Dossayev T. M., Zholdybayeva A.A.
Annotation. Formation of the transmitter
development phase in n. glossopharyngeus was studied at 79 embryos.
Heterochronia was ascertained between formation of the neurofibrous component of
n. glossopharyngeus and appearance of the basic neurotransmitters - acetylcholines and catecholamines. The time equal to 2 weeks was revealed
between the beginning of acetylcholine and
catecholamine synthesis.
Key words: embryo, n. glossopharyngeus, neurotransmitters.
I.
Introduction.
During the formation of the autonomic nervous system,
in particular nervous interlacements of various organs, neurotrasmitters appear in nerve fibers not immediately,
but only after dendrites, axons and neuroblasts penetrate organs or
typical areas of neuroganglion
site. In connection with this,
pretransmitter and transmitter phases are marked out in the development and
functioning of the autonomic nervous system [1]. The time of the transition to
the transmitter phase of the nervous system development coincides with the
beginning of a fetal period and at this particular time the formation of cholino-
and adrenoreceptors occurs in the target cells
[2]. The beginning of the transmitter
phase also concurs with active synaptogenesis and apoptopic elimination of
neurons, which didn’t generate functioning interneuronic and
neurohistionic synaptic bonds [3, 4].
The autonomic nervous system in embryogenesis is
developed in cranial and caudal
direction and the beginning of the
transmitters synthesis heterochronically occurs in embryo plexus, starting in
chest, then in lumbar and finally in pelvic plexus. For example, basic
transmitters begin to define in heart plexus by the week 8-9 of ontogenesis,
while in kidneys only by the week 10-11 [5,6].
In conjunction with this, the study of the transmitter
phase of different parts of the vegetal nervous system is a key of
understanding of the mechanism of its further normal development and of the interneuronic and
neurohistionic bonds dynamics [1,2].
II.
Target setting.
The analysis of the literature reveals that at present
the formation of the autonomic nervous system development transmitter phase has
been studied in detail in several internal organs (heart, kidneys and aorta) but
to less degree in embryogenesis of the craniocerebral nerves. In this connection,
we set the target to study the dynamic of the transmitter phase start in the
human embryo n. glossopharyngeus.
The stude of the fibrocellular components development
of human embryos n. glossopharyngeus and formation of the transmitter phase of
autonomic nervous system functioning was conducted on serial longitudinal and
transverse sections of human embryos. There were studied 79 human embryos at the age
of 4 to 12 weeks. The sections were dyed according to Veigert-Pal, Vizel, impregnated by the silver nitrate
according to Bilshovsky-Buke.
To reveal the basic neurotransmitters on the cryostat-made
sections the neurohistochemical reaction was conducted on acetylcholinesterase
according to Karnovsky-Roots, and on luminescence of catecholamines with
sections incubation in glyoxylic acid.
III. Results.
In the result of the study it was established that n. glossopharyngeus
enters into the side of a back cerebral vesicle by 3-5 roots. In all monitored
cases, beginning from 6 weeks embryos, n. glossopharyngeus intracerebral bonds
with n. facialis and n. vagus were discovered, which corresponds with data,
received by the previously classic neurohistological monitoring [7].
In the process of embryogenesis, n. glossopharyngeus caudal
ganglion was the first to be formed, which is revealed in a 4 weeks embryo, and
a 6 weeks embryo has a well-defined formation of an oval form, which consists of
a neoroblasts cluster.
N. glossopharyngeus cranial ganglion was defined for
the first time in 7 weeks embryos as a small cluster of neuroblasts and only in
8 weeks embryos it took an oval form typical for a ganglion. At this stage of
development among neuroblasts forming cranial ganglion there were separate
groups of cells with a growth cone. But
in all monitored cases beginning from 8 weeks and further periods of the
development 1-2 additional groups of neuroblasts were found together with
cranial ganglion.
Further, as the embryo develops, in most cases the n.
glossopharyngeus cranial ganglion conjugated with much bigger (2-3 times) n.vagus
cranial ganglion, which is located at the caudal end of n. glossopharyngeus cranial
ganglion.
First branches of the n. glossopharyngeus development
were discovered in a 7 weeks embryo. From this period on there were revealed 2-5
pharyngeal branches, which were directed to the primordial pharynx wall, and
also primordial tympanic nerve and sino-carotid branch. Further on, as these
branches grew along the nerve tracts some small groups of undifferentiated
neuroblasts were observed. The basic trunk of n. glossopharyngeus went to the
primordial tongue root, separating n. lingvalis on its way, along which on the
way of nerve fibers small accumulations of neuroblasts were discovered. As the embryo developed, neuroblasts were
differentiated, diffusingly located along nerve fibers and forming ganglions.
The quantity of neuroblasts and their accumulations sizes grew and, as a result
of it n. glossopharyngeus looked like a cellular- fibrous and ganglionic chorda.
During the neurohistochemical study of sections
according to Karnovsky-Roots for choline esterase in 8 weeks embryos single
cholinergic neurons were discovered for the first time with an ill-defined
reaction on copper sulfide. Such neurons, equal to 8 –
The study of the sections incubated in glyoxylic acid
to detect catecholamine revealed of single actively fluorescent neurons (SIF
cells) in 10 weeks embryos. Single SIF
neurons were located near accumulation of neuroblasts, forming n.
glossopharyngeus and n. vagus caudal and cranial ganglia and also along their
branches.
Around the cranial ganglion in all cases there were
observed 1 or 2 small paraganglia, which had cells with weak specific
fluorescent cytoplasm and non fluorescent nucleus.
Additionally, in most cases of monitoring, along n.
glossopharyngeus sinocarotid branch there was a group of neurons which showed
weak specific fluorescent of catecholamines.
IV. Summary.
1)
The n. glossopharyngeus
and its basic branches in embryogenesis of a human are being formed during the
2nd month of the pre-natal life in pretransmitter phase of the autonomic
nervous system development.
2)
The transmitter phase of the
progressive n. glossopharyngeus starts from the week 8 of the pre-natal life
with appearance of single cholinergic neurons consisting of the forming caudal
ganglion.
3)
Catecholamines were
discovered in single neurons only on the week 10 of the pre-natal life.
4)
The appearance of the
basic transmitters in n. glossopharyngeus nerve structures concurs with the
placentation period.
5)
There is heterochronia
between formation of n. glossopharyngeus neuro-fibrous component and beginning of
the basic neurotransmitters’ synthesis.
6)
The progressive human
embryo n. glossopharyngeus acetylcholine synthesis is 2 weeks ahead of
catecholamine synthesis.
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About the authors.
Professor
Tasbulat Dossaev (Mr.) Doctor of Medicine, the Head of Anatomy Department,
Mail address –
Aisulu Zholdybayeva
(Mrs.)
Mail
address –