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1541 Brain stem projections from the medial vestibular nucleus in the albino rat
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1539
CUTANEOUS REFLEX MODULATION DURING FICTIVE LOCOMOTION IN THE CAT FOREUMB KAZUHIKO ~EKI 1 AND TAKA~HI YAMA(~U(~HI2,1Dfpt. of Phvsi. Educ.. Internatl. B0do Univ., 841 Shinkan, Katsu-ura, Chiba 299-52. Jaoan. and 2Inst. of Basic Meal. Sci.. Tsukuba Univ.. Tsukuba. Ibaraki 305, Japan. A previous report (Brain Res, 482('89)184-188) from this laboratory has shown that forelimb flexion reflex is rhythmically
modulated dudng fictive locomotion in immobilized decerebrate cats with the thoracic cord transected. The present study extended this by focussing on cutaneous rellex. Intracellular recordings were made from elbow flexor motoneurons during forelimb fictive locomotion evoked by stimulation of the C1-C2 lateral funiculus. It was found that oligosynaptic EPSPs from superficial radial nerve /'ythmically changed in amplitude. However, patterns of modulation were rather heterogeneous. In brachialis motoneurons the EPSPs exhibited maximal (minimal) amplitudes mainly in the flexion (extension) phase, while a reverse pattern was observed in biceps brachii. A small number of brachialis motoneurons showed such a reverse pattern, too. The depth of modulation also varied, as indicated by the fact that ratios ot maximal to minimal EPSP amplitudes were widely distributed (1.1 - 2.4). Furthermore, the EPSPs at rest (control) took diverse ampIiludes relative to maximal (Max) and minimal (Min) ones; i.e., control > Max > Min in some neurons, Max > control > Min, or Max > Min > control in others. The results suggested that the central pattern generator for locomotion adjust the reflex gain through several synaptic mechanisms.
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ANALYSIS OF VESTIBULAR INPUT TO THE CA UDAL MEDULLARY RAPHESPINAL NEURONES BY NATURAL STIMULATION IN THE CAT. TAKAHIRO GQTO: ILAN A. KERMAN: PHILIP S. BOLl'ON AND BILLY J. YATES, Laboratory' of Neurophysiology: The Rockefeller University. 1230 York Avenue. New York. NY 10021-6399. USA Caudal medullary raphespinal neurones (RSN) include cells mediating motor, antinociceptive and autonomic effects. We previously sh6wed that more than 70% of RSN responded to electrical stimulation of the vestibular nerve. In the present study we determine which vestibular endorgans prrvide inputs to RSN by analysing their responses to sinusoidal ~vhole body tilts in vertical planes and to sinusoidal horizontal rotations. Experiments were performed on decerebrate cats which were baroreceptor-denen'ated and vagotomized, and had a spinal transection at C8. Floating electrodes were placed in the C4 or C6 white matter for antidromic stimulation. Most (34/37) RSN whose spontaneous firing rates were modulated by vertical whole body tilt had response gains that remained relatively flat across stimulus frequencies, suggesting that their vestibular inputs were chiefly from otolith organs. For man2, (24/34) RSN with predominant otolith inputs, the plane of vertical tilt which produced maximal modulation or the r e s p o n s e v e c t o r o r i e n t a t i o n was closer to pitch than to roll. On the other hand. RSN rarely responded to horizontal rotations, which activate the horizontal semicircular canals. These data suggest that changes in head position in the sagittal plane (pitch) may influence the excitability of the spinal cord antonomic and motor function via RSN.
1541
BRAIN STEM PROJECTIONS FROM THE MEDIAL VESTIBULAR NUCLEUS IN THE ALBINO RAT. TAKEHIKO UMETANI, .F.irst Department of Anatomy, Kobe University School of Medicine, 7 Chome, Kusunoki-cho, Chuo-ku, Kobe 650, Japan
Brain stem projections from the medial vestibular nucleus (MVe) were studied in the albino rat by an anterograde tracing method using biocytin. 1. Association projections. The MVe projected to the ipsilateral dorsolateral and central parts of the superior vestibular nucleus, the ventral part of the lateral vestibular nucleus, and diffusely to the spinal vestibular nucleus. Minor subdivisions of the vestibular complex, subnuclei f, x, y, z, and infracerebellar and interstitial nuclei, also received the association projections. 2. Commissural projections. The commissural fibers crossed the floor of the 4th ventricle and terminated in almost the same locations to the ipsilateral complex, including the contralateral MVe. 3. Projections to the cranial nerve nuclei related to the oculomotor function. The MVe projected to the 6th, 4th and 3rd cranial nerve nuclei with contralateral predominance. The periocular nuclei (interstitial nucleus of Cajal and Darkschewitch nucleus) also received the projection. 4. Vestibuloreticular projections. The MVe projected to the bilateral paramedian, gigantocellular, and dorsal and lateral paragigantocellular reticular nuclei and sparsely to the contralateral caudodorsal part of the reticulotegmental nucleus. 5. Projections to the perihypoglossal nuclei. The MVe projected to the bilateral prepositus hypoglossal and Roller nuclei with contralateml predominance. 6. Vestibuloolivary projections. The MVe projected sparsely to the ipsilateral medial accessory olive and the contralateral dorsal cap.
