Animal model of anxiety: the effect of methyldopa in the genetically hypertensive non-obese rats of Koletsky type and in the rats of Wistar strain.

: The experiments were carried out in the adult normotensive rats of Wistar strain and in the genetically hypertensive rats which were developed by Koletsky; the experiments were performed in the both sexes. The behavior of control and methyldopa treated rats were traced in the holeboard and in the elevated plus-maze. In the control animals when compared to the normotensive rats of both sexes, the genetically hypertensive rats of both sexes show elevated aversion towards open space and height (when the number of visits of centre and open arms is considered), elevated locomotor-exploratory activity and reduced rate of habituation of the latter activity; the genetically hypertensive males than show reduced percentage of time spent head dipping relative to the normotensive males. Methyldopa decreases locomotor-exploratory activity and increases intra-session rate of habituation of the latter activity in the both strains of rats. This drug shows in the first session decrease in the normotensive males and increase in the genetically hypertensive rats of both sexes the percentage of time spent head dipping. Methyldopa shows in the first session increase in the number of entries in centre and in open arms in elevated plus-maze solely in the genetically hypertensive rats of both sexes. When time spent in centre and in open arms of the elevated plus-maze is taken into consideration, methyldopa shows in the normotensive males decrease and in the genetically hypertensive males increase.