Lecture 14 Hindbrain

what becomes the hindbrain?

rhombencephalon

hindbrain is composed of

pons, medulla, cerebellum

hindbrain is involved with

respiratory rhythm, mood, motor activity, sleep, autonomic functions, wakefulness

serotonin (5-HT) is a ___ derived from ___

indolamine

tryptophan

__% of 5-HT is produced in the __

90

GI-tract

centrally, 5-HT is produced in the ___

raphe nucleus (dorsal)

where else is 5-HT found?

- skin's Merkel cells

- pulmonary endocrine cells

- tongue's taste receptor cells

5-HT is involved in

Mood, cognition, reward, learning, memory, vomiting, sleep, thermoregulation, sex, feeding, vasoconstriction

what are the 3 main families of 5-HT receptors (more or less)

5-HT1

5-HT2

5-HT other

dopamine is found in the ___

serotonin is found in the ___

midbrain

pons

5-HT in the brain is almost exclusively produced by neurons originating in the

raphe nucleus

raphe nucleus sends 5-HT projections to the

cortical, limbic, midbrain, and hindbrain regions

all brain regions have ___ receptors

5-HT

classical antidepressants

selective serotonin reuptake inhibitors (SSRIs)

SSRIs do what

increase extracellular levels of 5-HT by limiting reuptake (DA and NE as well)

SSRIs are given for what conditions?

•Depression

•Social anxiety disorder

•PTSD

•GAD

•OCD

•Panic

•Eating

•Stroke

•Premature ejaculation

side effects of SSRIs

•Sexual dysfunction (over 50% !)

•increase bone fractures

•Akathisia

•suicide ideation

raphe nucleus is greek for

"seam"

raphe nucleus is the ___ portion of the ___ in the ___

medial

reticular formation

brainstem

what are the two functional regions of raphe nucleus?

median and dorsal

median raphe

projects 5-HT mainly to hippocampus for long term memory formation

dorsal raphe

largest 5-HT nucleus and sends projections to most of forebrain

caudal raphe project to ___ and ___, involved with ___

spinal cord

brainstem

pain modulation

rostral raphe project to ___

higher order brain regions (dorsal and median are included)

periaqueductal gray (PAG)

"circle" of gray matter that surrounds the cerebral aqueduct in the tegmentum of midbrain

ascending ___ tract breaks off into ___ tract to convey ___ and ___ to PAG

spinothalamic

spinomesencephalic

pain

temperature

key site for brain stimulation in patients with chronic pain

PAG

PAG plays a role in

- analgesia (produces enkephalin)

- defensive behaviors

- reproductive behaviors

- maternal behaviors (vasopressin and oxy receptors and sends connections to OFC)

PAG is involved with ___ modulation of pain perception

descending

stimulation of PAG ___ anesthesia requirements

decreases

PAG activates ___ which in turn activates ___. this will...

raphe

enkephalin

inhibit C fiber afferents

PAG is the "generator" of ___

migraines (iron deposits and structural changes in PAG of patients with chronic migraines)

nucleus of solitary tract (NTS) is a ___ column of ___ matter in the ___

vertical

gray

medulla oblongata

NTS is pure ___ nuclei

sensory

NTS is innervated by fibers from ___, ___, and the ___ nerve

facial

glossopharyngeal

vagus

NTS is involved in

- taste and gustation (mediates the gag reflex)

- respiration

- blood pressure

along with the gut, the NTS produces

glucagon-like peptide I (GLP-1)

GLP-1 does what?