1539
CUTANEOUS REFLEX MODULATION DURING FICTIVE LOCOMOTION IN THE CAT FOREUMB KAZUHIKO ~EKI 1 AND TAKA~HI YAMA(~U(~HI2,1Dfpt. of Phvsi. Educ.. Internatl. B0do Univ., 841 Shinkan, Katsu-ura, Chiba 299-52. Jaoan. and 2Inst. of Basic Meal. Sci.. Tsukuba Univ.. Tsukuba. Ibaraki 305, Japan. A previous report (Brain Res, 482('89)184-188) from this laboratory has shown that forelimb flexion reflex is rhythmically
modulated dudng fictive locomotion in immobilized decerebrate cats with the thoracic cord transected. The present study extended this by focussing on cutaneous rellex. Intracellular recordings were made from elbow flexor motoneurons during forelimb fictive locomotion evoked by stimulation of the C1-C2 lateral funiculus. It was found that oligosynaptic EPSPs from superficial radial nerve /'ythmically changed in amplitude. However, patterns of modulation were rather heterogeneous. In brachialis motoneurons the EPSPs exhibited maximal (minimal) amplitudes mainly in the flexion (extension) phase, while a reverse pattern was observed in biceps brachii. A small number of brachialis motoneurons showed such a reverse pattern, too. The depth of modulation also varied, as indicated by the fact that ratios ot maximal to minimal EPSP amplitudes were widely distributed (1.1 - 2.4). Furthermore, the EPSPs at rest (control) took diverse ampIiludes relative to maximal (Max) and minimal (Min) ones; i.e., control > Max > Min in some neurons, Max > control > Min, or Max > Min > control in others. The results suggested that the central pattern generator for locomotion adjust the reflex gain through several synaptic mechanisms.
1 540
ANALYSIS OF VESTIBULAR INPUT TO THE CA UDAL MEDULLARY RAPHESPINAL NEURONES BY NATURAL STIMULATION IN THE CAT. TAKAHIRO GQTO: ILAN A. KERMAN: PHILIP S. BOLl'ON AND BILLY J. YATES, Laboratory' of Neurophysiology: The Rockefeller University. 1230 York Avenue. New York. NY 10021-6399. USA Caudal medullary raphespinal neurones (RSN) include cells mediating motor, antinociceptive and autonomic effects. We previously sh6wed that more than 70% of RSN responded to electrical stimulation of the vestibular nerve. In the present study we determine which vestibular endorgans prrvide inputs to RSN by analysing their responses to sinusoidal ~vhole body tilts in vertical planes and to sinusoidal horizontal rotations. Experiments were performed on decerebrate cats which were baroreceptor-denen'ated and vagotomized, and had a spinal transection at C8. Floating electrodes were placed in the C4 or C6 white matter for antidromic stimulation. Most (34/37) RSN whose spontaneous firing rates were modulated by vertical whole body tilt had response gains that remained relatively flat across stimulus frequencies, suggesting that their vestibular inputs were chiefly from otolith organs. For man2, (24/34) RSN with predominant otolith inputs, the plane of vertical tilt which produced maximal modulation or the r e s p o n s e v e c t o r o r i e n t a t i o n was closer to pitch than to roll. On the other hand. RSN rarely responded to horizontal rotations, which activate the horizontal semicircular canals. These data suggest that changes in head position in the sagittal plane (pitch) may influence the excitability of the spinal cord antonomic and motor function via RSN.
1541
BRAIN STEM PROJECTIONS FROM THE MEDIAL VESTIBULAR NUCLEUS IN THE ALBINO RAT. TAKEHIKO UMETANI, .F.irst Department of Anatomy, Kobe University School of Medicine, 7 Chome, Kusunoki-cho, Chuo-ku, Kobe 650, Japan
Brain stem projections from the medial vestibular nucleus (MVe) were studied in the albino rat by an anterograde tracing method using biocytin. 1. Association projections. The MVe projected to the ipsilateral dorsolateral and central parts of the superior vestibular nucleus, the ventral part of the lateral vestibular nucleus, and diffusely to the spinal vestibular nucleus. Minor subdivisions of the vestibular complex, subnuclei f, x, y, z, and infracerebellar and interstitial nuclei, also received the association projections. 2. Commissural projections. The commissural fibers crossed the floor of the 4th ventricle and terminated in almost the same locations to the ipsilateral complex, including the contralateral MVe. 3. Projections to the cranial nerve nuclei related to the oculomotor function. The MVe projected to the 6th, 4th and 3rd cranial nerve nuclei with contralateral predominance. The periocular nuclei (interstitial nucleus of Cajal and Darkschewitch nucleus) also received the projection. 4. Vestibuloreticular projections. The MVe projected to the bilateral paramedian, gigantocellular, and dorsal and lateral paragigantocellular reticular nuclei and sparsely to the contralateral caudodorsal part of the reticulotegmental nucleus. 5. Projections to the perihypoglossal nuclei. The MVe projected to the bilateral prepositus hypoglossal and Roller nuclei with contralateml predominance. 6. Vestibuloolivary projections. The MVe projected sparsely to the ipsilateral medial accessory olive and the contralateral dorsal cap.