Psy 137 Behavioral Endocrinology

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Psy 137 Behavioral Endocrinology Lecture 11
Male Reproductive Behavior II
Website http//mentor.lscf.ucsb.edu/course/summer
/psyc137/
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Divisions of Male Sexual Behavior
Male Rats
Male Human
For rats, appetitive aspects of sexual behavior
are highly modifiable. For men, almost all
aspects of sexual behavior are highly modifiable
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Hormonal Control of Male Sexual Behavior Summary

• Sexual behavior in both rodent and primate males
  is regulated by steriod hormones.
• Males have relatively constant levels of steroids
  and behavior.
• Both male sexual behavior is influenced by both
  androgen receptor (erection) and estrogen
  receptor (brain) stimulation.

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Objectives

• Description Framework for male (and female)
  sexual behavior
• Hormonal control of male sexual behavior
• Central NS circuits in male sexual behavior

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(Sexual) Brain Overview

• Medial Preoptic Area
• Roles of dopamine, glutamate, NO
• Steroids in the mPOA
• Chemosensory and genital inputs to mPOA
• Corticolimbic circuits involved in sexual
  behavior
• Nucleus accumbens, lateral hypothalamus
• Primate neural circuits.

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Central Effects of Testosterone.
Central aromatase inhibitor decrease anticaptory
sexual behavior (level changes)
Central aromatase inhibitor decrease consummatory
sexual behavior.
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Activation mapping and Male Sexual Behavior

• A widely distributed set of brain structures are
  activated (i.e. increased c-Fos expression)
  following mating
• We will only focus on a subset.

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Medial Preoptic Area

• mPOA is stimulated during copulation (increased
  c-Fos expression).
• mPOA lesions impair all aspects of male
  copulatory behavior (not necessarily all sexual
  behaviorcome back to this later).
• Convergence site for sex stimulation
  (somatosensory olfactory).

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Sexual Experience Sensitizes MPOA
Copulation

• Neuroplasticity occurs in mPOA with sexual
  experience.
• Also differences in c-fos stimulation by
  dopamine naïve show additive mating D1R
  agonist effects on c-Fos but experienced males do
  not.
• Lumley Hull, 1999

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mPOA Dopamine Release during Sex

• T not necessary for copulation or increase in DA
• But more males copulate with TP (90) than
  vehicle (40) following castration.

Levels of extracellular DA in the MPOA of male
rats during baseline (BL), a precopulatory
exposure to an estrous female (PRECOP), and three
6-min copulation samples (COP). Gonadally intact
male rats showed an increase in extracellular DA
during precopulatory exposure to an inaccessible
estrous female, and all intact males copulated
males castrated 2 weeks before showed no DA
release in response to the female, and none
copulated. Hull et al., 1995.
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mPOA DA in Copulation

• Roles of DA receptors in the mPOA during
  copulation.
• A low dose of a D3/D2 agonist (quinelorane)
  decreased the latency to the first reflexive
  erection or seminal emission, but did not affect
  the numbers of erections or seminal emissions
  (Hull et al 1989)
• low threshold D2R respond to sensory stimuli
  (e.g. chemosensory) to facilitate erection.
• A moderate dose of a D1 agonist
  (dihydroxyphenyl-tetrahydrothienopyridine, THP)
  increased the numbers of parasympathetically
  mediated erections and facilitated copulation,
  but the D1 agonist also decreased the number of
  sympathetically mediated seminal emissions in ex
  copula reflex tests (Markowski et al., 1994)
• D1R respond to senory and genital (copulation)
  stimulation to maintain erection.
• a high dose of the D3/D2 agonist shifted the
  balance of autonomic influence to favor
  ejaculation and inhibit erection (Basset et al.,
  1991)
• High threshold D2R initiate ejaculation.

