Psychopathopharmacology 1 MSN 671 quiz 3

Correct Answer:

B. Hydrophobic signaling molecules

Explanation:

Hydrophobic signaling molecules (such as steroid hormones, thyroid hormones, and some lipids) are poorly soluble in the aqueous extracellular environment. To travel in blood or extracellular fluid, they require carrier proteins (e.g., albumin or hormone-specific binding proteins). These carriers protect the molecules, prolong their half-life, and ensure delivery to their target tissues.

Why Other Options Are Wrong:

A. Autocrine signals

This is incorrect because “autocrine” refers to the type of signaling (cells signaling to themselves), not the solubility of molecules. These signals can be either hydrophilic or hydrophobic.

C. Hydrophilic signaling molecules

This is incorrect because hydrophilic molecules (e.g., peptides, proteins, neurotransmitters) are water-soluble and can freely float in the extracellular space without carrier proteins.

D. Endocrine signals

This is incorrect because endocrine refers to signals (like hormones) released into the bloodstream to act on distant targets. While some endocrine hormones are hydrophobic and require carriers, not all endocrine signals need carrier proteins. The correct distinction is hydrophobicity, not the signaling route.

Correct Answer:

A. Pentameric Subtypes

Explanation:

Pentameric ligand-gated ion channels (pLGICs) are assembled from five protein subunits, each containing four transmembrane regions. These five units come together to form a central ion channel pore. Examples include the GABA-A receptor, nicotinic acetylcholine receptor, glycine receptor, and 5-HT3 receptor. Their pentameric structure explains how they function as fast ionotropic receptors in the central nervous system.

Why Other Options Are Wrong:

B. Tetrameric Subtypes

This is incorrect because tetrameric channels are associated with voltage-gated ion channels (e.g., sodium, potassium, calcium channels). They are not ligand-gated pLGICs with five subunits.

C. Neurogranin Subtypes

This is incorrect because neurogranin is a calmodulin-binding protein involved in synaptic plasticity and learning, not a subtype of ligand-gated ion channels.

D. Classified CN5 Subtypes

This is incorrect because there is no recognized "CN5 subtype" classification in receptor biology. It does not describe ligand-gated ion channels.

Correct Answer:

B. Outside the channel

Explanation:

Ligand-gated ion channels have receptor sites located on the extracellular portion of the protein, outside the channel pore. When a neurotransmitter (ligand) such as GABA, glutamate, or acetylcholine binds to these sites, it induces a conformational change that opens the ion channel. This allows specific ions to pass through, producing rapid excitatory or inhibitory postsynaptic potentials. The binding occurs externally, not within the channel itself.

Why Other Options Are Wrong:

A. Inside the channel

This is incorrect because the channel pore is where ions pass through, not where neurotransmitters bind. Binding inside the channel would block ion flow rather than regulate it.

C. Both inside and outside the channel

This is incorrect because ligand-gated ion channels only have extracellular binding sites for neurotransmitters. Ion flow is regulated after external binding, not by dual internal and external sites.

D. Ligand-gated ion channels do not have receptor sites

This is incorrect because the defining feature of ligand-gated ion channels is the presence of specific receptor sites where neurotransmitters bind to trigger channel opening.

Correct Answer:

A. Ketamine

Explanation:

Ketamine, an NMDA receptor antagonist originally used as an anesthetic, has been found effective in treating treatment-resistant depression and rapidly reducing suicidal thoughts. Unlike traditional antidepressants that may take weeks to work, ketamine produces effects within hours. It is often administered intravenously in specialized clinics, and a related formulation, esketamine (Spravato®), is FDA-approved as a nasal spray for treatment-resistant depression.

Why Other Options Are Wrong:

B. Propofol

This is incorrect because propofol is an intravenous anesthetic used for induction and maintenance of anesthesia. It is not used in psychiatric treatment for depression or suicidality.

C. Hydroxyzine

This is incorrect because hydroxyzine is an antihistamine with sedative and anxiolytic properties. It may reduce anxiety but is not indicated for resistant depression or suicidal ideation.

D. Valium

This is incorrect because Valium (diazepam) is a benzodiazepine used for anxiety, muscle spasms, and seizures. It does not treat depression or suicidal thoughts and carries risks of dependence.

Correct Answer:

B: Synaptic backward transmission from postsynaptic neuron B to presynaptic neuron A

Explanation:

Retrograde transmission occurs when chemical messengers travel from the postsynaptic neuron back to the presynaptic neuron, reversing the usual direction of synaptic communication. Retrograde messengers include nitric oxide, endocannabinoids, and certain peptides. These signals modulate presynaptic activity, often regulating neurotransmitter release or synaptic plasticity. This process plays a crucial role in feedback mechanisms such as long-term potentiation (LTP) and long-term depression (LTD).

