Dissociation in the effects of stress and D1 receptors activation on basolateral amygdalar LTP in juvenile and adult animals

- The medial prefrontal cortex and the amygdala were thought to have similar roles in extinction in juvenile and adult rats.
- We present findings to show that the two groups of age have distinctive mechanisms of plasticity following stress.
- The induction of LTP is differentially regulated by the activation of D1 receptors.
- There is some overlap in the engagement of the NMDA partial agonists.
- The profile response of the circuit responsible on the regulation of fear in adults and juveniles is different.
- Developmental differences in the response to stress in juvenile and adults.
- These differences are critical when pharmacologically treating juveniles with stress disorders.

Post-weaning or juvenility is a critical developmental stage during which neural structures as the medial prefrontal cortex (mPFC) and amygdala and the neurotransmitter systems undergo major reorganization and thus are susceptible to the effects of environmental factors. Interactions between the mPFC and the amygdala are critical for fear regulation. Changes in plasticity in the projections from the mPFC to the basolateral amygdala (BLA) were previously shown following stress and fear. In the present study, we examined possible differences between adult and PW animals in the (1) effects of exposure to stress on BLA- LTP and (2) the possible dependency of mPFC-BLA LTP on N-methyl-d-aspartate (NMDA) and Dopamine (D) receptors activation.The results show that similarly to the adults, the mPFC- BLA pathway in the PW animals is not amenable to the induction of LTP. However, in contrast to adult animals, exposure to stress in PW animals did not result in enhanced BLA-LTP. Interestingly, only under activation of the D1 receptors, PW animals expressed LTP in the BLA. In both groups of age, the NMDA partial agonist d-cycloserine (DCS) did not result in any change in the levels of potentiation.Our results confirm differences between the PW and the adult animal and show that stress and the activation of Dopamine are associated with different effects; which may have potential implications for the treatment of anxiety and stress disorders across development.