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 V_max and K_m 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 >0.05) as evidenced by the increased R_max values. However, carbaryl simultaneously decreased the kinetics of the process in the hypothalamus since t_0.5max values were enhanced (insignificantly at the 5% LD₅₀ dose level,p >0.05). Carbaryl produced a dosedependent increase of t_0.5max 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.