(vi) Efficacy of diazepam and adrenaline (during infusion of chloroquine)
Twenty-seven rats was included, but 3 died before the end of the experiment – one from each of the control, diazepam, and diazepam + adrenaline groups. During the first 30 minutes of infusion, chloroquine caused significant changes in all parameters, with the exception of the QRS and QTc intervals in the adrenaline group. The lack of an effect with diazepam (2 mg kg-1) alone was consistent with trial (ii). The effects of adrenaline alone did not deviate significantly from the control group in any parameter other than the QRS interval, but this was not prolonged following chloroquine (Figure 2). The combined administration of diazepam and adrenaline resulted in an improvement of cardiac contractility compared to the control and diazepam groups but not the adrenaline group (84 ± 3 versus 78 ± 8 s-1; p=0.063). No significant differences were observed in the other parameters (Table 3).
Pre-chloroquine potassium concentrations were in the range expected for rats (Burns and De Lannoy, 1966). Chloroquine alone did not cause any significant changes in arterial PO2, PCO2 or pH values over a period of 30 minutes infusion. The combined administration of diazepam and adrenaline, however, reduced PO2 when compared to pre-intervention values but not when compared to the other groups. Chloroquine did not alter electrolyte concentrations; but intervention groups containing adrenaline were more hypokalaemic than the diazepam and control groups (Table 4).