Serious problem in drug dependence results from the compulsive use of the drugs beyond recreational use. The conversion of the drug seeking pattern into compulsive use is not well studied and control after compulsive behavior is also unknown. Our lab studies neuroscience in drug addiction with cocaine addiction model in mouse. After inducing compulsive cocaine seeking, we proceed electrophysiological observation and optogenetical behavior control. We are especially interested in inhibitory neural circuit in midbrain which can affect dopamine neuron in VTA. We study the effect of (particular subtypes of) inhibitory neurons in addictive behaviors by introducing various types of Cre-expressing mouse lines.