Just came across an article on homocysteine - I was somewhat aware of its role in heart disease, but this also talks about its role in hitting the NMDA receptors, which trigger the calcium channels to dump.... that could be relevant to clusters.
NMDA receptors have been discussed in terms of cluster headaches before - less studied than serotonin, but there is evidence they are involved. Glutamate (including MSG) is one thing that makes the NMDA receptors very active.
Blocking the calcium channels, of course, is how verapamil works.
High levels of homocysteine are usually linked to diet, especially low levels of methyl donors (folate and vitamin B-12). Choline is a methyl donor that is know to be very low in clusterheads - it could be low in CH from some specific metabolic glitch, but it could low due to a general deficiency in methyl donors. Other methyl donors related to choline include trimethylglycine and dimethyl glycine.
Quote:Biochemistry (Mosc). 2009 Jun;74(6):589-98.Links
Molecular mechanisms of homocysteine toxicity.
Boldyrev AA.
Biological Faculty, Lomonosov Moscow State University
Hyperhomocysteinemia is a risk factor for a number of cardiovascular and neurodegenerative processes as well as a complicating factor in normal pregnancy. Toxic effects of homocysteine and the product of its spontaneous oxidation, homocysteic acid, are based on their ability to activate NMDA receptors, increasing intracellular levels of ionized calcium and reactive oxygen species. Even a short-term exposure of cells to homocysteic acid at concentrations characteristic of hyperhomocysteinemia induces their apoptotic transformation. The discovery of NMDA receptors both in neuronal tissue and in several other tissues and organs (including immunocompetent cells) makes them a target for toxic action of homocysteine. The neuropeptide carnosine was found to protect the organism from homocysteine toxicity. Treatment of pregnant rats with carnosine under conditions of alimentary hyperhomocysteinemia increases viability and functional activity of their progeny.
Carnosine is a relatively cheap compound composed of two amino acids. Not sure that it is a methyl donor per se, but it seems to reduce the ability of NMDA neurons to trigger a calcium dump. It has a good safety profile, but I would not mix it with other calcium channel blockers since there might be an additive or multiplicative increase in the effects of verapamil.
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Quote:Neuroscience. 1999;90(4):1371-6.
Trigeminovascular nociceptive transmission involves N-methyl-D-aspartate and non-N-methyl-D-aspartate glutamate receptors.
Storer RJ, Goadsby PJ.
Institute of Neurology, The National Hospital for Neurology and Neurosurgery, London, UK.
Interest in the fundamental mechanisms underlying headache, particularly the pathophysiology of migraine and cluster headache, has lead to the study of the physiology and pharmacology of the trigeminovascular system and its central ramifications. Cats were anaesthetized (60 mg/kg alpha-chloralose, i.p., along with halothane for all surgical procedures) and prepared for physiological monitoring. The animals were placed in a stereotaxic frame and ventilated. A midline craniotomy and C2 laminectomy were performed for access to the superior sagittal sinus and C2 dorsal horn, respectively. The sinus was isolated from the underlying cortex and stimulated electrically after the animals had been paralysed with gallamine (6 mg/kg, i.v.). Units linked to stimulation were recorded with a tungsten-in-glass microelectrode placed in the most caudal part of the trigeminal nucleus, the trigeminocervical complex. Signals from the neurons were amplified, filtered and passed to a microcomputer, where post-stimulus histograms were constructed on-line to analyse the responses to stimulation. Units responded to sagittal sinus stimulation with a typical latency of 8-10 ms. All units studied had a probability of firing of 0.6 or greater. Intravenous injection of the non-competitive N-methyl-D-aspartate receptor antagonist, dizocilpine maleate (4 mg/kg, i.v.), resulted in a substantial and prolonged blockade of firing of units in the trigeminocervical complex. Similarly, administration of the non-N-methyl-D-aspartate excitatory amino acid receptor blocker, GYKI 52466, lead to a dose-dependent inhibition of trigeminovascular-evoked responses in the trigeminocervical complex. These data demonstrate the participation of both N-methyl-D-aspartate- and non-N-methyl-D-aspartate-mediated mechanisms in transmission within the trigeminocervical complex, and suggest a clear preclinical role of glutamatergic mechanisms in primary headache syndromes, such as migraine and cluster headache.