Shuhei Niiyama

Neuroprotective mechanisms of lidocaine against in vitro ischemic insult of the rat hippocampal CA1 pyramidal neurons.

To compare neuroprotective effects of lidocaine and procaine against ischemic insult, intracellular recordings were made from rat hippocampal CA1 pyramidal neurons in slice preparations. Superfusion of the slices with oxygen- and glucose-deprived medium (in vitro ischemia) produced a rapid depolarization 6 min from the onset. When oxygen and glucose were reintroduced, the membrane depolarized further until it reached 0 mV, and thereafter the membrane showed no functional recovery. Pretreatment with lidocaine (10 microM), but not procaine (50 microM), restored the membrane potential after the reintroduction of oxygen and glucose. Lidocaine, compared to procaine, significantly inhibited the reduction in both tissue ATP content and flavoprotein fluorescence during and after in vitro ischemia. Under electron microscopy, only lidocaine well preserved the structure of mitochondria in the CA1 pyramidal cell body. Extracellular recordings revealed that procaine reduced the field postsynaptic potential whereas lidocaine augmented it. Both drugs reduced the presynaptic volley dose-dependently. Neither lidocaine nor procaine significantly affected a rapid rise of the intracellular Ca2+ level produced by in vitro ischemia in the CA1 region. All the results suggest that the neuroprotective lidocaine action is due to the protection of the mitochondria to maintain the tissue ATP content during and after in vitro ischemia.

Bupivacaine, but not tetracaine, protects against the in vitro ischemic insult of rat hippocampal CA1 neurons.

Neuroprotective actions of local anesthetics, bupivacaine and tetracaine, against the irreversible membrane dysfunction induced by in vitro ischemia were investigated. Intracellular recordings were made from hippocampal CA1 neurons in rat brain slice preparations. Oxygen and glucose deprivation (in vitro ischemia) produced a rapid depolarization after approximately 5 min of exposure. When oxygen and glucose were reintroduced, the membrane depolarized further and reached at 0 mV: the membrane showed no functional recovery (irreversible membrane dysfunction). Pretreatment with tetracaine or bupivacaine significantly prolonged the latency of rapid depolarization. Bupivacaine, but not tetracaine, restored the membrane potential after the reintroduction of oxygen and glucose. Tetracaine and bupivacaine depressed both field postsynaptic potentials and presynaptic volleys. The drugs also reduced the dV/dt of Ca(2+)-dependent spikes and the rapid rise of [Ca(2+)](i) induced by in vitro ischemia. Compared with tetracaine, bupivacaine markedly suppressed the resting K(+) conductance and the ATP-sensitive and Ca(2+)-dependent K(+) conductances. Moreover, in the presence of tetraethylammonium (TEA), a majority of CA1 neurons impaled with Cs acetate-filled electrodes showed complete or partial recovery of the membrane potential after reintroducing oxygen and glucose. These results suggest that the neuroprotective action of bupivacaine is mainly due to the suppression of the K(+) conductances.

Intraperitoneal adipose tissue is strongly related to survival rate in a mouse cecal ligation and puncture model

Cecal ligation and puncture (CLP) models exhibiting polymicrobial sepsis are considered as the gold standard in sepsis research. However, despite meticulous research being conducted in this field, only few treatment drugs are available, indicating that CLP sepsis models do not completely mimic human sepsis models. The greatest flaw in CLP models is abscess formation because the localization of inflammation caused by abscess formation increases the survival rate. Therefore, by resecting intraperitoneal adipose tissue, we developed a mouse CLP model wherein abscess formation was unlikely. Survival rates at 7 days postoperatively were compared using the Kaplan–Meier method for an intraperitoneal adipose tissue resection group (resection group, n=34), an intraperitoneal adipose tissue non‐resection group (non‐resection group, n=35) and a sham group (n=10). Results indicated that the survival rate was significantly higher in the non‐resection group compared with the resection group. Intraperitoneal macroscopic findings in the non‐resection group revealed the localization of inflammation caused by abscesses formation covered in adipose tissue. The survival rate for the sham group was 100%. Measurement of interleukin 6 (IL‐6) indicated that during the 12 h after the creation of the CLP model, the median level of IL‐6 was 1300 (552–3000) pg ml−1 in the non‐resection group (n=19) and 3000 (1224–8595) pg ml−1 in the resection group (n=19). Meanwhile, for the sham group, IL‐6 values were below measurement sensitivity in most cases (9/10 mice). Thus our results suggest that, in CLP models, intraperitoneal adipose tissue has an important role in abscess formation and is strongly related to the survival rate.