Amygdala inputs to the prefrontal cortex elicit heterosynaptic suppression of hippocampal inputs.

Whereas cooperative communication between the hippocampus (HP) and prefrontal cortex (PFC) is critical for cognitive functions, an antagonistic relationship may exist between the basolateral amygdala (BLA) and PFC during emotional processing. As PFC neurons integrate information from converging excitatory BLA and HP inputs, we explored whether the ability of BLA inputs to evoke feedforward inhibition in the PFC affects converging HP synaptic inputs using in vivo intracellular recordings in anesthetized rats. BLA train stimulation decreased HP synaptic responses in the PFC in vivo. This effect was dependent on the timing of HP-evoked responses and the strength of BLA activation. BLA train stimulation also produced heterosynaptic suppression of responses from the amygdalo-piriform cortex, an associative temporal cortical structure. Heterosynaptic suppression was unidirectional as HP trains failed to modify BLA synaptic responses. These findings provide a mechanism by which BLA activation could decrease PFC neural activity and transiently attenuate the HP influence on PFC function.