Neurotransmitters drugs affecting

Figure 5.5 Diagrammatic representation of a synapse showing the sites at which drugs may act to increase or decrease the concentration and action of a neurotransmitter. Drugs can affect the synthesis (1), storage (2), release (3), action (4) and destruction (5) of the transmitter. The different ways in which they achieve this (a, b, c) are outlined in Table 5.1...

Psychoactive drugs can influence neurotransmission at its five different stages (Chapter 2). First, they may modify the biosynthesis of a neurotransmitter. Second, they can increase or decrease their storage within the presynaptic neuron. Third, they may stimulate or inhibit neurotransmitter release from the synaptic bouton. Fourth, they may affect the binding of the neurotransmitters to its receptor. Finally, they can retard the neurotransmitter s inactivation. Some examples of each of these stages will be given below, but it should be noted that many drugs affect several of these processes. 

As mentioned herein, other neurotransmitters are affected by hallucinogens. Accordingly, the opposite changes in 5-HT and DA neurotransmission produced by these drugs seem necessary but insufficient to evoke hallucinations. Current studies on the effects of hallucinogens on recently detected neuroactive com-... 

Consistent with alterations in neurotransmission associated with sleep onset, SWS and REM sleep (Chapters 6-8), drugs affecting neurotransmitter function have specific effects on the sleep-wake cycle. Thus reduced levels of conscious-... 

Studies of sudden death in novice as well as experienced drug abusers found that cocaine causes vasoconstriction of the coronary arteries which seems to result from an enhancement of Ca2+ influx across myocardial membranes. However, remember that this class of drug affects other neurotransmitter systems. Cocaine inhbiits reuptake of NE and 5-HT as well as binds to the DA transporter. It increases catecholamine receptor sensitivity but does not seem to directly influence enkephalinergic receptors. In addition it also affects neurotransmission the H, Ach and phenylethylamine pathways. Activation of DA, NE or 5-HT neurons independently does not produce the euphoria associated with cocaine misuse. Euphoria seems to be related to simultaneous inteeraction between catecholamine and serotoninergic systems. 

Because of their selective action on serotonin, the manufacturer of SSRIs claim there are fewer side effects from this class of drug than those of the tricyclics and MAOIs. These other drugs affect many neurotransmitters in the brain and therefore result in many side effects. However, the SSRIs can cause stomach upset, insomnia, and anxiety. 

Summary of blocking agents and drugs affecting neurotransmitter uptake or release. 

Despite knowledge of the effects of stimulants on neurotransmitter activity, how these drugs affect the primary symptoms of ADHD is unclear. To varying degrees the central nervous system (CNS) stimulants inhibit the reuptake of DA and NE, enhance release of DA and NE from the presynaptic neuron, or inhibit the enzyme monoamine oxidase (MAO). Because stimulants work through slightly different mechanisms, lack of response to one stimulant does not preclude response to another. ... 

There has been a clear military interest in manipulation of the noradrenaline neurotransmitter system in relation to the arousal level of the central nervous system for some time.8 That interest apparently continues one recent report suggesting that drugs affecting the system were appropriate for immediate consideration as a non-lethal technique. 9... 

Methylphenidate is similar to amphetamine and, like amphetamine, stimulates the central nervous system (CNS), which consists of the brain and spinal cord. Stimulant drugs affect mood and alertness, and depress food appetite by increasing levels of several neurotransmitters in the brain. Although the exact therapeutic mode of action of methylphenidate is not known, the drug has been shown to elevate levels of some of these neurotransmitters, primarily dopamine and norepinephrine (noradrenaline). 

Lthanol (or alcohol) is a two-carbon molecule that, in contrast to many other drugs of abuse, such as opioids, cocaine, and nicotine, does not bind to specific brain receptors. Nonetheless, alcohol affects a variety of neurotransmitter systems, including virtually all of the major systems that have been associated with psychiatric symptoms (Kranzier 1995). Alcohol affects these neurotransmitter systems indirectly by modifying the composition and functioning of... 

Important products derived from amino acids include heme, purines, pyrimidines, hormones, neurotransmitters, and biologically active peptides. In addition, many proteins contain amino acids that have been modified for a specific function such as binding calcium or as intermediates that serve to stabilize proteins—generally structural proteins—by subsequent covalent cross-hnk-ing. The amino acid residues in those proteins serve as precursors for these modified residues. Small peptides or peptide-like molecules not synthesized on ribosomes fulfill specific functions in cells. Histamine plays a central role in many allergic reactions. Neurotransmitters derived from amino acids include y-aminobutyrate, 5-hydroxytryptamine (serotonin), dopamine, norepinephrine, and epinephrine. Many drugs used to treat neurologic and psychiatric conditions affect the metabolism of these neurotransmitters. 

This book is about neurotransmitters, the substances released from neurons to act on neurons. It covers what they do, how they do it and how their activity is involved in brain function and affected by drugs and disease. 

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