Expression of metabotropic glutamate receptors positively coupled to CAMP formation in neuroendocrine cells

113

114

PHARMACOLOGY OF FLUORlDE CCC ANALOGUES AS NOVEL AGONISTS FOR METABOTROPIC GLUTAMATE RECEPTORS.

LOCATION

Peter B.

H. Shinozaki. The Tokyo Metro.

I’OSTSYNAI’TIC

OF

RIXATION

TO

Sonwgyi

TRASSI\IITT~R

Ilitoshi

*,

IN

SITES.

Shigemcltu *S. Rafael Lujan *, I.

*, Ryuichi

Roherts

hIGI,URs

REL15AS15

Ohishi

S.

Zohan

Nusser

*;

David *MRC

Anatomical Nruroph:~nna~ol~~gy Llnit. Oxford, OX 13TH, U.K.; .$ Dept. of Morph. Brain Science. Kyoto Univ., Kyoto 606, Japan.

Inst. Med. Sci.. Tokyo 113

2-(carboxycycIopropyI)glycine (CCC+) is a useful compound for the study of the interaction of glutamate with its receptors conccming their prelPrence for particular conformers of the glutamate molecule. Some CCC derivatives such as DCG-IV and tmns-MCG-I have already been proved to be potent agonists for metabotropic glutamate receptors (mGluRs). These mGIuR agonists take an extended conformation of the glutamate skeleton. CCG compounds would be expected to become conformationally more restricted by fluoridation at the position of 3’-carbon. In the present paper, we examined pharmacological actions of eight tsomers of 3’,3’-difluoro-CCG (3’-FzCCG) to compare with those of CCG in the isolated spinal cord of newborn rats. L-3’-FZCCG-I (extended form, corresponding to L-CCG-I) caused both depolarization and depression of monosynaptic excitation in a dose dependent manner, and the former was inhibited by MCPG and the latter was blocked by MCCG L-3’-F2CCG-I was about 3 and 1.5 times more potent than L-CCG-1 to activate Group I and Group II mGluRs, respectively. One of the most characteristic actions of L-3’-F2CCG-I is related to a marked difference in the sensitivities of some acidic amino acids disclosed before and after application of this new mGluR agonist (‘CCG priming’ ?). The distinguishing actions of L-3’-FzCCG-I as an mGluR agonist would be useful for elucidating physiological roles of mG1uP.s.

Ionotropic

and the nwrnhouopic

‘are xgmgarcd

at

synapses

glutamate

on

Purkinje

receptors

cells

and

mGluRla hippoeampnl

intemeurons (Neuron 1993.1 I, 771). High resolution irmnunogold localization of mGluRlh/c and mGluRS shows that they are also found outside synaptic specialisations on hippoc-nmpal principal cells and GABAergic neurons. Pymmidal cell spines in the CA1 ‘area &nreparticularly enriched in mGluR5. In the spine membrane, the highest mG1uR.S density is in a perisynaptic nnnulus followed by gmdutily decreasing receptor level (tig. I). The receptor is also present in tbe perforations of postsynnptic densities. 50 Fig. 1. Distribution of mGluR5 on % of

40

immunolabelled membrane segments

3o ~

pyramidal

relation

denddtic spines in

to the postsynaptic membrane specialisation. Normalised noparticle (n=348) distribution 7 spines in slratum radialurn of

10 distance on spine

0

4 40 120 zio 360 480 6w 900 (nm) middle & edge 01 poslsynaptic membrane specialisalion

In contrast to group I mGluRs, mGluR2/3 appear to he distrihutrd in a more uniform m;uiner in the somato-dendritic pkc;ma memhranc ofcereb4ar Golgi cells. 77~ highly compcrr~N~nftr[isrd distribution of mChRs sqg~~.s fhrlt the precise plucemmt receprors is on imporftrnf firclor conrrihtfing 10 .ynuplicJitnction.

116

115 ESPRESSIOS

0.F

RECEPTORS

Sortiuo

M.A.~,

Canonicd. 3Chair

R.

Kuhn2.

‘Institute

of

METABOTROPIC

POSITIVELY IN NEtiROEXDOCRISE

FOR>I:\TIOS

Italy;

of

of

T.

