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Segregated projections of two different types of corticothalamic neuron in cat primary auditory cortex
S248
16-04
NEUROTENSIN-EXPRESSING NEURONS IN THE RAT DORSAL COCHLEAR NUCLEUS: CELL PROFILES AND PROJECTIONS. KAZUO SATO, TAKESHI HOUTANI, TEIZO UEYAMA, MICHIKO IKEDA AND TETSUO SUGIMOTO,
Department
of Anatomy,
Kansai Medical University,
Moriauchi,
Osaka 570, Japan
Neurotensin (NT) is known to activate some neurons in discrete brain sites. Since this peptidc has been localized to fiber components in some stations of the ascending auditory system, we here explored neuronal expression of this peptide in the rat auditory system. Sprague-Dawley rats (180-250 g b. wt.) were deeply anesthctizcd with sodium pentobarbital and perfused with a fixative containing paraformaldehyde and pmric acid. Coronal sections through the brainstem were immunostained for NT employing the avidin-biotin-peroxidase labeling technique. Some NTimmunoreactive neurons were found in the dorsal cochlear nucleus. Following intracerebroventricular colchicine administration, NT- ositive neurons increased in cell number, and their processes and spines also became visible. These neurons were Poeated in the middle layer of the nucleus and they contained polygonal or pyramidal cell bodies
of medium or large size. From the cell body, several well-developed dendrites extended toward the pial surfaces. Double label studies combined with a retrograde fluorescent tracer True Blue revealed that most of the NT-positive neurons project to the contralateral inferior colliculus. Expression of mRNA encoding NT was then analyzed with tissue from normal rats by using digoxigenin-labeled oligonucleotide probes for NT/neuromedin N cDNA. In the dorsal cochlear nucleus, hybridization signal for NT mRNA was highly localized to cytoplasm of the polygonal or pyramidal neurons that correspond to the NT-immunoreactive neurons. In summary, NT was shown to be expressed in the neurons of the dorsal cochlear nucleus that project to the contralateral inferior colliculus.
16-05
SEGREGATED
PROJECTlONS
OF TWO DIFFERENT TYPES OF CORTICOTHALAMIC
CAT PRIMARY AUDITORY CORTEX, Systems
Laboratoty,
Frontier
Research
Program,
HISAYUKI OJIMA RIKEN,
NEURON IN
AND EDWARD G. JONES,
2-1 Hirosawa,
Wako, Saitama
Neural
351-01, Japan
We have previously shown that in the cat primary auditory cortex (AI),layer 5 pyramidal neurons projecting to the medial geniculate body (MOB) have exclusively horizontal intraconical
axon collaterals, while medium-sized
layer 6 pyramids
projecting also to MGB have only recurrent vertical collaterals. To visualize the thalamic projection patterns of these two neuronal types, two anterograde tracers, PHA-L for large injections spanning small injections covering
either layer 5 or 6 were made into cat AI.
PHA-L injections resulted in staining of two types of boutons, coursing tine axons
entire infragranular depth and biocytin for
small boutons distributed mainly along dorso-ventrally
in the ventral division of MGB and large boutons in grape-like clusters on fiberes localized in the
dorsal and medial divisions.
Injections of biocytin involving
layer 5 without layer 6 always stained fibers with large
boutons. In contrast, localized injections solely into layer 6 stained no large boutons but always demonstrated number of small boutons
in the ventral division.
a significant
The results indicate the presence of a dual corticothalamic
systems
originating in different cortical layers.
16-06 University
AVIAN SONG CONTROL NUCLEI, BVc AND 1MAN RESPOND DIFFERENTLY TO CONSPECIFIC SONG. MASAO MAEKAWA AND NOZOMU SAITO, Department of Physiology, Dokkyo School of Medicine, Mibu, Tochigi. 321-02, Jauan
The descending motor pathway Birdsong is controlled by several brain nuclei. A second pathway directly from the HVc to the RA controls the avian vocal organ. (recursive loop) from the BVc to the RA including the LMAN is important to song Nottebohm (1991) determined the significance of the 1MAN during song learning. learning by its lesion. We recorded auditory responses to conspecific songs in the 1MAN and the BVc of the adult zebra finch brain to clarify the difference between Zebra finch song notes are composed of two components, constant both nuclei. The CF component consist of a frequency (CF) and frequency modulation (FM). BVc neurons responded to one harmonic, fundamental frequency and its harmonics. combinations of harmonies. while 1MAN neurons responded exclusively to specific Neurons in the 1MAN are much more specific to categorical pattern of conspecific The significance of the 1MAN in song learning will be songs than those in the BVc. discussed.
