Neuropeptidergic regulation of affiliative behavior and social bonding in animals. Flashcards
This review provides a conceptual framework for understanding social bond formation. In this framework, the formation of social bonds depends on three processes that depend on somewhat different neural networks. What are the three processes?
The organism must be motivated to approach and engage another individual
Animal must be able to identify the individual based on social cuts through the formation of social memory
Given the appropriate conditions, a bond can form, leading to preferential interaction with that individual
What is social recognition memory? How is it measured?
Social recognition memory: the recognition of a familiar individual and the formation of social a social memory. It involves the processing of social cues.
Measure the duration of social investigation during subsequent exposures to the same individual. If the rodent recognizes individual, it will spend less time investigating it.
What is the evidence that oxytocin (OT) is important for social recognition memory?
Transgenic mice that lack OT gene are unable to recognize familiar individuals despite repeated exposures.
Social deficit of OT knockout mice can be temporarily restored by a single injection of OT into the lateral ventricles, prior to initial encounter
Where in the brain does OT act to facilitate social recognition memory? What is the evidence?
OT acts at the amygdala during a social encounter for the normal processing of social information required for intact social recognition
Microinjections of OT into the amygdala (not into olfactory bulb) could rescue social recognition deficits in OT knock out mice
What is the evidence that vasopressin (AVP) is important for social recognition memory?
Where in the brain does AVP act to facilitate social recognition memory? What is the evidence?
Evidence
The Brattelboro rat, a naturally occurring AVP-deficient mutant, displays a total disruption of social recognition
Social memory in the Brattelboro rat can be restored by infusing AVP into the lateral septum
Administration of V1aR antagonist block social recognition in rats
Transgenic male mice with null mutation in the gene encoding for V1aR lack the ability to recognize a familiar conspecific, despite repeated exposures.
Spatial learning and memory and sensorimotor processing are normal in V1aR knock out mice – suggesting that the deficit is specific for the leaning and/or recall of social cues
Brain region & evidence
Lateral septum
Overexpression of V1aR in lateral septum can facilitate social recognition in normal rats
Social bonding is a complex social behavior that requires the integration of many cognitive processes including
social approach, motivation, and memory formation.
Describe the differences b/t OT receptor expression in the brains of female prairie voles and female montane voles. Describe the difference b/t AVP receptor expression in males of these two species. What is the reason for comparing these particular species of voles? What method was used to visualize OT and AVP receptors in the brains of voles?
he OTR and v1aR are distributed differently between monogamous prairie and pne boles compared to promiscuous montane and meadow voles
The release of OT or AVP would stimulate different neural circuits in monogamous vs promiscuous species, depending on which brain circuits express OTR and V1aR
Prairie voles have elevated levels of OTR and V1aR in brin regions implicated in reward and reinforcement such as the NAcc and ventral pallidum
Promiscuous montane and meadow voles have low levels of receptors in these regions
Microinjections of OTR antagonist into the NAcc blocks pair bonding in female prairie voles
Microinjections of V1aR antagonist into the ventral pallidum blocks pair bonding in male prairie voles
Montane voles are solitary – do not exhibit social bonding, an often abandon their young just after 2 weeks of care
All four species of voles have similar distribution of OT and AVP projections in the brain
They make a good control for comparison
Inject either an agonist or antagonist and observe the behaviour.
What is the evidence for the conclusion that variations in the promoter region of the V1aR gene influences partner preference in male prairie voles, i.e. within this species? How does this genetic variation affect the brain in a way that could change the potential to form a partner preference?
Genetic sequencing of the prairie and montane vole OTR gene reveals a few species differences between promoter sequences (located on 5’ flanking region of the gene) that could potentially disrupt regulatory elements of the gene
To determine if sequences in the 5’ flanking region of the prairie vole OTR gene could direct OTR expression within a prairie vole, transgenic mice were created with the prairie vole OTR 5’ flanking region sequence directly in front of a lacZ reporter
These mice showed lacZ expression in brain regions in which prairie voles normally express OTR, suggesting region-specific OTR gene expression is at least partly controlled by cis-regulatory elements in the 5’ flanking region of the gene.
Genetic sequencing of the prairie and montane vole avpr1a gene revealed much larger differences in the avpr1a promoter sequence, concentrated in a large stretch of tandem repeats
This species divergence in regulatory sequence is a functional polymorphism that has been shown to modulate gene expression in cell-typedependent manner
Transgenic mice were created carrying the prairie vole avpr1a gene and promoter region; these mice displayed a “prairie vole-like” v1aR distribution pattern, different from their wild-type littermates
These mice showed increase affiliative behaviour when infused icv with AVP, a response not seen in normal wild-type mice
This strongly suggests that species differences in social bond formation result from different in NT/neuromodulators V1aR distribution in specific brain regions, and this can be traved back to difference in the promoter sequence of the gene.
Male prairie voles (Microtus pinetorum) and marmoset monkeys
have high levels of the V1a receptor in their brains,
tend to be monogamous, and
help with care of their young.
Male meadow voles (Microtus montanus) and rhesus monkeys
have lower levels of the V1a receptor in their brains,
are promiscuous, and
give little or no help with the care of their young
Prairie voles have more copies of the repeat than meadow voles, and they express higher levels of the receptor in the parts of the brain associated with these behaviors