mPOA serves complex role in regulating sexual
behavior -integration of environmental stimuli
to trigger arousal/excitement. -integration of
genital stimulation to trigger ejaculation.
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mPOA Glutamate and Copulation.
Glutamate increases in mPOA during copulation
with peak at ejaculation. Dominguez et al.,
2006.
Changes in extracellular MPOA glutamate during
copulation. Samples analyzed included baseline
(BL), precopulation (PRE female placed above the
male's cage), copulation (COP only mounts and
intromissions), ejaculation (EJAC),
post-ejaculatory interval (PEI), and
post-copulation (POST) samples. Samples were
collected at 2 min intervals.
MK-801 reduces intromission ratio and ejaculation
frequency Powell et al (2003) Behav Neurosci.
117(1)69-75.
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Glutamate in mPOA facilitates copulation.
Dominguez et al., 2006 J Neurosci 26(6)1699-703
Infusion of uptake inhibitor (UPTKi) increases
glutamate levels and facilitates ejaculation and
reduces postejaculatory inhibition
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Glutmate Increases Dopamine in mPOA via NO
Dominguez et al (2004) Neuroscience 125(1)
203-210
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Sexual Experience increase NOS
Protein concentration for nNOS in the MPOA of
male rats in the following groups sexually naive
rats that did (NS, naive/sex) or did not (NNS,
naive/no-sex) mate on the day of testing and
sexually experienced rats that did (ES,
experienced/sex) or did not (ENS,
experienced/no-sex) mate on day of testing. (b)
Average number of nNOS-immunoreactive cells in
the MPOA of male rats undergoing these experience
and mating conditions. Dominguez et al., 2007.
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Nitric Oxide is necessary for copulation.
Sensitization of copulation occurs via exposure
(without access to female) and is blocked by
inhibition of NOS.
Total mounts, intromissions, and ejaculations in
sexually naive rats treated with the nitric oxide
synthase inhibitor l-NAME (100 µg/µl) or saline
before each of seven non-copulatory exposures to
a receptive female and tested drug free on Day 8
and in untreated naive males not pre-exposed to a
female. Open bars indicate naive rats that did
not receive pre-exposure, gray bars indicate rats
that received a saline microinjection before each
exposure, and black bars indicate naive rats that
received an l-NAME microinjection before each
exposure. Exposure to females consisted of
placing the female in a wire mesh cage over the
male's home cage for 30 min. Lagoda et al., 2004.
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Glutamate-Dopamine Interactions in mPOA during
copulation.

• Glutamate is increased by sexual stimulation.
• Glutamate stimulates NMDA receptors which
  activates NOS.
• Increased NO stimulates DA release and/or reduces
  reuptake.

Model showing possible interactions between
glutamate, nitric oxide (NO), and dopamine in the
MPOA. (1) Glutamate (GLUT gray hexagon)
activates NMDA receptors, which opens calcium
channels. (2) The resultant increase in
intracellular calcium (gray diamonds) then
activates calmodulin (CaM), (3) which in turn
activates the enzyme NO synthase (NOS) this
leads to an immediate production of NO. NOS links
to the carboxy-terminal tail of the NMDA
receptor, via a PSD-95 proteinprotein
interaction domain. Once synthesized, NO freely
diffuses from cell to cell, (4) where it can
alter activity in the presynaptic neurons. (5)
Additionally, in dopamine-producing neurons, NO
has been shown to inhibit the dopamine
transporter (DAT) (6) and increase
calcium-dependent and/or calcium-independent
vesicular release. Therefore, increased NO in the
MPOA, after glutamate release, would increase
levels of extracellular dopamine and prolong the
presence of dopamine in the synapse. Hull
Dominguez, 2006.
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What about the Sexually-Dimorphic Nucleus of the
POA?

• Selective lesions of the SDN-mPOA appear to alter
  male-typical approach of female vs male.
• copulation not changed Arendash Gorski (1983)
  Yahr Gregory (1993) Cherry Baum (199).
• effect in female not examined
• unreplicated results???

Alekseyenko et al., 2006 Physiol Behav. Epub
ahead of print
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Steroid Receptors in mPOA

• mPOA contains both androgen and estrogen
  receptors.
• Some cells express both receptors.
• Note ARs (in the septum, amygdala, raphe) are
  crucial for levels of intra-male aggression which
  is important for control of access to mates.

