الفهرس 
ANATOMY, HISTOLOGY AND EMBRYOLOGY OF OPTIC NERVE IN HUMAN
Histological ResultsOnly 14 pages are availabe for public view
 |  | from | 139 |  |  |
| | | from | 139 | | |
Abstract
Sildenafil citrate is one of the most commonly used drugs
worldwide and the drug has proved its great effect in
treatment of erectile dysfunction in men of different ages, but it
has been found that the drug has multiple adverse effects which
appear when the drug used in high doses and for long duration.
These adverse effects include headache hypotension, facial
flushing, indigestion and nasal congestion.
It has been found that one of the most important adverse
effects of sildenafil is non artertic anterior ischemic optic
neuropathy (NAION) which appears in the form of sudden
painless loss of vision which has been spread greatly between
users of the drug. WHO reports a large number of NAION
cases of different ages every year but most of these cases are
old age who suffer from diabetes mellitus, atherosclerosis,
hypotension or hypercholestramia which considered to be
important risk factors for development of the disease.
Multiple studies have discussed the causal relation
between usage of sildenafil citrate and development of NAION
but all these studies concentrated on the clinical aspects of the
disease, so the main aim of this study was focusing on the
histological changes induced by application of sildenafil citrate
on adult and senile optic nerve of albino rats.
Twenty four rats had been used in this study and they
were divided into 4 groups:- Group1 (adult control group): this group consisted of 6
adult rats, they received oral DMSO,.2% for 30 days.
- Group2 (senile control group): this group consisted of 6
senile rats, they received oral DMSO,.2% For 30 days.
- Group3 (adult experimental group): this group consisted
of 6 adult rats, they received oral sildenafil citrate
1.43mg/kg dissolved in DMSO,.2% for 30 days.
- Group4 (senile experimental group): this group consisted
of 6 senile rats, they received oral sildenafil citrate
1.43mg/kg dissolved in DMSO,.2% for 30 days.
The rats were sacrificed after 4 weeks and the optic nerve
was dissected and fixed in 10% formaldehyde for H&E and
luxol fast blue stain and glutraldhyde 2% for semithin sections,
Epon blocks and toludine blue stain.
When samples are examined it revealed that:
By examination of H&E sections, the adult control group
revealed that the optic nerve consisted of nerve fibers and each
one of them surrounded by oligodendrocytes, nuclei of
astrocytes in between, the nerve surrounded by three meningeal
layers arranged from outside to inside dura matter, pia matter
and arachnoid matter. The pia matter sends pial septa to
separate the nerve fibers from each other.
In comparison with control group, the adult experimental
group revealed marked change in the shape of the nuclei of
oligodendrocytes which became flattened and elongated increased spaces between nerve fibers, marked pleomorphism
which indicate occurrence of atrophy and degeneration of some
nerve fibers and there were some vacuolations started to
appear.
The control senile group revealed some histological
changes such as widened spaces between nerve fibers and some
vacuolations which possibly induced by aging. In comparison
with the senile control group The experimental group revealed
marked decrease in number of oligodendrocytes, change in the
shape of their nuclei which became flattened, in addition to
marked swelling of nerve fibers and marked pleomorphism
Luxol fast blue stain for senile control group gave the
same results which were shown with H&E stain in the adult
control group, but it revealed drastic changes in the senile
experimental group as extensive large sized vacuoles, marked
patches of degeneration and deeply stained nuclei of
oligodendrocytes.
Examination of semithin sections of the control adult
and senile groups revealed tightly packed axon bundles
surrounded by individual thin septa. The myelinated nerve
fibers each one surrounded by its own myelin sheath and nuclei
of oligodendrocytes.
After treatment, and in comparison with the control
group the experimental adult group showed extensive areas of
degeneration, the nerve fibers lose their myelin sheaths in some
areas, while the healthy nerve bundles appear irregular with
their myelin sheaths also there is a marked pleomorphism.The semithin sections of the senile experimental group
revealed extensive areas of degeneration; loss of myelinated
axons, large sized vacuoles and marked pleomorphism in
comparison with the senile control group.
Significant numbers of inflammatory cells accumulate
within the ischemic area, primary infarct area. Extrinsic
macrophages (blood-borne macrophages which invade the
damaged tissue) are identifiable early in their generation by the
presence of ED1 (CD68) protein.
The present study showed an increased number and size
of astrocytes as detected by GFAP stained sections and
presence of activated microglia which in the treated groups
more than the control groups and showed marked increase in
size and number and thickness of their cytoplasmic processes
Finally, this study revealed that the usage of sildenafil
citrate drug in high doses or for prolonged duration has a great
effect on the histology of optic nerve through decrease of blood
flow in the short posterior ciliary arteries causing atrophy and
degeneration of optic nerve fibers and affecting the visual
acuity of the patients.