Effect of somatostatin on the mass accumulation of inositol-1,4,5-trisphosphate in rat hypothalamus, striatum, frontoparietal cortex and hippocampus

Abstract

Somatostatin-14 (SS) si gnificantly increased inositol-l,4,5-trisphosphate (IP3) accumulation in rat hypothalamic, striatal, frontoparietal cortical and hippocarapal slices. However, this stimulation of IP 3 accumulation by SS was highest in the frontoparietal cortex and hippocampus. The effect was already significant with 0.01/~M in the frontoparietal cortex (P < 0.05) and hippocampus (P < 0.05) and the maximal accumulation was evident with 0.1/tM SS, in all areas studied. A concentration of 1/~M SS, lacked this effect in hypothalamus and striatum. SS rapidly increased IP 3 accumulation in all brain areas studied. This effect was maximal at 15 s of incubation and decreased subsequently. At 60 s incubation, levels were still elevated in frontoparietal cortex and hippocampus but had returned to basal values in hypothalamus and striatum. Somatostatin-28 (SS-28) and the SS analogues, D-Trp8-D-Cys 14 and SMS 201-995, also significantly stimulated IP~ accumulation although the effect of SMS 201-995 was greater than that of SS in the striatum in comparison with controls (P < 0.001 and P < 0.01, respectively). These results suggest that SS action at the hypothalamus, striatum, frontoparietal cortex and hippocampus is mediated at least in part by the accumulation of IP 3, which may initiate intracellular processes responsible for some biological SS effects.

Diazepam Attenuation of Somatostatin Binding and Effect of Somatostatin on Accumulation of Inositol 1,4,5-Trisphosphate in the Rat Frontoparietal Cortex

“…-10 Ϫ8 M) on IP 3 accumulation in the rat brain (Muñoz-Acedo et al 1995). In agreement with other studies (Lachowicz et al 1994), the stimulatory effect of SRIF on IP 3 was maximum at 10 Ϫ7 M in all rat brain areas studied (Muñoz-Acedo et al 1995).…”

“…Diazepam had no effect on IP 3 accumulation in the frontoparietal cortex, coinciding with other studies (Raskovsky and Medina 1992). SRIF increases the IP 3 accumulation in the control rats in agreement with reports by other authors (Lachowicz et al 1994) and our own (Muñoz-Acedo et al 1995). Recent studies suggest that all five human SRIF receptors ex- pressed in COS-7 cells are coupled to activation of phosphoinositide (PI)-specific PLC-␤ (Akbar et al 1994).…”

“…In agreement with other studies (Lachowicz et al 1994), the stimulatory effect of SRIF on IP 3 was maximum at 10 Ϫ7 M in all rat brain areas studied (Muñoz-Acedo et al 1995). Therefore, subsequent studies were carried out at 10 Ϫ7 M SRIF.…”

Effect of Chronic Ethanol Exposure on Inositol Trisphosphate Receptors in WB Rat Liver Epithelial Cells

“…The cells were washed with PBS and lysed with 1 ml of 10% trichloracetic acid (TCA). The lysates were centrifuged and the supernatants were extracted five times with two volumes of water-saturated diethyl ether and neutralized by the addition of SO p1 0.3 M EDTA and 9.6 p1 0.6 M NaHCO, (Munoz-Acedo and Izquierdo-Claros, 1995). The samples were then applied to columns containing 1 ml of Bio-Rad AG 1-X8 anion exchange resin (formatc form, 200-400 mesh), and inositol phosphates were separated by stepwise elution, as described previously (Joseph et al, 1989).…”

“…In contrast to the effects of acute ethanol treatment, an enhanced Ca2+ mobilization in response to agonists has been observed in hepatocytes isolated from ethanol-fed rats (Higashi and Hoek, 1991b;Nomura et al, 1994). This enhancement was not due to an increase in agonistmediated IP, generation (Hoek et al, 1990).…”