What does low serum corticosterone, but high plasma ACTH indicate in stressed rats?
Answers
Answer:
Explanation:
Elevated ACTH but low CORT is sometimes seen in rodent models of post-traumatic stress disorder (only in males though, are you using males? There are significant sex differences in the HPA axis response to stress). Diminished CORT release in response to stress could be due to a sensitization (or increase in number) of glucocorticoid receptors (GR) in the pituitary, and if all GR are saturated with ligand, no more suppression of ACTH can occur so that's where you can get high ACTH and low CORT. Due to this, the adrenal glands can become insensitive to ACTH--you can quantify ACTH receptors or just give them an ACTH injection and measure their CORT response to see.
Answer:
Explanation:
While I am not an expert and it is possible that it could indicate adrenal disorder, I think the greater possibility is that corticosterone is binding to stress sensitive mineralocorticoid and glucocorticoid receptors. Based on a quick PubMed search I found an article (see below) which indicates differences in rat species MR and GR expression and how this may affect serum corticosterone levels. I think it may be helpful to look at adrenal hypertrophy in addition to corticosterone levels as well as MR and GR expression/binding to figure out what exactly is going on in these animals. I hope this helps.