Protective Effects of a Rhodiola Crenulata Extract and Salidroside on Hippocampal Neurogenesis against Streptozotocin-Induced Neural Injury in the Rat

Previously we have demonstrated that a Rhodiola crenulata extract (RCE), containing a potent antioxidant salidroside, promotes neurogenesis in the hippocampus of depressive rats. The current study was designed to further investigate the protective effect of the RCE on neurogenesis in a rat model of Alzheimer's disease (AD) induced by an intracerebroventricular injection of streptozotocin (STZ), and to determine whether this neuroprotective effect is induced by the antioxidative activity of salidroside. Our results showed that pretreatment with the RCE significantly improved the impaired neurogenesis and simultaneously reduced the oxidative stress in the hippocampus of AD rats. In vitro studies revealed that (1) exposure of neural stem cells (NSCs) from the hippocampus to STZ strikingly increased intracellular reactive oxygen species (ROS) levels, induced cell death and perturbed cell proliferation and differentiation, (2) hydrogen peroxide induced similar cellular activities as STZ, (3) pre-incubation of STZ-treated NSCs with catalase, an antioxidant, suppressed all these cellular activities induced by STZ, and (4) likewise, pre-incubation of STZ-treated NSCs with salidroside, also an antioxidant, suppressed all these activities as catalase: reduction of ROS levels and NSC death with simultaneous increases in proliferation and differentiation. Our findings indicated that the RCE improved the impaired hippocampal neurogenesis in the rat model of AD through protecting NSCs by its main ingredient salidroside which scavenged intracellular ROS

Intrastriatal injection of choline accelerates the acquisition of positively rewarded behaviors

The prediction was made that by increasing the synthesis of striatal acetylcholine, through local injection of its precursor choline, the acquisition of a lever-pressing response in two different autoshaping situations would be accelerated. In the first experiment, choline was injected into the striatum or parietal cortex of rats immediately after dipper training; 24 h later and during 5 consecutive days the animals were submitted to an autoshaping procedure of the operant kind. In the second experiment, choline was administered to the same regions shortly after each of three classical-operant autoshaping sessions; during the next two sessions, autoshaping contingencies of the operant kind were in effect. In both experiments choline injection into the striatum induced a marked facilitation of acquisition of the conditioned responses, although cortical injection of choline produced a milder improvement only in the first experiment. These results indicate that striatal cholinergic activity is, indeed, involved in the early phases of positively reinforced learning. © 1993