Dopamine and Serotonin Receptors Cooperatively Modulate Pacemaker Activity of Intestinal Cells of Cajal.

The neurotransmitters dopamine and serotonin control the peristaltic movement of the gut that consists of propagating waves of rhythmic contraction and relaxation. While intestinal cells of Cajal (ICC) serve as a pacemaker in the gut, the effect of dopamine on the pacemaker activity of ICC remains unknown. Here, we report that together with serotonin receptors, the dopamine receptor D₂ contributes to maintaining [Ca²⁺]i oscillations in ileum ICC.

Serotonin augments gut pacemaker activity via 5-HT3 receptors.

Serotonin (5-hydroxytryptamine: 5-HT) affects numerous functions in the gut, such as secretion, muscle contraction, and enteric nervous activity, and therefore to clarify details of 5-HT's actions leads to good therapeutic strategies for gut functional disorders. The role of interstitial cells of Cajal (ICC), as pacemaker cells, has been recognised relatively recently. We thus investigated 5-HT actions on ICC pacemaker activity.

Calcium-associated mechanisms in gut pacemaker activity.

A considerable body of evidence has revealed that interstitial cells of Cajal (ICC), identified with c-Kit-immunoreactivity, act as gut pacemaker cells, with spontaneous Ca(2+) activity in ICC as the probable primary mechanism. Namely, intracellular (cytosolic) Ca(2+) oscillations in ICC periodically activate plasmalemmal Ca(2+)-dependent ion channels and thereby generate pacemaker potentials. This review will, thus, focus on Ca(2+)-associated mechanisms in ICC in the gastrointestinal (GI) tract, including auxiliary organs.

Pacemaker phase shift in the absence of neural activity in guinea-pig stomach: a microelectrode array study.

Gastrointestinal (GI) motility is well organized. GI muscles act as a functional syncytium to achieve physiological functions under the control of neurones and pacemaker cells, which generate basal spontaneous pacemaker electrical activity. To date, it is unclear how spontaneous electrical activities are coupled, especially within a micrometre range.

Tyrosine kinase inhibitors and ATP modulate the conversion of smooth muscle L-type Ca2+ channels toward a second open state.

Properties of smooth and cardiac L-type Ca2+ channels differ prominently in several physiological aspects, including sympathetic modulation. To assess the possible underlying mechanisms, we applied the whole cell patch-clamp technique to guinea pig detrusor smooth muscle cells, in which only L-type Ca2+ channel currents are observed in practice. During depolarization to large positive potentials, the conformation of the majority of L-type Ca2+ channels is converted from the normal (O1) to a second open state (O2), which undergoes little inactivation during depolarization.

Sulphonylurea receptors differently modulate ICC pacemaker Ca2+ activity and smooth muscle contractility.

Appropriate gastrointestinal motility is essential to properly control the body energy level. Intracellular Ca2+ ([Ca2+]i) oscillations in interstitial cells of Cajal (ICCs; identified with c-Kit immunoreactivity) are considered to be the primary mechanism for the pacemaker activity in gastrointestinal motility. In the present study, RT-PCR examinations revealed predominant expression of the type 1 isoform of sulphonylurea receptors (SUR1) in ICCs of the mouse ileum, but expression of SUR2 was predominant in smooth muscle.

[Design and development of cerebrospinal fluid container].

The cerebrospinal fluid container is a device for storage of medicaments. By means of surgical operation, a ventricle catheter can be embedded in the ventricle of the brain. This safe and reliable device provides for neurosurgeons a new method of intracranical therapy and reestablishment of the circulating passage of the cerebrospinal fluid.

Involvement of ryanodine receptors in pacemaker Ca2+ oscillation in murine gastric ICC.

Using a cell cluster preparation from the stomach smooth muscle tissue of mice, we measured intracellular Ca(2+) oscillations in interstitial cells of Cajal (ICCs) in the presence of nifedipine. Pacemaker [Ca(2+)](i) activity in ICCs was significantly suppressed by caffeine application and restored after washout. Application of either ryanodine or FK-506 terminated the pacemaker [Ca(2+)](i) activity irreversibly.

Co-contribution of IP3R and Ca2+ influx pathways to pacemaker Ca2+ activity in stomach ICC.

Intracellular Ca2+ oscillations in interstitial cells of Cajal (ICCs) are thought to be the primary pacemaker activity in the gut. In the present study, the authors prepared small tissues of 100-to 300-microm diameter (cell cluster preparation) from the stomach smooth muscle (including the myenteric plexus) of mice by enzymatic and mechanical treatments. After 2 to 4 days of culture, the intracellular Ca2+ concentration ([Ca2+]i) was measured.

Presynaptic activity and Ca2+ entry are required for the maintenance of NMDA receptor-independent LTP at visual cortical excitatory synapses.

We have shown that some neural activity is required for the maintenance of long-term potentiation (LTP) at visual cortical inhibitory synapses. We tested whether this was also the case in N-methyl-d-aspartate (NMDA) receptor-independent LTP of excitatory connections in layer 2/3 cells of developing rat visual cortex. This LTP occurred after 2-Hz stimulation was applied for 15 min and always persisted for several hours while test stimulation was continued at 0.

[Simulation of effects to tropospheric ozone over South East Asia and south China from biomass burning].

The ozone variation led by biomass burning in Spring 2000 over South East Asia and South of China region was simulated with a combined regional climate model and atomospheric chemical model. It was found that ozone was added by the pollutant of biomass burning both over source area and down wind area. The ozone of lower troposphere was affected by the pollutant over source area, so did the ozone in middle troposphere over down wind area.