2CNS

Research.

Knopfr12,

School

of

TO

CA111

CELLS 8.

Pharmacology.

Pharmacolo,gy.

TIIE ROLE OF METABOTROPIC RKEF’TORS IS ESCITOI‘OSIS-ISI)[:(‘ED R4T CEREBELI,4R GR4NliLE CELL DEATII

GLL-TAMATE

COUI’LED

Malitschek2,

University

Dentistry,

of

and

P.L.

Catzmia,

University

of

and

Pavia,

.Pharm. Div., Ciba. Basle, Switzerland.

Penelope

C

Division It,

Staton

and Dabid

of Neuroscience.

w/w

studies

have

methylamino-I.-alanine Immortalized

hypothalamic

glutamate

and -7, as, assessed by immunocitochrmistry.

mGlu

receptors,

hydroxyphenylglycine hydrolysis

agonists

(HPG)

in subconfluent

role for group-1 Confluent

cultures with

potency

for this effect

they

CCG+quisqualatr>L/\P4.

secretagogue

in in

in CAMP

GTI-7 CAMP

usually was

including IS,3R-ACPD

cultures,

of CAMP

the following:

or

3(PI)

suggesting mGlu

Surprisingly. types.

a

by

receptor all these

forskolin.

The

as

that functional

particular, linked to

the Ihe

produced by mGlu receptor

in these cells.

A29

receptors

Cerebellar

ofhlanchester, the

Ilowever.

glutamate This cells

for

excitotorin

study

is also a potent

coupled

investigated

ACPD

and propidium killed

iodide

a maximum

to

inositol

the

in

prepared

role

d‘

from

S-day

old

serum-free Neurobasal”’

medium betbre exposure to (IS,3R)-ACPD (ACPD) The features of cell death \\ere examined using DAPI, diacetate

through

cell death

were

dayr

O-x-

damage

BZIAA

receptors

(CGC)

17-11

plant

I: K

causes neuronal

in BMAA-induced

granule

maintained

Bristw

that

receptors

hydrolysis

metabotropic

or

BMAA

tluorescein

staining of 42

*

6”‘0 (mean

*

SEM.

n=4)

above control ar 3mM after- 2411. 3mhl ACPD-induced death uas reduced 9250 by lmhl (RS)-hlCPG and increased 34% hy IOOpM D-AP5 BMAh killed a maxiniuni of 32 f 2% (mean * ST.hl. n=3) CGC above control at 3mM after 2411 .3mM B\t.4.4induced cell death was reduced 370/b with (RS)-MCPG and 94”; by D-APS. ACPD and Bhl.4.4 both induced necrotic- and apoptotictypes ofCGC death over 1411 3mhl ACPD caused a maximum d‘ 36 i 6?,0 (mean f SEM. n-4) necrosis at 2411and 35 + 10% (mean f SEM, n=4) apoptosis ar 18h 3mM BM.4.4 caused a maximum of 38 * 4% (mean f SE>!. n=3) necrosis at 1811 and 30 + l?‘b (mean i SEM, n=3) apoprosis at 21h These finding she\\ that ACPD kills CGC via both necrotic and apoptotic mechanisms. Similarly. BhlAA causes necrotic and apoptotic CGC death and this death is due partly to metabotropic receptor activation CGC

mGlu receptors

ofNhlDA

rats and

shown (6hIA.A)

of metabotropic

phospholipid

rank order

DCG-IV>IS,3R-ACPDzL-

hypothalamic neurons. In formation may be causally

effect, i.e. the release ofGsRH,

agonist of

of cell proliferation.

formation

do in other cell

activation

mGlula,

Agonists

to group-11 or -III formation.

We conclude

multiple

polyphosphoinositide

but not in contluent

the stimulation

to what

are present enhancement

quisqualata.

stimulated

insb:ad responded

an incrwssr

drugs enhanced

RI

mGh1 ireceptors in the regulation

opposed

agonists

such

subtypes,

express

-lb,

group-1

receptor

neurons

mrtabotmpic -5. -2/3,

(mGlu)

GTI-7

R

lJni\ersity