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Rhythmic intracellular potential changes of laryngeal motoneurons during fictive calling behavior in the Japanese toad
S131 DISTRIBUTION PT~I'I'~/iNOF 1/94BAR EPAXIAL, ESPECIALLY M. 5~JLTIFIDUS MfYlDNEURONS IN THE SPINAL CORD OF THE CAT:
A SqUDY BY THE RETROGRADE HORSERADISH PEROXIDASE METHOD.
YOICHI KUROSAWA* and MAMORU AOKI, Department of Physiology, Sapporo Medical College, S.I, W.17, Chuo-ku, Sapporo 060, Japan Distribution patterns of motoneurons supplying the lumbar epaxial muscles in the spinal ventral horn have been investigated by the horseradish peroxidase
(HRP) method in 8 cats.
1.2-5.7mg) injections into multifidus muscle in 7 cases, and for ~ i z o n ,
HRP (30-40%,
longissimus itmlbort~n
muscle in one case were made at vertebral levels from L5 to L7 at multiple sites.
After 2 days,
frozen sections in the transverse or horizontal plane of the spinal cord were made from the L1 to L7 segments.
For the operation and the perfusion of the fixative, cats were deeply anesthetized
with pentobarbital.
Each section was reacted histochemically with the TMB method.
Labeled multi-
fidus motoneurons were found mainly in the ventromedial part (VM) of the ventral horn, rostrocaudally frcxn the L2 to L6 (most nt~nerous in L4) segments. ranged fram 83 to 436 on the injected side.
in the centromedial part (C~4) of the ventral horn. fusiform and round in shape, respectively.
The total number of labeled cells
Longissimus l~nbor~n metoneurons were more restricted Labeled cells observed in the VM and C~ were
These cells had average soma diameters
(ASD) of from
18 to 72 (mean: 47) ~in in the transverse plane and were pres~ned to be ~ or T motoneurons. labeled cells observed in the medial ventral c o l ~ n
A few
(VC) were s~aller than these (VM, rIM) cells.
Contralaterally labeled cells observed in VM and/or VC (range: 2-66) may suggest the possibility of the existence of neurons innervating the contralateral muscles.
In scme cases, the dendrites
of labeled cells in the VM and VC extended dorsome~ially in the VC, in part, across the midline in the anterior white cc~missure. RHYTHMIC INTRACELLULAR POTENTIAL CHANGES C A L L I N G B E H A V I O R IN T H E J A P A N E S E TOAD.
OF
LARYNGEAL
MOTONEURONS
DURING
M A K O T O K U S U N O K I , M A S A H I K O S A T O U and K A Z U O UEDA. Z o o l o g i c a l Institute, Science, U n i v e r s i t y of Tokyo, H o n g o 7-3-1, B u n k y o - k u , T o k y o 113, J a p a n
FICTIVE
Faculty
of
The calling behavior of the Japanese toad, Bufo japonicus, has a simple stereotyped motor pattern consisting of the cyclic activity of several muscles, such as the l a r y n g e a l , h y o i d a l and a b d o m i n a l muscles. By e l e c t r o m y o g r a p h i c (EMG) study, the rhythmic alternation of a brief activity (ca 20 m s e c ) o f m. h y o laryngeus (HL) a n d a r a t h e r long burst activity (ca i 0 0 m s e c ) o f m. d i l a t a t o r l a r y n g i s (DL) is o b s e r v e d . T h i s b e h a v i o u r is e v o k e d by e l e c t r i c a l s t i m u l a t i o n (i00 Hz, 5 - 5 0 zA) o f t h e b r a i n s t e m . To analyze the neural mechanisms underlying this behaviour, intracellular recordings of laryngeal motoneurons were carried out during fictive calling behaviour occurring spontaneously or e v o k e d by e l e c t r i c a l stimulation in i m m o b i l i z e d a n i m a l s . F o u r t e e n m a l e J a p a n e s e t o a d s w e r e used. S u r g e r y was performed under MS-222 anesthesia. Laryngeal motoneurons identified by the antidromic r e s p o n s e to v a g a l or long l a r y n g e a l n e r v e s t i m u l a t i o n showed rhythmic membrane potential changes during fictive calling behaviour. They were classified into three types according to t h e t i m e r e l a t i o n between the membrane potential changes and DL burst activity determined b y E M G or p e r i p h e r a l efferent nerve discharges. Intracellular c u r r e n t or c h l o r i d e ion i n j e c t i o n w a s u s e d to i d e n t i f y E P S P s and IPSPs. (1)The 'DL type' m o t o n e u r o n s depolarized simultaneously w i t h DL burst activity (DL b u r s t p h a s e ) a n d h y p e r p o l a r i z e d between successive DL burst phases (DL i n t e r b u r s t phase). (2)The 'late DL type' motoneurons started depolarizing shortly a f t e r t h e o n s e t of t h e DL b u r s t p h a s e a n d h y p e r p o l a r i z e d d u r i n g t h e DL i n t e r b u r s t phase. In b o t h t y p e s of m o t o n e u r o n s , these depolarizations and hyperpolarizations were produced by EPSPs and IPSPs, respectively, and additional small EPSPs were superimposed in the m i d s t of IPSPs o b s e r v e d d u r i n g the DL i n t e r b u r s t phase. ( 3 ) T h e 'anti DL type' m o t o n e u r o n s were characterized by hyperpolarization at t h e DL b u r s t p h a s e b y IPSPs and depolarization by EPSPs during the DL interburst phase associated with HL activity. These results demonstrated the alternative synaptic inputs in m o t o n e u r o n s exerted from the c e n t r a l p a t t e r n g e n e r a t o r of the c a l l i n g b e h a v i o u r .
A SqUDY BY THE RETROGRADE HORSERADISH PEROXIDASE METHOD.
YOICHI KUROSAWA* and MAMORU AOKI, Department of Physiology, Sapporo Medical College, S.I, W.17, Chuo-ku, Sapporo 060, Japan Distribution patterns of motoneurons supplying the lumbar epaxial muscles in the spinal ventral horn have been investigated by the horseradish peroxidase
(HRP) method in 8 cats.
1.2-5.7mg) injections into multifidus muscle in 7 cases, and for ~ i z o n ,
HRP (30-40%,
longissimus itmlbort~n
muscle in one case were made at vertebral levels from L5 to L7 at multiple sites.
After 2 days,
frozen sections in the transverse or horizontal plane of the spinal cord were made from the L1 to L7 segments.
For the operation and the perfusion of the fixative, cats were deeply anesthetized
with pentobarbital.
Each section was reacted histochemically with the TMB method.
Labeled multi-
fidus motoneurons were found mainly in the ventromedial part (VM) of the ventral horn, rostrocaudally frcxn the L2 to L6 (most nt~nerous in L4) segments. ranged fram 83 to 436 on the injected side.
in the centromedial part (C~4) of the ventral horn. fusiform and round in shape, respectively.
The total number of labeled cells
Longissimus l~nbor~n metoneurons were more restricted Labeled cells observed in the VM and C~ were
These cells had average soma diameters
(ASD) of from
18 to 72 (mean: 47) ~in in the transverse plane and were pres~ned to be ~ or T motoneurons. labeled cells observed in the medial ventral c o l ~ n
A few
(VC) were s~aller than these (VM, rIM) cells.
Contralaterally labeled cells observed in VM and/or VC (range: 2-66) may suggest the possibility of the existence of neurons innervating the contralateral muscles.
In scme cases, the dendrites
of labeled cells in the VM and VC extended dorsome~ially in the VC, in part, across the midline in the anterior white cc~missure. RHYTHMIC INTRACELLULAR POTENTIAL CHANGES C A L L I N G B E H A V I O R IN T H E J A P A N E S E TOAD.
OF
LARYNGEAL
MOTONEURONS
DURING
M A K O T O K U S U N O K I , M A S A H I K O S A T O U and K A Z U O UEDA. Z o o l o g i c a l Institute, Science, U n i v e r s i t y of Tokyo, H o n g o 7-3-1, B u n k y o - k u , T o k y o 113, J a p a n
FICTIVE
Faculty
of
The calling behavior of the Japanese toad, Bufo japonicus, has a simple stereotyped motor pattern consisting of the cyclic activity of several muscles, such as the l a r y n g e a l , h y o i d a l and a b d o m i n a l muscles. By e l e c t r o m y o g r a p h i c (EMG) study, the rhythmic alternation of a brief activity (ca 20 m s e c ) o f m. h y o laryngeus (HL) a n d a r a t h e r long burst activity (ca i 0 0 m s e c ) o f m. d i l a t a t o r l a r y n g i s (DL) is o b s e r v e d . T h i s b e h a v i o u r is e v o k e d by e l e c t r i c a l s t i m u l a t i o n (i00 Hz, 5 - 5 0 zA) o f t h e b r a i n s t e m . To analyze the neural mechanisms underlying this behaviour, intracellular recordings of laryngeal motoneurons were carried out during fictive calling behaviour occurring spontaneously or e v o k e d by e l e c t r i c a l stimulation in i m m o b i l i z e d a n i m a l s . F o u r t e e n m a l e J a p a n e s e t o a d s w e r e used. S u r g e r y was performed under MS-222 anesthesia. Laryngeal motoneurons identified by the antidromic r e s p o n s e to v a g a l or long l a r y n g e a l n e r v e s t i m u l a t i o n showed rhythmic membrane potential changes during fictive calling behaviour. They were classified into three types according to t h e t i m e r e l a t i o n between the membrane potential changes and DL burst activity determined b y E M G or p e r i p h e r a l efferent nerve discharges. Intracellular c u r r e n t or c h l o r i d e ion i n j e c t i o n w a s u s e d to i d e n t i f y E P S P s and IPSPs. (1)The 'DL type' m o t o n e u r o n s depolarized simultaneously w i t h DL burst activity (DL b u r s t p h a s e ) a n d h y p e r p o l a r i z e d between successive DL burst phases (DL i n t e r b u r s t phase). (2)The 'late DL type' motoneurons started depolarizing shortly a f t e r t h e o n s e t of t h e DL b u r s t p h a s e a n d h y p e r p o l a r i z e d d u r i n g t h e DL i n t e r b u r s t phase. In b o t h t y p e s of m o t o n e u r o n s , these depolarizations and hyperpolarizations were produced by EPSPs and IPSPs, respectively, and additional small EPSPs were superimposed in the m i d s t of IPSPs o b s e r v e d d u r i n g the DL i n t e r b u r s t phase. ( 3 ) T h e 'anti DL type' m o t o n e u r o n s were characterized by hyperpolarization at t h e DL b u r s t p h a s e b y IPSPs and depolarization by EPSPs during the DL interburst phase associated with HL activity. These results demonstrated the alternative synaptic inputs in m o t o n e u r o n s exerted from the c e n t r a l p a t t e r n g e n e r a t o r of the c a l l i n g b e h a v i o u r .