Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Chapter 20 Introduction to Central Nervous System Pharmacology

2Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. CNS Drugs  Agents that act on the brain and spinal cord  Medical uses  Psychiatric disorders, suppression of seizures, pain relief, production of anesthesia  Nonmedical uses  Stimulant, depressant, euphoriant, and other “mind-altering” abilities

3Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Transmitters of the Central Nervous System  Currently, there are 22 known transmitters.  More are likely to be discovered.

4Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. The Blood-Brain Barrier (BBB)   Impedes entry of drugs into the brain   Passage across the BBB limited to lipid-soluble drugs   Protein-bound or highly ionized drugs cannot cross   Mixed blessing of BBB

5Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. How Central Nervous System Drugs Produce Therapeutic Effects  Precise mechanism vs. plausible hypotheses

6Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Adaptation of the CNS to Prolonged Drug Exposure  Different effects possible when drug is taken chronically vs. initial use of drug  Increased therapeutic effects  Decreased side effects  Tolerance and physical dependence

7Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Development of New Psychotherapeutic Drugs  Complexity of mental health  Lack of adequate animal models of mental illness  Mentally healthy individuals cannot be used as subjects  No effect or paradoxical effects  Psychopharmacologic accidental discoveries

8Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Development of New Psychotherapeutic Drugs   The Process   Structural analogs synthesized   Biochemical and physiologic screening tests   Serious toxicity ruled out, then tested in humans   Small advances vs. major therapeutic breakthroughs

9Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Approaching the Study of CNS Drugs   Key points for study: Recognize that   there are numerous neurotransmitters.   their precise functional roles are not clear.   their complexity makes it difficult to know with certainty just how CNS drugs produce their effects.