Age-related changes in response of brain stem vessels to opening of ATP-sensitive potassium channels.
OBJECTIVE
This study was designed to determine regional differences and age-related changes in the contribution of ATP-sensitive potassium (KATP) channels to vasodilator responses in the brain stem circulation in vivo.


METHODS
Changes in diameter of the basilar artery (baseline diameter, 270 +/- 5 microns [mean +/- SEM]), its large branch (112 +/- 5 microns), and its small branch (49 +/- 2 microns) in response to KATP channel openers levcromakalim and Y-26763 were measured through a cranial window in anesthetized adult (4 to 6 months) and aged (24 to 26 months) Sprague-Dawley rats.


RESULTS
Topical application of levcromakalim and Y-26763 produced concentration-dependent vasodilation that was similar among the three vessel groups in adult rats. In aged rats, dilator responses of the branches, but not of the basilar artery, to the KATP channel openers were smaller than those in adult rats (P < .05). Glibenclamide, a selective KATP channel blocker, almost abolished this vasodilation in both groups of rats. Vasodilator responses to sodium nitroprusside were preserved in aged rats.


CONCLUSIONS
In adult rats, there is no regional heterogeneity in vasodilator response to KATP channel openers in the brain stem circulation in vivo. In aged rats, although KATP channels are also functional in the brain stem circulation, dilator response of the microvessels but not of the large arteries to direct activation of KATP channels is impaired.
Toyoda
K
K
Department of Internal Medicine, Kyushu Dental College, Kitakyushu, Japan.
Fujii
K
K
Takata
Y
Y
Ibayashi
S
S
Kitazono
T
T
Nagao
T
T
Fujikawa
M
M
Fujishima
M
M
D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D000959:Antihypertensive Agents; D001488:Basilar Artery / Q000254:growth & development / Q000502:physiology*; D001578:Benzopyrans / Q000494:pharmacology; D001933:Brain Stem / Q000098:blood supply* / Q000254:growth & development; D019806:Cromakalim; D015640:Ion Channel Gating; D008297:Male; D024510:Muscle Development; D009131:Muscle, Smooth, Vascular / Q000254:growth & development / Q000502:physiology; D009599:Nitroprusside / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011758:Pyrroles / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
D000959:Antihypertensive Agents; D001578:Benzopyrans; D015221:Potassium Channels; D011758:Pyrroles; D014665:Vasodilator Agents; D019806:Cromakalim; D009599:Nitroprusside; C074338:Y 26763