Abstract
The effect of cutaneous mechanical stimulation on choroidal blood flow (ChBF) of the
eyeball measured using a laser Doppler flowmeter was examined in anesthetized rats.
Noxious pinching stimulation of a forepaw for 20 s produced increases in ChBF and
mean arterial blood pressure (MAP), whereas brushing of a forelimb produced no changes
in either parameter. After spinal transection at the fourth thoracic (T4) level, forepaw
pinching stimulation did not produce any MAP changes in 9 of 11 spinalized rats. In
these nine spinalized animals, pinching stimulation of a forepaw produced no significant
responses in ChBF. After the cutting of cervical sympathetic trunks in five spinal
rats, forepaw pinching showed no effect on MAP, but produced an increase in ChBF,
which was abolished by an intravenous (i.v.) injection of 1-(2-trifluoromethylphenyl)
imidazole (TRIM), a selective inhibitor of neuronal nitric oxide synthase (nNOS).
In another four spinalized rats, whose cervical sympathetic trunks were intact and
the superior salivary nucleus (SSN) was destroyed, forepaw pinching showed no effect
on MAP, but produced a decrease in ChBF, which was abolished by an i.v. injection
of phentolamine, an α-adrenoceptor antagonist. The present experiment shows that somatic
afferent stimulation can produce reflex responses of the ChBF of the eyeball, either
a vasodilative response using parasympathetic efferent fibers or a vasoconstrictive
response using sympathetic efferent fibers, independent of systemic blood pressure.
It was also shown that the somatically induced vasodilative response was due to a
release of nitric oxide (NO) from parasympathetic nerves and the vasoconstrictive
response was due to a release of noradrenaline from sympathetic nerves.
Keywords
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Article info
Publication history
Accepted:
January 15,
2002
Received in revised form:
January 10,
2002
Received:
September 12,
2001
Identification
Copyright
© 2002 Elsevier Science B.V. Published by Elsevier Inc. All rights reserved.
