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Social Novelty Investigation in the Juvenile Rat: Modulation by the μ‐Opioid System
Author(s) -
Smith C. J. W.,
Wilkins K. B.,
Mogavero J. N.,
Veenema A. H.
Publication year - 2015
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/jne.12301
Subject(s) - novelty , eticlopride , psychology , social preferences , preference , oxytocin receptor , developmental psychology , preference test , social relation , oxytocin , dopamine , neuroscience , dopamine receptor , social psychology , sch 23390 , economics , microeconomics
The drive to approach and explore novel conspecifics is inherent to social animals and may promote optimal social functioning. Juvenile animals seek out interactions with novel peers more frequently and find these interactions to be more rewarding than their adult counterparts. In the present study, we aimed to establish a behavioural paradigm to measure social novelty‐seeking in juvenile rats and to determine the involvement of the opioid, dopamine, oxytocin and vasopressin systems in this behaviour. To this end, we developed the social novelty preference test to assess the preference of a juvenile rat to investigate a novel over a familiar (cage mate) conspecific. We show that across the juvenile period both male and female rats spend more time investigating a novel conspecific than a cage mate, independent of subject sex or repeated exposure to the test. We hypothesised that brain systems subserving social information processing and social motivation/reward (i.e. the opioid, dopamine, oxytocin, vasopressin systems) might support social novelty preference. To test this, receptor antagonists of each of these systems were administered i.c.v. prior to exposure to the social novelty preference test and, subsequently, to the social preference test, to examine the specificity of these effects. We find that μ‐opioid receptor antagonism reduces novel social investigation in both the social novelty preference and social preference tests while leaving the investigation of a cage mate (social novelty preference test) or an object (social preference test) unaffected. In contrast, central blockade of dopamine D 2 receptors (with eticlopride), oxytocin receptors (with des‐ G ly‐ NH 2 ,d( CH 2 ) 5 [ T yr( M e) 2 , T hr 4 ] OVT ) or vasopressin V 1a receptors [with ( CH 2 ) 5 T yr( M e 2 ) AVP ] failed to alter social novelty preference or social preference. Overall, we have established a new behavioural test to study social novelty‐seeking behaviour in the juvenile rat and show that the μ‐opioid system facilitates this behaviour, possibly by reducing risk avoidance and enhancing the hedonic and/or motivational value of social novelty.