L-NAME differentially alters ventilatory behavior in Sprague-Dawley and Brown Norway rats.
Nitric oxide (NO) is a regulating factor in respiration. The question was whether NO synthase (NOS) blockade would affect posthypoxic ventilatory behavior similarly in two rat strains with known differences in steady-state hypoxic and hypercapnic responses and in posthypoxic ventilatory behavior. Ventilatory behavior [respiratory frequency (f) and minute ventilation (VE)] was measured by body plethysmography on unanesthetized, unrestrained adult male Sprague-Dawley (SD; n = 8) and Brown Norway rats (BN; n = 8) at baseline and 1 min after rapid transition to 100% O(2) after 5 min of isocapnic hypoxia (10% O(2)-3% CO(2)-balance N(2)). Testing was performed 30 min after intraperitoneal injection of either saline (vehicle) or 100 mg/kg of N(G)-nitro-L-arginine methyl ester (L-NAME). Resting f and VE increased after L-NAME in both strains, more markedly in SD compared with BN (77 vs. 47% for f, and 42 vs. 16% for VE, respectively; P < 0.05). With vehicle, posthypoxic f and VE decline (Dejours phenomenon) was present only in BN and was absent in SD. With L-NAME, the Dejours phenomena were still present in BN but also were apparent in SD (f: 95.3 vs. 134.4 beats/min at baseline; VE: 66.3 vs. 88.8 ml/min at baseline; P < 0.05). Thus NOS blockade results in a strain-specific alteration in resting ventilation and uncovers the Dejours phenomenon in the SD strain.
Subramanian
Shyam
S
Department of Medicine, Case Western Reserve University, Cleveland Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA.
Erokwu
Bernadette
B
Han
Fang
F
Dick
Thomas E
TE
Strohl
Kingman P
KP
D000818:Animals; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D007274:Injections, Intraperitoneal; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010507:Periodicity; D010993:Plethysmography, Whole Body; D051381:Rats; D011914:Rats, Inbred BN; D017207:Rats, Sprague-Dawley; D012119:Respiration / Q000187:drug effects*
D004791:Enzyme Inhibitors; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester