Inter-trial neuronal activity in inferior temporal cortex: a putative vehicle to generate long-term visual associations.

When monkeys perform a delayed match-to-sample task, some neurons in the anterior inferotemporal cortex show sustained activity following the presentation of specific visual stimuli, typically only those that are shown repeatedly. When sample stimuli are shown in a fixed temporal order, the few images that evoke delay activity in a given neuron are often neighboring stimuli in the sequence, suggesting that this delay activity may be the neural correlate of associative long-term memory. Here we report that stimulus-selective sustained activity is also evident following the presentation of the test stimulus in the same task. We use a neural network model to demonstrate that persistent stimulus-selective activity across the intertrial interval can lead to similar mnemonic representations (distributions of delay activity across the neural population) for neighboring visual stimuli. Thus, inferotemporal cortex may contain neural machinery for generating long-term stimulus-stimulus associations

Chlorogenic Acid Increases Basal Tone with No Effect on Relaxation of Rat Ileal Smooth Muscles by Mechanisms Independent of PKG Mediated Effects on Myosin Light Chain Phosphorylation

Chlorogenic acid (CGA) is a dietary polyphenolic compound commonly present in coffee, fruits and vegetables. The pharmacological properties of CGA include antioxidant, antibacterial, anti-inflammatory, and antithrombotic effects. Previous experimental studies have shown that CGA induces nitric oxide-sGC-PKG pathway to cause relaxation of the vascular smooth muscles. But the effects of CGA on ileal smooth muscles are still unknown. The present study is designed to test the effect of CGA on PKG mediated relaxation of rat ileal smooth muscle. Effects of CGA on basal tension and maximum contractile tension induced by physiological salt solution (PSS) containing 140 mM potassium in isolated rat ileal rings (3mm) were determined using tissue bath apparatus. CGA effects on myosin light chain phosphorylation at maximum contractile tension were also measured by freezing the ileal rings and extracting the protein and running Western blots. The role of PKG in regulating smooth muscle relaxation is tested by incubating ileal rings with specific PKG inhibitor Rp-8-Br-cGMPS and measuring the basal tension, maximum contractile tension and myosin light chain phosphorylation as described above. The results show that basal tension increases from 0.27±0.1 (control group) to 0.91±0.3 and 0.87±0.2 (mV) when treated with CGA (10μM) and PKG inhibitor (4μM) respectively. The peak contractile tension in response depolarization by 140 mM K+ PSS changes from 100% (control group) to 101±12.2 % and 117±17.2 % when treated with CGA and PKG inhibitor respectively. The results from Western blots show that myosin light chain phosphorylation didn’t change significantly between CGA (36.3±0.8 %) and PKG inhibitor (35.8±0.5 %) treatments. These results suggest that CGA is involved in increasing the basal tone of ileal smooth muscles when compared with the control group. In addition, CGA did not have any effect on the peak contractile tension and myosin light chain phosphorylation, suggesting that it may not be involved in ileal smooth muscle relaxation. However, PKG inhibitor in presence of CGA did increase basal and maximum contractile tension without any corresponding changes in myosin light chain phosphorylation indicating that other mechanisms that doesn’t include PKG mediated effects on myosin light chain phosphorylation may be important in regulating basal tone of ileal smooth muscle by CGA

Chlorogenic Acid Increases Basal Tone with No Effect on Relaxation of Rat Ileal Smooth Muscles by Mechanisms Independent of PKG Mediated Effects on Myosin Light Chain Phosphorylation

