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Rapid pinealectomy in hamsters and other small rodents.

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Rapid Pinealectomy in Hamsters and
other Small Rodents
Physiology Division, Directorate of Medical Research,
Edgewood Arsenal, Maryland
Removal of the pineal organ from small rodents may be rapidly accomplished by ( 1 ) immobilizing the skull in a head mounting device and (2) by cutting
and removing a circular disc of bone overlying the pineal area with the use of a dental
machine and a specially designed circle cutter.
Recent investigations in this laboratory
have required the use of large numbers of
pinealectomized hamsters. Initially, the
operation performed with a hand trephine
or a dental machine using a n ordinary burr
drill was fraught with technical difficulties,
excessive bleeding and relatively high mortality. The following procedure using a
standard dental machine was developed
which permits rapid pinealectomy, minimal bleeding and nearly 100% survival.
The hamster skull is small and the skin
is so loose that the necessary immobilization of the head to permit drilling is almost
impossible. This difficulty was solved by
building a base of lucite fitted with ear
bars and a n adjustable tooth bar. Essentially this head holder is simply a modification of any standard stereotaxic instrument
A disc drill was made from stainless steel
stock turned down and drilled so as to form
a thin walled tube as shown in figure 1.
Coarse teeth were filed at one end of a short
piece which was attached to the shaft of
an ordinary dental drill either by silver
solder or by boring and tapping holes in
the sides to accommodate 0-80 stainless
steel Allen screws. A collar was fitted
around the drill, adjusted to the desired
depth of cut and tightened with Allen
screws. Although figure 1 shows serrations
with positive rake when rotating in a clockwise direction, further study has shown
that teeth with negative rake are a s good
or better; the latter appears to produce less
hemorrhage from the diploic vessels.
The animals are anesthetized, the bases
of the ears are slit vertically to expose the
ear canals (not mandatory) and the head
of the animal is rigidly mounted i n the
ANAT REC., 153: 19-22.
holder (fig. 2). The scalp is cut anteroposteriorly along the midline from between
the eyes to beyond the base of the skull.
The skin flaps are reflected and the underlying fasciae and the insertions of the temporal and occipital muscle masses are
scraped free in a n area wider than the diameter of the collar. Careful removal of
these tissues from the field is necessary to
prevent entanglement with the drill and
collar during the subsequent step. At this
.0b 2”
Fig. I Diagram of the drill complex. C, collar
(outer diameter, 0.353”); DD, dental drill shaft
(0.092”); HS, hollow shaft (outer diameter,
0.220”; inner diameter, 0.185”) ; SSAS, stainless
steel Allen screw (0-80).
Fig. 2 A photograph of a hamster head mounted i n head holder with bone disc removed.
Re-touched sagittal and transverse sinuses are visible. The freed bone disc lies anterior to
the opening.
point the large venous sinuses of the brain
are visible through the skull. The drill is
centered on the confluence of the superior
sagittal and transverse sinuses. The hole
is drilled to the desired depth as set by the
adjustable collar. We find that the optimal
depth is not quite equal to the thickness of
the skull. At this depth, the bone disc is
movable but still adherent to the dura.
With care, the disc can be removed with
little or no bleeding from the underlying
vascular channels. Although the pineal
gland is not visible, a little practice permits
one to remove it by inserting a n open pair
of watchmaker’s forceps into the junction
of the two sinuses, grasping the stalk and
removing gland and stalk in one motion
(fig. 3 ) . The white pineal body is about
0.5 mm in diameter (in hamsters) and is
Excessive hemorrhage is prevented by
rapidly returning the bone disc to its original position and by the application of a
cotton pledget with moderate pressure.
Bleeding (and possible infection) is further controlled by application of a powdered sulfa compound. The skin flaps are
pulled together and stapled. We find that
Fig. 3 Diagram of a mid-sagittal section of
a n adult hamster brain showing the relationships
of the pineal organ with the surrounding structures and the direction of approach for pinealectomy. CC, corpus callosum; CER, cerebellum;
HN, habenular nucleus; IC, inferior colliculus;
PC, posterior commissure; SC, superior colliculus;
SSS, superior sagittal sinus.
a standard desk stapler from which the
anterior end of the base has been ground
off to the front margin of the stapling plate
is rapid and quite satisfactory.
Normally, we maintain the animals on
oxytetracycline hydrochloride (Cosa-Terramycin, Pfizer) i n the drinking water for the
first 2-3 days postoperatively a s a prophylactic measure. Penicillin has been
found to have adverse effects on anesthetized hamsters.
While other procedures are undoubtedly
adequate (see Kitay and Altschule, '54),
the use of the head holder and the disc
drill permits the operator to pinealectomize
an animal in 1-2 minutes. Rats and ground
squirrels have been pinealectomized with
equal facility by adjusting the collar to
change the depth of cut. While the dimensions of the drill and collar as given in
figure 1 are those which we have used and
found optimal for use on hamsters, they
are not critical. The hole size and the
collar can be varied to suit other animals.
The authors are indebted to Mr. Milton
Wirth for the construction of the drill complex and stereotaxic instrument base.
Kitay, J. I., and M. D. Altschule 1954 The
Pineal Gland, Harvard University Press, Cambridge, pp. 8-12.
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hamster, rapid, pinealectomy, rodents, small
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