acetylcholine has been linked to Alzheimer’s disease, an illness resulting inprogressive and incurable memory loss. Alzheimer’s disease is specificallyassociated with a loss of acetylcholine in neurons that connect with thehippocampus, an important memory structure in the brain.Norepinephrine, also known as noradrenaline, is involved in controllingalertness and wakefulness.Dopamineis a neurotransmitter that has an important function in relation tocognition, sleep, movement, mood, reward, memory, motivation and learning. Italso plays an important role in movement and posture. For example, Parkinson’sdisease is theorized to come from a loss of dopamine-sensitive neurons in thebasal ganglia.Serotoninis thought to play roles in regulating mood, eating, sleeping, andarousal. Like norepinephrine, serotonin is thought to plays role in depression andmania.GABAis a neurotransmitter that produces inhibitory postsynaptic potentials andis thought to play an important role in stabilizing neural activity in the brain.GABA exerts its effects by causing hyperpolarization in the postsynapticmembrane.NeurotransmitterFunctionMalfunctionsAcetylcholineMuscle action, learning andmemoryAlzheimer’s-too littleDopamineMovement, learning, attention,emotion, rewardSchizophrenia–too muchParkinson’s-too littleSerotoninMood, hunger, sleep, andarousalDepression– too littleNorepinephrineAlertness, arousalDepression-too littleAgonistsincrease the effects of a neurotransmitter. For example, agonists canwork by mimicking the effect of a neurotransmitter by stimulating receptors orby slowing the breakdown of a neurotransmitter so that it is in the systemlonger.For example, caffeine is an acetylcholine agonist. It increases the effects ofacetylcholine. Black widow spider venom contains an acetylcholine antagonist. Itdecreases the effects of acetylcholine.Antagonistsblock the effects of a neurotransmitter, for example by disruptingsynthesis or causing the neurotransmitter to leak from vesicles.
