Passive and synaptic properties of hippocampal neurons grown in microcultures and in mass cultures

Abstract

1. We used whole cell recordings to compare passive membrane properties and synaptic properties of postnatal rat hippocampal neurons grown for 7-15 days in either conventional mass cultures or on physically restricted microisland cultures. Despite matching microisland and mass culture cell across several variables, there were significant differences between neurons in the two groups regarding passive membrane characteristics and synaptic properties. 2. Microisland neurons displayed significantly faster charging of the membrane capacitance than mass culture counterparts matched with microisland neurons for age, somal diameter, and transmitter phenotype. When we used a two-compartment equivalent circuit model to quantify this result, microisland neurons displayed approximately half the distal capacitance of mass culture neurons. These data suggest that microisland neurons elaborate less extensive neuritic arborizations than mass culture neurons. 3. Evoked synaptic responses were enhanced on microislands compared with mass cultures. Excitatory and inhibitory autaptic currents were more frequent and displayed larger amplitudes on single-neuron microislands than in matched mass culture neurons. 4. In recordings from pairs of neurons in the two environments, we observed a significantly higher probability of obtaining a monosynaptic response on two-neuron microislands than in matched mass culture pairs (85% vs. 42%). Evoked excitatory postsynaptic currents were also significantly larger in the microisland environment, with evoked excitatory synaptic currents from two-neuron microislands exhibiting a mean amplitude 20-fold larger than mass culture monosynaptic responses. 5. The differences in evoked synaptic responses were not reflected in differences in the amplitude or frequency of spontaneous miniature excitatory postsynaptic currents (mEPSCs). Analysis of mEPSC rise times, decay times, and peak amplitudes within individual cells suggests that electrotonic filtering is not an important contributor to the variability of peak amplitudes and decay times of synaptic currents in cells of either culture environment. However, composite data across neurons in both cultures reveal a significant correlation between mEPSC rise and decay times. 6. Out results suggest that the microisland preparation may be a useful tool for exploring factors that influence synapse formation and development. Additionally, the preparation is a particularly convenient model for the study of single-neuron-mediated synaptic events.

In VitroSynaptogenesis between the Somata of IdentifiedLymnaeaNeurons Requires Protein Synthesis But Not Extrinsic Growth Factors or Substrate Adhesion Molecules

“…Various researchers interested in synapse formation have resorted, therefore, to simple cell culture techniques in which individually definable neurons can be extracted from the nervous system and studied in isolation under controlled experimental conditions (Dagan and Levitan, 1981;Bulloch and Syed, 1992;Haydon and Drapeau, 1995). Notwithstanding the fact that these cell culture conditions are artificial and may not reflect those that occur naturally, these studies have provided insights into cellular mechanisms that are fundamental to synapse formation (Chow and Poo, 1985;Bulloch and Syed, 1992;Hawver and Schacher, 1993;Catarsi et al, 1995;Haydon and Drapeau, 1995;Mennerick et al, 1995).…”

Extracellular acidosis increases neuronal cell calcium by activating acid-sensing ion channel 1a

“…Cultures of hippocampal neurons from mice with a disrupted ASIC1 gene and from wild-type littermates were prepared from postnatal day 1-2 pups as described (28). Cultures were maintained at 37°C with 5% CO 2 in air for 10-14 days before use in the experiments.…”

A Specific Role for Ca2+-Dependent Adenylyl Cyclases in Recovery from Adaptive Presynaptic Silencing

“…Hippocampal cultures were prepared as described previously (Mennerick et al, 1995). In brief, dissected postnatal (postnatal days 0 -3) rat or mouse hippocampi were incubated with papain and then mechanically dissociated and plated at either ϳ650 cells/mm 2 as "mass" cultures or 100 cells/mm 2 on microdots of collagen as "microisland" cultures.…”

“…The whole-cell pipette solution contained the following (in mM): 140 K-gluconate, 0.5 CaCl 2 , 5 EGTA, and 10 HEPES, pH 7.25. For synaptic recordings, cells were stimulated with 1.5 ms pulses to 0 mV from Ϫ70 mV to evoke transmitter release (Mennerick et al, 1995).…”