beta-Adrenoceptor and nNOS-derived NO interactions modulate hypoglycemic pial arteriolar dilation in rats.
We examined the relative contributions from nitric oxide (NO) and catecholaminergic pathways in promoting cerebral arteriolar dilation during hypoglycemia (plasma glucose congruent with 1.4 mM). To that end, we monitored the effects of beta-adrenoceptor (beta-AR) blockade with propranolol (Pro, 1.5 mg/kg iv), neuronal nitric oxide synthase (nNOS) inhibition with 7-nitroindazole (7-NI, 40 mg/kg ip) or ARR-17477 (300 microM, via topical application), or combined intravenous Pro + 7-NI or ARR-17477 on pial arteriolar diameter changes in anesthetized rats subjected to insulin-induced hypoglycemia. Additional experiments, employing topically applied TTX (1 microM), addressed the possibility that the pial arteriolar response to hypoglycemia required neuronal transmission. Separately, Pro and 7-NI elicited modest but statistically insignificant 10-20% reductions in the normal ~40% increase in arteriolar diameter accompanying hypoglycemia. However, combined Pro-7-NI was accompanied by a >80% reduction in the hypoglycemia-induced dilation. On the other hand, the combination of intravenous Pro and topical ARR-17477 did not affect the hypoglycemia response. In the presence of TTX, the pial arteriolar response to hypoglycemia was lost completely. These results suggest that 1) beta-ARs and nNOS-derived NO interact in contributing to hypoglycemia-induced pial arteriolar dilation; 2) the interaction does not occur in the vicinity of the arteriole; and 3) the vasodilating signal is transmitted via a neuronal pathway.
Santizo
R A
RA
Neuroanesthesia Research Laboratory, University of Illinois at Chicago, Chicago, Illinois 60607, USA.
Koenig
H M
HM
Pelligrino
D A
DA
D000200:Action Potentials / Q000187:drug effects; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000578:Amidines / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000502:physiology; D001786:Blood Glucose; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007003:Hypoglycemia / Q000378:metabolism*; D007191:Indazoles / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D010841:Pia Mater / Q000098:blood supply*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
C102136:ARL 17477; D000319:Adrenergic beta-Antagonists; D000578:Amidines; D001786:Blood Glucose; D004791:Enzyme Inhibitors; D007191:Indazoles; D011943:Receptors, Adrenergic, beta; D013779:Tetrodotoxin; D011433:Propranolol; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; C080122:7-nitroindazole