Glutamate and GABA are the main information carrying neurotransmitters in the brain. Their action is modulated by a further series of small molecules called neuromodulators. The major neuromodulators in the brain are acetylcholine (both muscarinic and nicotinic), dopamine, norepinephrine, epinephrine and serotonin. These have an enormous range of functions in a wide variety of brain mechanisms. This book attempts to give a general overview of this field with a section devoted to each of these. Each section starts with anatomy, both structural and functional. The various types of receptors for these agents are described, and then the effects of stimulating these receptors. These receptors trigger a variety of electrical reactions that generally involve potassium, sodium or calcium channels. Also reviewed are other receptors that trigger a wide variety of post-synaptic signaling cascades that influence a large number of neuronal functions including receptor sensitivity, synaptic plasticity and gene manipulation. Finally the relevance of these systems to disease states is detailed. There are many reviews of individual neuromodulators but this is the only book where one author attempts to cover the whole field.