The influence of carbaryl on the uptake of (3H)-noradrenaline (3H)-NA by rat hypothalamic slices.

The uptake of (3H)-NA by rat hypothalamic slices was investigated following carbaryl poisoning. The insecticide was administered to rats orally in a single dose of 50% LD50 and of 20% LD50, and in repeated dosing for 14 days (5% LD50 daily). The kinetics of (3H)-NA uptake was defined by the modified Lineweaver-Burk plots (Rmax was used instead of Vmax and Km was replaced with t05 max). The results indicated that in all the experiments carbaryl elevated the (3H)-NA uptake by hypothalamic slices in a dosage dependent fashion (insignificantly at the 20% LD50 dose level, p greater than 0.05) as evidenced by the increased Rmax values. However, carbaryl simultaneously decreased the kinetics of the process in the hypothalamus since t0.5max values were enhanced (insignificantly at the 5% LD50 dose level, p greater than 0.05). Carbaryl produced a dose-dependent increase of t0.5max values. The changes in the (3H)-NA uptake may be related to the increase of NA level in the hypothalamus following exposure to carbaryl observed by other authors.