Effects of intracerebroventricular administration of 6-hydroxydopamine on ouabain-like immunoreactivity in plasma and the hypothalamo-pituitary axis in rats.
OBJECTIVE
To examine the role of central mechanisms on the production and release of an ouabain-like factor, the effects of intracerebroventricular injections of 6-hydroxydopamine on the tissue content and on the plasma level of the ouabain-like factor were determined in rats.


METHODS
The vehicle (0.1% ascorbic acid in 0.9% saline) and 6- hydroxydopamine (250 micrograms/rat) were injected into the left lateral ventricle in ether-anaesthetized Wistar rats. Hypothalamus, pituitary, adrenal and venous blood was sampled 24h and 7 days later. The procedure was repeated using another rat group 7 days later. Characteristics of immunoreactive ouabain-like factor were determined by a combination of high-performance liquid chromatography and a highly sensitive enzyme-linked immunosorbent assay for ouabain. The level of the ouabain-like factor in these tissues and in plasma extracts measured by the enzyme-linked immunosorbent assay was compared between the two groups receiving 6-hydroxydopamine and the vehicle.


RESULTS
Twenty-four hours after the intracerebroventricular injections of 6-hydroxydopamine, the ouabain-like factor level in the pituitary, hypothalamus and plasma had decreased significantly, whereas the ouabain-like factor level in the adrenal had not changed. The content of noradrenaline in the hypothalamus was also decreased markedly 7 days later and the content of ouabain-like factor in the pituitary remained low. On liquid chromatography the elution pattern of the ouabain-like factor in plasma and in tissue extracts coincided with that of authentic ouabain.


CONCLUSIONS
Intracerebroventricular treatments with 6-hydroxydopamine elicited decreases in ouabain-like factor contents in the pituitary, the hypothalamus and the plasma. These results suggest that the production and release of ouabain-like factor are closely associated with the brain, particularly the hypothalamus-pituitary axis, and that noradrenergic or dopaminergic neurons, or both, play a key role in this mechanism.
Komiyama
Y
Y
Department of Clinical Sciences and Laboratory Medicine, Kansai Medical University, Japan.
Mori
T
T
Okuda
K
K
Munakata
M
M
Murakami
T
T
Masuda
M
M
Goto
A
A
Yamada
K
K
Takahashi
H
H
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D007031:Hypothalamus / Q000737:chemistry*; D007276:Injections, Intraventricular; D008297:Male; D009638:Norepinephrine / Q000032:analysis; D010042:Ouabain / Q000032:analysis* / Q000276:immunology; D010902:Pituitary Gland / Q000737:chemistry*; D051381:Rats; D017208:Rats, Wistar
D010042:Ouabain; D009638:Norepinephrine