Jr. Abbott et Mj. Litzinger, DIFFERENT OMEGA-CONOTOXINS MARK THE DEVELOPMENT OF SWISS WEBSTER MOUSE CORTEX SUGGESTING N-TYPE VOLTAGE-SENSITIVE CALCIUM-CHANNEL SUBTYPES, International journal of developmental neuroscience, 12(1), 1994, pp. 43-47
omega-GVIA conotoxin has been used to mark presynaptic N-type voltage
sensitive calcium channels (VSCC).(3,13,19,21-23) Litzinger er al.(9)
used omega-conotoxin binding to describe a critical period of neurodev
elopment in Swiss Webster mice between postnatal days (PND) 11 and 14,
which appears to be important to the initiation of proper final devel
opment of the central nervous system. In this study, we compare how th
ree different omega-conotoxins (i.e. GVIA from Conus geographus, MVIIA
from Conus magus, and RVIA from Conus radiatus) mark N-type VSCC duri
ng this critical period in Swiss Webster mouse cortex. I-125-GVIA was
bound to Swiss Webster mouse cortex synaptosomal membrane fractions at
postnatal days 8 and 14. I-125-GVIA binding displacement curves were
obtained by incubating membranes with increasing concentrations of unl
abeled GVIA, MVIIA, and RVIA. Displacement curves and IC50 were calcul
ated for each of these three omega-conotoxins, and then compared. At P
ND 14, GVIA, MVIIA and RVIA were able to displace greater than 95% of
I-125-GVIA binding. At PND 8, however, MVIIA was only able to displace
83% of I-125-GVIA binding, and RVIA was only able to block 84%. The I
C50 does not appear to change significantly during this period of deve
lopment for any of the omega-conotoxins. The inability of MVIIA and RV
IA to completely block I-125-GVIA binding in pre-critical period Swiss
Webster cortex denotes an alteration in the composition of N-type VSC
C binding sites. With this data, we have suggested the presence of sub
types of the N-type VSCC in the cortex of pre-critical period Swiss We
bster mouse.