From the Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS, USA (Drs. Berman, Puri, Chandrala, Macgregor, and Klein); and Department of Biochemistry, Panjab University, Chandigarh, India (Dr. Puri).
Serotonin in Trigeminal Ganglia of Female Rodents: Relevance to Menstrual Migraine
Article first published online: 12 JUL 2006
Headache: The Journal of Head and Face Pain
Volume 46, Issue 8, pages 1230–1245, September 2006
How to Cite
Berman, N. E.J., Puri, V., Chandrala, S., Puri, S., Macgregor, R., Liverman, C. S. and Klein, R. M. (2006), Serotonin in Trigeminal Ganglia of Female Rodents: Relevance to Menstrual Migraine. Headache: The Journal of Head and Face Pain, 46: 1230–1245. doi: 10.1111/j.1526-4610.2006.00528.x
- Issue published online: 12 JUL 2006
- Article first published online: 12 JUL 2006
- Accepted for publication March 28, 2006.
- tryptophan hydroxylase
Objectives.—We examined changes in the serotonin system across the estrous cycle in trigeminal ganglia of female rodents to determine which components are present and which are regulated by the variations in levels of ovarian steroids that occur during the estrous cycle.
Background.—Migraine is 2–3 times more prevalent in women than in men and attacks are often timed with the menstrual cycle, suggesting a mechanistic link with ovarian steroids. Serotonin has been implicated in the pathogenesis of migraine, and the effectiveness of triptans, selective 5HT-1B/D/F agonists, has provided further support for this concept. It is not known whether serotonin, its rate-limiting enzyme tryptophan hydroxylase (TPH), or its receptors are regulated by ovarian steroids in trigeminal ganglia.
Methods.—We used reverse transcription-polymerase chain reaction to examine gene expression in cycling mice, Western blots to examine protein expression, double-labeling immunohistochemistry using markers of nociceptors and nonnociceptors and confocal microscopy to identify specific types of neurons, and primary tissue culture to examine effects of estrogen on trigeminal neurons in vitro.
Results.—In C57/BL6 mice mRNA levels of TPH-1, the rate-limiting enzyme in serotonin synthesis, were over 2-fold higher and protein levels were 1.4-fold higher at proestrus, the high estrogen stage of the cycle than at diestrus, the low estrogen stage. TPH protein also was present in primary trigeminal cultures obtained from female Sprague-Dawley rats, but levels were not affected by 24-hour treatment with physiological levels (10−9 M) of 17β-estradiol. Gene expression of 5HT-1B and 5HT-1D receptors in trigeminal ganglia was not regulated by the estrous cycle. Serotonin was present in trigeminal neurons containing CGRP, a potent vasoactive neuropeptide, peripherin, an intermediate filament present in neurons with unmyelinated axons, neurofilament H, which is present in neurons with myelinated axons, and in neurons binding IB4, a marker of nonpeptidergic nociceptors. Serotonin was also present in neurons containing 5HT-1B. The serotonin-positive population was significantly larger in diameter than the serotonin-negative population.
Conclusions.—Expression of the rate-limiting enzyme required for serotonin synthesis is regulated during the natural estrous cycle, and serotonin is present in larger trigeminal neurons of all the major subtypes. Colocalization of serotonin with 5HT-1B suggests that this receptor functions as an autoreceptor to regulate serotonin release. Cyclical changes in serotonin levels in trigeminal ganglia could contribute to the pathogenesis of menstrual migraine.