Acamprosate, MK-801, and ifenprodil inhibit neurotoxicity and calcium entry induced by ethanol withdrawal in organotypic slice cultures from neonatal rat hippocampus

Background: The antirelapse drug acamprosate has previously been reported to inhibit activating effects of polyamines on N-methyl-D-aspartic acid receptor (NMDAR) function. Because increased synthesis of polyamines has been suggested as a mechanism for potentiation of NMDAR function during ethanol withdrawal, we evaluated the effects of acamprosate, MK-801, and ifenprodil in a cell culture model of ethanol withdrawal-induced neurotoxicity. Methods: Organotypic hippocampal cultures from 8-day-old neonatal rats were maintained in vitro for 23 days before experimental use. The ethanol withdrawal model consisted of exposing cultures to ethanol (70-100 mM) for 4 days before being "withdrawn" into Calcium-Locke's buffer for 1 hr and then into minimal medium for 23 hr. Uptake of ⁴⁵CaCl₂ and propidium iodide by damaged cells was assessed 1 hr and 24 hr after the start of ethanol withdrawal, respectively. Additional studies examined effects of exposure to NMDA (50 μM) or spermidine (100 μM) on withdrawal-induced hippocampal damage. Last, these studies examined the ability of the sodium salt of acamprosate (Na-acamprosate, 200 μM), ifenprodil (50 μM), or MK-801 (30 μM) to inhibit neurotoxicity and ⁴⁵Ca²⁺ entry produced by these insults. Results: Ethanol withdrawal was associated with significantly greater toxicity and ⁴⁵Ca²⁺ entry, relative to controls. Exposure to spermidine and NMDA during ethanol withdrawal further increased neurotoxicity and ⁴⁵Ca²⁺ entry. Acamprosate, ifenprodil, and MK-801 almost completely prevented ethanol withdrawal-induced toxicity and ⁴⁵Ca²⁺ entry. Acamprosate also reduced spermidine-induced neurotoxicity during ethanol withdrawal but was ineffective against NMDA-induced toxicity or ⁴⁵Ca²⁺ entry at this time. Conclusions: The results support the contention that acamprosate, like ifenprodil, interacts with polyamines and that these compounds may be effective in reducing consequences of ethanol withdrawal. NMDAR activation is also strongly implicated in ethanol withdrawal neurotoxicity, but whether acamprosate causes any of these effects in this preparation directly via the NMDAR remains uncertain.