N through Z

N

Neuron (nerve cell): A unique type of cell found in the brain and body that is specialized to process and transmit information.

Neurotransmission: The process that occurs when a neuron releases neurotransmitters to communicate with another neuron across the synapse.

Neurotransmitter: A chemical produced by neurons to carry messages to other neurons.

Nicotine: The addictive drug in tobacco. Nicotine activates a specific type of acetylcholine receptor.

Nitrites: A special class of inhalants that act primarily to dilate blood vessels and relax the muscles. Whereas other inhalants are used to alter mood, nitrites are used primarily as sexual enhancers. (See also amyl nitrite and butyl nitrite).

Nitrous oxide: Medical anesthetic gas, especially used in dentistry. Also called "laughing gas." Found in whipped cream dispensers and gas cylinders.

Noradrenaline: A chemical neurotransmitter that is made in the brain and can affect the heart.

Nucleus: A cluster or group of nerve cells that is dedicated to performing its own special function(s). Nuclei are found in all parts of the brain but are called cortical fields in the cerebral cortex.

Nucleus accumbens: A part of the brain reward system, located in the limbic system, that processes information related to motivation and reward. Virtually all drugs of abuse act on the nucleus accumbens to reinforce drug taking.

O

Occipital lobe: The lobe of the cerebral cortex at the back of the head that includes the visual cortex.

P

Parietal lobe: One of the four subdivisions of the cerebral cortex; it is involved in sensory processes, attention, and language.

Physical dependence: An adaptive physiological state that occurs with regular drug use and results in a withdrawal syndrome when drug use is stopped; usually occurs with tolerance.

Polyneuropathy: Permanent change or malfunction of nerves. Sudden sniffing death - A type of death that can occur when inhaled fumes fill up the cells in the lungs with poisonous chemicals, leaving no room for the oxygen needed to breathe. This lack of oxygen can lead to suffocation, respiratory failure, and death.

Psychedelic drug: A drug that distorts perception, thought, and feeling. This term is typically used to refer to drugs with actions like those of LSD.

Psychoactive: Having a specific effect on the mind.

Psychoactive drug: A drug that changes the way the brain works.

R

Receptor: A large molecule that recognizes specific chemicals (normally neurotransmitters, hormones, and similar endogenous substances) and transmits the message carried by the chemical into the cell on which the receptor resides.

Relapse: In drug abuse, relapse is the resumption of drug use after trying to stop taking drugs. Relapse is a common occurrence in many chronic disorders, including addiction, that require behavioral adjustments to treat effectively.

Reuptake: The process by which neurotransmitters are removed from the synapse by being "pumped" through transporters back into the axon terminals that first released them.

Reuptake pump (transporter): The large molecule that actually transports neurotransmitter molecules back into the axon terminals that released them.

Reward: The process that reinforces behavior. It is mediated at least in part by the release of dopamine into the nucleus accumbens. Human subjects report that reward is associated with feelings of pleasure.

Reward system (or brain reward system): A brain circuit that, when activated, reinforces behaviors. The circuit includes the dopamine-containing neurons of the ventral tegmental area, the nucleus accumbens, and part of the prefrontal cortex. The activation of this circuit causes feelings of pleasure.

Route of administration: The way a drug is put into the body. Drugs can enter the body by eating, drinking, inhaling, injecting, snorting, smoking, or absorbing a drug through mucous membranes.

Rush: A surge of pleasure that rapidly follows administration of some drugs.

S

Serotonin: A neurotransmitter that regulates many functions, including mood, appetite, and sensory perception.

Sex hormones: Hormones that are found in higher quantities in one sex than in the other. Male sex hormones are the androgens, which include testosterone; and the female sex hormones are the estrogens and progesterone.

Stimulants: A class of drugs that elevates mood, increases feelings of well-being, and increases energy and alertness. These drugs produce euphoria and are powerfully rewarding. Stimulants include cocaine, Methamphetamine, and methylphenidate (Ritalin).

Synapse: The site where presynaptic and postsynaptic neurons communicate with each other.

Synaptic space (or synaptic cleft): The intercellular space between the presynaptic and postsynaptic neurons.

T

Temporal lobe: The lobe of the cerebral cortex at the side of the head that hears and interprets music and language.

Tetrahydrocannabinol: See THC

Thalamus: Located deep within the brain, the thalamus is the key relay station for sensory information flowing into the brain, filtering out important messages from the mass of signals entering the brain.

THC: Delta--tetrahydrocannabinol; the main active ingredient in marijuana, which acts on the brain to produce its effects.

Tobacco: A plant widely cultivated for its leaves, which are used primarily for smoking; the tabacum species is the major source of tobacco products.

Tolerance: A condition in which higher doses of a drug are required to produce the same effect as during initial use; often leads to physical dependence.

Toluene: A light colorless liquid solvent found in many commonly abused inhalants, including airplane glue, paint sprays, and paint and nail polish removers.

Transporter: A large protein on the cell membrane of the axon terminals. It removes neurotransmitter molecules from the synapse by carrying them back into the axon terminal that released them.

Trichloroethylene: A liquid used as a solvent and in medicine as an anesthetic and analgesic. Found in cleaning fluid and correction fluid.

V

Ventral tegmental area (VTA): The group of dopamine-containing neurons that make up a key part of the brain reward system. These neurons extend axons to the nucleus accumbens and the prefrontal cortex.

Vertigo: The sensation of dizziness.

Vesicle: A membranous sac within an axon terminal that stores and releases neurotransmitter.

W

Withdrawal: Symptoms that occur after chronic use of a drug is reduced or stopped.