Acute and constitutive increases in central serotonin levels reduce social play behaviour in peri-adolescent rats.
BACKGROUND
Serotonin is an important modulator of social behaviour. Individual differences in serotonergic signalling are considered to be a marker of personality that is stable throughout lifetime. While a large body of evidence indicates that central serotonin levels are inversely related to aggression and sexual behaviour in adult rats, the relationship between serotonin and social behaviour during peri-adolescence has hardly been explored.


OBJECTIVE
To study the effect of acute and constitutive increases in serotonin neurotransmission on social behaviour in peri-adolescent rats.


METHODS
Social behaviour in peri-adolesent rats (28-35 days old) was studied after genetic ablation of the serotonin transporter, causing constitutively increased extra-neuronal serotonin levels, and after acute treatment with the serotonin reuptake inhibitor fluoxetine or the serotonin releasing agent 3,4-methylenedioxymethamphetamine (MDMA). A distinction was made between social play behaviour that mainly occurs during peri-adolescence, and non-playful social interactions that are abundant during the entire lifespan of rats.


RESULTS
In serotonin transporter knockout rats, social play behaviour was markedly reduced, while non-playful aspects of social interaction were unaffected. Acute treatment with fluoxetine or MDMA dose-dependently inhibited social play behaviour. MDMA also suppressed non-playful social interaction but at higher doses than those required to reduce social play. Fluoxetine did not affect non-playful social interaction.


CONCLUSIONS
These data show that both acute and constitutive increases in serotonergic neurotransmission reduce social play behaviour in peri-adolescent rats. Together with our previous findings of reduced aggressive and sexual behaviour in adult serotonin transporter knockout rats, these data support the notion that serotonin modulates social behaviour in a trait-like manner.
Hubrecht Institute, Uppsalalaan 8, 3584 CT, Utrecht, The Netherlands. j.homberg@niob.knaw.nl
Judith R
JR
Homberg
Olga J G
OJ
Schiepers
Anton N M
AN
Schoffelmeer
Edwin
E
Cuppen
Louk J M J
LJ
Vanderschuren
D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D030801:Animals, Genetically Modified; D004305:Dose-Response Relationship, Drug; D005473:Fluoxetine / Q000494:pharmacology; D008297:Male; D009154:Mutation; D018817:N-Methyl-3,4-methylenedioxyamphetamine / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000378:metabolism*; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology; D012919:Social Behavior
D005473:Fluoxetine; D018817:N-Methyl-3,4-methylenedioxyamphetamine; D012701:Serotonin; D050486:Serotonin Plasma Membrane Transport Proteins; D017367:Selective Serotonin Reuptake Inhibitors