There are many symptoms and treatments for AD. Tacrine and Aricept are two drugs that provide some temporary relief from symptoms in some patients with AD. These drugs work at the site where two nerve cells connect-termed synapses. Electrical nerve impulses pass along processes of the nerve cell. When they reach the nerve terminal (at the synapse), the electrical signal must be converted into a chemical signal that is released and can stimulate or inhibit a target cell by binding to specific receptors. The small chemical molecules that are released at the synapse and bind to receptors are called neurotransmitters. Acetylcholine is one such neurotransmitter. Some nerve cells in the brain that are involved in AD release acetylcholine to stimulate targets. Unfortunately, acetylcholine normally breaks down rapidly and has a short activity. Tacrine and Aricept inhibit acetylcholinesterase and slow down the destruction of acetylcholine. Therefore acetylcholine remains in the synapse to stimulate the target cell and promote the normal function of the cholinergic system. However, these drugs do not stop the course of the disease but only make some of the patient's remaining brain cells function as efficiently as possible. Over fifteen years of work were needed to bring them to market, beginning with research at places like Johns Hopkins Medical Institutions. Since depression in one-third to one-half of all people with AD; there are certain treatments for this as well. Some of the more recently antidepressants are often prescribed, such as fluoxetine (Prozac), sertraline (Zoloft), paroxetine (Paxil), venlafaxine (Effexor), and bupropion (Wellbutrin). People with AD will also appear to have anxiety and agitation, such as restlessness, pacing, and shaking. Drugs designed to treat this are lorazepam (Ativan) or buspirone (Buspar). Many people with AD experience psychotic symptoms such as paranoia and delusions.