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Localization and efferent connections of medullary respiratory neurons in rats
$35 IDENTIFICATION OF THE CIRCULATORY AND RESPIRATORY CENTERS IN THE MEDULLA OBLONGATA OF THE RAT BY CHEMICAL STIMULATION MAKOTO SAJI, KIYOSHIGE TAKAYAMA AND MITSUHIKO MIURA, Med., 3-39-22 Showa-machi, Maebashi 371, Japan
Dept. Physiol.,
I s t Div., Gunma Univ. Sch.
By chemical s t i m u l a t i o n using i o n t o p h o r e t i c a l l y applied kainate(2.5 - 5 mM), we examined whether the c i r c u l a t o r y and r e s p i r a t o r y responses to e l e c t r i c a l s t i m u l a t i o n evoked in I0 areas of the medulla oblongata of the r a t are due to e x c i t a t i o n of passing f i b e r s or t h a t of neurons. Wister rats anesthetized with urethane and c h l o r a l o s e were used. Among 4 depressor areas and 6 pressor areas in the medulla oblongata, we determined t h a t the responses in the f o l l o w i n g 6 areas were due to the e x c i t a t i o n of neurons: I) d e p r e s s o r - b r a d y c a r d i a c - a p n e i c responses in the dorsomedial p a r t of the s o l i t a r y t r a c t nucleus(NTS), 2) p r e s s o r - t a c h y c a r d i a c - a p n e i c responses in the ventromedial part of NTS, 3) s i n g l e depressor response in the medial region of the ambiguus nucleus(AMB), 4) d e p r e s s o r - b r a d y c a r d i a c - a p n e i c responses in the dorsomedial region of AMB, 5) p r e s s o r - t a c h y c a r d i a c - a p n e u s t i c responses in the v e n t r o l a t e r a l medulla(VLM) of the r o s t r a l and i n t e r m e d i a t e medulla and 6) p r e s s o r - t a c h y c a r d i a c - p o l y p n e i c responses in VLM of the caudal medulla. We concluded: I) the area with neuronal pressor response in VLM formed a narrow zone d i s t r i b u t i n g from the r o s t r a l to the caudal medulla and the s i t e s of maximum response were located in the i n t e r m e d i a t e and caudal medulla, 2) the area w i t h neuronal apneustic response in VLM d i s t r i b u t i n g from the r o s t r a l to the i n t e r m e d i a t e medulla was c o n s i s t e n t w i t h the l o c a l i z a t i o n of neurons p r o j e c t i n g to the phrenic motor nucleus, and 3) both depressor response in the dorsomedial region of NTS and pressor response in the ventromedial region of NTS were due to the e x c i t a t i o n of neurons.
LOCALIZATION
AND E F F E R E N T CONNECTIONS OF MEDULLARY R E S P I R A T O R Y NEURONS IN RATS.
