Seasonal variations dopamine, cortisol and serotonin
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beverly meyer
I found this study extremely interesting, but it doesn't match "seasonal rise" as I understand it. Blood samples from March, June, September and December were compared for a Cushings group and a Control group. Findings: Cortisol was the same in both groups, except higher in June in the Cushings group Dopamine was the same in March and December in both groups, but notably lower in Cushings group in June and September. Serotonin was erratic in both groups, but lower in Cushings group in June. Both groups had similar melatonin patterns. So JUNE was the peak month for high Cortisol and the low month for Serotonin. Dopamine was low in June and December. June gets the worst marks all around, not September. Can Dr. Kellon comment? I understood PPID was an issue late summer, fall and early winter, but not high summer (June). Also, have we discussed management support of low Serotonin, or does pergolide theoretically manage that? http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658710/ Thanks, Beverly 6/14 Beverly Texas |
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janieclougher@...
Not Dr. Kellon here, but thanks for the link to that study. It is so interesting that serotonin is lower in these horses (might lead to the observation of lethargy and depression, over and above the feeling of sore feet, lack of muscle, and general hormonal upset). Ditto dopamine concentrations being lower in the Cushing's group.
The initial assignation of the Cushing's horses was certainly based on ACTH levels as well as observed clinical signs; but after that, there was no testing of ACTH, insulin, or glucose in the two groups. I would like to have seen that, as problems during the seasonal rise are likely due to increased ACTH and insulin, as well as (possibly) prolactin and other hormones. There weren't really enough horses in this study to say anything definitively (six horses and six controls aren't very different from a "one rat study"); but it is very suggestive, and certainly points to where further research is needed. The variations in hormones between the Cushings and the normal horses are indeed interesting - I will freely confess here that experimental design and statistics are very much not my forte, so hopefully Dr. Gustafson or Dr. Kellon will comment. Jaini (BVSc),Merlin,Maggie,Gypsy BC 09 ECIR mod/support https://groups.yahoo.com/neo/groups/ECHistory/files/Jaini%20Clougher%2C%20Smithers%20BC/
---In EquineCushings@..., <bmeyer@...> wrote : I found this study extremely interesting, but it doesn't match "seasonal rise" as I understand it. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658710/ Thanks, Beverly 6/14 Beverly Texas |
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One problem I have with this study is that the horses were all older (21 to 36) and with an upper normal for ACTH of 50 pg/mL there could easily have been some early PPID animals in the control group. It has been known for a very long time for both human and equine that cortisol is not a reliable marker. There are simply too many things that can influence it, it's secretion is pulsatile and metabolism by the peripheral tissues prevents single "spot" samples from accurately predicting how much is being produced. Serotonin changes between the two groups did not reach statistical significance and with groups this small I would forget about that. The dopamine data is the most significant. What it says to me is that the dopamine levels in PPID horses do not change significantly with the seasons, but they do in normal horses. There is less variability over the day in PPID horses and less effect of season/day length. Melatonin alone does not explain the pattern in the normal horses - ? maybe because they are not all normal and maybe because, as Jaini said, other hormones are involved. We know thyroid hormone levels change with season and that prolactin is involved in seasonal reproduction and coat changes. Eleanor in PA www.drkellon.com
EC Co-owner Feb 2001 |
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beverly meyer
Thanks Dr. Kellon for the comments on this study.
Can you comment further please on the distinct RISE in Dopamine in the Cushings horses in December? It appears about 25% above their "normal" which as you observe is fairly flat the rest of the year and below the control group. If this is true, why is Pergolide in December so important? Oddly, it seems to be the opposite. Thanks! Beverly 6/14 Here's the study link again for those who want to look. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658710/ |
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Pergolide is important in December because PPID horses are abnormal all year long. There are times when they are worse, but never normal (with the exception of very early cases). December isn't terribly different from March, especially if you look at the standard deviation. The length of the vertical line above each data point corresponds to the standard deviation. The differences between the groups only reach statistical significance for a few isolated time points at any time of year in this study. In other words, they overlap. The most likely reason for this is that the control group actually contained one or more PPID horses, or vice versa, but that is assuming that plasma dopamine is a reliable diagnostic test and this has never been established. Dopamine is also produced by a variety of tissues outside the brain. Eleanor in PA www.drkellon.com EC Co-owner Feb 2001 |
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