Love or hate: differential expression of synaptic receptors following odor preference versus aversive learning in rat pups?

Ibrahim, Khadija (2016) Love or hate: differential expression of synaptic receptors following odor preference versus aversive learning in rat pups? Masters thesis, Memorial University of Newfoundland.

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Abstract

Odor plus 0.5mA shock conditioning paradoxically induces odor preference in rat pups (≤PD10), while a strong 1.2mA shock results in odor aversion (Sullivan, 2001). Previous research showed that anterior piriform cortex (aPC) is activated following odor preference training with a 0.5mA shock, while posterior piriform cortex (pPC) is activated following odor aversive learning with a 1.2mA shock. The olfactory bulb (OB) is activated by both and serves as a common structure (Raineki, Shionoya, Sander, & Sullivan, 2009a). As a first step to delineate synapses involved in preference and avoidance learning, we measured expressions of glutamatergic AMPA GluR1 and NMDA NR1 receptors in the OB, aPC, & pPC using a synaptoneurosome preparation following odor+shock conditioning. Our results show that a shock of 0.5mA and 0.1mA, produced preference 24-hours following learning indicating that aversive experiences can produce preference in neonatal rodents as previously reported by Sullivan (2001).. Moreover, our results illustrated that this shock resulted in down-regulation of NMDARs 3-hours following training but not of AMPARs in the OB. Our behavioural results did not produce odor aversion with the strong shock training and likewise there was no change in pPC, suggesting no change in total number of NMDARs and AMPARs perhaps due to an absence of odor aversion learning. Future experiments can delineate whether different paradigms will produce odor aversion to produce synaptic expression in the pPC. Additional experimental protocols can also assess if each region is engaged in synaptic trafficking of NMDAR and AMPARs within the extrasynaptic and synaptic sites.

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