We (Carolyn Barrett and myself) performed a series of experiments using anodal block of the rabbit aortic depressor nerve. We cannot say how quickly recovery occurs. However, in our protocol, 10 minutes after removing the block A fiber responsiveness had returned to pre-block levels. So you can count on this, and will probably find quite recovery is quite quick (possibly rely on it occurring after 1 minute?). I'd be interested.

These data have not appeared in publication...

Hope this information is useful.

Thanks, Chris. We too had success with an anodal ADN block which worked quite nicely. In that case, we used fairly short pulses - onset within 5 sec - see Fig. 1 of Fan, et al. Graded and dynamic reflex summation of myelinated and unmyelinated rat aortic baroreceptors. Am.J.Physiol Regul.Integr.Comp Physiol 277 (3):R748-R756, 1999. Not sure about how long the block lasted as our output was blood pressure response which developed over many seconds to minute.

Presently we are looking to record NTS neural responses rather than reflex blood pressure responses and are wondering about lower limits - perhaps millisecond range. I am having a hard time finding information that has directly tested such brief pulses.

Again thanks for the quick response.

Mike

Look in: Skoglund CR (1945). Modification by electrotonus of the transmission in the artificial synapse formed by severed mammalian nerve. J Neurophysiol 8, 377-386 and in related papers but after-effects of analectrotonus may depend on the duration of its application.

Great. This article is really helpful but I was really not finding it on my own through PubMed. Thank you for zeroing in on it so quickly.

Mike

I am not fully aware of the detailed membrane properties of vagal fibres, but many have HCN channels. The anodal stimulation will lead to substantial hyperpolarization, which in turn opens the HCN channels. Thus, shutting down of the anodal current will lead to strong rebound cationic inward current resulting in offset discharge of one or more action potentials. In other words, the anodal block is potentially lifted in many axons already milliseconds after switching off of the anodal current by active membrane conductivity. There is only on recent paper on these properties (Zhou et al Functional impact of the hyperpolarization-activated current on the excitability of myelinated A-type vagal afferent neurons in the rat. Clin Clin Exp Pharmacol Physiol. 2010 Aug;37(8):852-61), which is freely available for download and you may look it up under this link

Hope this may help http://www.ncbi.nlm.nih.gov/pubmed/20456426

P.S.: Visited your university a couple of years ago. Nice place to live and do science.

Interesting point about the prominent HCN and likely a key contributor to the single spikes accompanying on and off of anodal current. John Schild added the point that ramping the anodal current on and off can mitigate these transient activations.

And yes Portland is a nice place to live as well as do science. Many years ago I spent the better part of year as a language "student" out in Neunenheimer Feld before science. I have fond memories of gentle snowfalls and spring asparagus.

There is a paper of mine on Arch Ital Biol 108, 52-71, 1970 ("Differential block of larger fibers in peripheral nerve by direct current") containing all the story. Best regards. Mario Manfredi

Prof.. Manfredi - unfortunately our library does not have a copy of this journal and although I found it in PubMed, I cannot find a copy online in the archives of the journal. Is it possible for you to send me a PDF of your publication? Sorry for the trouble.

I do not have any more reprints, but I will do a copy as soon as I am back in Rome by midseptember. Meanwhile have a look at J. Physiol. 273:539-60, 1977 (Accornero, Bini, Lenzi, Manfredi, "Selective activation of peripheral nerve fiber groups of different diameter by triangular shaped stimulus pulses"). Best regards. Mario Manfredi

Thanks this should be a big boost to getting me up to speed. Mike