Regulation of thalamic axon growth by neurotrophins

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REGULATION OF THALAMIC AXON GROWTH BY NEUROTROPMNS

KENJI HANAMURA, KAYO INUI, AKIKO HARADA, FUJI0 MWWKAMI AND NOBUHIKO YAMAMOTO Laboratory of Neuroscience, Division of Biophysical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560 Japan. To reveal the role of neurotrophins in axonal growth and arborization in neocortical circuits, thalamic axon growth was studied on a fixed cortical slice. Rat thalamic blocks (E15) were juxtaposed to the lateral edge of cortical slices (P7) that had been fmed with paraforamaldehyde. Under these conditions the effect of intrinsic neurotrophic factors released from cortical cells could be largely excluded. After a few days in culture neurotrophins including NGF, BDNF, NT3 or NT4 (200 rig/ml) were added to the culture medium, and the cultures were further incubated for an additional several days. Then, axonal projection patterns were examined by implanting diI in thalamic explants. Thalamic axons extended longer in the deep layers (layers 5 and 6) than in the upper layers (layers 1 to 4) on fixed cortical slices. This elongation pattern was not changed by adding NGF, BDNF or NT4. However, axonal growth was increased in each layer in NT3-containing medium. ‘Ihis finding suggests that developing thalamic neurons extend axons that respond to neurotropbins through trkC receptors. NEURITE GROWTH AND TPKIIGSK-3t3-DEPENDENT PHOSPHORYLATION OF JUVENILE TAU IN CULTURED RAT HIPPOCAMPAL NEURONS.

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MIHO TAKAHASHI, Integrative

KAORI YASUTAKE,

Project Center,

Mitsubishi

KAYOKO TOMIZAWA

Kasei Institute

of Life Sciences,

Minamiooya 11, Machida-shi, Tokyo

194-8511. Tau protein kinase I (TPKI) / glycogen developing

neurons

on neuronal

growth

by staining

changes

with antibodies

of phosphorylated

serines-199

increased

30 has an important

656

in the cultured

blot analyses

role in the neurite

ceils under various

INOSITOL

Phosphatase

conditions inhibitors,

of TPKI/GSK-313, dose-dependently

phosphotylation

in developing

the role

hippocampal

Lithium, an inhibitor

of tau and the neurite growth.

growth

cultured

showed that lithium decreased

and -396, TPKI/GSK-30

the phosphorylation

ROLE OF

in primarily

of MAP2, O-tubulin, tau, synaptophysin.

were okadaic

inhibited the amount

sites in tau. An activator

of TPKI/GSK-

These results indicate

that TPKI/GSK-

brain.

1,4,5TRISPHOSPHATE

RECEPTORS

IN NEURITE

OUTGROWTH

OF CHICK DRG NEURONS.

KOHTARO TAKE1 I, RYONG-MOON ‘Mikoshiba Calciosignal

Net Project,

‘Dept. of Molecular Neurobiology,

The inositol 1,4,5trisphosphate intracellular Ca” is considered IICR in neurite outgrowth

SHIN ’ AND KATSUHIKO

ERATO, Japan Science and Technology

receptor (IP,R) acts as an IP,-induced

inhibits neurite outgrowth. in growth

‘,* Meguro-ku,

for neurite outgrowth

using chromophore-assisted

but the extent of involvement was distributed

of

in neuronal

an inhibitor of Ca*‘-

IP,R blocker resulted in neurite

by observing

growth cone motility in

laser inactivation (CALI).

in the growth cone caused neurite retraction, but there was no effect of CAL1 of IP,Rl

findings suggest that IP,Rl

153-0064,

A transient increase in

Depletion of internal Ca*’ stores by thapsigargin, of heparin, a competitive

Tokyo

Tokyo 108-007 1.

Ca*’ release (IICR) channel.

We found that type 1 IP,R (IP,Rl)

Microinjection

cones is required

response to the acute and localized loss of the IP,Rl functions of IP,Rl

Corporation,

to be a key step in the signaling cascade for neurite outgrowth,

has remained to be determined.

We asked if IP,RI

MIKOSHIBA

The Institute of Medical Science, The Univ. of Tokyo, Minato-ku,

growth cones of chick dorsal root ganglion neurons. ATPase significantly retraction.

of neurons

in the

tau occurs in the same period. To elucidate

of tau was examined

A have no effect on the neurite growth.

growth of the cells. Western

30, heparin

(GSK-313) has been shown to be abundant

juvenile

phosphorylation

of rat. lmmunohistochemical

acid and cyclosporin neurite

kinase-30

rat brain and the highly phosphorylated

of TPKIIGSK-30

examined

synthase

Temporal loss of in neurites.

These

in the growth cone have crucial roles and the IICR may play important roles in neurite outgrowth.