I've been very interested in the hippocampus, since this UCLA study on depression, stress, cortisol and hypocampal atrophy in MS came out in 2010.
http://www.sciencedaily.com/releases/20 ... 145533.htm
The researchers examined three sub-regions of the hippocampus region ― CA1, CA3 and the dentate gyrus area of the hippocampal region called CA23DG (CA stands for cornu ammonis). They imaged 29 patients with relapsing remitting multiple sclerosis and compared them with 20 healthy control subjects who did not have MS. They also measured participants' cortisol level three times a day; cortisol is a major stress hormone produced by the HPA axis that affects many tissues in the body, including the brain.
In addition to the difference between MS patients and healthy controls, the researchers found that the multiple sclerosis patients diagnosed with depression showed a smaller CA23DG sub-region of the hippocampus, along with excessive release of cortisol from the HPA axis.
"Interestingly, this idea of a link between excessive activity of the HPA axis and reduced brain volume in the hippocampus hasn't received a lot of attention, despite the fact that the most consistently reproduced findings in psychiatric patients with depression (but without MS) include hyperactivity of the HPA axis and smaller volumes of the hippocampus," Sicotte said
What I found most interesting was the release of cortisol and a heightened or hyper-active HPA axis response. (This is why stress is so harmful to pwMS. Cortisol is a major endothelial disrupter and vasoconstrictor. It messes with nitric oxide.) Cortisol and the stress response also mess with the cholinergic system...cortisol activates the response, but what happens in chronic stress? Cholinergic uticaria, or hives, are known to be caused by stress.
Considerable data have emerged which strongly indicate that the septohippocampal cholinergic system is involved in the adaptive response to stress. Neurotransmitter regulatory mechanisms in cholinergic synaptic terminals of this part of the limbic system undergo adaptive changes in response to stress and recover slowly after stress. The initial stress-induced response is characterized by activation of hippocampal cholinergic terminals within minutes, as indicated by a rapid and transient elevation in high affinity choline uptake and increased newly synthesized acetylcholine release. The response of this cholinergic system to stress is influenced by both neuronal and hormonal stimuli. Among the several neuronal systems converging in the septum, terminals of the dopaminergic mesolimbic system have been found to be selectively involved in the early response to stress. Pharmacological interference with dopaminergic neurotransmission, with agonist and antagonist treatments, revealed that changes in the tonic inhibitory influence of septal dopaminergic terminals can modulate the response of hippocampal cholinergic terminals to stress. A similar activation of hippocampal cholinergic terminals as after short-term stress was observed after treatments with a large dose of either adrenocorticotropic hormone or corticosterone. Furthermore, glucocorticoids and not adrenocorticotropic hormone can directly enhance acetylcholine release, but only from excited terminals. This indicates that stress-induced activation of the septo-hippocampal system may occur secondary to, but not directly by, increased levels of pituitary-adrenocortical hormones. Yet, it is possible that under stressful conditions the increased glucocorticoid levels may modulate the activity of the stimulated hippocampal cholinergic terminals. Together the findings support the notion that the stress-induced response of the septo-hippocampal cholinergic system represents an integrated output of converging neuronal and hormonal stimuli which convey signals of stress to this limbic brain region.
I guess this just brings up more questions....is it a heightened stress response which causes this disregulation in the MS brain, or does the disregulation come first?
Stress reduction and ways to limit the flood of cortisol seems to be an effective practice for those with MS...I know my husband has benefitted from meditation and relaxation. He used to be a type A workaholic, but is more relaxed now. Certainly, more research ahead! Good find--