Carbon monoxide involved in modulating HCO3- secretion in rat duodenum.

We examined the effect of the tricarbonyl-dichlororuthenium (II) dimer (CORM-2), a carbon monoxide (CO) donor, on duodenal HCO(3)(-) secretion in rats and investigated whether endogenous CO produced by heme oxygenase (HO) is involved in the regulation of this secretion. Under urethane anesthesia, a duodenal loop was perfused with saline, and HCO(3)(-) secretion was measured at pH 7.0 using a pH stat method. CORM-2, biliverdin, FeCl(2), or ruthenium (III) chloride hydrate (RuCl(3)) was applied to the loop for 5 min. The mucosal application of CORM-2 dose-dependently increased HCO(3)(-) secretion, whereas neither RuCl(3), FeCl(2), nor biliverdin had an effect. The stimulatory effect was significantly attenuated by indomethacin but not N(G)-nitro-L-arginine methyl ester. The application of CORM-2 increased the mucosal prostaglandin (PG) E(2) content of the duodenum. The acid-induced HCO(3)(-) response was markedly inhibited by indomethacin and Sn(IV) protoporphyrin IX dichloride (SnPP; an inhibitor of HO) but not Cu(II) protoporphyrin dichloride, and the inhibitory effect of SnPP was significantly reversed by pretreatment with hemin, a substrate of HO. Perfusion of the duodenal loop with 100 mM HCl for 2 h caused a few hemorrhagic lesions in the mucosa, and this response was significantly worsened by the prior administration of SnPP and indomethacin. The expression of HO-1 but not HO-2 protein was up-regulated in the duodenum after the acid treatment. These results suggest that CO, generated endogenously or exogenously, stimulates HCO(3)(-) secretion in the duodenum, and this effect is mediated by endogenous PGs. It is assumed that HO/CO plays a role in maintaining the integrity of the duodenal mucosa.

Prostaglandin EP receptor subtypes involved in regulating HCO(3)(-) secretion from gastroduodenal mucosa.

Gastroduodenal HCO(3)(-) secretion is a key process that aids in preventing acid-peptic injury. The HCO(3)(-) secretion in rats and mice was increased in response to PGE(2) as well as mucosal acidification, the latter response occurring with a concomitant enhancement of mucosal PG production. The duodenal responses to PGE(2) and acid were decreased in mice lacking EP3 receptors and reduced by coadministration of an EP3 or EP4 antagonist in rats, complete inhibition being observed when the EP3 and EP4 antagonists were given together. By contrast, the gastric responses disappeared in EP1-knockout mice and were prevented by an EP1 antagonist but not other EP antagonists. Furthermore, duodenal HCO(3)(-) secretion was stimulated by the EP3 and EP4 agonists, whereas gastric HCO(3)(-) secretion was increased only by the EP1 agonist. In addition, the HCO(3)(-) stimulatory effect of sulprostone (an EP1/EP3 agonist) in the duodenum was inhibited by verapamil, a Ca(2+) antagonist, and enhanced by isobutyl- methylxanthine, a phosphodiesterase (PDE) inhibitor, but the response in the stomach was inhibited by verapamil and not affected by isobutylmethylxanthine. In the mouse duodenum but not stomach, the response to PGE(2) was potentiated by both vinpocetine (a PDE1 inhibitor) and cilostamide (a PDE3 inhibitor). These results suggest that the HCO(3)(-) stimulatory effect of PGE(2) in the duodenum is mediated by both EP3 and EP4 receptors, being coupled intracellularly with Ca(2+) and cAMP, while that in the stomach is mediated by EP1 receptors, coupled with Ca(2+). In addition, both PDE1 and PDE3 are involved in the regulation of duodenal HCO(3)(-) secretion.

In vivo imaging of the dendritic arbors of layer V pyramidal cells in the cerebral cortex using a laser scanning microscope with a stick-type objective lens.

In the field of neuroscience, low-invasive in vivo imaging would be a very useful method of monitoring the morphological dynamics of intact neurons in living animals. At present, there are two widely used in vivo imaging methods; one is the two-photon microscope method, and the other is the fiber optics method. However, these methods are not suitable for the in vivo imaging of deeper subcortical structures. In our study, we have developed a novel method for the in vivo imaging of pyramidal neurons in layer V of the cerebral cortex, utilizing a MicroLSM system and a stick-type objective lens that can be directly inserted into the target tissue. By using this method, we succeeded in obtaining clear images of pyramidal neurons in layer V of the cerebral cortex under a low-invasive condition. The MicroLSM system is a useful and versatile in vivo imaging system that will be applicable not only to the brain but also to other organs.