Chapter 5 (Part A):

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Chapter 5 (Part A) Male Reproductive
Behavior (Note Chapter 6 covers Female
Reproductive Behavior)
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In this chapter, we examine the hormonal aspects
of males that leads to their particular
reproductive behaviors. Topics of focus include
the examination of
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Territoriality in elephant seals. The fights
erupt as males guard prime locations in terms of
resources.
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5.2 Male sexual behavior
Proximate basis of male sexual behaviors can be
subdivided as follows
Appetitive phase the period when the male is
actively seeking sexual encounters Consumatory
phase the period when the male is actively
engaged in copulation
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Charles Edouard Brown-Sequard endocrinologist
who in the late 1800s proclaimed extracts of
testes injected in the body had rejuvinating
effects on sexual behavior..
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5.4 Testosterone treatment maintains sexual
behavior after castration
Sexual behavior can be maintained in animals
following castration via replacement
testosterone. Note that there is a threshold
dosage of testosterone that is needed.
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5.5 The Columbia University obstruction test was
used to measure sexual motivation
The motivation of the male rat is assessed in
this device by the use of an electrified grid B.
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Some common terms to describe aspects of male
reproductive behavior Copulatory Lock - during
copulation, the penis of some male mammals (some
breeds of dogs and mice are examples increases in
size in a region along the shaft that it cannot
be removed from the females vagina for a
measurable amount of time. Believed to increase
likelihood of paternity in species with multiple
mating partners in an ovulatory
period. Thursting during copulation, the
movement of the penis within the vagina.
Designed to stimulate sensory nerve endings that
can culminate in ejaculation in the male (and
vagino-cervical orgasm in the female). Intromissi
ons - a behavior where the male will engage in
very brief insertions of his penis into the
female vagina (in rats this behavior is roughly
0.25 seconds each occurance). The role for this
behavior in species that have variable sized
litters is to induce great number of ova to be
released by the female. Ejaculation - The
neuroendocrine pathway that results in the
release of sperm by the male. It is a result of
reaching the threshold level of stimulation of
the penis resulting in the initiation of a neural
circuit that triggers the release of semen from
the stimulation level being reached by tissues on
the penis which trigger contraction of the
bulbospongiosus muscle (under the control of a
spinal reflex at the level of the spinal nerves).

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5.7 Male copulatory patterns in mammals
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5.8 Sexual behavior in the dog
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5.9 Sexual behavior can be restored by
testosterone therapy
A study in guinea pigs.
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Start of Exam 3 Materials
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5.10 Maintenance versus restoration of sexual
behavior by testosterone therapy
What do you think could explain the difference in
ejaculation rates?
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5.13 Regions that are essential to the control
of sexual performance in male rats
POA lesions abolish male sexual behavior and
regulates neuroendocrine function in the brain.
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5.14 The vomeronasal organ (VNO)
The vomeronasal organ (VNO) is absent in most
primates, but essential in rodent reproductive
behavior. because it is used by the male in his
investigatory behavior to assess if the female is
ready in the right part of her ovulatory phase.
The males investigation will lead to both liquid
and gaesous chemicals being taken in. Typically
gaseous chemicals will enter the nasal cavity and
stimulate the VMO, whereas liquid chemicals that
are brought into the oral cavity by the tongue
will pass through the nasopalatine duct to
stimulate the VMO.
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5.15 The amygdala
The amygdala is the brain region that is a pair
of almond-shaped groups of nuclei located deep
within the medial temporal lobes of the brain.
It is the site for routing of many aspects of
behavior including memory emotions in
humans. In rats, the olfactory bulbs feed into
the amygdala, and hence there is a shaping of the
signals by this region.
In rat studies, two amydaloid regions are
identified Basolateral not involved in rodent
sex behavior Corticomedial involved in rodent
sex behavior
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5.16 Neural pathways in the rat olfactory system
The olfactory amygdala is therefore distinct from
the vomeronasal amygdala.
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5.17 Castration reduces neural responsiveness in
the MPOA
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5.18 The distribution of sex steroid receptors
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5.19 Brain regions in rodents that show fos
activation after sexual stimulation
fos one of the IEGS (intermediate early genes
responsible for developing sex behavior.
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5.20 Schematic depiction of neural activity in
circuits underlying male sexual behavior
Difficult to learn just by talking about it,
please exam in detail this figure in the text.
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5.21 Extracellular dopamine in the MPOA is
elevated by cues from the female
Dopamine can be supplied as a medication that
acts on the sympathetic nervous system.
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5.22 Copulatory sequence of rats mating in groups
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5.23 LH secretion can be modified by classical
conditioning
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5.24 Individual differences in sex drive
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5.25 Clinically low testosterone concentrations
can restore mating behavior
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5.29 The frequency of male sexual behavior
changes with age
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5.30 Plasma testosterone concentrations in human
males
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5.31 Individual variation in weekly frequency of
sexual outlet in men
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5.32 Effects of testosterone treatment on
hypogonadal men (Part 1)
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5.32 Effects of testosterone treatment on
hypogonadal men (Part 2)
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5.41 Hormones mediate pseudocopulation in
parthenogenetic whiptail lizards
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Box 5.1 Battles of the Sexes
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Box 5.2(A) Anatomy of the Penis (Part 1)
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Box 5.2(B) Anatomy of the Penis (Part 2)
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Box 5.3(A) Erectile Dysfunction, Nitric Oxide,
and Viagra (Part 1)
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Box 5.3(B) Erectile Dysfunction, Nitric Oxide,
and Viagra (Part 2)
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