Tonic glutamatergic input in the rostral ventrolateral medulla is increased in rats with chronic heart failure

Full cite: Wang WZ, Gao L, Wang HJ, Zucker IH, Wang W. 2009. Tonic glutamatergic input in the rostral ventrolateral medulla is increased in rats with chronic heart failure. Hypertension 53:370–374.

Wang WZ, Gao L, Wang HJ, Zucker IH, Wang W.

Department of Cellular and Integrative Physiology (W.-Z.W., L.G., H.-J.W., I.H.Z., W.W.), University of Nebraska Medical Center, Omaha; and the Department of Physiology (W.-Z.W.), Second Military Medical University, Shanghai, China.

The headline of this paper essentially sums up the message of this paper; chronic heart failure animals have heightened glutamatergic tone. While the finding of this paper is pretty straightforward, what I thought was particularly cool was how they used triple barrel pipettes and paired it when electrophysiology. They used kynurenic acid, an NMDA/non-NMDA receptor antagonist, non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), and NMDA antagonist D-2-amino-5-phosphonopentanoate (D-AP5) to block glutamate reception and recorded the responses via single-unit electrophysiology. In addition to the triple barrel pipette they used, they had a 5-barrel micropipette containing an electrode. Using a penta barrel pipette sounds like a huge technical difficulty, that being said, if we could get some way for it to work, we could easily test the responsiveness of neurons to various direct stimuli, something we’ve never done before. With a 5-barrel micropipette, it might actually be possible to record in one piece of the pipette, have neurobiotin in another, and maybe some kind of antagonists, say bicuculline, xanthurenic acid, and kynurenic acid. I could imagine that it would be really difficult to ensure that the pipette is successfully able to inject out of each portion, but the ability to sit on a neuron and inject a slew of drugs would be incredibly powerful. It would be cool to do a similar study in runners & seds in order to get some definitive proof onto the tonic input of glutamate in seds. I believe though, we would likely see a prevalence of glutamatergic tone in the sedentary animals; it just would not be as distinct as that of the heart failure animals. -MTL