NEUR 303 - lecture 7

Who conducted the first behavioural neuroendocrinology experiment?

Arnold Berthold (1849).

What did Berthold study?

Sexual maturation and behaviour in roosters.

What happened to castrated roosters?

They failed to develop adult traits and showed no mating or aggressive behaviour.

What happened when testes were transplanted into castrated roosters?

They developed normal adult morphology and behaviour.

What did Berthold conclude from his experiment?

The testes release a substance into the blood (hormones) that regulates behaviour and development.

What are the three types of parental care strategies?

Uniparental female, uniparental male, and biparental care.

Which parental care strategy is most common in mammals?

Uniparental female (maternal care).

What is maternal behaviour?

Behaviours that support offspring survival (e.g., nursing, grooming, retrieving).

Are mechanisms controlling maternal behaviour conserved?

Yes, they are highly conserved across species.

Do virgin rats show maternal behaviour immediately?

No, they initially ignore pups.

How can virgin rats develop maternal behaviour?

Through repeated exposure to pups over 10–15 days.

What is hypophysectomy?

Surgical removal of the pituitary gland.

What did hypophysectomy + ovariectomy experiments show?

Maternal behaviour can still develop without hormones.

What did blood transfusion experiments show about maternal behaviour?

Hormones near parturition can rapidly induce maternal behaviour.

When was maternal behaviour induced by blood transfusion?

When blood was taken shortly after birth - didn’t work after - suggests that hormones are important for timing maternal behaviour after birth

What sensory system is critical for maternal behaviour in rodents?

The olfactory system.

What is a pheromone?

A chemical signal that triggers social responses in the same species.

What brain region processes olfactory social signals?

The medial amygdala (mAMY).

What pathway promotes pup avoidance in virgin females?

OB/AOB → mAMY → VMH/AH → PAG.

What is the role of the PAG?

Mediates fear and defensive behaviours.

What happens if the mAMY or VMH is lesioned?

Virgin females display maternal behaviour.

What is anosmia and its effect on maternal behaviour?

Loss of smell; facilitates maternal behaviour.

What changes at parturition in the maternal brain?

Reduced avoidance signalling and increased attraction to pups.

Which brain region is critical for maternal motivation?

The medial preoptic area (MPOA).

How does the MPOA promote maternal behaviour?

It inhibits avoidance circuits (VMH and PAG).

What type of neurons in the MPOA are important?

GABAergic (inhibitory) neurons.

What is the overall mechanism controlling maternal behaviour?

Balance between avoidance circuits (VMH/PAG) and maternal circuits (MPOA).