Journal of Neuroscience, Vol 13, 3173-3179, Copyright © 1993 by Society for Neuroscience
Purkinje cell survival is differentially regulated by metabotropic and ionotropic excitatory amino acid receptors
HT Mount, CF Dreyfus and IB Black
Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, UMDNJ, Piscataway 08854-5635.
We previously reported that trophic factors and neurotransmitters in
concert regulate survival of cultured cerebellar Purkinje cells. In
particular, excitatory amino acid (EAA) transmitters and NGF increased
survival, whereas neither alone was effective. In the present studies, we
sought to identify molecular mechanisms through which EAAs participate in
the survival-promoting interaction. Initially, we characterized the
potential role of ionotropic EAA receptors by exposing cultures to the
antagonists MK-801, D-2-amino-5- phosphonovaleric acid, and
6,7-dinitroquinoxalinedione. Each increased cell number, suggesting that
endogenous ionotropic activity decreased survival. To determine whether
metabotropic EAA receptor stimulation modulates survival, the metabotropic
agonist ACPD ([1S,3R]-1- aminocyclopentane-1,3-dicarboxylic acid; 1 microM)
was tested. ACPD alone had no effect on survival. However, simultaneous
exposure to ACPD and NGF significantly increased Purkinje number. Moreover,
this increase in survival was blocked by L-AP3 [L(+)-2-amino-3-
phosphonopropionic acid; 1 microM], a putative antagonist of certain
metabotropic responses. L-AP3 also reduced cell number in the absence of
exogenous EAA. Thus, endogenous metabotropic stimulation is normally
necessary for survival. In sum, these studies reveal a novel mechanism
whereby an excitatory neurotransmitter shapes neural development by
simultaneous trophic and regressive actions that are, respectively,
mediated by metabotropic and ionotropic EAA receptors.