspring of rats, and particularly on serotonin-controlled hormone release. During the second half of gestation, tryptophan (200 mg/kg/day) was given daily by stomach intubation to pregnant rats and the brain concentrations of serotonin and 5-hydroxyindole acetic acid and the plasma concentrations of prolactin, progesterone, oestradiol and luteinizing hormone were quantified in the adult female offspring. The offspring showed an increase in hypothalamic serotonin and serum progesterone and prolactin. In addition, maternal ingestion of tryptophan induced a marked rise in 665-day-old offspring in the incidence of both pituitary prolactinomas (62%) and mammary adenomas (49%). Present data suggest that tryptophan regulates serotonergic differentiation during early development. A transitory modification of the tryptophan concentration in the fetal brain induces a permanent increase in hypothalamic serotonin level and, in addition to modifying the release of prolactin, increases the incidence of tumours in the hypophysis and mammary gland.

Tryptophan ingestion by gestant mothers alters prolactin and luteinizing hormone release in the adult male offspring

The effect of tryptophan administration to pregnant rats on the development of serotonergic systems and serotonin-related hormones in the offspring was studied. The male offspring of rats treated with tryptophan (200 mg/kg/day) during the second half of gestation showed a 4- to 7-fold increase in serum prolactin 40 and 70 days after birth and a 2-fold increase in serum luteinizing hormone 70 days after birth. The forebrain of adult offspring of tryptophan-treated rats showed an increase in serotonin and 5-hydroxyindoleacetic acid levels. Present data suggest that tryptophan regulates serotonergic differentiation during early development.

Maternal ingestion of tyrosine during rat pregnancy modifies the offspring behavioral lateralization

It was previously reported that oral administration of tyrosine (500 mg/kg) to pregnant rats increases tyrosine and monoamines level in the fetal brain and modifies locomotion during postnatal life. In the present study, it was found that this treatment alters behavioral lateralization in the offspring. Neonatal rats whose mothers received tyrosine during the second half of gestation showed a low level of absolute and population laterality in both tail and head movements. The alteration of behavioral lateralization was also found during postnatal development and during adulthood. The T-maze behavioral ontogeny was different for tyrosine-mother and sham-treated or untreated mother rats. During adulthood, the T-max lateralization after stress sessions (a procedure that decreases alternation behavior and facilitates the quantification of behavioral lateralization) was also different in control and tyrosine-mother groups. Neonatal and adult rats showed an increase in right-side movements probability. These data provide evidence that maternal ingestion of a catecholamine precursor during gestation may induce a long-lasting modification of the behavioral lateralization of the offspring.

Tyrosine ingestion during rat pregnancy alters postnatal development of dopaminergic neurons in the offspring

It has been previously reported that tyrosine ingestion by the mother rat during gestation modifies different behavioral patterns in the adult offspring. In the present study, the action of maternal mother tyrosine ingestion on the postnatal development of the dopaminergic system of the offspring was evaluated. The offspring of tyrosine-treated mothers showed a decrease in dopamine (DA) levels during the first 15 days of postnatal life and an increase in DA levels from day 30 to adulthood. The DOPAC level and the DOPAC/DA index were higher in the tyrosine group from postnatal life to adulthood. These differences reach statistical significance in both forebrain and mesencephalon. During adulthood the DA concentration in both s. nigra and ventral tegmental area were higher in the tyrosine group than in the control group. The behavioral postsynaptic response to a DA receptor agonist (apomorphine) was higher in the offspring of tyrosine treated rats than in the control group. These data suggest that the bioavailability of the DA precursor tyrosine during gestation may modify during postnatal life DA synapsis at both pre- and postsynaptic level.

