Age And Gender Affect Alloparenting Development Modes Via The Dopamine D1,D2 And Serotonin 5-HT2A Receptors

Alloparenting is the caring behaviors of individuals other than biological parents towards younger pups of the same species.In the animal model,it is manifested as pup retrieval,pup licking,pup crouching.Alloparenting is widespread in human society,such as babysitters,adoptive parents and teachers,all of which can provide alloparenting to children.It has been found that age affected the latency of alloparenting in rats.However,few studies have explored how age and gender affected the alloparenting development modes,or how alloparenting changed over time.The first study was aimed at elucidating how age and gender affected the alloparenting development modes and psychological mechanisms behind it.Using homecage alloparenting behavior test,we found that juvenile rats could faster arrive the criterion of alloparenting than adult rats,and spent more time on crouching,licking,nest building and rearing,alloparenting could occur after2-3 days of pup exposure.However,in adult rats,the process from avoiding the pups to approaching the pups was similar to reward learning,and it took 5-6days of pup exposure to be alloparenting.Alloparenting motivation was observed in pup preference test,it was found that the alloparenting motivation of juvenile rats was always higher,so alloparenting could appear quickly.However,the adult rats experienced a gradual increasing alloparenting motivation.When the alloparenting motivation of the adult rats increased to a degree similar to that of the juvenile rats,the alloparenting behavior also appeared.Besides,age affected the pup retrieval on an elevated plus maze.Although the anxiety level of adult rats was higher,their executive function was stronger,so they could retrieve more pups in the elevated plus maze.We then used real-time RT-PCR in the second study,aimed at analyzing the mRNA expression levels of dopamine D2 receptors(hippocampus,medial prefrontal cortex,amygdala,ventral striatum)and dopamine D1 receptors(ventral striatum,hypothalamus)in subjects of different age and gender.The results showed that the mRNA expression of D2 receptor in hippocampus,amygdala and ventral striatum of adult rats were all higher,meanwhile the mRNA expression of D1 receptor in adult rats were higher in ventral striatum.In initial pup exposure,higher dopamine D2 receptor expression in the amygdala of adult rats,kept them avoid the pups;higher dopamine D2 receptorexpression in the ventral striatum made them less alloparenting motivation;higher dopamine D1 receptors expression in the ventral striatum promoted them learn reward value of pups so as to make them gradually increase alloparenting motivation;higher dopamine D2 receptor expression in hippocampus was associated with stronger executive function.In the third study,real-time RT-PCR was used to analyze the mRNA expression levels of the 5-HT2 A receptor(hippocampus,medial prefrontal cortex,amygdala,ventral striatum,and hypothalamus)in subjects of different age and gender.It was found that the 5-HT2 A receptor mRNA expression were all higher in the medial prefrontal cortex,amygdala,striatum and hypothalamus of adult rats.In initial pup exposure,higher 5-HT2 A receptor expression in the medial prefrontal cortex of adult rats resulted in lower pup retrieval number;higher 5-HT2 A receptor expression in the amygdala kept them more fearful and disgusted of pups,so as to avoid pups;higher 5-HT2 A receptor expression in the ventral striatum made them less approach pups.The present study enriched how individual differences affect alloparenting,with age affected the quality of alloparenting and alloparenting motivation in initial pups exposure,and subjects with different ages had different alloparenting development modes over time.It also revealed the physiological mechanism of alloparenting,which investigated the mRNA expression of D1,D2 receptors and 5-HT2 A receptor,not only these three receptors associated withmaternal behavior,but also the important targets of antipsychotics,revealing the neural mechanisms of alloparenting,it provided a theoretical basis for pharmacologic intervention of alloparenting.