The Role of Membrane Proteins in… ADDICTION

Neurotransmitters conduct nerve impulses. Neurons (nerve cells) have a gap between them called a synapse. Neurotransmitters are chemicals that take signals across the synapse so that one neuron can communicate with the next neuron. Neurotransmitters bind to receptor proteins on the next axon which stimulates the neuron. The neurotransmitters are quickly broken down by enzymes or reabsorbed into the sending neuron through a transporter or reuptake protein for recycling so that another message can cross the synapse

Drugs effect signal transmission. A psychoactive drug = chemical that alters brain function, resulting in temporary changes in perception, mood, consciousness or behavior. Some examples: cocaine, heroine, nicotine, codeine These drugs can work in many different ways… prevent the nerve cell from starting the signal preventing NT synthesis, packaging or release mimic the original NTs and activate the receptors * bind to the receptor and block activation prevent re-uptake *

Dopamine is a neurotransmitter. Dopamine is a neurotransmitter that plays an important role in the sensation of pleasure Reuptake receptors reabsorb dopamine into the sending neuron for later use

Cocaine prevents reabsorption of dopamine. Cocaine prevents reabsorption of the NT dopamine result > more dopamine in synapse repeatedly stimulates neurons > feeling of well being number of dopamine receptors decrease > results in a less sensitive neuron > more cocaine needed to stimulate absence of cocaine - the number of receptors has to increase again (withdrawl)

Cocaine decreases receptors.

Nicotine imitates acetylcholine. Acetylcholine is a neurotransmitter that stimulates skeletal muscles Nicotine binds to receptors in the brain which results in a mild, short-lived pleasurable sensation Result > less receptor proteins… so body needs nicotine to feel normal

Narcotics imitate enkephalins. Enkephalins are neuropeptides made by the nervous system They stop pain signals by binding to receptor proteins in the spinal neurons (potassium channels open inhibiting pain messages from traveling to the brain) Narcotics (morphine, heroine, codeine) imitate enkephalins because they have similar structures