I would suggest that you read the following paper: Boumans, T., Theunissen, F. E., Poirier, C., & Van Der Linden, A. (2007). Neural representation of spectral and temporal features of song in the auditory forebrain of zebra finches as revealed by functional MRI. The European Journal of Neuroscience, 26(9), 2613‑2626. doi:10.1111/j.1460-9568.2007.05865.x

The choice of the anesthetic will partly depend on your research question. If you want to control the depth of the anesthesia, e.g. have the animal more deeply anesthetized during surgery than during the recordings, isoflurane will work better than urethane. It also depends on what other agents you are planning to use along with those anesthetics, e.g. analgesics. Can you provide more details about your study project? How long will the recordings take? What surgical procedures are you performing?

We changed our anaesthesia managment to thiopenthal i.p. . Under this conditions the neuronal activity and the nerovascular coupling are still intact.

This book reviews the subject very thoroughly:

Anesthesia and Analgesia in Laboratory Animals

edited by Dennis F. Kohn, Sally K. Wixson, William J. White, G. John Benson

Elsevier/Academic Press - 2008 - Hardback - 656 pages - ISBN 0123738989

Two chapters in particular may be helpful:

1) Meyer, R. E. and R. E. Fish (2008). Chapter 2 - Pharmacology of Injectable Anesthetics, Sedatives, and Tranquilizers. Anesthesia and Analgesia in Laboratory Animals (Second Edition). E. F. Richard, J. B. Marilyn, J. D. Peggy, M. J. B. P. J. D. Alicia Z. KarasA2 - Richard E. Fish and Z. K. Alicia. San Diego, Academic Press: 27-82.

2) Brunson, D. B. (2008). Chapter 3 - Pharmacology of Inhalation Anesthetics. Anesthesia and Analgesia in Laboratory Animals (Second Edition). E. F. Richard, J. B. Marilyn, J. D. Peggy, M. J. B. P. J. D. Alicia Z. KarasA2 - Richard E. Fish and Z. K. Alicia. San Diego, Academic Press: 83-95.

A combination of ketamine (100 mg/kg body weight; Nimatek, Eurovet, Bladel, Netherlands) and Medetomidine (1 mg/kg body weight; Domitor, New York, NY) has also been used succesfully in mice. For rats, we typically use isoflurane. See Battaglia et al., Journal of Neuroscience Methods 178 (2009) 291–300

From your description of your research and the recorded regions I imagine you are at least partially interested in synchronization/coherence between oscillatory signals in the dopaminergic midbrain and the PFC. If that is true, you should probably use urethane or chloral hydrate, since with these anesthetics you preserve the spontaneous slow oscillations (up/down states) in cortex and VTA. If spontaneous oscillations are not that important for your research question, then isofluorane would probably be best, as it allows for very quick induction and recovery and fine control of anesthesia depth, even though it suppresses burst activity in the cortex.

These papers might be useful for you:

http://jn.physiology.org/content/94/5/3516.full

http://www.jneurosci.org/content/27/20/5414.long

http://www.jneurosci.org/content/29/31/9850.full#ref-31

http://www.jneurosci.org/content/27/39/10597.full

http://www.sciencedirect.com/science/article/pii/S0361923011003005

Urethane works really well in rats. It is long lasting and rather stable. Chloral Hydrate has a shorter life time, therefore you need to supplement more frequently than urethane. Isofluorane allows you to better manipulate the level of anesthesia desired. The problem with the isofluorane respect to injectable anesthetics would be that you need an extra pump for the gas and in the long run it is much more expensive.

Sevorane should be used with Ketamin to reduce the expense.

isoflurane

Claudia, my main question involves the functional coupling between the PFC and VTA. So I would like to preserve as much brain activity as possible while keeping the animal under. At the moment, I am not planning any to give any drugs but am considering the possibility of probably giving psychostimulants in the future.

Kaue, yes coherence is a large part of our work. In terms of neural activity, do you see any advantage between urethane and chloral hydrate? Thank you for the links.

Elwood, as far as I have seen chloral hydrate is the standard in studies involving oscillation research in midbrain dopaminergic neurons, but for cortical recordings both urethane and chloral hydrate seem to work equally well. Personally, if I was in a hurry, I would stick to chloral hydrate to allow for a better comparison with the literature; if I had a bit of time, I would conduct some pilot experiments with both kinds of protocols and see which one would be better suited for my ultimate goals.

We used chloral hydrate for extracellular electrophysiology (spike recording) and it worked well. It really has a short life time, but after an initial intraperitoneal dose we administered it continuously through a jugular vein cannula. Continuous intravenous administration provide better control of anesthesia, however it isn't perfect at all (it's difficult to set the appropriate speed of administration). Sometimes neurons are a little too "silent" in chloral hydrate (compared with e.g. ketamine, but in my opinion ketamine is not recommended in your experiment because it can have effect on dopamine system).

I've never used urethane and isoflurane. Obviously inhalational anesthesia (isoflurane) is the most precise but it needs a lot of equipment.

All in all, after my experience chloral hydrate isn't a bad choice, but there is no perfect anesthetic.

Isoflurane is the best choice of anesthesia mild effect and recover soon but for this need special gaseous unit.. in this case urethane is next choice of anesthesia this has the minimal cardiopulmonary suppression effect..