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Abstract #8285 Published in IGR 4-3
Reflex choroidal blood flow responses of the eyeball following somatic sensory stimulation in rats
Shimura M; Uchida S; Suzuki A; Nakajima K; Aikawa YAuton Neuroscience 2002; 97: 35-41
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 seconds 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 nine 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 alpha-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.
M. Shimura, MD, Graduate School of Humanities and Sciences, Ochanomizu University, Bunkyo, Tokyo, Japan. mshimura@asa.email.ne.jp
Classification:
6.11 Bloodflow measurements (Part of: 6 Clinical examination methods)