AR
ER
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mPOA dopamine and ERa

• Male mice lacking ERa show no social preference
  for female over male and fail to mount.
• Apomorphine (DA agonist) restores male sexual
  behavior in male ERaKO

Wersinger Rissman (2000). J Neurosci. 2000
20(11)4248-54
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T Metabolites mPOA DA
Oil-no copulation DHTB-mount only EB-mount,
intromit only TB-mount, intromit, ejaculate
Temporal changes in dialysate concentrations of
dopamine during copulation in the MPOA of male
rat castrates treated with various hormone
regimens (EB, estradiol benzoate DHTB,
dihydrotestosterone benzoate Oil, vehicle TP,
testosterone propionate). Samples include
baseline (BL), two precopulatory periods with an
estrous female behind a barrier (EST1 and EST3),
and three periods (10 min) after the barrier was
removed and the animals were free to copulate
(COP1, COP3, and COP5). Putnam et al., 2003.
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T metabolites DA content

• Castration increases total DA in mPOA and is
  restored with TP or E2DHT.
• Therefore, release of DA is disrupted by
  castration.

Tissue content of DA in the MPOA of castrates
treated with various hormone regimens. (a)
Comparison among animals without or with
estradiol benzoate (EB) (E2- vs. E2) and/or
dihydrotestosterone benzoate (DHTB) (DHT- vs.
DHT). Castrates with only EB (E2/DHT-) had
lower levels of tissue dopamine content, compared
to castrates treated only with oil (E2-/DHT-).
The difference between castrates with only DHTB
(E2-/DHT) and those with EB  DHTB (E2/DHT)
was not statistically significant. (b) Comparison
between EB  DHTB and TP-treated animals. Putnam
et al., 2005.
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Steroid Receptors colocalize with nitric oxide
synthase (NOS)
Quantitative analysis of immunoreactivity for
nNOS and proportion of co-localization with AR
or ERa in the MPOA of gonadally intact male rats
Sato et al., 2005 Brain Res. 1043(1-2)205-13.
Photomicrographs of sections stained for
nNOS-/AR-ir and nNOS-/ERa-ir. Open arrows
indicate single-stained nNOS-ir cells,
indicates AR-ir or ERa-ir cells, and closed arrow
indicates cells double-stained for nNOS-ir/AR-ir
or nNOS-ir/ERa-ir. nNOS/AR staining (b, d, f) and
nNOS/ERa (a, c, e) in AVPV (a, b), MPN (c, d),
and MePN (e, f).
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Steroids and NOS in mPOA
Putnam et al., 2005 Hormones and Behavior 47(2)
513-522.

• E2 elevates NOS in the mPOA
• DHT no increase
• NB TP may be higher than E2 DHT mechanism???

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Steroids in mPOA function
ER stimulation increases NOS making mPOA more
responsive to glutamate during sexual stimulation
AR stimulation role is still not completely
understood
But where does glutamate come from
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But where does Glutamate come from?-afferents to
MPOA

• Left bidirectional connections
• Right unidirectional connections
• Swann et al 2003

Focus on genital inputs from thalamus via brain
stem spinal cord
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Olfactory Inputs to mPOA

• mPOA DA increases with chemosensory input from
  females
• Gets there from multiple routes including through
  the Medial Amygdala (shortest route).

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Medial Amygdala Lesions
Medial Amygala lesions impair (but do not
prevent) copulation via disruption of olfactory
cues resulting in erection inhibition genital
stimulation can still lead to erection. MeA also
expresses c-Fos following exposure to receptive
female ejaculation-responsive subregions.
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Medial Amgydala-MPOA interactions.

• Medial Amygdala (MEA) provides a glutamate input
  to mPOA actiaved when exposed to pheromones
• Medial Amygdala (MEA) lesions impair copulation
  and prevent mPOA DA increases.
• Intra-mPOA apomorphine restores copulation.
• Stimulation of MEA increases mPOA DA.
• Dominguez 2001 J Neurosci. 21(1)349-55

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Chemosensory System and T-treated mPOA necessary
for sexual behavior.

• All males castrated.
• Male receive T (solid bar) or vehicle (open bar)
  in mPOA unilateral
• All males received unilateral lesion of olfactory
  bulb either contra- or ipsi-lateral to implant

?
lesion
Restoration of mounting (and anogenital
investigation) with intact OB to T-treated mPOA
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mPOA Circuits

• Ascending circuits converge with inputs
  chemosensory systems.
• Ascending inputs are critical for bringing
  information from genital stimulation that
  contribute to the central control of ejaculation.
• Lesions of bed nucleus stria terminalis block
  ejaculation (but not copulation).

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mPOA Summary

• MPOA is critical for copulation in all species
  examined.
• Integrates chemosensory and genital information
  to regulate sexual arousal and ejaculation
  (involves BNST).
• Glutamate stimulates NMDA receptors coupled to
  NOS increasing NO which act in a retrograde
  fashion to increase DA.
• Testosterone stimulates ERa to increase NOS.

