Introduction
Several aspects of neurochemistry have been previously examined in this text, including the synthesis and degradation of several neurotransmitters and the role of various ions in impulse conduction and muscle contraction. Still, we have not looked at all into the chemical activity within the brain and spinal cord.  Here we will examine the activity of various neuroactive chemicals in the brain, including the catecholarnines, indoleamines, amino acids, neuropeptides, prostaglandins, and others as well as energy metabolism within the brain itself.
 

Brain characteristics
The brain, like other organs of the body, requires an adequate vascular system in order to supply it with nutrients and oxygen and to remove metabolic wastes and carbon dioxide. Unlike most other organs, however, capillary exchange of these and other materials in the brain is complicated by the presence of a transport-limiting system, the blood-brain barrier.