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CA (168,426)
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PSYC62H3 (333)
Chapter 10

chapter 10

9 Pages
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Department
Psychology
Course Code
PSYC62H3
Professor
Suzanne Erb

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CHAPTER 10 NOTES; DRUGS
OPIODS (Narcotics) AND THEIR ANTAGONISTS
Some of the oldest psychotropic drugs used by humans are morphine and codeine;
their use may go back 7,000 years.
Originally these drugs were used in the form of extracts from the poppy plant, which
contain opium, and in purified form they are still used extensively.
They belong to a class of drugs that includes the most effective pain relievers
available, so they are the most commonly used analgesic treatments for moderate to
severe pain.
Since users often experience euphoria, drowsiness, and mental cloudingperhaps
resulting in the feeling that all their problems are trivialthese drugs are also used
recreationally and are highly subject to abuse
The most common term for morphine and similar-acting drugs is narcotic.
It has been used primarily to refer to a class of drugs that promote sleep and induce
analgesia, but many laypersons often think of narcotics as any highly abusable or
addicting drugs.
From this perspective, drugs that bear little similarity to morphine in terms of their
neurochemical actions or their psychological effects (like cocaine and marijuana)
have been designated as narcotics for legal purposes.
Pharmacologically, only a drug with the following qualities can be appropriately
classified as a narcotic: 1) It generally has sedative-hypnotic and analgesic
properties; 2) it acts stereospecifically on endorphin/enkephalin receptors; and 3) its
actions are antagonized by naloxone (Narcan)
It is restricted to extracts of opium (opiates), opiate derivatives, and synthetic drugs
with opiate properties. AKA opiods
Endogenous Opioid Peptides and Their Receptors
Because there are numerous substances with opioid; researchers often refer to these
as endogenous opioid and peptides
3 distinct families have been identified thus far: ENKEPHALINS, ENDORPHINS,
DYNORPHINS; these are often categorized in a general sense as ENDORPHINS
www.notesolution.com
Each family is derived from different precursor polypeptides, more than 200 amino
acids long, with different anatomical distributions
Each precursor contains a number of biologically active opioid and nonopioid
peptides, which are cleaved (split) at specific sites by specific enzymes (called
proteases) to produce the active agents. For example, the precursor pro-
opiomelanocortin contains 3 separate hormones, one of which contains the opioid
peptide beta-endorphin , which in turn contains the opioid peptide met-enkephalin
(a peptide of 5 amino acids with methionine at one end)
The precursor proenkephalin contains several met-enkephalin except segments and
a leu-enkephalin segement (same amino acid sequence as met-enkephalin except
that leucine is substituted for methionine)
The precursor prodynorphin contains 2 endorphin segments, 3 leu-enkephalin
segments, & 2 types of the opioid peptide dynorphin
Pro-opiomelanocortin peptides are found in the pituitary gland (indicating that they
play a role in a variety of neuroendocrine functions) & in relatively limited areas of
the CNS
Peptides from the other 2 precursors are distributed widely throughout CNS, spinal
cord & midbrain) , affective states (ex. , amygdala , hippocampus, locus ceruleus &
cerebral cortex) & the autonomic nervous system (ex. medulla)
They are also found in other parts of the body such as stomach & intestines
Though the endogenous opioid peptides are believed to function as
neurotransmitters, neurohormones, or neuromodulators , their physiological role is
not well understood
They frequently coexist with other hormones or neurotransmitters within a given
neuron.
Ch. 5- endogenous opioid peptides have been implicated in a myriad of psychological
processes & activities, eg. Acute stress responses, pain perception, social attachment
in primates, & placebo responses in humans
All opioid receptors identified so far are G protein coupled ( metobotropic) receptors.
3 major classes of opioid receptors have been recognized since 1970s (called mu,
delta, & kappa)
www.notesolution.com
Fourth class, called nociceptin/orphanin FQ (N, OFQ) receptors was identified in
early 1990s.
A number of subtypes have been proposed for each of these classes which may
account for why opiates that appear to act selectively on one class of opioid receptor
dont always induce the same effects. The actions & selectivities of representative
ligands and drugs for these various opioid receptors shown in table 10.1.
Those designated as mu receptors are morphine-and naloxone-selective (that is,
morphine and naloxone bind to these receptors more readily than enkephalins do) &
probably mediate prominent effects of mu receptor agonists include supraspinal &
spinal analgesia, respiratory depression, cardiovascular effects, slowing of G.I
motility, &| sedation
Delta receptors are more enkephalin-selective & induce spinal analgesia .
Kappa receptors have a high affinity for dynorphin &may mediate spinal analgesia
as well as sedation
www.notesolution.com

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Description
CHAPTER 10 NOTES; DRUGS OPIODS (Narcotics) AND THEIR ANTAGONISTS Some of the oldest psychotropic drugs used by humans are morphine and codeine; their use may go back 7,000 years. Originally these drugs were used in the form of extracts from the poppy plant, which contain opium, and in purified form they are still used extensively. They belong to a class of drugs that includes the most effective pain relievers available, so they are the most commonly used analgesic treatments for moderate to severe pain. Since users often experience euphoria, drowsiness, and mental cloudingperhaps resulting in the feeling that all their problems are trivialthese drugs are also used recreationally and are highly subject to abuse The most common term for morphine and similar-acting drugs is narcotic. It has been used primarily to refer to a class of drugs that promote sleep and induce analgesia, but many laypersons often think of narcotics as any highly abusable or addicting drugs. From this perspective, drugs that bear little similarity to morphine in terms of their neurochemical actions or their psychological effects (like cocaine and marijuana) have been designated as narcotics for legal purposes. Pharmacologically, only a drug with the following qualities can be appropriately classified as a narcotic: 1) It generally has sedative-hypnotic and analgesic properties; 2) it acts stereospecifically on endorphinenkephalin receptors; and 3) its actions are antagonized by naloxone (Narcan) It is restricted to extracts of opium (opiates), opiate derivatives, and synthetic drugs with opiate properties. AKA opiods Endogenous Opioid Peptides and Their Receptors Because there are numerous substances with opioid; researchers often refer to these as endogenous opioid and peptides 3 distinct families have been identified thus far: ENKEPHALINS, ENDORPHINS, DYNORPHINS; these are often categorized in a general sense as ENDORPHINS www.notesolution.com
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