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Source of mPOA DA

• mPOA receives DA from intra-hypothalamic sources
  intercohypothalamic DA system (cell bodies in
  PVN and zona incerta)
• mPOA has inputs to ventral tegmental area
  (later).
• VTA does NOT project to mPOA.

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c-Fos mapping and Sex Odors

• There are two olfactory pathways
• Accessory olfactory pathway
• Main olfactory pathway

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Conditioned versus pheromonal c-Fos

• Distinct pathways process sex-paired odors and
  pheromones (Kippin et al., 2002).

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Nucleus Accumbens and Male Sexual Behavior

• A.K.A ventral striatum limbic-motor interface
• Involved in motivation, attention, reinforcement
  for food, drugs, and aversive stimuli what about
  sex?
• Pheromones, copulation-paired stimuli (odors or
  context), or copulation increase c-Fos
  expression.

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Nucleus Accumbens Lesions (experienced males)

• NAc lesions selectively impair psychogenic
  (chemosensory stimulated) erection (Lui et al
  1998) in experienced males

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Dopamine in the N. Acc during Sexual Behavior.
N.ACC DA increases in presence of female then
falls after ejaculation (during PEI).
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Dopamine antagonism in the N. Acc during Sexual
Behavior.
LC anticipatory level changes.

• Intra-accumbens dopamine antagonism impairs
  anticipatory sexual behavior.

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Dopamine in the N. Acc during the Coolidge Effect.
Prolonged copulation with a single female is
associated with declines in dopamine and
copulation.
Following cessation of copulation, re-exposure to
a NOVEL female is associated with increased
Dopamine levels and renewal of copulation.
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Nucleus Accumbens Lateral Hypothalamus

• NAc in naïve male rats impairs both psychogenic
  erections and copulation (i.e. learning occurs
  during copulation)
• LHA lesions in naïve male rats facilitates
  erection (i.e. normally serves an inhibitory
  role) but blocks ejaculation.
• (Kippin et al., 2003)

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Serotonin in Lateral Hypothalamus during
copulation
Lorrain et al 1999
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Increased Lateral Hypothalamus 5HT impairs
copulation and reduces mPOA (and NAC) Dopamine
Alaproclate selective serotonin reuptake
inhibitor.

• Increased serotonin in LH reduces sexual behavior
  by inhibiting DA levels in mPOA.
• Explains inhibitory effects of serotonin reuptake
  blockers (e.g. antidepressants) on sexual
  behavior.

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Operant Behavior
What about appetitive sexual behaviors?

• The circuits mediating the maintenance of
  sexually-reinforced behavior are distinct from
  those mediating copulation.
• BLA lesions disrupt responding but not
  copulation mPOA disrupt copulation but not
  responding.
• BLA effects are reversed by increasing intra-NAc
  dopamine (amphetamine).
• Castration or opiates can reduce both suggesting
  a common control of sexual motivation.
• Appears to be mediated by cortico-limbo-striatal
  circuits similar to other reinforcers.

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Rewarding effects of copulation.

• Opioid activity can be measured by
  internalization of receptors
• Copulation increases internalization in a number
  of brain regions, including the mPOA, NAC, and
  ventral tegmental area.
• Copulation is reduced by systemic and intra-mPOA
  administration of opioids.

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Ejaculation and Reward.

• Conditioned place preference can be established
  by ejaculation
• In this case, a bias design is employed and
  change from preferred indicates rewarding
  aspects of ejaculation.
• Opioid antagonism blocks acquisition of CPP
• Unclear as to site of action as there are mixed
  results for intra-mPOA and intra-NAC infusions.
• Intra-vta not examined (but get extremely robust
  CPP for opiates into this region can block ).
• Dopamine antagonism does not block CPP (may
  facilitate???) will block expression of CPP
• Thus, dopamine involved in motivational and
  copulatory aspects of sexual behavior but not
  rewarding aspects of ejaculation.

