Chapter 17: Disorders of Anxiety and Impulsivity

Question 1

What neurotransmitters play a role in anxiety?

Answer 1

1. CRF
2. Norepinephrine
3. GABA
4. Serotonin

Question 2

What are the major neurobiological components of anxiety?

Answer 2

1. central nucleus of the amygdala produces the fear response when threatening stimuli appear suddenly and end abruptly
2. the bed nucleus of the stria terminalis (BNST) produces sustained preparedness for unclear danger

Question 3

What role does CRF play in anxiety?

Answer 3

CRF regulates stress hormone secretion and activates neuronal circuits of emotion that produce anxious behaviors in animal models.

Question 4

What role does NE play in anxiety?

Answer 4

When the amygdala releases CRF in response to stress, noradrenergic neurons in the LC fire at a high tonic rate increasing NE release. This produces hypervigilance and fearfulness. NE mediates the formation and reconsolidation of traumatic memories. NE and EP are released during sympathetic activation and are responsible for physiological symptoms of anxiety.

Question 5

What role does GABA play in anxiety?

Answer 5

GABA modulates anxiety by:

1) controlling the excitability of local circuits
2) regulating the activation of the central nucleus of the amygdala
3) glutamatergic neurons from the prefrontal cortex stimulate GABA neurons on the amygdala, thus providing top-down control of amygdaloid activity

Question 6

What role does serotonin play in anxiety?

Answer 6

1. serotonin-A1 agonists bind to somatodendritic receptors in the raphe nucleus inhibiting the firing and release of serotonin and reduce anxiety
2. serotonin-1A agonists acting on postsynaptic receptors in the amygdala increase anxiety

Question 7

What role does serotonin play in uncontrollable stress?

Answer 7

Exposure to uncontrollable stress leads to increased anxious behavior. A high extracellular level of 5-HT desensitizes the somatodendritic autoreceptors in the raphe nucleus and subsequently increases the firing of projection neurons and release of 5-HT in limbic regions.

Question 8

What are the categories of drugs used for treating anxiety, OCD, and PTSD?

Answer 8

The drugs used to treat anxiety are called anxiolytics. Most of them are in the class called sedative-hypnotics. The categories of anxiolytics are:

1. barbiturates
2. benzodiazepines
3. second-generation anxiolytics
4. antidepressants

Question 9

How do barbiturates work?

Answer 9

Barbiturates increase the opening of GABA-activated chloride ion channels and can directly open these channels without the presence of GABA. This increases the affinity of the GABA-A receptor for GABA and enhances its inhibitory effects. They are not used to treat anxiety anymore because they have significant side effects, physical dependence, and potential for abuse.

Question 10

How do benzodiazepines work?

Answer 10

Benzodiazepines increase the number of times that the chloride ion channels open when they bind to their modulary sites on the GABA-A complex. They also enhance the inhibitory effects of GABA. Unlike the barbiturates, benzodiazepines do not open the chloride ion channels without GABA present.

Question 11

How do second-generation anxiolytics work?

Answer 11

The best known second-generation anxiolytic is buspirone. Buspirone acts as a partial agonist at serotonin-1A receptors. It reduces anxiety and depression without sedation or mental clouding, does not enhance other sedative–hypnotics, and has no withdrawal syndrome or abuse potential.

Question 12

What are the types of antidepressants used to treat anxiety?

Answer 12

SSRIs, tricyclic antidepressants, and monoamine oxidase inhibitors (MAOIs). SSRIs are considered the first line treatment for anxiety because they have a high therapeutic index and there is low fear of abuse. However, they can take 4-6 weeks to become effective and individual drug treatment response is variable. Tricyclic antidepressants and MAOIs have worse side effects than SSRIs.

Question 13

What is the pathophysiology of GAD?

Answer 13

GAD is associated with enlargement and hyperactivity of the amygdala and too little inhibitory control by the PFC. Increasing PFC and amygdala inhibition with GABA agonists reduces symptoms.

Question 14

What is the pathophysiology of panic disorder?

Answer 14

1. dysregulation of adrenergic neurons in the autonomic nervous system and LC
2. genetic polymorphism of the NE transporter gene
3. reduced volume of the amygdala and hippocampus
4. during a panic attack there is increased neural activity in the amygdala, cingulate cortex, and insula and decreased activity in the PFC

Question 15

What is the pathophysiology of social anxiety disorder?

Answer 15

increased blood flow in the amygdala during challenge that normalizes after treatment

Question 16

What is the pathophysiology of PTSD?

Answer 16

1. increased neural activity in the amygdala

2. the anterior cingulate and the medial PFC are less active and fail to inhibit the limbic structures

Question 17

What is the pathophysiology of OCD?

Answer 17

The cortico-striatal-thalamic-cortical loop is believed to be central to OCD symptomatology. There is increased metabolic activity in the caudate nucleus (part of the striatum) in response to provocative stimuli and there is coordinated activity of the caudate nucleus with several cortical regions.

Question 18

What are the therapeutic uses of benzodiazepines?

Answer 18

1. presurgical anesthesia
2. anxiolysis
3. sleep induction
4. muscle relaxation
5. seizure control
6. termination of alcohol withdrawal

Question 19

What are the advantages of benzodiazepines?

Answer 19

1. high therapeutic index
2. availability of a competitive antagonist to reverse overdose
3. reduced tolerance and drug interactions
4. less physical dependence and milder withdrawal
5. less reinforcement value
6. lower abuse potential
7. no fatalities unless combined with another sedative–hypnotic

Question 20

What are the disadvantages of SSRIs?

Answer 20

1. take 4 to 6 weeks to show effectiveness following neural adaptations to chronic use
2. increased anxiety
3. insomnia
4. sexual dysfunction
5. withdrawal symptoms following drug cessation