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1909 MORPHINE APPLIED INTO THE NUCLEUS TRACTUS SOLITARIUS (NTS) AUGMENTS BOTH A-

AND C-REFLEX DISCHARGE COMPONENTS OF THE SOMATO-SYMPATHETIC REFLEX IN ANESTHETIZED RATS. WEI-MIN LI *. AK10 SAT0 I, YUKO SAT0 2. ROBERT F. SCHMIDT3 ’ Dept. of the Autonomic Nervous Svstem, Tokvo Metrooolitan Institute of Gerontoloev. Tokyo 173. * Laboratory of Physioloev. Tsukuba College of Technoloee. Tsukuba 305. Jaoan. 3 Phvsioloeisches Institut der Universitat Wtirzburrz. Germanv.

In anesthetized rats, single electrical stimulation of myelinated (A) and unmyelinated (C) afferent fibers in a limb nerve elicits the early A-reflex and late C-reflex discharges in a sympathetic efferent nerve. It has been reported that intrathecal injection of morphine suppressed the C-reflex, while injection of morphine either into a femoral vein or the cisterna magna (i.c.m.) augmented both A- and C-reflexes. The present study aimed to specify the effective regions of morphine for enhancing both A- and C-reflexes were studied using microinjection of morphine into the several specific regions in the brain. Both A- and C-reflexes, elicited in a cardiac sympathetic efferent nerve by single shock stimulating A and C afferent fibers of a tibial nerve, were augmented by morphine when applied into the nucleus tractus solitarius (NTS). After destroying bilateral NTS, intravenous injection of morphine became less effective for the reflexes. The present result suggests that augmentation

of both A- and C- reflexes induced by i. v. or i. c. m. injection of morphine in rats is resulted by either suppressing inhibitory baroreceptor afferent pathways or augmenting excitatory chemoreceptor afferent pathways in the NTS.

1910 TOPICAL APPLICATION OF Ca2+CHELATING AGENT (EDTA) MARKEDLY PREVENTS THE NEUROTOMIA-INDUCED FOS EXPRESSION IN THE DORSAL HORN OF RATS.

HONDA, NO: TONOSAYAMA. AND WI. Dept. of Anatomy, Fukushima Med. Cal., Fukushima 960-12 Japan.

Transection of the peripheral nen’e makes the primar). afferent neurons to produce the neuronal nitric oxide sy-nthase

(nNOS) w.hich ma)’ ha1.e an important role to conduct the inlormation accompanied with ner1.e inJury. To clanfy~ a functional

role of Ca*+ mlloned mto neurons by the transient membrane-disruptton of the peripheral nenc, we immunohtstochemically

esammed Fos expression m the spmal cord Induced by. transection of the sciatic ner1.e m the absence of Ca2+. Topical

applicatton of colchicine to the transected part of the sciatic ner\c ( IOmM, 10~1) sigrnhcantly. rcduccd the number of Fos-

immunoreacttv’e cells m the dorsal horn of the lumbar spinal cord.

Our present results Indicated that Caz+ -mtlus accompanied with the membrane disruption of neurons might be required

tbr actt\.ation of NOS m the Injured primar) afferent neurons

1911 DISTRIBUTION OF C-FOS EXPRESSING CELLS IN THE TRIGEMINAL NUCLEUS CAUDALIS FOLLOWING INFRAORBITAL NERVE TRANSECTION IN THE RAT. Rvuii Teravamall, matsu 21

Nishimor i21 D Svmio.1). Nahoko

'1 r r?$" aoa de k 2).

xi11 ToshikazQ

, -aa. ih r

) 'M. zaki

eBioloovz) M' lvazaki Medical Colleae. -16. Janan.

Fos and related proteins are expressed in the spinal dorsal horns after noxious stimulation including tissue injury and nerve transection. To expand this into trigeminal system, changes in a temporal and spatial distribution of c-Fos positive neurons in the trigeminal nucleus caudalis were examined after tissue injury and transection of the infraorbital nerve in the adult rats.

Rats were served unilateral transection of the infraorbital nerve or sham-operation(tissue injury), and allowed to survive for various intervals followed by perfusion. 50 w serial frozen sections of brainstem were collected and immunostained for c-Fos protein. The rostro-caudal and medio-lateral distributions of c-Fos positive neurons within this nucleus were examined by counting or mapping these neurons in each layer of this nucleus.

The number of C-Fos positive neurons in laminae I and II of this nucleus ipsilateral to both nerve transection and tissue injury was prominently elevated two hours after operation. day of operation,

After one the majority of c-Fos positive neurons in sham-operated rats were bilaterally

located within laminae III and IV with a wide rostra-caudal and medio-lateral extension in this nucleus and that persisted over the two weeks study period. number of C-Fos positive neurons in the

In the nerve-transected rats, the central terminal field corresponding to the transected

nerve was markedly smaller than that of sham-operated rats although the distribution of c-Fos positive neurons in the side contralateral to nerve transectioc was not so different from that of sham-operation, suggesteing that C-Fos expressions in the trigeminal nucleus caudalis after nerve transection and tissue injury are differentially regulated.