Differential distribution of premotor neurons for jaw-closing versus jaw-opening trigeminal motor nucleus neurons in the rat

St83

PROJECTION OF EMESIS-RELATEDNEURONSOF THE mZINGER COMPLEXTO THE VENTRAL RESPIRATORYAREA IN DECEREBRATE DOGS. TOMOSHIGE KOGA AND HIROYUKI FUKUDA.Dent. of Physiol., Kawasaki MedicalSchool, Kurashiki701-01. .Tanan

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Neurons in the B&zinger complex (m) have been reported to produce the basic activity pattern of retching and expulsion. Our previous study suggested that respiratory neurons of the ventral respiratory group (VRG) participate in emetic contraction of the diaphragm and abdominal muscles. Therefore, in the present study, we investigated whether or not the emesis-related B& neurons project to the VRGarea in decerebrate, paralyzed dogs. We recorded 24 inspiratory (I), 62 expiratory (E) and 27 non-respiratory (NR) I3@Tneurons which exhibited bursts of high frequency discharges phase-locked with retches. Of these I, E and NRm neurons, 38 % (g/24), 42 % (26/62) and 33 96(g/27), respectively were identified as projecting to the VRGarea by the collision test. Thus, it may be concluded that some of the emesis-related B&’neurons transfer the pattern of retching bursts to the spinal cord via the VRGrespiratory neurons.

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DIFFERENTIAL DISTRIBUTION OF PREMOTOR NEURONS FOR JAW-CLOSING VERSUS JAW-OPENING TRIGEMINAL MOTOR NUCLEUS NEURONS IN THE RAT.

YUN-OING LI, MASAHIKO TAKADA. TAKESHI KANEKO m

NOBORU MIZUNO, Demutment of Moroholoaical

9. The differential distribution of premotor neurons for jaw-closing

versus jaw-opening

motoneurons

motor nucleus (Tm) was investigated in the rat by retrograde and anterograde labeling techniques.

in the trigeminal

The premotor neurons that

are distributed in the mesencephalic trigeminal nucleus, medial part of the parabrachial region, supratrigeminal

region, and

dorsal parts of the principal sensory, oral spinal and interpolar spinal trigeminal nuclei project preferentially to the dorsolateral division of the Tm that contains jaw-closing intermediate

parts of the principal

motoneurons,

whereas those in the lateral part of the parabrachial

sensory, oral spinal and interpolar

spinal trigeminal

to the ventromedial

region,

nuclei, and alpha part of the

gigantocellular

reticular nucleus project preferentially

motoneurons.

The dorsal and lateral parts of the medullary reticular formation, and the medullary raphe nuclei contain

premotor neurons of both types. The group k, a cluster of Tm motoneurons

division of the Tm that contains jaw-opening which innervate the tensor tympani muscle,

receives projection fibers predominantly from the dorsolateral part of the oral pontine reticular formation.

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LARYNGEAL REFLEX DURING ELECTRICALLY INDUCED ANESTHETIZED CATS. r awa. 078. Japan

VOCALIZATION

IN KETAMINE

Tonic electrical stimulation (0.2ms, 40-100 pA, 100 Hz, lasting 5 to 10 s) delivered to the midbrain periaqueductal gray (PAG) (Horsley-Clarke coordinates, A 1.5 to 0.5, L or R 1.0 to 2.0, H 1.5 to 0.5) induced vocalization and inspiration alternately with a newly developed rhythm. During the induced vocalization, the activity of the adductor of the vocal cord (thyroarytenoid muscle: TA) greatly increased, which was silent during quiet breathing, while, during induced inspiratory period, TA activity was silent like quiet breathing. In this study, the excitability of the adductor of the vocal cord during the induced inspiratory period is estimated by measuring the gain of the laryngeal reflex which is induced by stimulating the superior laryngeal nerve (SLN). Three cats (B.W.= 2.5 - 3.6 kg) of either sex were anesthetized with ketamine (4Omg/kg, i.m.). SLN was dissected at the entry of the larynx and stimulated with rectangular pulses (0.05 ms, 1 to 3 V) at mid inspiratory phase every 2 or 3 respiratory cycle during quiet breathing. The rectified and integrated TA EMG during 8 to 20 msec after the SLN stimulation was employed as a control of laryngeal reflex. During PAG stimulation, SLN was stimulated once every inspiratory period. The laryngeal reflex during induced inspiratory period was greatly reduced. The magnitude of the laryngeal reflex became less than 60 % of the control value. Although the TA activity was silent during inspiratory period, the present results revealed that the excitability of the adductor of the vocal cord was further suppressed than that during inspiratory period of quiet breathing.