Differential DAergic Control of D1 and D2 Receptor Agonist Over Locomotor Activity and GABA Level in the Striatum

The basal ganglia, a group of nuclei, are associated with a variety of functions, including motor control. The striatum, which is the major input station of the basal ganglia in the brain, is regulated in part by dopaminergic input from the substantia nigra. The striatum is made up 96% of medium spiny neurons which are GABAergic cells. GABAergic cells are known to contain DA receptors which divide into two main branches- the D1 receptor (D1R)-expressing direct pathway and the D2 receptor (D2R)-expressing indirect pathway. The role of these two efferent pathways has not been clear in control of motor behaviors. To establish the influence of the different DA subtypes on GABAergic systems in the striatum, D1 selective receptor agonist (SKF 38393) and D2 selective receptor agonist (Quinpirole) were administered to mice. SKF 38393 and quinpirole were administered intraperitoneally in a volume of 0, 1, 5, 10 (mg/kg) and motor activity was assessed for 60 min immediately after the injection of DA agonists. Mice were sacrificed after behavioral test and the striatum in the brain were dissected for analysis of GABA level with HPLC. Both SKF 38393 and quinpirole dose-dependently increased locomotor activity but, GABA level in the striatum was clearly different in two agonists. These findings provide insight into the selective contributions of the direct and indirect pathways to striatal GABAergic motor behaviors.

The Central and Peripheral Production of Pro-inflammatory Cytokine, IL-1b after Immune and Stress Stimulation in Rats

Interleukin-1beta (IL-1beta), one of the pro-inflammatory cytokines, acts as an endogenous pyrogen and is an important mediator of behavioral and physiological responses to immune stimulation as well as exposure to stressors. The objective of the present study was to examine the pattern of central or peripheral IL-1beta response to lipopolysaccharide (LPS) or exposure to the foot shock stress (FS) in rats. After treatment of LPS (100microgram/kg) or exposure to the FS [ten times (0.8 mA) foot shocks for 5 sec each and 90 sec interval], body temperature and IL-1beta levels in plasma, spleen and brain were measured. Both LPS and FS stimuli elicited increased body temperature but showed different patterns of peripheral IL-1beta levels. LPS produced a widespread increase in IL-1beta levels in the plasma, spleen and brain, whereas FS produced a significant increase in IL-1beta levels only in the brain regions but not in plasma and spleen. The present study suggests that IL-1beta is, centrally or peripherally in different patterns, regulated by immune stimulation or exposure to stressors and IL-1beta plays an important role in mediating responses of sickness-like behaviors induced by immune stimuli or stressors.