help needed with intranasal administration in mice - methodology (Feb/23/2011 )

Hopefully someone of you can help us out with a problem with intranasal injections in mice. We are administrating 20 µl LPS (5 mg/kg in PBS) intranasally and look at neutrophil recruitment 4 hours later. However, about 1/3 of the mice don’t seem to respond to the LPS (no neutrophils in the BAL-fluid). We think that it’s the intranasal administration is the problem. Do any of you have suggestions to improve the reproducibility of the assay?
Thanks in advance!

Hi labbie,

If you want to recruit neutrophils to the lungs, you're better off using a model of infection in the lungs. If you just want a way to recruit neutrophils for isolation, better to purify them from bone marrow, blood, or using a chemoattractant injected i.p. and lavaging the peritoneum. As for intranasal administrations, are the mice fully anaesthetised and breathing deeply when you do your i.n.s? That could be one issue if they are not asleep properly and not breathing the full dose in. Also, the i.n. technique doesn't actually reach all parts of the lung; only the main airways are exposed, the lower half of the airways gets very little exposure from an i.n..

Cheers

In case you haven't seen it already, here is a paper on optimizing intranasal administration of LPS: A murine model of pulmonary damage induced by lipopolysaccharide via intranasal instillation by Szarka et al. J of Immun. Meth. 202(1) 1997
http://www.sciencedirect.com/science/article/pii/S0022175996002360