- regulates blood sugar

- slows gastric emptying

- promotes satiety upon food consumption

GLP-1 is very effective in weight loss, BUT...

as soon as patient stops administering, weight comes back

ozempic is thought to mimic ___ to promote ___

NTS-brainstem GLP-1

satiety

Ozempic and other GLP-1 drugs do/do not cross blood brain barrier

do not

parabrachial nuclei are in the ___ that surround the ___

dorsolateral pons

superior cerebellar peduncle

parabrachial nucleus is involved in

•Arousal

•Pain

•Blood sugar control

•Thermoregulation

•Taste

•Pleasure

-- "liking"

parabrachial nuclei receives input from ___ and relays ___ to ___

NTS

noxious stimuli

amygdala

thought to be one of the key centers for fibromyalgia

parabrachial nuclei

pontine nuclei (PN) is located in

ventral pons

pontine nuclei (PN) is a ___ structure that receive info from ___ and relay to ___

"bridge"

primary motor cortex

cerebellum

function of PN

motor activity (learning motor skills)

what brain area is active to sexual cues?

amygdala

what brain areas are involved with sexual interest?

- anterior cingulate cortex

- orbitofrontal cortex

- ventral striatum

what brain areas are involved with sexual responsiveness?

- anterior cingulate cortex

- orbitofrontal cortex

- hippocampus

are steroid hormones necessary for engaging in sexual behavior?

yes

castration leads to a ___ of sexual behavior. this is presumed to be a result of the ___ of testosterone. testosterone injections ___

reduction and most often a cessation

loss

can restore sexual behavior

does the amount of circulating testosterone affect sex-drive?

yes (in guinea pigs)

in males, steroid hormones appear to act on distinct regions of the brain to facilitate sexual behaviors. what is one of these areas?

medial preoptic area of the hypothalamus (mPOA)

lesion of mPOA results in ___.

___ implants here in castrated males ___

abolishment of male copulatory behavior

androgen

restores copulatory behavior

mPOA neurons send their axons to ___ regions of the brain which, in turn, project to the ___ to produce ___ sequences involved in ___

motor-related

spinal cord

motor

male copulatory behavior

like in most female mammals, female rats have ___ in gonadal steroid hormones

cyclic fluctuations

rats have a ___ day estrus cycle; humans have ___ day cycle

4

28

female rats will only be receptive towards a male and his advances during

behavioral estrus

receptivity of female sexual behavior is entirely dependent on

gonadal hormones

___ females are not receptive to males at any time

ovariectomized

___ can lead to female receptivity in ovariectomized females

mimicking the natural estrus cycle with exogenous (experimenter delivered) hormones

in the presence of a male and an attempt by him to mount, a receptive female will adopt a posture called ___ which is characterized by ___ and ___

lordosis

elevated rump

tail deflected to one side

without gonadal steroid hormones...

no lordosis

what brain regions are critical for lordosis?

Ventromedial nucleus of the hypothalamus (VMN)

Periaqueductal gray (PAG)

Medullary reticular formation

Spinal cord

estrogen and progesterone delivered directly to ___ induce lordosis

Ventromedial nucleus of the hypothalamus (VMN)

lesions of VMN will

wipe out lordosis

___ stimulation of ___ promotes lordosis

electrical

VMN

male and female pathways for sexual behavior (simplified)

males: medial preoptic area --> lateral tegmental field

females: ventromedial nucleus --> PAG

the neurotransmitter ___ is released in response to the delivery of rewarding stimuli such as ___ and ___

dopamine (DA)

food

drugs (e.g. cocaine)

Coolidge effect

males exhibit renewed sexual interest in new receptive females after mating

- increased sexual responsiveness (increases of DA to new partners)

- evolutionary benefit to males to spread their genetic material

activation of orbitofrontal cortex is involved with what aspects of sexual behavior?

- mate selection

- desirability

- visual stimuli

damage to ____ can induce abnormal sexual preferences

OFC

constant perusal of internet pornography can lead to altered ___ function

OFC

activation of amygdala can lead to what aspects of sexual behavior?

•Erection

•Sexual feelings

•Sensations of extreme pleasure

•Ovulation

•Uterine contractions

•Orgasm

activation of ventral striatum can lead to what aspects of sexual behavior?

orgasm

damage to dorsolateral PFC can lead to what aspects of sexual behavior?

- reduce sexual drive

- similar effects are seen in depression and can sometimes be triggered by SSRI use

damage to temporal lobe can lead to what aspects of sexual behavior?

- hypersexuality