Chapter 21: Introduction to CNS Pharmacology
Which of the following chemicals does not satisfy the criteria for a neurotransmitter role in the CNS?
Cyclic AMP (cAMP) is a mediator in many receptor mechanisms in the CNS, including those for acetylcholine (M2), and norepinephrine (β1). However, the characteristics of cAMP do not satisfy the criteria for a neurotransmitter role (see A. Criteria for Transmitter Status). The answer is B.
(A) Increase chloride conductance to cause inhibition
(B) Increase potassium conductance to cause inhibition
(C) Increase sodium conductance to cause excitation
(D) Increase calcium conductance to cause excitation
(E) Exert all of the above actions
Activation of chloride or potassium ion channels commonly generates inhibitory postsynaptic potentials (IPSPs). Activation of sodium and calcium channels (and inhibition of potassium ion channels) generate excitatory postsynaptic potentials (EPSPs). The answer is E.
All of the listed neurotransmitters change membrane excitability by decreasing K+ conductance EXCEPT
A decrease in K+ conductance is associated with neuronal excitation. With the exception of dopamine, all of the neurotransmitters listed are able to cause excitation by this mechanism via their activation of specific receptors: acetylcholine (M1), glutamate (metabotropic), norepinephrine (α1 and β1), and serotonin (5-HT2A). The answer is B.
Which of the following receptors shares the same potassium channel as the 5-HT1A receptor?
(D) Muscarinic M1 receptor
GABAB receptors and 5-HT1A receptors share the same potassium ion channel, with a G protein involved in the coupling mechanism. The spasmolytic drug baclofen is an activator of GABAB receptors in ...