Place preference in animals exposed to an
ovariectomized (OVX) female, permitted one
ejaculation, permitted one ejaculation after
treatment with naloxone (NX) 16 mg/kg, or
permitted one ejaculation after treatment with
pimozide (PIM) 1 mg/kg. (Values are M SE.
Symbols are as in Figure 1 .) Open bars, pretest
striped bars, test. Different from pretest or
control, p lt .05 p lt .01.)
Agmo et al 1990.
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Prefrontal cortex

• Copulation increases c-Fos levels in infralimbic
  and prelimbicbut not the anterior
  cingulatesubregions of the medial prefrontal
  cortex.
• Infralimbic area and prelimbic area sent
  projections to nucleus accumbens, medial preoptic
  area, principal nucleus of the bed nucleus of the
  stria terminalis, basolateral amygdala, and
  parvocellular subparafasicular thalamic nucleus.

Balfour et al 2006 Neuroscience 137(4) 1259-1276.
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Cortical Involvement in Coolidge Effect
Perirhinal/entorhinal cortices are critical for
memory formation Also, involved in Coolidge
effect (H hippocampus not involved).
Petrulis Eichenbaum (2003). Neurosci.
122(3)599-607
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The Sexual Brain of the Male Rat Summary

• mPOA critical for integration of chemosensory and
  genital information for control of sexual arousal
  and ejaculation.
• NAC LH opposing roles in stimulating and
  inhibiting sexual motivation.
• Involvement of cortex and other limbic structures
  (regulate emotions and memory) have been poorly
  described

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The Sexual Brain
NAc
LH
VTA

• The medial preoptic area (MPOA) is critical for
  copulatory behavior it receives direct and
  indirect input from brain areas that are
  important for the assimilation of sexually
  relevant information.
• Pheromonal stimulation is received by the
  olfactory bulbs (OB), the OB project to the
  medial amygdala (MeA), which relays information
  to the bed nucleus of stria terminalis (BST) and
  the MPOA.
• Additionally, the MPOA and MeA receive
  somatosensory input (from genitals) via the
  central tegmental field (CTF).
• In turn, the MPOA projects to the ventral
  tegmental area (VTA) and the brain stem (BS)
  which project to cortico-limbic structures.
• Nucleus accumbens (NAc), basolateral amygdala,
  and cortical structures are critical for
  motivational processes particularly for
  sexually-conditioned stimuli.
• Lateral hypothalamus involved in inhibiting mPOA
  and NAc.

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What about primate species?
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c-Fos in primate males after copulation.

• Only one study
• Mate males to ejaculation (15min)
• Return to home cage
• Sacrifice 60 min later therefore hard to tell
  what has induce c-Fos.

Comparison of Fos expression in nine brain
regions of unmated (horizontally hatched bars),
social control (diagonally hatched bars), and
mated (black bars) male macaques.
VMHventromedial hypothalamus ARC arcuate
nucleus LMAM lat. Mammillary body BST bed
nuc stria terminalis MPOA med preoptic area
PVN paraventricular nucleus mAMG med
amygdala cAMG central amygdala LSEP lat
septum.
Michael et al 1999 Physiol Behav. 66(4)591-7.
However, stimulation of mPOA causes erection,
lesions block copulation, and copulation
increases mPOA cell firingwhen there is no Fos
it means just that there is no Fos
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FMRI and Sexual imagery Men
Areas of significant BOLD signal increases in
male subjects during (brain activation
associated with) viewing the erotic film excerpts
via subtraction procedure compared emotionally
neutral film excerpts. A Medial prefrontal
cortex, anterior cingulate cortex, thalamus and
hypothalamus. B Orbitofrontal cortex. C
Insular cortex. D Amygdala. E Ventral
striatum and hypothalamus. F Occipitotemporal
cortex.
Karama et al 2002 Hum Brain Mapp. 16(1)1-13
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Male Sexual Arousal and hypothalamic activation
mPOA????
Regression map showing significant positive
correlation between individual BOLD signal
increases in the hypothalamus and individual
reported sexual arousal in male subjects. Height
threshold is set at P lt 0.004 (z 2.65).
Karama et al 2002 Hum Brain Mapp. 16(1)1-13
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Ejaculation fMRI
Several discrete cortical structures in frontal,
temporal, and parietal, as well as cerebellum are
activated during ejaculation.
Mesodiencephalic transition zone (mes-di) extends
from the rostral midbrain into the ventral parts
of the caudal thalamus are activated during
ejaculation.
Lack of activation in mPOA???
Holstege et al 2003 The Journal of Neuroscience,
23(27)9185-9193