Pharmacology of Fear, Induced by Periaqueductal Gray Stimulation in the Rat

The effect of drugs on escape induced by aversive stimulation of the periaqueductal gray (PAG) matter is reviewed. Strongest influences were observed with compounds influencing GABA-ergic and serotonergic neurotransmission. Activation of the 5-HT1C-receptor is an effective way towards inhibition of the aversive effect of brain stimulation. An opposite effect was obtained by stimulation of 5-HT1A and 5-HT2-receptors. Dopaminergic D2-receptor activation seems to have weak enhancing effects on the stimulation induced aversive state. In view of these pharmacological characteristics it is not possible to conclude that there is a straight forward parallelism between brain stimulation-induced fear and a particular anxiety disorder.