Glutamic acid represents the most abundant
stimulatory neurotransmitter in the central nervous
system. Monosodium glutamate (MSC), subcutaneously
administered to newborn rats in the perinatal period,
induces lesions in 80 to 90% of the neurocytes of arcuate
nuclei in the hypothalamus. These nuclei are the site of
production of numerous stimulatory and inhibitory
hormones including growth hormone releasing hormone
(GHRH).
The present studies were performed on male Wistar
strain rats, subcutaneously injected on days 2, 4, 6, 8,
and 10 of postnatal life with MSC at a dose of 4 mglg
body weight. Eighteen-month-old rats were additionally
treated with Ambinon. When the animals reached the
ages of 6 or 12 months, their body weight, body length
and weight of pituitary were determined. On parafrin
sections, using imrnunohistochemical techniques, TSHimmunoreactive
cells were detected and characterised by
computerised image analysis. The results were subjected
to statistical analysis using Student's t test.
The rats which were perinatally treated with MSC
and examined after 6 or 12 months of life were obese
and shorter than control rats by 7% and 10%
respectively. They also exhibited a reduction in the
weight of the pituitary of 30% and 40% respectively in
the two age groups.
The proportion of TSH-immunoreactive cells in the
pituitary remained unchanged and amounted to 4.5% in
the 6-month-old and 5.4% in the 12-month-old rats
respectively. The number of TSH-positive cells per mm 2
area remained unchanged. The area and circumference
of the cells in the 12-month-old rats were reduced by
22% and 18%, respectively.
Perinatal injury to hypophyseal arcuate nuclei
induced by monosodium glutamate injection, was not
associated with any significant alterations in pituitary
structure, as defined by the proportion of pituitary
volume occupied by TSH-immunoreactive cells