Rearrangement of centromeric satellite DNA in hippocampal neurons exhibiting long-term potentiation.

In situ hybridization in conjunction with three-dimensional reconstruction was used to examine the topology of satellite DNA (sDNA) sequences in hippocampal CA1 neurons. In slices fixed immediately after preparation, 4-5 signals/nucleus were detected in CA1, CA3 and dentate neurons. 70-80% of 154 neurons examined in these 3 areas displayed all signals at the nuclear periphery. In the remaining fraction of neurons, sDNA signals were divided between the nucleolus and the nuclear periphery. sDNA signals were consistently localized to the nuclear midplane. Slices left to equilibrate in artificial cerebral spinal fluid for 1 h, in the absence of potentiation, exhibited a significant increase in the total number of signals/nucleus in CA1 and dentate neurons. This increase in the number of signals occurred in both nucleolar and peripheral compartments, with the number of the nucleolar compartment nearly doubling. The total number of signals/nucleus was found to be consistently reduced in tetanized CA1 neurons (4.89 +/- 0.09 signals/nucleus, n = 195, P less than 0.05) as compared to neurons from unpotentiated slices (5.27 +/- 0.10 signals/nucleus, n = 81). A similar decrease in the total number of signals/nucleus was also observed in CA1 neurons exposed to N-methyl-D-aspartate (NMDA), from 5.27 +/- 0.10 signals/nucleus (n = 81) to 5.00 +/- 0.08 signals/nucleus (n = 215, P less than 0.05). In contrast, dentate neurons, employed as internal controls, did not exhibit any change in number and compartmentalization of sDNA signals.(ABSTRACT TRUNCATED AT 250 WORDS)