We are looking to inject a single dose into PND21 rats stereotactically via the ICV space. I know rats at PND21 are a bit larger than adult mice, so what is the maximum feasible amount of solution I can inject into a rat of that age? We normally do a maximum of 3 ul per hemisphere for adult mice.
Thanks in advance!
Hi Melinda Peters ,
It depends on what behavioral aspect or cellular and molecular mechanism you are going to study (effects of a drug or peptide on memory restoration in disease or learning enhancement in health or a systems neurobiology of the function of another region), what drug or solution you are going to microinject into the cerebral ventricles (a neuropeptide and its vehicle or a neurotoxic agent) and its dose or concentration.
Often times, it is not a matter of how much a ventricle capacity is. It is important to know how much is an effective dose or concentration of a drug, bilateral or unilateral injections in each rat, EP50 of the treatment and drug's pharmaco-kinetics and the duration of injection or repetition per day.
I had conducted a study by ICV microinfusion of a neuropeptide for 2 weeks with 0.7 ul bilaterally (once a day). On the other hand, there was another study that I only needed to inject a neurotoxin to induce AD-like pathology in a group and 2 out of 10 rats died even with a single unilateral dose of 0.2 ul that toxin (in our pilot study).
However, if you want to just have a tentative idea or an image of the CVs volume in rats with different ages and disparate brain volumes, check the following:
https://www.researchgate.net/figure/Ventricular-volumes-and-brain-weights-in-the-developing-rat-A-The-volumes-of-the_fig4_7628129
Thank you Bahman Sadeghi I guess I could clarify and indicate that it is a gene therapy and the control is PBS. We did a study a long time ago in adult rats with 50ul per ventricle and it seemed a bit much to inject. Once I injected 5ul into the lateral ventricles of mice and had lots of cortical damage so 2ul in a mouse had big consequences.