The vestibulothalamic connections in the rat: A morphological analysis using wheat germ agglutinin horseradish peroxidase

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TOPOGRAPHICAL CORTICO-PARABRACHIAL PROJECTIONS IN THE CAT: AN HRP STUDY YUKIHIKO YASUI*, KAZUO ITOH, MASAHIKO TAKADA*, AKIRA MITANI*, TAKESHI KANEKO* and NOBORUMIZUNO, Department of Anatomy ( i s t D i v i s i o n ) , Faculty of Medicine, Kyoto University, Kyoto 606, Japan. After injecting HRP into the parabrachial nucleus (PBN), cerebral c o r t i c a l neurons are retrogradely labeled. They are d i s t r i b u t e d in the deep pyramidal cell layer of the o r b i t a l gyrus, l a t e r a l bank of the presylvian sulcus, and i n f r a l i m b i c cortex, bilaterally, with an i p s i l a t e r a l predominance. After injecting WGA-HRP into these c o r t i c a l regions, axon terminals are anterogradely labeled in the PBN, b i l a t e r a l l y , with an i p s i l a t e r a l predominance. After WGA-HRP injection into the o r b i t a l gyrus, axon terminals are labeled heavily in the medial PBN, and s l i g h t l y in the l a t e r a l PBN. The injection into the l a t e r a l bank of the presylvian sulcus labels axon terminals moderately in the dorsal part of the l a t e r a l PBN. After the injection into the i n f r a l i m b i c cortex, labeled axon terminals are d i s t r i b u t e d widely in the PBN regions. The c o r t i c a l f i b e r s from the o r b i t a l gyrus and l a t e r a l bank of the presylvian sulcus run down i p s i l a t e r a l l y through the internal capsule and the cerebral peduncle to the lower brainstem. These f i b e r s send terminals to the thalamic taste area (the medial part of the parvocellular d i v i s i o n of the posteromedial ventral nucleus) and the medullary taste area (the rostral part of the nucleus of the s o l i t a r y t r a c t ) , as well as to the pontine taste area (the PBN regions). The c o r t i c a l f i b e r s from the i n f r a l i m b i c cortex run down i p s i l a t e r a l l y through the medial forebrain bundle to the ventral tegmental region of the lower brainstem. The c o r t i c a l fibers to the PBN possibly subserve cortical control upon autonomic and/or limbic functions; in p a r t i c u l a r , some fibers running down through the internal capsule may p r i m a r i l y be concerned with cortical control upon the sensory coding of gustatory information.

THE V E S T I B U L O T H A L A M I C C O N N E C T I O N S

IN THE RAT: A M O R P H O L O G I C A L

ANALYSIS USING WHEAT GERM AGGLUTININ HORSERADISH PEROXIDASE SHINJI N A G A T A and TAKESHI KANASEKI, D e p a r t m e n t of Anatomy, F a c u l t y of Medicine, K y u s h u University, 3-1-1 Maidashi, Higashiku, F u k u o k a 812, Japan. The d i s t r i b u t i o n s terminals,

of a n t e r o g r a d e

and r e t r o g r a d e

respectively,

l a b e l l i n g of fibers and

l a b e l l i n g of cells were studied

in the rat, by i n j e c t i n g W G A - H R P into the

v e s t i b u l a r n u c l e a r complex, p r o j e c t i o n to the central

and the thalamus.

lateral nucleus o r i g i n a t e s m a i n l y in

the c o n t r a l a t e r a l medial(M), v e s t i b u l a r nucleus via m e d i a l

and i p s i l a t e r a l superior(S) longitudinal

a s c e n d i n g tract of Deiters(ATD). the v e n t r o b a s a l

fasciculus(MLF)

and

The v e s t i b u l a r p r o j e c t i o n s

complex and the v e n t r a l

to

lateral nucleus o r i g i n a t e

m a i n l y in the b i l a t e r a l M and S via MLF, ATD, conjunctivum(BC).

The v e s t i b u l a r

and b r a c h i u m

The p r o j e c t i o n to the rostral p a r t of the

dorsal m e d i a l g e n i c u l a t e nucleus o r i g i n a t e s d e s c e n d i n g v e s t i b u l a r nucleus via lateral

in the c o n t r a l a t e r a l

lemniscus,

BC and MLF.