Why Other Options Are Wrong:

A: Synaptic forward transmission from presynaptic neuron A to a postsynaptic neuron B

This is incorrect because it describes the normal, forward direction of synaptic communication, not retrograde signaling.

C: Non-synaptic transmission from Neuron A back to Neuron A

This is incorrect because it describes autocrine signaling, where a cell releases signals that act on itself, not retrograde synaptic signaling.

D: Non-synaptic transmission from Neuron B to neighboring neuron B1 or B2

This is incorrect because it refers to paracrine or volume transmission, not retrograde transmission. Retrograde signaling specifically involves communication from the postsynaptic neuron back to its presynaptic partner.

Correct Answer:

C. Benign Neutropenia

Explanation:

Clozapine carries a risk of agranulocytosis, so prescribers monitor the absolute neutrophil count (ANC) before and during treatment. Some African American patients may have benign ethnic neutropenia (BEN) — a genetic variation leading to lower baseline neutrophil counts without an increased risk of infection. This can hinder initiation of clozapine because standard ANC cutoffs may falsely exclude these patients. Adjusted guidelines now allow for BEN, but prescribers must be aware of this factor before ruling out clozapine.

Why Other Options Are Wrong:

A. Low plasma dimension

This is incorrect because there is no recognized genetic factor called "low plasma dimension" influencing clozapine use.

B. Low Seizure Threshold

This is incorrect because clozapine does lower the seizure threshold at high doses, but this effect is not a specific genetic factor tied to African Americans.

D. None

This is incorrect because benign neutropenia is a real genetic factor in African Americans that impacts clozapine initiation.

Correct Answer:

C. A and B

Explanation:

A partial agonist binds to the same receptor as a full agonist but produces a lower maximal response. When neurotransmission is deficient, partial agonists provide enough receptor activity to increase signaling (net agonism). When neurotransmission is excessive, they compete with full agonists for receptor binding but produce less activation, effectively reducing signaling (net antagonism). This stabilizing effect is why partial agonists are often described as “functional stabilizers” of neurotransmission.

Why Other Options Are Wrong:

A. Net agonism when neurotransmission is deficient

This is incomplete because partial agonists can also exert antagonistic effects under conditions of excess neurotransmission, not just agonism when deficient.

B. Net antagonism when neurotransmission is excessive

This is also incomplete. While true for high neurotransmission, it fails to account for the agonist effect when transmission is low.

D. Neither A nor B

This is incorrect because partial agonists clearly demonstrate both agonistic and antagonistic properties depending on the state of neurotransmission.

Correct Answer:

D: Heritable trait resulting from a change in gene expression

Explanation:

Epigenetics refers to heritable changes in gene expression that occur without altering the underlying DNA sequence. These changes are mediated by mechanisms such as DNA methylation, histone modification, and noncoding RNAs. Epigenetic modifications can be passed on during cell division and, in some cases, across generations, influencing traits, disease susceptibility, and development.

Why Other Options Are Wrong:

A: Acquired trait resulting from a change in DNA sequence

This is incorrect because a change in DNA sequence describes a mutation, not an epigenetic change.

B: Acquired trait resulting from a change in gene expression

This is incomplete because epigenetic changes are not just acquired but are also heritable across cell generations.

C: Heritable trait resulting from a change in DNA sequence

This is incorrect because genetic mutations (changes in DNA sequence) cause heritable traits, but epigenetics specifically refers to changes in gene expression without altering the DNA code.

Correct Answer:

C. Transcriptional Regulation

Explanation:

Transcriptional regulation refers to the control of gene expression at the stage where DNA is transcribed into RNA. This involves transcription factors binding to promoters, enhancers, and silencers to either activate or repress RNA polymerase activity. It is a critical step because it determines whether a gene is turned “on” or “off,” thus controlling protein production.

Why Other Options Are Wrong:

A. Translational Regulation

This is incorrect because translational regulation controls gene expression at the level of mRNA translation into protein, not at transcription.

B. Epigenetic Modifications

This is incorrect because epigenetic modifications (e.g., DNA methylation, histone acetylation) regulate gene accessibility broadly, not specifically through promoters and transcription factors.

D. Regulation

This is incorrect because “regulation” is too vague a term. The precise term for control at the transcription stage is transcriptional regulation.