Histamine H1 receptor mRNA is expressed in capsaicin-insensitive sensory neurons with neuropeptide Y-immunoreactivity in guinea pigs.
Histamine H1 receptor mRNA-expressing sensory neurons in guinea pigs are unmyelinated and are not immunoreactive to substance P and calcitonin gene-related peptide (CGRP) [Mol. Brain Res. 66 (1999) 24], which are implicated in the nociceptive transmission of the primary sensory system. In this study, we examined whether these H1 receptor mRNA-expressing neurons are sensitive to capsaicin by using in situ hybridization histochemistry. Of lumbar dorsal root ganglion (DRG) neurons in control animals, 17% were positive for CGRP. In guinea pigs neonatally treated with capsaicin (50 mg/kg), few CGRP-immunoreactive neurons were seen in the DRGs. However, the percentages of H1 receptor mRNA-expressing neurons (15-20%) and the intensity of the mRNA signals in these neurons were not affected by neonatal capsaicin treatment. We also revealed the presence of both capsaicin-sensitive and insensitive neuropeptide Y (NPY)-immunoreactive neurons in the DRGs. These neurons were exclusively small. H1 receptor mRNA was expressed in NPY-immunoreactive neurons in naive guinea pig DRGs. These results suggest that H1 receptor mRNA is expressed in capsaicin-insensitive DRG neurons with NPY-immunoreactivity in guinea pigs.
Kashiba
H
H
Department of Physiology, Kansai College of Oriental Medicine, 2-11-1 Wakaba, Kumatori, Sennan, 590-0433, Osaka, Japan.
Fukui
H
H
Senba
E
E
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D002211:Capsaicin / Q000494:pharmacology*; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006168:Guinea Pigs; D006632:Histamine / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D009475:Neurons, Afferent / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009478:Neuropeptide Y / Q000378:metabolism*; D009619:Nociceptors / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010146:Pain / Q000378:metabolism / Q000503:physiopathology; D020671:Posterior Horn Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D011969:Receptors, Histamine H1 / Q000235:genetics*
D009478:Neuropeptide Y; D012333:RNA, Messenger; D011969:Receptors, Histamine H1; D006632:Histamine; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin