Chapter 21: Introduction to CNS Pharmacology

Chapter 21: Introduction to CNS Pharmacology

An increase of chloride conductance is the most important result of activation of

(A) Acetylcholine M₁ receptors

(B) Beta₁ adrenoceptors

(C) 5-HT₃ receptors

(D) GABA_A receptors

(E) Glutamate NMDA receptors

GABA is the most important inhibitory transmitter in the brain (glycine is also important in the spinal cord) and, via GABA_A receptors, causes hyperpolarization mediated by increased chloride conductance. The answer is D.

Neurotransmitters may

(A) Increase chloride conductance to cause hyperpolarization

(B) Increase potassium conductance to cause inhibition

(C) Increase sodium conductance to cause excitation

(D) Inhibit calcium conductance to reduce transmitter release

(E) Exert all of the above actions

Activation of chloride or potassium ion channels commonly generates inhibitory postsynaptic potentials (IPSPs) and hyperpolarization. Activation of sodium and calcium channels (and inhibition of potassium ion channels) generates excitatory postsynaptic potentials (EPSPs). Inhibition of presynaptic calcium channels may reduce transmitter release. The answer is E.

All of the listed neurotransmitters change membrane excitability by decreasing K⁺ conductance except

(A) Acetylcholine

(B) Dopamine

(C) Glutamic acid

(D) Norepinephrine

(E) Serotonin

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 activation of their specific receptors: acetylcholine (M₁), glutamate (metabotropic), norepinephrine (α₁ and β₁), and serotonin (5-HT_2A). The answer is B.

Which of the following receptors shares the same potassium channel as the 5-HT_1A receptor?

(A) Dopamine D₂ receptor

(B) GABA_B receptor

(C) Mu opioid receptor

(D) Muscarinic M₁ receptor

(E) Substance P receptor

GABA_B receptors and 5-HT_1A receptors share the same potassium ion channel, with a G protein involved in the coupling mechanism. The spasmolytic drug baclofen is an activator of GABA_B...