Role of nitric oxide in the regulation of spinal arteriolar tone.
OBJECTIVE
The important role played by nitric oxide (NO) in the maintenance of cerebral arterial tone, both in the resting state and after injury, has been demonstrated, but the role of NO in spinal arteries is unknown. The aim of this study was to verify, by topical application of a NO synthase inhibitor in vivo, the hypothesis that NO plays an important role in the maintenance of spinal arteriolar tone.


METHODS
Closed spinal windows were prepared at the C6 level, for observation of arteriolar reactivity. Male Wistar rats were divided into four groups in the resting state and three groups in the compressed state (which was produced by increasing the intrathecal window pressure). The control group underwent superfusion of artificial cerebrospinal fluid into the spinal window. The nitro-L-arginine-methyl ester (L-NAME) and nitro-D-arginine-methyl ester groups underwent superfusion of the NO synthase inhibitor L-NAME and its inactive enantiomer nitro-d-arginine-methyl ester, respectively. The L-NAME/S-nitroso-acetylpenicillamine (SNAP) group underwent mixed superfusion of L-NAME and the direct NO donor SNAP, for investigation of the effects of an exogenous NO donor.


RESULTS
In the resting state, the arterioles constricted significantly in the L-NAME group, compared with values before L-NAME superfusion and those for the other groups. In the L-NAME/SNAP group, the arterioles dilated significantly after SNAP superfusion, compared with values before superfusion and those for the other groups. In the compressed state, the arterioles dilated after compression in all three groups but the dilation was significantly attenuated in the L-NAME group, compared with values for the control and nitro-D-arginine-methyl ester groups.


CONCLUSIONS
It is suggested that NO plays an important role in the maintenance of spinal arteriolar tone in the resting and compressed states of the spinal cord.
Ishikawa
Mami
M
Department of Neurosurgery, Philipps University Hospital, Marburg, Germany. mishik@lsuhsc.edu
Sekizuka
Eiichi
E
Krischek
Boris
B
Sure
Ulrich
U
Becker
Ralf
R
Bertalanffy
Helmut
H
D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000503:physiopathology; D008297:Male; D018715:Microscopy, Video; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D013116:Spinal Cord / Q000098:blood supply*; D013117:Spinal Cord Compression / Q000503:physiopathology; D014655:Vascular Resistance / Q000502:physiology*
D020030:Nitric Oxide Donors; C110881:S-nitro-N-acetylpenicillamine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D010396:Penicillamine; D019331:NG-Nitroarginine Methyl Ester