Project 2

Ionic and second messenger basis of stress induced prefrontal cortex dysfunction

Project Leaders:  Amy Arnsten and Mark Yeckel
Team of Investigators: John Krystal, Sherry McKee, Daniele Piomelli, Bruce Rounsaville, & Jane Taylor

Stress diminishes regulatory control of behavior by the prefrontal cortex (PFC), while heightening subcortical mediation of habits. Project 2 of this consortium will examine the molecular and cellular basis of PFC dysfunction during acute and chronic stress, with the aim of identifying novel therapeutic targets.

Previous research has found that stress impairs PFC function through 1) excessive production of cAMP via dopamine (DA) D1 and norepinephrine (NE) beta1 receptors, and 2) NE alpha-1-activation of phosphotidyl inositol (PI) DAG-protein kinase C (PKC) signaling, suppressing PFC cell firing. The proposed research will further explore the signaling cascades contributing to PFC dysfunction by examining the role of the IP3-Ca2+ component of PI signaling. Consistent with this possibility, in vitro recordings from PFC neurons show that IP3-mediated internal Ca2+ release opens SK channels thereby suppressing PFC cell excitability.

The proposed research will examine whether this mechanism contributes to stress-induced PFC dysfunction at 3 levels: Aim 1 will use in vitro recordings and Ca2+ fluorescence imaging of PFC pyramidal neurons to examine the cellular basis of the PI cascade, Aim 2 will extend these results to in vivo recordings of PFC neurons in animals performing working memory tasks, and Aim 3 will test whether PFC cognitive functions can be protected from stress by blocking IP3 receptors or SK channels. Aim 3 will also assess agents that can be administered to humans. We will test whether blocking alpha-1 and beta NE receptors with carvedilol protects PFC function from stress.

If successful in animals, carvedilol can be tested in humans exposed to stress in Project 9. We will also test the role of endocannabanoids (eCB) in stress-induced PFC dysfunction as an extension of Project 5. Because eCBs depend on DAG and Ca2+, this work is directly relevant to PI signaling. We will test whether pharmacological manipulation of eCB signaling with Rimonabant and URB597 alters PFC physiology and cognition as a prelude to possible human testing in Project 9. Finally, Aim 4 will determine whether PI signaling contributes to spine loss on PFC neurons during chronic stress. PKC phosphorylation of MARCKS disrupts actin, which may contribute to spine loss. We will test whether chronic PKC inhibition with chelerythrine protects PFC neurons from spine loss. As chelerythrine is in pre-clinical development, this may provide another strategy for increasing PFC regulation of behavior in humans.