STRESS-INDUCED CHANGES IN RESPIRATORY QUOTIENT, ENERGY-EXPENDITURE AND LOCOMOTOR-ACTIVITY IN RATS - EFFECTS OF MIDAZOLAM

Changes in O-2 consumption, CO2 production and locomotor activity were examined in rats exposed to (1) brief footshock, (2) an aversive cond itioned stimulus (CS) predicting footshock, or (3) the anxiogenic drug FG-7142. Respiratory quotient (RQ = CO2 produced/O-2 consumed) and en ergy expenditure [EE = O-2 consumed (364 + 113RQ)] were derived to giv e an estimate of the energy substrate (fat, carbohydrate or protein) b eing utilised and total substrate oxidation respectively. In experimen t 1, footshock (4 x 5 s 0.6 mA shocks over 2 min) produced an immediat e increase in RQ, EE and activity. The RQ and EE effects were attenuat ed by the benzodiazepine midazolam (1 mg/kg). In experiment 2, an aver sive CS, consisting of flashing light and buzzer that had 24 h earlier been repeatedly paired with footshock (20 x 5 s 0.6 mA shocks) caused a pronounced drop in RQ, an increase in EE and locomotor activity sup pression. The effects of the aversive CS on RQ and EE were reversed by midazolam (1 mg/kg). In experiment 3, FG-7142 (10 mg/kg) produced a s teep drop in RQ that persisted for at least 2 h and which was reversed by midazolam (1 mg/kg) and delayed by the benzodiazepine antagonist R O 15-1788 (10 mg/kg). FG-7142 also tend ed to inhibit EE and locomotor activity, but these effects did not reach statistical significance. O verall, these data show that stress causes profound alterations in RQ, EE and activity and that the pattern of change in these para meters d iffers with the nature of the stresser involved.