Most people will take medicine at some point in their lives, yet we have little understanding of how these chemicals work. Most of the time, this is determined by how a medicine affects the communication between brain cells. This can happen in a variety of different ways.
Any drug must first reach the bloodstream, which can take anywhere from seconds to hours depending on factors including how it is administered. Since a drug must be absorbed by our digestive system before it can take effect, taking it orally is the slowest approach. Inhaling a drug allows it to enter the bloodstream more quickly. Intravenously injecting a drug also works swiftly since the ingredients are pumped straight into the bloodstream. The drug swiftly reaches the blood-brain barrier, which keeps potentially toxic drugs out by separating blood from the nervous system. As a result, all medications must have a unique chemical composition that allows them to unlock and pass through this barrier.
Drugs enter the brain and begin to disrupt its regular functioning by targeting its web of neurons and synapses. A neuron is a type of brain cell with a nucleus, dendrites, and axon. Synapses are structures along the dendrites or axon, that allow electrochemical signals to be exchanged between neurons. Neurotransmitters are molecules that carry those messages. Each neurotransmitter regulates our behaviours, emotions and cognition in a unique way. However, they all function in one of two ways. They can either inhibit or stimulate the receiving neuron, resulting in a new electrochemical signal that travels across the network. Any neurotransmitter that is left over is frequently destroyed or reabsorbed by the transmitting cell. The ability of a medicine to influence synaptic transmissions at different stages of the process determines its effectiveness. As a result, the number of neurotransmitters distributed increases or decreases.
Antidepressants like SSRIs, for example, block the reabsorption of serotonin, a neurotransmitter that regulates our moods. Meanwhile, analgesics like morphine enhance serotonin and noradrenaline levels, which control energy, arousal, alertness and enjoyment. Endorphin receptors are influenced by the same neurotransmitters, which reduce pain perception. And tranquilizers work by increasing GABA production to block brain activity, resulting in a relaxed or sedated state.
Illegal drugs have profound effects on the brain that we are still learning about. Amphetamine crystal meth causes a long-lasting release of dopamine, a neurotransmitter connected to reward and pleasure perception. It also causes the body’s fight or flight reaction by activating noradrenaline receptors, which raises heart rate, dilates pupils and activates the fight or flight response. Cocaine inhibits the absorption of dopamine and serotonin, allowing more to enter the network, where they provide energy, euphoria and hunger suppression. Hallucinogenic drugs, in particular, produce some of the most perplexing side effects. Serotonin, which regulates mood and impulsivity, is blocked by substances like LSD, mescaline, and DMT. They also affect brain circuits involved in perception, learning, and behavioural regulation, which could explain why these drugs have such strong effects. Even if some of these effects appear to be thrilling, there are reasons why some of these drugs are heavily regulated and frequently illegal.
Drugs have the ability to change the chemistry of the brain, and long-term use can permanently rearrange the neuronal networks that underpin our ability to think, make decisions, learn, and remember. There is still a lot we do not know about drugs and their effects, both positive and negative. But the ones we do know about are the ones that have been thoroughly researched and developed into useful medicines. As our understanding of drugs and the brain expands, so will the prospects for addressing the myriad medical diseases that confound researchers today.