Dopaminergic neuron development in rats: biochemical study from prenatal life to adulthood

Dopaminergic cell development has been studied mainly using morphological techniques and especially histofluorescence. However, the biochemical characteristics of dopamine (DA) neuron development and its physiological role during ontogeny are much less known. In the present article, the biochemical development of DA neurons, from day 13 of prenatal life to adulthood, is evaluated in Sprague-Dawley rats. DA was first detected on day 14 of gestation. The brain increase in this neurotransmitter begins on day 17 in the proencephalon and on day 18 in the mesencephalon, reaching on day 20 a level similar to that found during adulthood in the latter but not in the former. DA levels in the proencephalon rise slowly to adulthood level when compared to DA in the mesencephalon. The modifications observed in tyrosine levels are also largely similar to those reported for DA. Finally, the study of the first 48 h of life shows an increase in tyrosine levels and a decrease in dihydroxyphenylacetic acid levels (with a reduction of DA turnover) during the first 4-5 h of postnatal life. Since the serotonergic modification was completely different from DA modification, we conclude that the biochemical alteration of DA neurons during early postnatal development is specific. The present data suggest that DA neurons play different roles before and after reaching adult development.

Maternal tyrosinaemia II: management and successful outcome

A 25-year-old woman with tyrosinaemia type II was treated from the 5th week of pregnancy with a protein-restricted diet supplemented with a tyrosine/phenylalanine-free amino acid mixture. Tyrosine concentrations were maintained in the range 100-200 mumol/l by restricting natural protein intake to 0.16 g/kg per 24 h in early pregnancy, with increases up to 0.38 g/kg per 24 h in the last trimester. This treatment maintained plasma phenylalanine concentrations in the range 20-40 mumol/l. Maternal weight gain and fetal growth were normal, and the mother remained asymptomatic throughout the pregnancy. A normal infant was born at term with length, weight and head circumference between the 25-50th per centiles.

Effects of maternal stress during pregnancy on forced swimming test behavior of the offspring

It has been reported that gonadal steroids modulate brain and behavioral sex differentiation during development. Prenatal maternal restraint also alters development by affecting gonadal steroid levels in the fetus. Prenatal maternal restraint of animals decreases sex differences for sexual behavior, locomotion, aggression, etc. In recent work on animal models, we reported that, like humans, laboratory rats show sex differences in depression. From the present study, performed on Sprague-Dawley rats, we conclude that: 1) there are sex differences for depression in two different animal models (swimming-induced immobility and natatory tests); 2) there are also sex differences in open-field behavior; 3) prenatal maternal restraint decreases sex differences for depression but does not affect sex differences in open-field behavior; 4) prenatal maternal restraint affects female but not male behavior in the two depression tests used. These results suggest that: 1) sex differences reported in animal models of depression are under the control of gonadal steroids during prenatal brain development; 2) stress during early phases of development increases the risk for depression in adulthood.

Fetal brain serotonin synthesis and catabolism is under control by mother intake of tryptophan

Previous morphological studies reported that serotonergic neurons appear in rats in the second half of prenatal life. Initially the biochemical differentiation of these neurons before birth was studied. Both serotonin (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) was detected in the fetal brain on day 15 of gestation. During prenatal development an increase was detected in the brain levels of 5-HT (200% higher on day 19 than on day 15) and 5-HIAA (700% higher on day 19 than on day 15). Oral administration of tryptophan to pregnant rats induced a dose-related increase of tryptophan concentration in different fetal tissues, including brain. The increase in tryptophan tissue concentration was detected for low doses (50 mg/kg) and remained unsaturated after administration of high doses (1000 mg/kg). This observation suggests that the placental barrier is not effective to block the influx of high levels of tryptophan to the fetus. Tryptophan concentration in the brain is 300% higher than in the carcass and 600% higher than in the placenta. These data suggest a mechanism to assume a role in concentrating of tryptophan in the brain. Finally, it was found that an increase in brain tryptophan induced changes in both serotonin and 5-HIAA brain levels, but did not modify tyrosine, dopamine or norepinephrine levels. Thus, under physiological conditions, tryptophan hydroxylase activity in prenatal brain is probably not saturated by its substrate tryptophan.

Sex differences in behavioral despair: relationships between behavioral despair and open field activity

Many studies have reported sex differences in the rates of depression in humans. Due to experimental problems, the nature of these sexual differences is still unknown. In the present study, we quantify the sex differences in depression using two animal models. Both the Porsolt et al. test and the Hilakivi and Hilakivi forced swimming test have shown that the duration of immobility is higher in the male than in the female. Sexual differences in the animal models of depression are probably unrelated to general activity differences because there is no significant correlation between activity in both tests. However, the correlation between the two models of depression used reached statistical significance. Finally, the immobility levels in the Porsolt test were similar in the different stages of the estrous cycle.

