Here, we describe the alterations of excitatory neurotransmitters (dopamine, serotonin, noradrenaline, acetylcholine), glutamate and GABA (a presynaptic inhibitory neurotransmitter) in the brain areas (brainstem, hypothalamus, hippocampus) involved in bipolar disorder. The coherence between the pituitary hypothalamicadrenocortical axis and the existing neurotransmitter alterations is pointed out. Neural networks are described in the concerned brain areas, including the neurotransmitters and the depending subreceptors, on which the prophylactic drugs exert their effects. A survey of the commonly used prophylactic drugs is also given.