The third chapter of the third edition of Adam J. Prus’ book, Drugs and the Neuroscience of Behavior, discusses Neurotransmission. It defines Neurotransmission as the movement of information from one neuron to another and involves biochemicals known as neurotransmitters (Andreae & Burrone, 2017). Neurotransmission occurs between one nerve cell and the target cell and is initiated by the release of neurotransmitters. Neurotransmitter release is spontaneous and is always facilitated by a chemical and electrical process in the presynaptic end of the nerves.
The neurotransmission process begins in the presynaptic neuron and then follows a sequential order, ultimately eliciting a physiologic action. The first step is the synthesis of the neurotransmitter. This step varies with the type of neurotransmitter involved, with each neurotransmitter requiring a different type of substrate. Upon synthesis, the neurotransmitter is packaged into vesicles for storage, awaiting release. The neurotransmitter is then released by exocytosis into the synaptic cleft. The released neurotransmitter may either bind to its receptors on the postsynaptic membranes or be metabolized by the metabolizing enzymes present at the synaptic cleft. These neurotransmitters will elicit a physiologic effect upon binding to their receptors on the postsynaptic membrane.
The two major types of neurotransmitters are the ionotropic and metabotropic receptors. Ionotropic receptors are ion channel receptors that open the ion channel upon the binding of a receptor. Metabotropic receptors, on the other hand, elicit their effect via a secondary transduction pathway. There are several types of neurotransmitters in the body. The major neurotransmitters in the brain are glutamate and Gamma-aminobutyric acid (GABA). GABA is an inhibitory neurotransmitter, while glutamate is an excitatory neurotransmitter.
Other significant neurotransmitters in the brain serving other physiological functions include serotonin, epinephrine, and dopamine of the monoamine chemical class, as well as acetylcholine. Acetylcholine is the primary neurotransmitter released from cholinergic neurons, while epinephrine is the primary neurotransmitter released from adrenergic neurons. Neurotransmitters are short-acting due to the presence of enzymes that scavenge on them upon their release (Andreae & Burrone, 2017). The chapter summarizes the significance of these neurotransmitters with specific mention of acetylcholine and its role in the development of pathologies such as Alzheimer’s.
The fourth chapter of the book discusses the properties of drugs. This chapter starts by highlighting what the body does to drugs as well as what the drug does to the body. Pharmacokinetics defines the absorption, distribution, metabolism, and excretion processes of the drug (Currie, 2018). Absorption defines the process that enables the entry of the drug into the bloodstream. Absorption varies with the intrinsic properties of the drug as well as the route of administration of the drug. Factors such as the drug’s molecular size, hydrophobicity profile, dosage form, and absorbing surface affect the overall drug absorption.
Distributions define the movement of the drug from the bloodstream to the target site. It enables the drug to reach its active site and elicit its effect. It is also dependent on the intrinsic drug properties. Metabolism defines how a drug is a biotransformation in the body. The liver is the primary site of metabolism in the body. Metabolism involves the enzymatic conversion of the drug into other by-products with either reduced or increased pharmacological effects. Excretion defines the elimination of the drug from the body. The liver and the kidneys are the two primary sites for drug elimination.
The pharmacodynamics of a drug defines how the drug acts to elicit a pharmacological effect on the body. For a drug to elicit its pharmacological effect, it must first reach its site of action. It then binds to receptors that modulate a pharmacological effect. This modulation can be in the form of causing alteration in neurotransmitter release, as seen with psychoactive drugs, or blocking the binding of other endogenous biomolecules (Currie, 2018). Other drugs elicit their effect by increasing the release of endogenous molecules. Drug binding to receptors, just like endogenous substrate binding, is specific, and drugs are made that target a specific group of receptors.
The chapter summarizes by highlighting the consequences of chronic use of drugs. Chronic use of drugs can lead to several effects. Sensitization, drug tolerance, and drug dependence are some of the effects of chronic drug use. Sensitization defines an increase in the pharmacological response of a drug with prolonged use. This is not so common. Drug dependence can either be physiologic or psychologic and is defined by the increased need to use the drug, failure to which withdrawal effects ensue. Tolerance defines the need for higher doses than usual to elicit similar pharmacological effects.
Andreae, L., & Burrone, J. (2017). The role of spontaneous Neurotransmission in synapse and circuit development. Journal Of Neuroscience Research, 96(3), 354-359. https://doi.org/10.1002/jnr.24154
Clinical Pharmacokinetics & Pharmacodynamics. (2017), 6, 3-72. https://doi.org/10.1002/cpdd.385
Currie, G. (2018). Pharmacology, Part 2: Introduction to Pharmacokinetics. Journal Of Nuclear Medicine Technology, 46(3), 221-230. https://doi.org/10.2967/jnmt.117.199638
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I need a summary of each chapter of the textbook Drugs and the Neuroscience of Behavior 3rd edition, Prus
1. Read the Textbook: Chapter 3 Neurotransmission
2. Read the Textbook: Chapter 4, Properties of Drugs
3. Watch the Video: Anyone Can Become Addicted
4. Submit the Text Summary of Chapters 3 and 4
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