HIROSHI Y A M A D A I , ~ A Z U H I S A EZURE 2, and MOTOMU M A N A B E 2 * , I D e p a r t m e n t of Anatomy and Embryology, and ~Department of Neurobiology, Tokyo M e t r o p o l i t a n Institute for Neurosciences, 2-6 Musashidai, Fuchu-shi, Tokyo 183, JAPAN In p e n t o b a r b i t a l - a n e s t h e t i z e d rats, the d i s t r i b u t i o n and efferent connections of m e d u l l a r y r e s p i r a t o r y n e u r o n s w e r e s t u d i e d . A l m o s t a l l the r e s p i r a t o r y neurons were located around the ambiguus nucleus and r e t r o a m b i g u a l nucleus, c o r r e s p o n d i n g to the ventral r e s p i r a t o r y group (VRG) of the cat. Only a few r e s p i r a t o r y neurons were found around the area v e n t r o l a t e r a l to the solitary tract. In the VRG, one group of e x p i r a t o r y neurons was located ventrally to the r o s t r a l p a r t of t h e a m b i g u u s n u c l e u s . A n o t h e r g r o u p of e x p i r a t o r y n e u r o n s extended from the caudal portion of t h e a m b i g u u s nucleus through the retroambigual n u c l e u s . In t h e m i d d l e of t h e s e t w o e x p i r a t o r y n e u r o n s , an assembly of p r e d o m i n a n t l y inspiratory neurons existed in the vicinity of the ambiguus nucleus. An anterograde tracer, PHA-L (phaseolus vulgaris leucoagglutinin) was iontophoretically a p p l i e d to the a r e a of i n s p i r a t o r y neurons of the VRG, and in a d d i t i o n a f l u o r e s c e n c e r e t r o g r a d e tracer, fast blue (FB), was injected in the cervical phrenic nerve. Twelve days after, PHA-Llabeled axons were observed d e s c e n d i n g b i l a t e r a l l y in the a n t e r o l a t e r a l funiculi of the spinal cord. They were n o t i c e a b l y denser in the ipsilateral funiculus than in the c o n t r a l a t e r a l one. They m i n g l e d with a column of the FB-labeled phrenic m o t o n e u r o n s in the m i d - c e r v i c a l anterior horn. P H A - L - l a b e l e d boutons in passing were observed on the F B - l a b e l e d neurosomata. On the other hand, when PHA-L was injected into the area v e n t r o l a t e r a l to the solitary tract, only a few d e s c e n d i n g axons were present in the spinal cord, and no contacts b e t w e e n the P H A - L - l a b e l e d axons and F B - l a b e l e d neurons were seen. I n t r a m e d u l l a r y projections from the VRG were d i s t r i b u t e d b i l a t e r a l l y in the caudal halves of the ambiguus nuclei, Cajal's interstitial nuclei, the d o r s o l a t e r a l margins of the medial solitary nuclei, the hypoglossal nuclei, the g i g a n t o c e l l u l a r reticular nuclei, and the raphe nucleus. A s c e n d i n g projections of the VRG were d i s t r i b u t e d densely in both K o e l l i k e r - F u s e ' s nuclei, and sparsely in both s u b c o e r u l e u s areas.
Dept. Physiol.,
I s t Div., Gunma Univ. Sch.
By chemical s t i m u l a t i o n using i o n t o p h o r e t i c a l l y applied kainate(2.5 - 5 mM), we examined whether the c i r c u l a t o r y and r e s p i r a t o r y responses to e l e c t r i c a l s t i m u l a t i o n evoked in I0 areas of the medulla oblongata of the r a t are due to e x c i t a t i o n of passing f i b e r s or t h a t of neurons. Wister rats anesthetized with urethane and c h l o r a l o s e were used. Among 4 depressor areas and 6 pressor areas in the medulla oblongata, we determined t h a t the responses in the f o l l o w i n g 6 areas were due to the e x c i t a t i o n of neurons: I) d e p r e s s o r - b r a d y c a r d i a c - a p n e i c responses in the dorsomedial p a r t of the s o l i t a r y t r a c t nucleus(NTS), 2) p r e s s o r - t a c h y c a r d i a c - a p n e i c responses in the ventromedial part of NTS, 3) s i n g l e depressor response in the medial region of the ambiguus nucleus(AMB), 4) d e p r e s s o r - b r a d y c a r d i a c - a p n e i c responses in the dorsomedial region of AMB, 5) p r e s s o r - t a c h y c a r d i a c - a p n e u s t i c responses in the v e n t r o l a t e r a l medulla(VLM) of the r o s t r a l and i n t e r m e d i a t e medulla and 6) p r e s s o r - t a c h y c a r d i a c - p o l y p n e i c responses in VLM of the caudal medulla. We concluded: I) the area with neuronal pressor response in VLM formed a narrow zone d i s t r i b u t i n g from the r o s t r a l to the caudal medulla and the s i t e s of maximum response were located in the i n t e r m e d i a t e and caudal medulla, 2) the area w i t h neuronal apneustic response in VLM d i s t r i b u t i n g from the r o s t r a l to the i n t e r m e d i a t e medulla was c o n s i s t e n t w i t h the l o c a l i z a t i o n of neurons p r o j e c t i n g to the phrenic motor nucleus, and 3) both depressor response in the dorsomedial region of NTS and pressor response in the ventromedial region of NTS were due to the e x c i t a t i o n of neurons.
