Barosensitive cardioinhibitory neurons in the medulla: comparison of FosB/ChAT-positive neurons with CT-HRP-labeled neurons.
The purpose of this study was to survey the distribution pattern of barosensitive cardioinhibitory preganglionic neurons in the medulla. This was done using Wistar rats anesthetized with fentanyl/midazolam. After stimulating arterial baroreceptors by blood pressure increase due to phenylephrine, c-Fos, FosB, c-Jun and JunD/choline acetyltransferase (ChAT)-positive neurons were surveyed in the medulla. After placing HRP conjugated by cholera toxin (CT-HRP) on the sino-atrial node, CT-HRP-labeled neurons were surveyed in the medulla. In the phenylephrine pressor test experiment, we ascertained that in the target neurons fosB was more sensitive to baroreceptor stimulation than any other immediate early genes such as c-fos, c-jun and junD. Using the FosB/ChAT method, we succeeded in determining sites of the barosensitive cardioinhibitory neurons that had never been found with the c-Fos/ChAT method. The distribution pattern of the FosB/ChAT-positive neurons was compared with that of the CT-HRP-labeled neurons. We found that the distribution pattern of the FosB/ChAT-positive neurons in the dorsal motor nucleus of the vagus nerve (DMX) and ambiguus nucleus (AMB) was similar to that of the CT-HRP-labeled neurons at the level between the caudal end of the area postrema (AP) and the caudal end of the nucleus of the trapezoid body. This suggests that the barosensitive FosB/ChAT-positive neurons in the DMX and AMB mediate the cardioinhibitory baroreceptor reflex.
Okada
J
J
Department of Physiology 1st Division, Gunma University School of Medicine, Maebashi-shi, Japan.
Miura
M
M
D000818:Animals; D002772:Cholera Toxin; D002795:Choline O-Acetyltransferase / Q000378:metabolism*; D006329:Heart Conduction System / Q000166:cytology / Q000502:physiology*; D006735:Horseradish Peroxidase; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology / Q000502:physiology*; D009433:Neural Inhibition; D009474:Neurons / Q000378:metabolism / Q000502:physiology; D011311:Pressoreceptors / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D016760:Proto-Oncogene Proteins c-fos; C052635:cholera toxin, B subunit-horseradish peroxidase; D002772:Cholera Toxin; D006735:Horseradish Peroxidase; D002795:Choline O-Acetyltransferase