The role of dopaminergic mechanisms on the brain in various models of anxious states.

In tests of "illuminated area" and the "threatening situation" avoidance by rats, apomorphine and phenamine, administered intraperitoneally, attenuate the state of alarm. A similar effect is observed when sulpiride, a selective blocker of D2-receptors of dopamine, and of picrotoxin, a GABA antagonist, are administered. Sulpiride effectively counteracts the anxiolytic effects of all of the dopaminomimetics investigated and of picrotoxin. Haloperidol, a nonselective blocker of the D1- and D2-receptors of dopamine removes the anxiolytic effect of apomorphine, phenamine, and picrotoxin. The microinjection into the ventral region of the midbrain tegmentum of dopamine, or of sulpiride into the nucleus accumbens of the septum, attenuates the state of alarm formed by aversive influences of various biological modalities. By contrast, sulpiride, introduced locally into the tegmentum, or chemical stimulation of the nucleus accumbens of the septum by dopamine, intensifies the state of alarm in the "illuminated area" avoidance test. The participation of dopaminergic mechanisms of the mesolimbic system of the brain in anxiety of various aversive causations is discussed.