Novel axonal projection from the caudal end of the ventrolateral medulla to the intermediolateral cell column.
We used an optical imaging technique to investigate whether axons of neurons in the caudal end of the ventrolateral medulla (CeVLM), as well as axons of neurons in the rostral ventrolateral medulla (RVLM), project to neurons in the intermediolateral cell column (IML) of the spinal cord. Brain stem-spinal cord preparations from neonatal normotensive Wistar-Kyoto and spontaneously hypertensive rats were stained with a voltage-sensitive dye, and responses to electrical stimulation of the IML at the Th2 level were detected as changes in fluorescence intensity with an optical imaging apparatus (MiCAM-01). The results were as follows: 1) depolarizing responses to IML stimulation during low-Ca high-Mg superfusion were detected on the ventral surface of the medulla at the level of the CeVLM, as well as at the level of the RVLM, 2) depolarizing responses were also detected on cross sections at the level of the CeVLM, and they had a latency of 24.0 +/- 5.5 (SD) ms, 3) antidromic action potentials in response to IML stimulation were demonstrated in the CeVLM neurons where optical images were detected, and 4) glutamate application to the CeVLM increased the frequency of excitatory postsynaptic potentials (EPSPs) and induced depolarization of the IML neurons. The optical imaging findings suggested a novel axonal and functional projection from neurons in the CeVLM to the IML. The increase in EPSPs of the IML neurons in response to glutamate application suggests that the CeVLM participates in the regulation of sympathetic nerve activity and blood pressure and may correspond to the caudal pressor area.
Iigaya
Kamon
K
Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan.
Kumagai
Hiroo
H
Onimaru
Hiroshi
H
Kawai
Akira
A
Oshima
Naoki
N
Onami
Toshiko
T
Takimoto
Chie
C
Kamayachi
Tadashi
T
Hayashi
Koichi
K
Saruta
Takao
T
Itoh
Hiroshi
H
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000502:physiology*; D001933:Brain Stem / Q000166:cytology / Q000502:physiology; D002118:Calcium; D004558:Electric Stimulation; D004594:Electrophysiology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D018698:Glutamic Acid / Q000494:pharmacology; D007091:Image Processing, Computer-Assisted; D008274:Magnesium; D008526:Medulla Oblongata / Q000166:cytology / Q000502:physiology*; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D008274:Magnesium; D002118:Calcium