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KMID : 0376219840210020243
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Chonnam Medical Journal
1984 Volume.21 No. 2 p.243 ~ p.253
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Change in the Clonidine Effect Following a Transitory Increase of Intracranial Pressure
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Abstract
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In an attempt to investigate functional changes of central a2-adrenoceptors following increased intracranial pressure (ICP) in urethane-anesthetized rabbits, the hypotensive and cardiac slowing effects of clonidine in control rabbits and those effects in rabbits which were subjected to increased ICP were compared.
1. Dose dependent hypotensive responses were noted in control rabbits (not subjected to increased ICP) by intraventricular (i. vt. , 10, 30,ug) ang intravenous (i.v., 50, 100, 200 ug) clonidine.
2. Cushing responses in control rabbits were markedly depressed by i. vt. clonidine (10, 30/ ug). By i. v. clonidine (200, ug), the highest level of blood pressure accompanying increased ICP in control rabbits was significantly lower than that of nonclonidine treated rabbits, but the rising rate of blood pressure accompanying increased ICP was not different.
3. In the rabbits in which ICP were increased up to 150 mm Hg, the hypotensive effect of i. vt. clonidine (3, 10, 30, ug) was decreased, while the effect of i. v. clonidine was not affected.
4. By both i. vt. clonidine (30, ug) and i. v. clonidine (200, ug), the cardiac slowing response was provoked in the control rabbits but suppressed markedly in the rabbits of increased ICP (150 ug Hg).
5. The hypotensive effect of i. vt. clonidine was decreased significantly in rabbits of which ICP was increased up to 100 mm Hg.
The above results suggest that the function of central a2-adrenoceptors mediating hypotension is impaired by elevation of ICP.
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