Metabolic responses to NMDA glutamate receptors antagonism in acute hypoxia in developing rats

Abstract

Newborn mammals reduce their metabolic rate and body temperature (Tb) in hypoxia, while adults increase minute ventilation (Ve). This increased Ve is related to NMDA glutamate receptors activation, while we reported that in rat pups NMDA glutamate receptors limits the drop of metabolic rate and Tb, but the developmental pattern of this response has not been studied. Thus we evaluated metabolic rate (VCO2), Tb, and Ve in male rats aged 4, 10, and 20 days in normoxia and hypoxia (30 minutes-12%O2) after injection of vehicle or the NMDA receptor antagonist MK-801 (1.5 mg/kg–ip). For all age, after saline, Tb dropped 0,4–0,5 °C in hypoxia, MK had no effect in P4, but Tb dropped 0,8 °C and 1,4 °C in P10 and P20 after MK. VCO2 decreased more in P4 and P10 compared to P20 rats, and MK injection resulted in a stronger VCO2 decrease only in P20 rats. Ve increased significantly in P10 and P20 hypoxic rats and MK injection had no clear effects. In P4 rats, Ve decreased in hypoxia after MK injection. As previously reported, after MK injection, Ve response during the first 10 minutes of hypoxic exposure was abolished in P20 rats only. Thus NMDA receptors are involved in the hypoxic regulation of Tb and VCO2 and produces age-dependent responses. Founded by Natural Sciences and Engineering Research Council of Canada