Neuropharmacology studies the effects of drugs on the nervous system, including the brain, spinal cord, and the nerves that carry information to and from different parts of the body. Psychopharmacology deals with drug effects on behavioural and cognitive functions. In both cases, drug actions may be studied from number of different perspectives. Some investigators in these areas research negative or toxic effects of drugs on neural and behavioural functions. Others focus on the development and testing of new drugs for the treatment or prevention of specific diseases of the nervous system, including neuropsychiatric disorders such as schizophrenia, epilepsy, depression, Parkinson's and Alzheimer's disease. Others may study drugs that are already in use, so as to understand more precisely the neurobiological targets and mechanisms of action of those drugs, or to gain new insights about the underlying neurobiology of disease processes. Researchers in these areas also use drugs as tools to elucidate basic mechanisms of neural and behavioural functions using a wide variety of model systems, from cultured cells to preserved neural tissues to intact behaving organisms.