Psy 137 Behavioral Endocrinology

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Psy 137 Behavioral Endocrinology Lecture 9 Male
Reproductive Behavior I
Website http//mentor.lscf.ucsb.edu/course/summer
/psyc137/
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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 (next
  day)

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What is sexual behavior?
Females
Males
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Lorodosis Tail Displacement

• Copulatory measures are unambiguous sexual
  behaviors (include latencies, frequencies, ratio,
  strengths, etc).
• But is that it?
• Does sexual behavior copulation?

Intromission
Ejaculation
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Why did the chicken cross the road?
The chicken can cross the road for different
reasons if it is to get to the rooster then it
is a sexually-motivated behavior
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Classifications of Behaviors

• Consummatory behavior behaviors exhibited
  during completion of a motivated behavior.
  Consummatory sexual behaviors copulation.
• Appetitive behavior all behaviors an organism
  exhibits when attempting to gain access to a
  positive reinforcer (or avoiding a negative
  reinforcer). Appetitive sexual behaviors
  behaviors exhibited in order to gain access to an
  sexual partner.

Appetitive behaviors facilitate or arouse
consummatory behaviors
Temporal-Relational Model
Appetitive behavior
Consummatory behavior
Consummatory behaviors tend to diminish
appetitive behaviors
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Classifications of Sexual Behaviors

• Reproduction includes a complex interaction of
  sexual behaviors
• These vary from species to species, individual to
  individual, and are modified by the environment

• Some basic definition
• Sexual behavior evolved/adaptive behavior
  necessary and sufficient to deliver sperm (male
  gamete) to ova (female gamete).
• Sex drive motivational force that propels
  individual to seek sexual union.
• Potency ability to achieve sexual arousal (i.e.
  blood flow).

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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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Sexually-reinforced behaviors

• When reinforced with copulation male and female
  rats will cross electrified grids (among other
  things) or performed arbitrary behaviors
  (operants).

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Male Courtship/Preparatory Behavior
?
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Male Rat Sexual RewardConditioned Place
Preference

• Males will spend more time in context paired with
  ejaculation.
• Equals good place or looking for something ???

Copulate to ejaculation
No Copulation
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Male Rat Sexual ExcitementConditioned Locomotion

• Bilevel chambers allow female to run away from
  male (pace). Male pursues in order to copulate
  with female.
• When male is placed back into the chamber
  (without the female), he shows hyperactivity.

Subsequent test, measure males behavior prior to
introduction of female
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Male Rat Sexual Behavior

• Sexual Arousal
• Measures penile erection blood flow controlled
  by autonomic nervous system.
• Direct analogy to male human arousal or potency
• Appears to have the same neuroendocrine basis.

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Sexual Inhibition

• Following ejaculation, there is a period of
  sexual inactivity, referred to as the
  postejaculatory interval or refractory
  period lasts 3-5 minutes
• Length of refractory period increases with
  successive copulation until sexual activity
  ceases sexual exhaustion or sexual satiety.
• During refractory period, electrical stimulation
  (flank shock) can re-arouse erection or
  copulation sometimes.
• Immediately following ejaculation no re-arousal
  is possible absolute refractory period
• At end of PEI, re-arousal is possible relative
  refractory period

Ejaculation induces sexual inhibition
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The Coolidge Effect
(Novelty re-arouses sexual behavior).
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Do polygamists fall in love?Or at least show a
preference?Male Rat Sexual Partner
PreferenceConditioned Ejaculatory Preference
Males allowed to copulate to ejaculation with
distinctive females display a subsequent
preference for a similar female
(Kippin et al., 1998)
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Social Aspects MaleMale competition
Male rats turn take during group copulation.
Order of turn is not random, dominant male always
goes first. But all males will mate.
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What about primates? Sneaky-Mating
In most regards, dominance appears to be a boon.
High-ranking males invariably win contests for
limited necessities and luxuries. They are
groomed more often and have largely
unrestricted access to females in estrus, who may
or may not choose to mate with them or even
suffer their presence. In contrast, a low-ranking
male does not mate with a female in the presence
of a higher male, who would disrupt such a
coupling.
The game is the low-ranking males hide, and the
females try to get to them. But the high-ranking
males follow the females and try to keep them
from mating with the low-ranking males,
DNA evidence shows the quick matings can be
effectivetwo high-ranking males managed to sire
two offspring apiece. But a male from a different
group managed to impregnate two females from
group S, and nine other males of mostly middle
and low ranks had one offspring apiece. Previous
work occasionally had similar findings, but
without the details on the circumstances of
sneaky mating and on diminishing mating
opportunities among high-ranking males
Zorpette (1995). The importance of being sneaky.
Dominance may not be key to mating of rhesus
macaques. Sci Am. 272(6)29-31.
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Human Consummatory Sexual Behavior

• Unlike rats, human copulation is highly varied.
• the only unnatural sex act is one that can not
  be performed- Kinsey, 1951
• In both rats and humans, anticipatory and
  preparatory acts occur in settings and are
  performed for access to preferred partners with
  high variablity
• and these behaviors are highly modified by the
  environment i.e. learned.