LOCALIZATION
AND E F F E R E N T CONNECTIONS OF MEDULLARY R E S P I R A T O R Y NEURONS IN RATS.
HIROSHI Y A M A D A I , ~ A Z U H I S A EZURE 2, and MOTOMU M A N A B E 2 * , I D e p a r t m e n t of Anatomy and Embryology, and ~Department of Neurobiology, Tokyo M e t r o p o l i t a n Institute for Neurosciences, 2-6 Musashidai, Fuchu-shi, Tokyo 183, JAPAN In p e n t o b a r b i t a l - a n e s t h e t i z e d rats, the d i s t r i b u t i o n and efferent connections of m e d u l l a r y r e s p i r a t o r y n e u r o n s w e r e s t u d i e d . A l m o s t a l l the r e s p i r a t o r y neurons were located around the ambiguus nucleus and r e t r o a m b i g u a l nucleus, c o r r e s p o n d i n g to the ventral r e s p i r a t o r y group (VRG) of the cat. Only a few r e s p i r a t o r y neurons were found around the area v e n t r o l a t e r a l to the solitary tract. In the VRG, one group of e x p i r a t o r y neurons was located ventrally to the r o s t r a l p a r t of t h e a m b i g u u s n u c l e u s . A n o t h e r g r o u p of e x p i r a t o r y n e u r o n s extended from the caudal portion of t h e a m b i g u u s nucleus through the retroambigual n u c l e u s . In t h e m i d d l e of t h e s e t w o e x p i r a t o r y n e u r o n s , an assembly of p r e d o m i n a n t l y inspiratory neurons existed in the vicinity of the ambiguus nucleus. An anterograde tracer, PHA-L (phaseolus vulgaris leucoagglutinin) was iontophoretically a p p l i e d to the a r e a of i n s p i r a t o r y neurons of the VRG, and in a d d i t i o n a f l u o r e s c e n c e r e t r o g r a d e tracer, fast blue (FB), was injected in the cervical phrenic nerve. Twelve days after, PHA-Llabeled axons were observed d e s c e n d i n g b i l a t e r a l l y in the a n t e r o l a t e r a l funiculi of the spinal cord. They were n o t i c e a b l y denser in the ipsilateral funiculus than in the c o n t r a l a t e r a l one. They m i n g l e d with a column of the FB-labeled phrenic m o t o n e u r o n s in the m i d - c e r v i c a l anterior horn. P H A - L - l a b e l e d boutons in passing were observed on the F B - l a b e l e d neurosomata. On the other hand, when PHA-L was injected into the area v e n t r o l a t e r a l to the solitary tract, only a few d e s c e n d i n g axons were present in the spinal cord, and no contacts b e t w e e n the P H A - L - l a b e l e d axons and F B - l a b e l e d neurons were seen. I n t r a m e d u l l a r y projections from the VRG were d i s t r i b u t e d b i l a t e r a l l y in the caudal halves of the ambiguus nuclei, Cajal's interstitial nuclei, the d o r s o l a t e r a l margins of the medial solitary nuclei, the hypoglossal nuclei, the g i g a n t o c e l l u l a r reticular nuclei, and the raphe nucleus. A s c e n d i n g projections of the VRG were d i s t r i b u t e d densely in both K o e l l i k e r - F u s e ' s nuclei, and sparsely in both s u b c o e r u l e u s areas.