NEUROENDOCRINOLOGY
LETTERS
including
Psychoneuroimmunology, Neuropsychopharmacology,
Reproductive Medicine, Chronobiology
and Human Ethology, ISSN 0172–780X
Effect
of superior cervical ganglionectomy on the ultrastructure of
pinealocytes in the Djungarian hamster (Phodopus sungorus):
Quantitative study
by
Michal Karasek, Anna Zielinska, Krystyna Marek
&
Jacek Swietoslawski
Submitted:
August 14, 2002 Accepted: September 23, 2002
Key
words: pineal gland, pinealocyte, ultrastructure, superior cervical
ganglia, sympathectomy
Abstract
OBJECTIVES:
Superior cervical ganglia are of crucial importance in regulating
the secretion of the pineal hormone – melatonin. Changes
in pineal morphology have been observed in many mammalian
species after sympathectomy. Therefore, we decided to investigate
the ultrastructure of Djungarian hamster pinealocytes following
superior cervical ganglionectomy.
MATERIAL
AND METHODS: Eight adult female Djungarian hamsters (Phodopus
sungorus) were used in this study. The superior cervical ganglia
were removed bilaterally in four animals, whereas the other
four animals served as sham-operated controls. The pineal
glands were removed four weeks after the operation and processed
for electron microscopic study. The cross-sectional areas
of pinealocyte and its nucleus, and relative volume of mitochondria,
Golgi apparatus, lysosomes, granular endoplasmic reticulum,
and glycogen particles as well as the numbers of dense-core
vesicles and “synaptic” ribbons were estimated using
a digital analyzer connected on-line to IBM-PC computer. Statistical
analysis of the data was performed using Student’s t
test and Snedecor F test.
RESULTS:
Significant reduction in the cross-sectional areas of the
pinealocyte and its nucleus as well as in the relative volumes
of mitochondria and glycogen particles was observed after
superior cervical ganglionectomy in comparison with sham-operated
controls. Sympathectomy resulted also in reduction of the
number of dense-core vesicles. On the contrary 2,5 fold increase
in the number of “synaptic” ribbons was observed
in ganglionectomized animals in comparison to sham-operated
controls.
CONCLUSION:
Deprivation of sympathetic innervation leads in Djungarian
hamsters not only to suppression of melatonin synthesis and
secretions but, as appears from our studies, induces also
morphological changes suggesting lower metabolic and secretory
activity of pinealocytes.
*
* *
Introduction
The
mammalian pineal gland is innervated primarily, if not entirely,
by postganglionic sympathetic nerve fibers arising from neurons
located in the superior cervical ganglia [1, 2]. These nerve
fibers play a crucial role in regulation of pineal function.
They contain and release norepinephrine which stimulates the
synthesis of the pineal hormone – melatonin [3, 4]. However,
ultrastructural studies, especially those using quantitative
methods, on the effects of sympathectomy on the pineal cells
are rare. Therefore, the aim of the present study was to investigate
the ultrastructure of pinealocytes in the Djungarian hamster
following bilateral superior cervical ganglionectomy.
