Coexistence of two forms of LTP in ACC provides a synaptic mechanism for the interactions between anxiety and chronic pain

Chronic pain can lead to anxiety and anxiety canenhance the sensation of pain.[U+3000]Unfortunately, little is known about the synaptic mechanisms that mediate these re-enforcing interactions. Here we characterized two forms of long-term potentiation (LTP) in the anterior cingulate cortex (ACC); a presynaptic form (pre-LTP) that requires kainate receptors and a postsynaptic form (post-LTP) that requires N-methyl-D-aspartate receptors. Pre-LTP also involves adenylyl cyclase and protein kinase A and is expressed via a mechanism involving hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. Interestingly, chronic pain and anxiety both result in selective occlusion of pre-LTP. Significantly, microinjection of the HCN blocker ZD7288 into the ACC invivo produces both anxiolytic and analgesic effects. Our results provide a mechanism by which two forms of LTP in the ACC may converge to mediate the interaction between anxiety and chronic pain.