Have you tried using propofol infusion?  Less effect on EPSPs, MEPPS and SEPS as far as I am aware.

Hi, I use isoflurane anesthesia before decapitation and manage record evoked LFP during 4-6 hours. Therefore I think that anesthesia is not an issue.  You problem comes probably from the oxygenation. How high is a perfusion rate in your recording chamber? In my setup perfusion rate is 5-8 ml/min but I use double flow chamber, ie ACSF bathes both upper and bottom  slice sides (Hajos N et al 2009, DOI: 10.1111/j.1460-9568.2008.06577.x). Of course it is not applicable when you record with MEA. You can try to increase perfusion rate in single flow chamber till 15ml/min to enhance a slice oxygenation. The oxygen availability is one of crucial parameters of synaptic transmission in slice  (Ivanov and Zilberter 2011 doi: 10.3389/fnene.2011.00009).

Also the MEA records signal generated mainly by superficial cells that are damaged during slicing process. To preserve these neurones you can use one of the pre-incubation methods described on  http://www.brainslicemethods.com. I tried CholineCloroide solution and it improved very much the state of the neurons that are close to surfaces.

Hi, yes that's the right answer, the problem is the oxygen supply and thus the perfusion rate (see Hajos 2009; Ivanov 2011).

you could also use the argument of Stepan et al. 2012, performing VSDI experiments and using 0.3µM bicuculline...

Thank you all for the valuable suggestions given, very helpful.

I have not tried propofol infusion as asked by Graeme.

I wish to know, whether excessive isoflurane anaesthesia will have some influence on EPSP's or population spikes.

Please share the experience (if any) with either urethane or avertin (tribromo ethanol) anesthesia on hippocampal slice electrophysiology recordings.

Also please add a note, whether survical dislocation can be performed following anaesthesia instead of using guillotine for decapitation in view of electrophysiological recordings of hippocampus.

Thanking you,

Best Regards,

Grandhi V Ramalingayya

I would avoid cervical dislocation because it causes the rupture of brain blood barrier in cortical blood vessels and damage neurons. Accordingly my experience isofluran anesthesia is the best for in vitro as well as for in vivo. When it is applied in vivo an animal recovers better and more rapidly than after application of injected anesthetic drugs. It can suggest that isofluran  is metabolised/removed rapidly having short lasting effect on the neuronal network.

In answer to your question about the influence of isoflurane on EPSPs: there is a dose dependent reduction in EPSPs with increasing MAC of isoflurane. This is an old study, but demonstrates it well:

Berg-Johnsen J & Langmoen I.The effect of isoflurane on excitatory synaptic transmission in the rat hippocampus. Acta Anaesthesiol Scand. 1992 May;36(4):350-5.