Experiment-time affects the cognitive behavior in aged Sprague-Dawley rats / 生理学报

In order to investigate if the experiment-time affects cognitive performance in aged rats in different learning and memory behavioral tests, the aged Sprague-Dawley (SD) rats were divided into two groups randomly and subjected to open field test, Morris water maze test and social discrimination test. The experiment of one group was conducted in 8:00 - 11:00 AM (AM group), and the other group in 15:00 - 18:00 PM (PM group). PM group exhibited higher locomotor activity than AM group in the open field test. Compared with AM group rats, PM group rats had significantly shorter swimming distance and escape latency to find the platform in Morris water maze training session, but no significant difference in the swimming velocity was observed between the two groups. And in probe-test, PM group spent more time in target quadrant than AM group. These results revealed that PM group showed better spatial learning and memory abilities than AM group. However, there was no significant difference between the two groups in social investigation index in social discrimination test. These results show that experiment-time may affect cognitive performance in Morris water maze but not in social discrimination task in aged rats. And the results indicate that experiment-time affects cognitive performance of aged rats selectively in different learning and memory behavioral tasks.

Inhibitory effect of anterior cingulate cortex on spontaneous activity of thalamic ventrobasal nucleus neurons / 生理学报

The purpose of this study was to investigate the influence of electrical stimulation of anterior cingulate cortex (ACC) on spontaneous activity of neurons in thalamic ventrobasal nucleus (VB). Experiments were performed on 12 male Sprague-Dawley rats weighing 250-310 g (4-5 months old). According to Paxinos and Watson's coordinate atlas of the rat, the frontal and parietal cortical areas were exposed by craniotomy, the recording electrodes were then inserted into the VB (P 2.4-4.1 mm, R 2.0-3.5 mm, H 5.2-6.8 mm) and the stimulating electrodes into the ACC (A 1.1-3.0 mm, R 0.0-1.0 mm, H 1.5-2.4 mm). Single-unit activities were recorded extracellularly in the VB by glass micropipettes (impedance 3-8 MOmega) filled with 0.5 mol/L sodium acetate solution containing saturated Fast Green. To study the effects of ACC activation on the spontaneous activities of VB cells, single electrical pulse (0.2 ms duration) was delivered to the ACC by a concentric bipolar stainless steel electrode (0.32 mm outer diameter). An effective ACC stimulation was determined for each VB neuron by gradually increasing the current intensity from 0.1 mA until either a significant change in the spontaneous activity of the VB neuron was observed, or the current intensity reached 0.4 mA. The results showed that ACC stimulation significantly suppressed the spontaneous activities in 12 out of 53 VB neurons (22.6%). (1) After the stimulation was delivered to ACC, the spontaneous activities of different VB neurons were totally suppressed for different time span. (2) There was obvious dose-effect relevance between ACC stimulation intensity and their inhibitory effect. The duration of complete inhibition was prolonged with the increases in the intensity and number of stimulation impulses in ACC. (3) The stimulation in the ACC depressed the spontaneous activities of VB neurons in different forms and this inhibition exhibited an accumulative effect. All these results indicate that the stimulation of ACC exerts an inhibitory influence on the spontaneous activities of VB neurons.

A novel derivative of xanomeline improved memory function in aged mice / 神经科学通报·英文版

<p><b>OBJECTIVE</b>To characterize the function of a new xanomeline-derived M1 agonist, 3-[3-(3-florophenyl-2-propyn-1-ylthio)-1,2,5-thiadiazol-4-yl]-1,2,5,6- tetrahydro-1-methylpyridine Oxalate (EUK1001), the acute toxicity and the effects on synaptic plasticity and cognition of EUK1001 were evaluated.</p><p><b>METHODS</b>To examine the median lethal dose (LD50) of EUK1001, a wide dose range of EUK1001 was administered by p.o. and i.p. in aged mice. Furthermore, novel object recognition task and in vitro electrophysiological technique were utilized to investigate the effects of EUK1001 on recognition memory and hippocampal synaptic plasticity in aged mice.</p><p><b>RESULTS</b>EUK1001 exhibited lower toxicity than xanomeline, and improved the performance of aged mice in the novel object recognition test. In addition, bath application of 1 micromol/L EUK1001 directly induced long-term potentiation in the hippocampus slices.</p><p><b>CONCLUSION</b>We conclude that EUK1001 can improve the age-related cognitive deficits.</p>