Direct evidence of parasympathetic vasodilatation in cat periodontal ligament.
Sympathetic regulation of periodontal ligament blood flow (PLBF) is well-attested; however, vasodilator responses mediated by parasympathetic nerve fibers have yet to be conclusively demonstrated in the periodontal ligament (PL). The present study was designed to determine whether parasympathetic vasodilator mechanisms do or do not exist in the cat PL. In our cats, the cervical sympathetic trunks were sectioned bilaterally prior to any stimulation in order to eliminate sympathetic effects on the vascular beds under study. Dynamic changes in PLBF, with mandibular lip blood flow (LBF) recorded for comparison, were investigated in cat mandibular canine teeth using laser Doppler flowmetry. The peripheral cut ends of the facial and glossopharyngeal nerve roots, which have been reported to contain parasympathetic nerve fibers to the oral tissues, were electrically stimulated intracranially. Such stimulation caused blood flow to increase in the ipsilateral PL and lip, without an increase in systemic blood pressure. These vasodilator responses in the PL and lip were sensitive to ganglion blockade (with hexamethonium), indicating vasodilation via activation of parasympathetic vasodilator fibers. In contrast, although intracranial stimulation of the trigeminal nerve root also induced increases in both PLBF and LBF, these were unaffected by hexamethonium, but reduced by tripelennamine, indicating antidromic vasodilatation via the trigeminal sensory nerve. These results suggest that parasympathetic vasodilator mechanisms do exist in feline PL.
Sasano
T
T
Department of Oral Diagnosis, Tohoku University School of Dentistry, Sendai, Japan.
Shoji
N
N
Kuriwada
S
S
Sanjo
D
D
Izumi
H
H
Karita
K
K
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000502:physiology; D002415:Cats; D003481:Cuspid / Q000098:blood supply / Q000294:innervation; D004558:Electric Stimulation; D005154:Facial Nerve / Q000187:drug effects / Q000502:physiology; D015171:Ganglionectomy; D005730:Ganglionic Blockers / Q000494:pharmacology; D005930:Glossopharyngeal Nerve / Q000187:drug effects / Q000502:physiology; D018738:Hexamethonium / Q000494:pharmacology; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D017078:Laser-Doppler Flowmetry; D008046:Lip / Q000098:blood supply; D008334:Mandible; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D010513:Periodontal Ligament / Q000098:blood supply / Q000294:innervation*; D012039:Regional Blood Flow / Q000502:physiology; D014276:Trigeminal Nerve / Q000187:drug effects / Q000502:physiology; D014309:Tripelennamine / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
D005730:Ganglionic Blockers; D006634:Histamine H1 Antagonists; D014309:Tripelennamine; D018738:Hexamethonium