Lecture 8 (Bechtold) Flashcards
what does bonding require?
olfaction, social recognition and social memory
varies by species
social recognition mouse models
Strange males are attacked and commonly killed by resident male
Resident males rapidly attempt mating with strange females
Roles, projections and responses of mouse main olfactory system?
Detects volatile compounds
Pathways project from olfactory bulb to Amygdala (OSNs of olfactory epithelium –> MOB)
Responds to wide range of social and non-social cues
Roles, projections and responses of mouse accessory olfactory system?
Vomeronasal organ (VNO)
Detects non-volatile compounds
Pathways project to Amygdala (via AOB)
Detects socially relevant non-volatile cues
VNO is a sexually dimorphic structure, ie rat and mice male>female due to testosterone.
What is a pheromone?
Karlson and Luscher
“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
Where is the VMO located?
roof of mouth, behind main olfactory bulb.
VMO lesion leads to?
abolition of Male/Maternal aggression towards intruder male (strongly dependent on a functional VNO)
also reduces sexual behaviours, mounting.
VNO pathways?
different structures and outputs, but eventually both converge downstream on amygdala.
anterior/posterior AOB
VNO receptors?
Vomeronasal sensory neurons (VSN), GPCR
V1R and 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
what is a releaser pheromone?
Many examples of single or few molecules which elicit dramatic and immediate behavioural effects
What is a primer pheromone?
Chemical signal which cause longer term effects on neuroendocrine or developmental pathways
examples of rabbit pheromones?
nipple searching pheromone in rabbits, as babies blind.
boar releaser pheromones?
2 testosterone derived molecules, spray on back of sow to check whether she is on eostrus
VNO GPCR second messenger signalling
Transient receptor potential (TRP) superfamily, ion channels. TRPC2 ion channel particularly.
(not cyclic nucleotides like most)
TRP2 knockout mice
can’t detect males over females.
male aggression eliminated, also sexual behaviour towards male increases.
V1Rab knockout mice
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.
ESP-1
from where by who
F- effect and M/F brain response differences
TRCP2
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
ESP22
from where by who
pheromone produced by females in tear fluid.
produced up to ~ 5 weeks old- cue to indicate sexual immaturity.
if put onto females, male sexual behaviour towards the female is reduced.
TRP2 knockout don’t show response.
Male mice do not exhibit sexual behaviour to juvenile females (but Trp2-/- do!)
sweaty t shirt study
(men wore t shirt for two days)
women were most attracted to men with an MHC most dissimilar from their own.
reports were reversed when women were taking oral contraceptives.
smells reminding the women of their own/former mates were more likely to be MHC dissimilar than MHC similar.
Evolution of the neural framework for social bonding
most forms of bonding are likely built upon the neural framework evolved for infant-mother bonding (similar pathways w/o E input)
oxytocin and vasopressin functions
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
oxytocin pathways?
post pituitary to PVN and SCN
oxytocin knockout
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.
role of amygdala?
involved in enforcive or affiliative behaviours.
modified by oxytocin
VNO projects where?
AOB accessory olfactory bulb, projects to amygdala
PVN projects where?
amygdala via oxytocin.
amygdala and testosterone/oestrogen?
check out some paper Sano et al 2016
sex steroids priming oxytocin signal?
oestrogen increases oxytocin production, also production of receptors in amygdala.
oestrogen receptor KO mice?
social defects similar to OT KO
VNO structure?
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).
Evolution of AVP and OT
AVP like found in cyclotosomes… precursor in invertebrates…. ancient
