Yasuyuki Ueki

Purification and structural analysis of hippocampal cholinergic neurostimulating peptide

Hippocampal soluble fraction stimulates acetylcholine (AcCho) synthesis of medial septal nuclei in explant culture system. This stimulating activity was purified from 10-12-day-old rat hippocampus. During purification, the activity was separated into two fractions and a previously unreported peptide was purified from one fraction. The structure of this novel peptide is acetyl-Ala-Ala-Asp-Ile-Ser-Gln-Trp-Ala-Gly-Pro-Leu and we designated it as hippocampal cholinergic neurostimulating peptide (HCNP). Synthesized HCNP and de-acetylated HCNP (free-HCNP) stimulated AcCho synthesis of medial septal nuclei culture, in a dose-dependent manner, but not cultures of corpus striatum or anterior spinal cord. Mean half-maximal concentrations of HCNP and free-HCNP in AcCho synthesis of medial septal nuclei culture were 1.0 +/- 0.3 x 10(-10) M and 1.0 +/- 0.6 x 10(-11) M, respectively. Affinity purified polyclonal antibody to the free-HCNP neutralized the activity of crude hippocampal extract, as well as synthetic HCNP and free-HCNP. These observations suggested that HCNP was present in the hippocampal extract and was involved in development of specific cholinergic neuron in central nervous system.

Release of pentobarbital-induced depression of metabolic rate during bilateral ischemia in the gerbil brain

Treatment of gerbils with 40 mg/kg of pentobarbital (i.p.) reduced the metabolic rate in the hippocampus and cerebral cortex by approximately 60%. However, the depression of metabolic rate was lost within 40 s of ischemia and further, pentobarbital delayed but did not prevent the depletion of energy metabolites observed in the ischemic brain.

Delayed hypometabolism induced by bilateral ischemia in the gerbil: Regional metabolic thresholds

The common carotid arteries were occluded in gerbils for 5 min and the metabolic rate was estimated by measuring the loss of high-energy phosphate equivalents at 4 days of reperfusion in the cerebral cortex, hippocampus, and striatum. Metabolites values at 4 days of reperfusion were not different from those of controls with the exception of glycogen, which was significantly elevated in the hippocampus. The metabolic rate, as determined by the “closed-box” method at 4 days of reflow, was decreased by more than 50% in all three regions after 5 min of bilateral ischemia. The ischemie time necessary to elicit the hypometabolic response at 4 days of reflow was 2, 3, and 4 min for the striatum, hippocampus, and cortex, respectively. It is suggested that delayed postischemic hypometabolism may be a component of an adaptive process which counteracts, to varying degrees, the deleterious effects of ischemia depending on the region examined.