Ginsenoside Rg 1 prevents histaminergic modulation of rat adaptive behavior from elevation of ambient temperature

Abstract

Effects of ginsenoside Rg 1 (Rg 1) on histaminergic modulation of both adaptive behavior and thermoregulation were investigated at high ambient temperature. Continuous infusion of Rg 1 using an osmotic minipump into the rat third cerebroventricle attenuated anorexia induced by elevation of ambient temperature from 21°C to 31°C. Intraperitoneal injection of α-fluoromethylhistidine (FMH), a specific suicide inhibitor of a histamine synthesizing decarboxylase enzyme, also prevented the anorexia induced by elevated temperature. The ratio of water intake to food intake, which showed no change on the first day after elevation of room temperature, was not influenced by treatment of either FMH or Rg 1. Rectal temperature, which was normally maintained at a constant level even after shifting ambient temperature from 21°C to 31°C, elevated after FMH treatment. The Rg 1 infusion, however, maintained rectal temperature normally at 31°C. Hypothalamic histamine content increased in response to elevation of ambient temperature. The Rg 1 infusion maintained constant histamine level against elevation of environmental temperature. Under the heated condition FMH reduced hypothalamic histamine. These findings suggest that Rg 1 may modulate rat adaptive behavior by blockade of temperature-related information into the hypothalamic histamine neurons.