How do drugs enter synapses?

Question

Many psychopharmaceutical drugs change synapse chemistry or directly agonize neuroreceptors in the brain. For example, cabergoline is a D₂ agonist.How do these compounds enter the physical synapses? Are they simply lipid soluble and diffuse throughout all cells?

Answer 1

Many drugs are lipid soluble and do simply diffuse into cells and across the blood-brain-barrier. Others need help and are transported into the brain (or into cells) via transporters. To get to the synapse, the drug must first be absorbed after administration (stomach, intestines, mucous membranes, skin, etc.). Following absorption, it must be distributed (circulatory system, blood-brain-barrier, etc.) and may be metabolized in the process. For psychoactive agents, they enter the brain (again via the BBB) and enter the CSF (cerebral spinal fluid) which bathes the brain, eventually finding their way to the synapse.