Lecture 8 olfaction, social recognition and social memory

Question 1

what does bonding require?

Answer 1

olfaction, social recognition and social memory

Question 2

describe imprinting

Answer 2

Imprinting is phase-dependent and non-associative learning

Influences behaviour, bonding and mate selection…

Question 3

how do mice recognise socially?

Answer 3

very dependent on olfaction and pheromones.

Strange males are attacked and commonly killed by resident.

Question 4

what is the role of the main olfactory system in rodents?

Answer 4

Detects volatile compounds

Pathways project from olfactory bulb to Amygdala

Responds to wide range of social and non-social cues

Question 5

what is the accessory olfactory system?

Answer 5

Vomeronasal organ (VNO)

Detects non-volatile compounds

Pathways project to Amygdala

Detects socially relevant non-volatile cues

VNO is a sexually dimorphic structure, ie rat and mice male>female due to testosterone.

Question 6

what is a pheromone?

Answer 6

“Substances secreted to the outside of an individual and received by a second individual of the same species in which they release a specific reaction, for example, a definite behaviour or developmental process”

Substances secreted by one individual which elicit specific behaviour in another of the same species

Question 7

Where is the VMO located?

Answer 7

roof of mouth, behind main olfactory bulb.

Question 8

VMO lesion leads to?

Answer 8

Male/Maternal aggression towards intruder male is strongly dependent on a functional VNO.

also reduces sexual behaviours, mounting.

Question 9

VNO pathways?

Answer 9

different structures and outputs, but eventually both converge downstream on amygdala.

anterior/posterior AOB

Question 10

VNO receptors?

Answer 10

Vomeronasal sensory neurons (VSN), GPCR
V1R & V2R

Detect pheromones - very sensitive mammalian chemoreceptors.

V1R very specific
V2R more general

V1R - anterior AOB
2R - posterior AOB
both converge downstream at amygdala

Complex with MHC class 1b and B2-microglobulin

Question 11

what is a releaser pheromone?

Answer 11

Many examples of single or few molecules which elicit dramatic behavioural effects

Question 12

What is a primer pheromone?

Answer 12

Chemical signal which cause longer term effects on neuroendocrine or developmental pathways

Question 13

examples of rabbit pheromones?

Answer 13

nipple searching pheromone in rabbits, as babies blind.

Question 14

boar releaser pheromones?

Answer 14

2 androgen derived, brings sow into oestrous and can see if ready to mate.

Question 15

why are VNO GPCRs weird?

Answer 15

dont use cyclic nucleotides as second messengers.
Instead use member of transient receptor potential (TRP) superfamily, ion channels.
TRPC2 ion channel particularly.

Question 16

TRP2 knockout mice

Answer 16

can’t detect males over females.

male aggression eliminated, also sexual behaviour towards male increases.

Question 17

V1Rab knockout mice

Answer 17

maternal protective behaviour attenuated (latency to attack, time attacking, number of attacks), but not pup directed behaviours (retrieval).

sexual behaviour attenuated but not male male aggression.

Question 18

ESP-1?

Answer 18

secreted by male mice in tears, detected by females.

increase in sexual behaviour for females when detected.
requires TRPC2.

both male and female amygdala responded, MPA high male response, VMH strong female response.
VMH goes on to produce sexual behaviour response.

ESP1 is not effective in female TRPC2 deficient mice

Question 19

ESP22

Answer 19

pheromone produced by females in tear fluid.

produced early 2-3 weeks old.

if put onto females, male sexual behaviour towards the female is reduced.

cue to indicate sexual immaturity.

TRP2 knockout don’t show response.

Male mice do not exhibit sexual behaviour to juvenile females (but Trp2-/- do!)

Question 20

sweaty t shirt study

Answer 20

worse t shirt 2 days, women smelt, reported attraction.

women were most attracted to men with an MHC most dissimilar from their own.

reports were reversed when women were taking oral contraceptives.

smells reminded the women of their own/former mates were more likely to be
MHC dissimilar than MHC similar.

we are driven to have diversity in immune system

Question 21

where does the neural framework for bonding usually come from?

Answer 21

most forms of bonding are likely built upon the neural framework evolved for infant-mother bonding

Question 22

oxytocin pseudofunction

Answer 22

trust/love hormone

Question 23

oxytocin and vasopressin functions?

Answer 23

They act as hormones – secreted from posterior pituitary.
Oxytocin: Labour, uterine contractions, and milk let down

Vasopressin: Water balance

They act as neurotransmitters within the brain.
Oxytocin: Mate and offspring recognition, feeding

Vasopressin: circadian system, sex drive, learning memory

both very old hormones.

Question 24

oxytocin pathways?

Answer 24

post pituitary to PVN and SCN

Question 25

oxytocin knockout

Answer 25

social recognition impaired in both sexes.

main olfactory system not impaired

normally male mice get bored of same female if put repeatedly into cage, KO treat her as if new everyday.
can’t recognise her. vice versa.

if test non social olfactory cues, ie scent, they show same acclimitisation to stimuant and get bored.

Question 26

role of amygdala?

Answer 26

involved in enforcive or affiliative behaviours.

modified by oxytocin

Question 27

VNO projects where?

Answer 27

AOB accessory olfactory bulb, projects to amygdala

Question 28

PVN projects where?

Answer 28

amygdala via oxytocin.

Question 29

amygdala and testosterone/oestrogen?

Answer 29

check out some paper Sano et al 2016

Question 30

sex steroids priming oxytocin signal?

Answer 30

oestrogen increases oxytocin production, also production of receptors in amygdala.

Question 31

oestrogen receptor KO mice?

Answer 31

social defects

Question 32

VNO structure?

Answer 32

sexually dimorphic.
Hormonal cascade from GnRH neurones initiates perinatal testosterone surge in males which masculinises the pathway

Allows sex specific response to pheromones
(male pheromones elicit gene activation in these structures in female mice).