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.
Department of Medicine, Case Western Reserve University, Cleveland Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA.
Shyam
S
Subramanian
Bernadette
B
Erokwu
Fang
F
Han
Thomas E
TE
Dick
Kingman P
KP
Strohl
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