ACTIVITY-DEPENDENT REGULATION OF DENDRITIC SPINE DENSITY ON CORTICAL PYRAMIDAL NEURONS IN ORGANOTYPIC SLICE CULTURES

In order to examine the effects of activity on spine production and/or maintenance in the cerebral cortex, we have compared the number of de ndritic spines on pyramidal neurons in slices of PO mouse somatosensor y cortex maintained in organotypic slice cultures under conditions tha t altered basal levels of spontaneous electrical activity. Cultures ch ronically exposed to 100 mu M picrotoxin (PTX) for 14 days exhibited s ignificantly elevated levels of electrical activity when compared to n eurons in control cultures. Pyramidal neurons raised in the presence o f PTX showed significantly higher densities of dendritic spines on pri mary apical, secondary apical, and secondary basal dendrites when comp ared to control cultures. The PTX-induced increase in spine density wa s dose dependent and appeared to saturate at 100 mu M. Cultures exhibi ting little or no spontaneous activity, as a result of growth in a com bination of PTX and tetrodotoxin (TTX), showed significantly fewer den dritic spines compared to cultures maintained in PTX alone. These resu lts demonstrate that the density of spines on layers V and VI pyramida l neurons can be modulated by growth conditions that alter the levels of spontaneous electrical activity. (C) 1994 John Wiley and Sons, Inc.