Neurosteroid modulation of GABA IPSCs is phosphorylation dependent.

The neurosteroid 3alpha-hydroxy-5alpha-pregnan-20-one (allopregnanolone) facilitates GABA(A) receptor-mediated ionic currents via allosteric modulation of the GABA(A) receptor. Accordingly, allopregnanolone caused an increase in the slow decay time constant of spontaneous GABA-mediated IPSCs in magnocellular neurons recorded in hypothalamic slices. The allopregnanolone effect on IPSCs was inhibited by a G-protein antagonist as well as by blocking protein kinase C and, to a lesser extent, cAMP-dependent protein kinase activities.

Effects of continuous and repetitive administration of a potent analog of GH-RH(1-30)-NH2 on the GH release in rats treated with monosodium glutamate.

To assess the efficacy of a potent GH-releasing hormone (GH-RH) analog (D-Ala2,Nle27,Gaba30-GH-RH-(1-30)-amide) in the treatment of GH deficiency, we investigated the effects of chronic administration of this analog (A-495) on growth responses in monosodium glutamate (MSG)-lesioned rats. Basal serum GH concentrations, GH responses to bolus injections of GH-RH, as well as acceleration of body gain and linear growth were compared after long-term continuous and repetitive administration of A-495. The effects of continuous and repetitive administration of the analog on GH responses in vitro were also compared using the superfused pituitary cell system method.

Effects of continuous and repetitive administration of a potent analog of GH-RH(1-30)NH2 on the GH release in rats.

We examined the desensitization and/or sensitization phenomenon in the pituitary GH responsiveness induced by continuous infusion and multiple pulses at different frequencies of a potent GH-RH analog [D-Ala2, Leu15, Nle27, GABA30-GH-RH(1-30)amide]. Further, we investigated the correlation between doses and GH responses, as well as between pulse frequency and GH responses in male rats in vivo and in vitro. Long-term, continuous administration was attained by osmotic minipumps releasing low and high doses of the analog for 14 days.