Chlorogenic acid (CGA) is a dietary polyphenolic compound commonly present in coffee, fruits and vegetables. The pharmacological properties of CGA include antioxidant, antibacterial, anti-inflammatory, and antithrombotic effects. Previous experimental studies have shown that CGA induces nitric oxide-sGC-PKG pathway to cause relaxation of the vascular smooth muscles. But the effects of CGA on ileal smooth muscles are still unknown. The present study is designed to test the effect of CGA on PKG mediated relaxation of rat ileal smooth muscle. Effects of CGA on basal tension and maximum contractile tension induced by physiological salt solution (PSS) containing 140 mM potassium in isolated rat ileal rings (3mm) were determined using tissue bath apparatus. CGA effects on myosin light chain phosphorylation at maximum contractile tension were also measured by freezing the ileal rings and extracting the protein and running Western blots. The role of PKG in regulating smooth muscle relaxation is tested by incubating ileal rings with specific PKG inhibitor Rp-8-Br-cGMPS and measuring the basal tension, maximum contractile tension and myosin light chain phosphorylation as described above. The results show that basal tension increases from 0.27±0.1 (control group) to 0.91±0.3 and 0.87±0.2 (mV) when treated with CGA (10μM) and PKG inhibitor (4μM) respectively. The peak contractile tension in response depolarization by 140 mM K+ PSS changes from 100% (control group) to 101±12.2 % and 117±17.2 % when treated with CGA and PKG inhibitor respectively. The results from Western blots show that myosin light chain phosphorylation didn’t change significantly between CGA (36.3±0.8 %) and PKG inhibitor (35.8±0.5 %) treatments. These results suggest that CGA is involved in increasing the basal tone of ileal smooth muscles when compared with the control group. In addition, CGA did not have any effect on the peak contractile tension and myosin light chain phosphorylation, suggesting that it may not be involved in ileal smooth muscle relaxation. However, PKG inhibitor in presence of CGA did increase basal and maximum contractile tension without any corresponding changes in myosin light chain phosphorylation indicating that other mechanisms that doesn’t include PKG mediated effects on myosin light chain phosphorylation may be important in regulating basal tone of ileal smooth muscle by CGA

Diffusion- and T2-weighted MRI of closed-head injury in rats: A time course study and correlation with histology

Diffusion- and T2-weighted MRI were used to evaluate changes in brain water characteristics following closed-head injury in rats. Images were collected within the first 2 h and at 24 h and 7 days following the traumatic event and then compared with histology. The ratios between the apparent diffusion coefficients (ADCs) of the traumatized tissues and normal brain tissues were significantly different from unity and were found to be 0.79 ± 0.25 (p < 0.01), 0.49 ± 0.33 (p < 0.0002), and 3.47 ± 1.36 (p < 10−6) at 1–2 h, 24 h, and 1 week after the trauma, respectively. In severe trauma, areas of hyperintensity which were not apparent on the T2-weighted images could be detected on the diffusion-weighted images within 1–2 h after the trauma. At 24 h following the traumatic event, large areas of hyperintensity are observed in both types of images. One week following the trauma, the ADCs of the traumatized tissues (1.84 ± 0.69 × 10−5 cm2/s) are much larger than those of normal brain (0.57 ± 0.19 × 10−5 cm2/s) and approach the value of free water. At 7 days, the areas of hyperintensity in the T2-weighted images seem to underestimate the injured areas found by histology. At this time point a good correlation is obtained between the areas of hypointensity observed on the diffusion-weighted images and the infarct areas obtained by histology (r = 0.88)

Diffusion and perfusion magnetic resonance imaging following closed head injury in rats

Diffusion-, perfusion-, T1-, and T2-weighted magnetic resonance imaging (MRI) were performed at 1–2 h, 24 h, and 1 week following closed head injury (CHI) in rats, and data was compared with hematoxylin and eosin histology. At 1–2 h, large areas of low perfusion in the damaged hemisphere overestimate the histological damage. In the first 2 h, the histological damage seems to be a superposition of abnormalities in the T1- and diffusion-weighted images. In areas with more than 10% reduction in the apparent diffusion coefficients (ADCs), reduced regional cerebral blood volume (r-CBV) was also observed. The decrease in ADCs and rCBV correlated with r = 0.78. Changes in the MRI parameters revealed the following: (a) Further reduction in ADC occurred from 83 ± 15% at 1–2 h after trauma to 69 ± 9% at 24 h, and 1 week later a marked elevation in the ADC values is observed. (b) Blood perfusion measurements performed 1–2 h posttrauma revealed a pronounced reduction in r-CBV (53 ± 18%) in the damaged hemisphere in all rats. At 24 h postimpact, areas of hyper- and hypoperfusion were observed. One week later, similar perfusion was found in both hemispheres of all rats. (c) T2 hyperintensity at 24 h overestimated the histological damage found at 1 week. At one week following the trauma, the T2 hyperintensity underestimated the histological damage. It is concluded that CHI, which is a heterogeneous insult, should be studied by a combination of MRI techniques. The superposition of the abnormalities seen on T1 and on the diffusion-weighted MR images at early time point represents best the histological damage. Both T2 and rCBV images are less informative in terms of actual histological damage