Anxiolytics and Hypnotics Flashcards
What are the four main proteins that make up the GABA-A receptor?
GABA receptor protein
Benzodiazepine receptor protein
Barbiturate receptor protein
Chloride channel protein
What protein links the GABA receptor proteins and the benzodiazepine receptor protein?
GABA modulin
Describe the normal physiological action of GABA.
GABA binds to the GABA receptor protein
GABA modulin links the GABA receptor protein and the benzodiazepine receptor protein
This results in opening of the chloride ion channel
Name a competitive antagonist of the GABA receptor protein.
Biciculline
Name a competitive antagonist of the benzodiazepine receptor protein.
Flumazenil
What are the two main effects of benzodiazepines that facilitate GABA neurotransmission?
They facilitate the GABA-mediated opening of the chloride channel
They facilitate the binding of GABA to its receptor protein (increase theaffinity of GABA to the GABA binding site) – this is reciprocated
What are the three main effects of barbiturates that facilitate GABA neurotransmission?
They enhance the normal physiological action of GABA
They enhance GABA binding to the GABA receptor protein (NOT reciprocated)
At higher concentrations, barbiturates can have a direct action on the chloride channel
What is the key difference in the mechanism of action of barbiturates and benzodiazepines?
Benzodiazepines – increase the frequency of chloride channel opening
Barbiturates – increase the duration of chloride channel opening
What is the relative difference in selectivity between barbiturates and benzodiazepines?
Barbiturates are LESS selective
This may explain why barbiturates induce surgical anaesthesia and why barbiturates are less safe than benzodiazepines
NOTE: barbiturates also reduce excitatory transmission
Name a barbiturate that is used as an anaesthetic.
Thiopentone
Name three barbiturates and benzodiazepines that are used as anti-convulsants.
Diazepam- benzodiazepine
Clonazepam- benzodiazepine
Phenobarbital- barbiturate
Name a benzodiazepine that is used as an anti-spastic.
Diazepam
What are two other clinical uses of benzodiazepines and barbiturates?
Anxiolytics
Hypnotics
Define anxiolytic.
Remove anxiety without impairing mental or physical activity
Define sedative.
Reduce mental and physical activity without producing loss of consciousness
Define hypnotic.
Induces sleep
What structure is common to all barbiturates?
Six-membered ring (4 carbons and 2 nitrogens)
Barbiturates have been largely superseded by benzodiazepines. Which barbiturate is still used relatively commonly?
Amobarbital