Determination of monoamines and indoles in amniotic fluid by high-performance liquid chromatography-electrochemical detection

A technique is presented for the separation and detection in amniotic fluid of various substances associated with catecholamine metabolism. Monoamines and their metabolites were separated using reversed-phase ion-pair high-performance liquid chromatography. Detection and quantification were performed electrochemically. The retention times of 28 standards associated with the monoamines and their precursors and metabolites were evaluated with 14 different eluents. On the basis of the retention times of each standard and the modification of the retention times of the various peaks detected in amniotic fluid, the following substances were identified in this biological fluid: 4-hydroxy-3-methoxyphenylacetic acid, 5-hydroxyindoleacetic acid, 3,4-dihydroxyphenylacetic acid, 4-hydroxy-3-methoxyphenylglycol, epinephrine, 4-hydroxy-3-methoxymandelic acid, octopamine, tyrosine and tryptophan.

Gonadal influences on behavioral deterioration with aging of male rats

There is much evidence that gonadal steroids modulate brain and behavioral development. However their possible influence on age-related deteroriation of brain and behavior has received little attention. We now present evidence that neonatal castration reduces the decline in locomotion, motor coordination, and circadian activity rhythms that normally accompanies old age in male rats. Three behavioral tests (open field, Rota-Rod, and wheel running) were conducted with aged male rats (24 months). Those castrated in the first 24 hr of postnatal life were more active in the open field (P less than 0.001) than aged rats that were sham-operated neonatally. The sham-operated aged males showed a more marked deterioration of motor coordination in the Rota-Rod (P less than 0.01) and greater disorganization of circadian wheel-running (P less than 0.05) than the neonatal castrates or than young rats neonatally sham-operated.

Tyrosine availability and brain noradrenaline synthesis in the fetus: control by maternal tyrosine ingestion

In spite of substantial evidence that tyrosine availability modulates catecholamine synthesis, under a variety of conditions, in adult brains, its possible influence during brain development has received little attention. In the present paper, the effect of tyrosine when administered to pregnant rats on tyrosine and noradrenaline brain levels in the fetus was investigated. In the first experiment noradrenaline (NA) was detected in the fetal brain by day 13 of development. NA levels increased from days 13 to 19. Administration of tyrosine to the mother raises both tyrosine and NA levels in the fetal brain. The increase in tyrosine was similar on days 13, 15, 17 and 19 of pregnancy. However, the increase of NA was more pronounced on days 17 and 19 than on days 13 or 15. Tyrosine and NA enhancement was detected 30 min after tyrosine administration, persisted for at least 2 h and disappeared completely 6 h after its administration. Both tyrosine and NA increase are tyrosine dose-related. The present studies suggest that there are no important barriers for tyrosine transport between the maternal blood and the fetal brain. Furthermore, during prenatal life the rate of NA synthesis is regulated by tyrosine brain concentration and therefore maternal intake of tyrosine is an important factor for noradrenaline synthesis regulation in the fetal brain. The possible functional significance of noradrenaline brain increase after tyrosine administration are unknown. However, the NA modification could be the cause of the persistent behavioral modification that we have found in adult rats whose mothers were treated with tyrosine during pregnancy.

Pre- and postnatal choline supplementation produces long-term facilitation of spatial memory

Although research has demonstrated that short-term improvement in memory function of adult rats can occur when the availability of precursors for the neurotransmitter acetylcholine is increased, little is known about whether memory function of adult rats can be permanently altered by precursor supplementation during early development. In the present study, male albino rats were exposed to choline chloride supplementation both prenatally (through the diet of pregnant rats) and postnatally (subcutaneous injections). At 60 days of age rats were tested on a 12- and 18-arm radial maze task. Results indicated that compared to control littermates, perinatal choline-treated rats showed more accurate performance on both working and reference memory components of the task. This performance difference was apparent on the first block of sessions and continued throughout training. Further analysis revealed that the difference between choline and control rats is not due to use of differential response or cue-use strategies. Instead, it appears that choline induced performance differences are due to long-term enhancement of spatial memory capacity and precision.