Cardiorespiratory alterations produced by pharmacological agents applied to the ventrolateral medulla (intermediate area) of the cat. Effect of exercise condition on glycine-induced inhibition
Tolentino-Silva, F.P.; Campos Júnior, R.R.; Russo, A.K.; Silva, A.C.; Freire, E.; Guertzenstein, P.G.
Brazilian Journal of Medical and Biological Research 26(8): 879-896
1993
ISSN/ISBN: 0100-879X PMID: 7905329 Document Number: 421684
1. To study the action of the intermediate area (IA), coextensive with the rostral ventrolateral medulla, on the neurophysiological mechanism involved in the regulation of respiration, in terms of inspiratory drive and respiratory timing, cats were submitted to topical application of sodium pentobarbital (30 mg/ml), leptazol (200 mg/ml), glutamate (50 mg/ml) and glycine (100 and 50 mg/ml) to the IA. The effects of electrically induced exercise on the ventilatory response and oxygen uptake ( ovrhdot VO-2) obtained by topical application of glycine (50 mg/ml) to the IA were also studied. 2. Leptazol reduced minute ventilation ( ovrhdot V-E) and inspiratory drive (V-T/T-1) and changed the timing mechanism. Glutamate only increased tidal volume (V-T), ovrhdot V-E and V-T/T-1. Arterial blood pressure (AP) increased and heart rate (HR) did not change with either drug. 3. Sodium pentobarbital reduced V-T and changed the timing mechanism. Glycine only reduced ovrhdot V-E, V-T and V-T/T-1. AP decreased and HR did not change with either drug. 4. Thee depressor effects of glycine on respiratory pattern, ovrhdot VO-2 and CO-2 production ( ovrhdot VCO-2) tended to be attenuated by exercise. 5. The fall in AP due to glycine application did not differ between resting and exercise conditions. 6. Our results indicate that at least two different nervous structures are involved in the IA: one responsible for the respiratory drive and sensitive to glycine and glutamate, and the other responsible for the regulation of the timing mechanism and sensitive to sodium pentobarbital and leptazol. 7. The changes obtained in ovrhdot VO-2 and ovrhdot VCO-2 during inhibition of IA support the idea of a central action of glycine in terms of reduction of oxygen uptake.