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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 (next
  day)

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• Remember Berthold Experiment
• Study of the interaction between hormones and
  behavior.
• Results
• Castration disrupted
• Copulation
• Interest in hens
• Crowing
• Aggression
• These were restored by
• implantation.
• Which Behaviors
• are Sexual?

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The Hypothalamus-Pituitary-Gonadal Axis

• The brain is the overall controller of
  circulating gonadal steriods.
• Gonatopropin Releasing Hormone (GnRH) release by
  hypothalamus to stimulate anterior pituitary.
• Gonadotroph cells in anterior pituitary release
  Luteinizing hormone (LH) follicle stimulatin
  hormoner (FSH).
• LH stimulates Leydig cells in testis to release
  testosterone.
• FSH stimulates sertoli cells to produce sperm.
• Testosterone feedbacks to influence brain
  function, particularly those relating to
  reproduction.

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Germline cells a.k.a Germ stem cells
But this is a preparatory step for
reproductionneed to get to ova
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Sex in the Autonomic NS

• Sexual behavior requires coordination of
  parasympathetic and sympathetic NS.
• Parasympathetic NS is activated during sexual
  arousal.
• Sympathetic NS is activated during orgasm.
• Sensory pathways carry information regarding
  genital stimulation to CNS.

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Autonomic Control of Sexual Arousal
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Penile vasodilation (erection) and DHT
Stimulate Penile Nervous
T acts on AR
Nitric Oxide
Pressure

• NO converts Guanylate cyclase to cGMP which
  produces vasodilation resulting in blood
  engouragement of penis.
• cGMP is inactivated by phosphodiesterase-5 (PDE-5
  which penile specific) limits erection.
• Castration prevent increase in ICP and in NO
  levels.
• Testosterone increases levels of the enzyme that
  makes NO, nitric oxide synthetase.
• Vigra inhibits action of PDE-5 enhances erection.

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Autonomic Control of Ejaculation
(involves central NS)
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Hormonal Control of Male Sexual Behavior

• Castration abolishes male sexual behavior in all
  species
• Testosterone restores male sexual behavior
• However, temporal aspects are variable!!!

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Maintenance versus Restoration

• Testosterone treatment is more potent when
  administered at time of castration than at later
  times.

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Testosterone and Individual Differences

• Individual differences in sex drive persist with
  equal testosterone levels.
• Under most circumstances, there is not a relation
  between testosterone levels and level of sex
  drive.

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Intact vs Replacement Testosterone Levels

• Intact males have supra-threshold levels of
  testosterone to achieve erection.

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Testosterone Metabolites

• Role of testosterone metabolism in restoration of
  sexual behavior
• Administration of aromatase inhibitors block
  recovery of copulation.
• Is estrogen necessary for activation of male
  sexual behavior?

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Testosterone Metabolites Erection

• Testosterone or Dihydrotestosterone, but not
  estrogen, maintain penile reflex.

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Testosterone Metabolites Copulation

• Testosterone or Estrogen, but not
  Dihydrotestosterone, maintains copulation.
• Estrogen is sufficient for steriod regulation of
  brain.

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Testosterone Human Male Sexual Behavior

• Huge variation in human sex drive
• Human castrates can maintain sex drive (i.e.
  function of prior sexual experience).
• Little correlation with testosterone levels
  except for hypogonadal men.

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Hypogonadal Men Testosterone

• Testosterone treatment dose-dependently increases
  sexual behavior in men with low testosterone
• Hypogonadal men appear to be responsive to erotic
  stimuli but lack motivation for sex (Davidson et
  al., 1982 Bancroft, 1980).
• Kallmans syndrome GnRH deficit heterosexual
  (Burris et al., 1991).

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Aging Testosterone Sex Drive

• Decline in testosterone explains drop in male
  potency.
• However, there is huge variation and effects of
  experience appears to be almost as important as
  hormones.

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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.