Impact of 2 doses of clorgyline on the rat preimplantation embryo development and the monoamine levels in urine

Stress exposure during the preimplantation period affects blastocyst lineages and offspring development

We found retardation of preimplantation embryo growth after exposure to maternal restraint stress during the preimplantation period in our previous study. In the present study, we evaluated the impact of preimplantation maternal restraint stress on the distribution of inner cell mass (ICM) and trophectoderm (TE) cells in mouse blastocysts, and its possible effect on physiological development of offspring. We exposed spontaneously ovulating female mice to restraint stress for 30 min three times a day during the preimplantation period, and this treatment caused a significant increase in blood serum corticosterone concentration. Microscopic evaluation of embryos showed that restraint stress significantly decreased cell counts per blastocyst. Comparing the effect of restraint stress on the two blastocyst cell lineages, we found that the reduction in TE cells was more substantial than the reduction in ICM cells, which resulted in an increased ICM/TE ratio in blastocysts isolated from stressed dams compared with controls. Restraint stress reduced the number of implantation sites in uteri, significantly delayed eye opening in delivered mice, and altered their behavior in terms of two parameters (scratching on the base of an open field test apparatus, time spent in central zone) as well. Moreover, prenatally stressed offspring had significantly lower body weights and in 5-week old females delivered from stressed dams, fat deposits were significantly lower. Our results indicate that exposure to stress during very early pregnancy can have a negative impact on embryonic development with consequences reaching into postnatal life.

Expression of adrenergic receptors in bovine and rabbit oocytes and preimplantation embryos

Catecholamines play an important role in embryogenesis, and data obtained in the rodent model indicate that they can act even during the preimplantation period of development. Using RT-PCR with specific oligonucleotide primers distinguishing among all members of the adrenergic receptor family, we examined expression of adrenergic receptors in bovine and rabbit oocytes, morulas and blastocysts. We found several profiles of adrenoceptor mRNA expression. Transcripts for some receptor subtypes (bovine alpha 2 receptors, rabbit α2A, α2C, β1 and β2 receptors) were detected at all examined stages, which suggests receptor expression throughout (or at most stages) the preimplantation developmental period. Expression in oocytes but not at later stages was found in only one adrenoceptor subtype (rabbit α1B). In contrast, mRNA for several adrenoceptors was found in embryos but not in oocytes (bovine beta adrenoceptors and rabbit α1A). Nucleotide sequences of our PCR products amplified in rabbit oocytes, and preimplantation embryos represent the first published mRNA sequences (partial sequences coding at least one transmembrane region) of rabbit α2C, β1 and β2 adrenoceptors. Our results suggest that the expression of adrenergic receptors can be a general feature of mammalian oocytes and preimplantation embryos. On the other hand, comparison of three mammalian species (cattle, rabbit and mouse) revealed possible interspecies differences in the expression of particular adrenoceptor subtypes. Our results support the opinion that stress mediators can act directly in cells of preimplantation embryos.

Monoamine oxidases in development

Monoamine oxidases (MAOs) are flavoproteins of the outer mitochondrial membrane that catalyze the oxidative deamination of biogenic and xenobiotic amines. In mammals there are two isoforms (MAO-A and MAO-B) that can be distinguished on the basis of their substrate specificity and their sensitivity towards specific inhibitors. Both isoforms are expressed in most tissues, but their expression in the central nervous system and their ability to metabolize monoaminergic neurotransmitters have focused MAO research on the functionality of the mature brain. MAO activities have been related to neurodegenerative diseases as well as to neurological and psychiatric disorders. More recently evidence has been accumulating indicating that MAO isoforms are expressed not only in adult mammals, but also before birth, and that defective MAO expression induces developmental abnormalities in particular of the brain. This review is aimed at summarizing and critically evaluating the new findings on the developmental functions of MAO isoforms during embryogenesis.

Biogenic monoamines in preimplantation development

BACKGROUND

The involvement of biogenic monoamines in early ('preneural') embryogenesis has been well documented in lower vertebrates, but much less information is available about the role of these molecules in the earliest stages of development in mammals, including humans.

METHODS

Databases (PubMed, ISI Web of Knowledge and Scopus) were searched for studies relating to biogenic monoamines functioning in early embryos. The available data on the expression of histamine, serotonin and adrenergic receptors during mammalian preimplantation development were summarized, and the potential roles of biogenic monoamines in very early pregnancy were discussed.

RESULTS

The roles of biogenic monoamines in mammalian preimplantation embryo development can be diverse, depending on the embryo developmental stage, and the physiological status of the maternal organism. Several receptors for biogenic monoamines are expressed and biologically functional in cells of preimplantation embryos. Activation of histamine receptors can play a role in embryo implantation and trophoblast invasion. Activation of adrenergic and serotonin receptors can influence proliferation and survival of early embryonic cells.

CONCLUSIONS

Biogenic monoamines can play an important role in physiological conditions, contributing to embryo-maternal interactions, or can influence the early embryo under unfavorable or pathological conditions (e.g. in maternal stress, or in women taking certain antidepressants, anti-migraine or anti-ulcer drugs).