OBJECTIVE-To develop and validate a model of cutaneous allodynia triggered by dural inflammation for pain associated with headaches. To explore neural mechanisms underlying cephalic and extracephalic allodynia. METHODS-Inflammatory mediators (IM)were applied to the dura of unanesthetized rats via previously implanted cannulas and sensory thresholds of the face and hindpaws were characterized.RESULTS-IM elicited robust facial and hindpaw allodynia which peaked within 3 hr. These effects were reminiscent of cutaneous allodynia seen in patients with migraine or other primary headache conditions, and were reversed by agents used clinically in treatment of migraine, including sumatriptan, naproxen, and a CGRP-antagonist. Consistent with clinical observations the allodynia was unaffected by an NK-1 antagonist. Having established facial and hindpaw allodynia as a useful animal surrogate of headache-associated allodynia, we next showed that blocking pain-facilitating processes in the rostral ventromedial medulla (RVM) interfered with its expression. Bupivacaine, destruction of putative pain-facilitating neurons or block of cholecystokinin receptors prevented or significantly attenuated IM-induced allodynia. Electrophysiological studies confirmed activation of pain-facilitating RVM ON cells and transient suppression of RVM OFF cells following IM.INTERPRETATION-Facial and hindpaw allodynia associated with dural stimulation is a useful surrogate of pain associated with primary headache including migraine and may be exploited mechanistically for development of novel therapeutic strategies for headache pain. The data also demonstrate the requirement for activation of descending facilitation from the RVM for the expression of cranial and extracranial cutaneous allodynia and are consistent with a brainstem generator of allodynia associated with headache disorders.

A rapid, high throughput readout for single-nucleotide polymorphism (SNP) analysis was developed employing single base chain extension and cytometric analysis of an array of fluorescent microspheres. An array of fluorescent microspheres was coupled with uniquely identifying sequences, termed complementary ZipCodes (cZipCodes), which allowed for multiplexing possibilities. For a given assay, querying a polymorphic base involved extending an oligonucleotide containing both a ZipCode and a SNP-specific sequence with a DNA polymerase and a pair of fluoresceinated dideoxynucleotides. To capture the reaction products for analysis, the ZipCode portion of the oligonucleotide was hybridized with its cZipCodes on the microsphere. Flow cytometry was used for microsphere decoding and SNP typing by detecting the fluorescein label captured on the microspheres. In addition to multiplexing capability, the ZipCode system allows multiple sets of SNPs to be analyzed by a limited set of cZipCode-attached microspheres. A standard set of non-cross reactive ZipCodes was established experimentally and the accuracy of the system was validated by comparison with genotypes determined by other technologies. From a total of 58 SNPs, 55 SNPs were successfully analyzed in the first pass using this assay format and all 181 genotypes across the 55 SNPs were correct. These data demonstrate that the microsphere-based single base chain extension (SBCE) method is a sensitive and reliable assay. It can be readily adapted to an automated, high-throughput genotyping system.

This study provides additional evidence of gastric stasis in migraineurs interictally during induced and spontaneous migraine.