Role of nicotinic acetylcholine receptors in the regulation of kainic acid-induced hippocampal cell death in mice.

Kainic acid (KA) is a well-known excitatory, neurotoxic substance. In mice, morphological damage of hippocampus induced by KA administered intracerebroventricularly (i.c.v.) was markedly concentrated on the CA3 pyramidal neurons. In the present study, the possible role of nicotinic acetylcholine receptors (nAchRs) in hippocampal cell death induced by KA (0.1 microg) administered i.c.v. was examined. Methyllycaconitine (MC; nAchRs antagonist, 20 microg) attenuated KA-induced CA3 pyramidal cell death. KA increased immunoreactivities (IRs) of phorylated extracellular signal-regulated kinase (p-ERK; at 30 min), p-CaMK II (at 30 min), c-Fos (at 2 h), c-Jun (at 2 h), glial fibrillary acidic protein (GFAP at 1 day), and the complement receptor type 3 (OX-42; at 1 day) in hippocampal area. MC attenuated selectively KA-induced p-CaMK II, GFAP and OX-42 IR in the hippocampal CA3 region. Our results suggest that p-CaMK II may play as an important regulator responsible for the hippocampal cell death induced by KA administered i.c.v. in mice. Reactive astrocytes, which was meant by GFAP IR, and activated microglia, which was meant by OX-42 IR, may be a good indicator for measuring the cell death in hippocampal regions by KA-induced excitotoxicity. Furthermore, it is implicated that niconitic receptors appear to be involved in hippocampal CA3 pyramidal cell death induced by KA administered i.c.v. in mice.