16-04
NEUROTENSIN-EXPRESSING NEURONS IN THE RAT DORSAL COCHLEAR NUCLEUS: CELL PROFILES AND PROJECTIONS. KAZUO SATO, TAKESHI HOUTANI, TEIZO UEYAMA, MICHIKO IKEDA AND TETSUO SUGIMOTO,
Department
of Anatomy,
Kansai Medical University,
Moriauchi,
Osaka 570, Japan
Neurotensin (NT) is known to activate some neurons in discrete brain sites. Since this peptidc has been localized to fiber components in some stations of the ascending auditory system, we here explored neuronal expression of this peptide in the rat auditory system. Sprague-Dawley rats (180-250 g b. wt.) were deeply anesthctizcd with sodium pentobarbital and perfused with a fixative containing paraformaldehyde and pmric acid. Coronal sections through the brainstem were immunostained for NT employing the avidin-biotin-peroxidase labeling technique. Some NTimmunoreactive neurons were found in the dorsal cochlear nucleus. Following intracerebroventricular colchicine administration, NT- ositive neurons increased in cell number, and their processes and spines also became visible. These neurons were Poeated in the middle layer of the nucleus and they contained polygonal or pyramidal cell bodies
of medium or large size. From the cell body, several well-developed dendrites extended toward the pial surfaces. Double label studies combined with a retrograde fluorescent tracer True Blue revealed that most of the NT-positive neurons project to the contralateral inferior colliculus. Expression of mRNA encoding NT was then analyzed with tissue from normal rats by using digoxigenin-labeled oligonucleotide probes for NT/neuromedin N cDNA. In the dorsal cochlear nucleus, hybridization signal for NT mRNA was highly localized to cytoplasm of the polygonal or pyramidal neurons that correspond to the NT-immunoreactive neurons. In summary, NT was shown to be expressed in the neurons of the dorsal cochlear nucleus that project to the contralateral inferior colliculus.
16-05
SEGREGATED
PROJECTlONS
OF TWO DIFFERENT TYPES OF CORTICOTHALAMIC
CAT PRIMARY AUDITORY CORTEX, Systems
Laboratoty,
Frontier
Research
Program,
HISAYUKI OJIMA RIKEN,
NEURON IN
AND EDWARD G. JONES,
2-1 Hirosawa,
Wako, Saitama
Neural
351-01, Japan
We have previously shown that in the cat primary auditory cortex (AI),layer 5 pyramidal neurons projecting to the medial geniculate body (MOB) have exclusively horizontal intraconical
axon collaterals, while medium-sized
layer 6 pyramids
projecting also to MGB have only recurrent vertical collaterals. To visualize the thalamic projection patterns of these two neuronal types, two anterograde tracers, PHA-L for large injections spanning small injections covering
either layer 5 or 6 were made into cat AI.
PHA-L injections resulted in staining of two types of boutons, coursing tine axons
entire infragranular depth and biocytin for
small boutons distributed mainly along dorso-ventrally
in the ventral division of MGB and large boutons in grape-like clusters on fiberes localized in the
dorsal and medial divisions.
Injections of biocytin involving
layer 5 without layer 6 always stained fibers with large
boutons. In contrast, localized injections solely into layer 6 stained no large boutons but always demonstrated number of small boutons
in the ventral division.
a significant
The results indicate the presence of a dual corticothalamic
systems
originating in different cortical layers.
16-06 University
AVIAN SONG CONTROL NUCLEI, BVc AND 1MAN RESPOND DIFFERENTLY TO CONSPECIFIC SONG. MASAO MAEKAWA AND NOZOMU SAITO, Department of Physiology, Dokkyo School of Medicine, Mibu, Tochigi. 321-02, Jauan
The descending motor pathway Birdsong is controlled by several brain nuclei. A second pathway directly from the HVc to the RA controls the avian vocal organ. (recursive loop) from the BVc to the RA including the LMAN is important to song Nottebohm (1991) determined the significance of the 1MAN during song learning. learning by its lesion. We recorded auditory responses to conspecific songs in the 1MAN and the BVc of the adult zebra finch brain to clarify the difference between Zebra finch song notes are composed of two components, constant both nuclei. The CF component consist of a frequency (CF) and frequency modulation (FM). BVc neurons responded to one harmonic, fundamental frequency and its harmonics. combinations of harmonies. while 1MAN neurons responded exclusively to specific Neurons in the 1MAN are much more specific to categorical pattern of conspecific The significance of the 1MAN in song learning will be songs than those in the BVc. discussed.