Behav Brain Res. 2016 May 6. pii: S0166-4328(16)30276-5. doi: 10.1016/j.bbr.2016.05.010.
Liu C1, Wang J2, Zhan B1, Cheng G1.
Although drug rewards and natural rewards share neural substrates, the neuronal activation patterns and mechanisms behind the interaction between cocaine and social reward are poorly understood. Here, we investigate the conditioned place preference (CPP) in social (conspecific) vs cocaine conditioning, and the expression of central c-Fos, oxytocin (OT) and vasopressin (AVP) in the conditioned ICR mice. We found that the mice produced CPP when conditioned with unfamiliar conspecific or cocaine alone.
However, the mice failed to produce CPP when the two stimuli were concurrently conditioned. Compared to conditioning with conspecific alone, mice decreased preference for conspecific when conditioning with social vs cocaine. We observed differential expression of c-Fos-immunoreactive neurons in the ventral anterior cingulate cortex, posterior cingulate cortex, accumbens (shell and core), medial nucleus of the amygdale and the ventral pallidum when comparing the control (CK), social (SC) or cocaine conditioning (CC) group, and social vs cocaine conditioning (SCC) group. Compared to the CK group, the SC or CC group had higher OT expression in the paraventricular nucleus (PVN) and lower AVP expression in the PVN and supraoptic nucleus. The SCC group showed lower OT expression compared to the SC group, and higher OT and AVP expression in the PVN compared to the CC group.
These results indicate that cocaine impairs social preference through competing with social reward. The differential activations of neurons within specific reward areas, and differential expression of OT and AVP are likely to play an important role in mediating the interaction between social and cocaine reward.
Cocaine; Conditioned place preference; Neuropeptide; Reward