Comparison of handling-injection stress with noise stress on learning and memory in the early life of male rats

BACKGROUND AND OBJECTIVE: Various stressful stimuli have different effects on memory and learning. With technology development, the human exposes to different stressful factors. The aim of this study was to investigate the combined effects of handling-injection stress with noise stress in the passive avoidance task in rats. METHODS: Twenty-four male Wistar rats (22 days aged) with weight of 55gr were used. Male Wistar rats were divided into 4 groups, of 6 animals for 4 weeks: subcutaneous injection of sodium chloride 0.9 and handling stress (I+H), subcutaneous injection of sodium chloride 0.9 and handling with noise exposure (I+N), noise exposure (N) and control (C). After 4 weeks, we studied passive avoidance conditioning test in a shuttle box. FINDINGS: The step-through latency after training animals significantly increased in (I+H) group as compared with (I+N) and (N) groups (p=0.001). But using noise stress with handling-injection stress significantly attenuated learning and memory in the (I+N) group than other 3 groups (p=0.01). CONCLUSION: The data suggested that using moderate stress with sound stress decreases learning and memory in the early life of male Wistar rats

The Thickness of the Mantle Lithosphere and Collision-Related Volcanism in the Lesser Caucasus

The Lesser Caucasus mountains sit on a transition within the Arabia–Eurasia collision zone between very thin lithosphere (<100 km) to the west, under Eastern Anatolia, and a very thick lithospheric root (up to 200 km) in the east, under western Iran. A transect of volcanic highlands running from NW to SE in the Lesser Caucasus allows us to look at the effects of lithosphere thickness variations on the geochemistry of volcanic rocks in this continental collision zone. Volcanic rocks from across the region show a wide compositional range from basanites to rhyolites, and have arc-like geochemical characteristics, typified by ubiquitous negative Nb–Ta anomalies. Magmatic rocks from the SE, where the lithosphere is thought to be thicker, are more enriched in incompatible trace elements, especially the light rare earth elements, Sr and P. They also have more radiogenic ⁸⁷Sr/⁸⁶Sr, and less radiogenic ¹⁴³Nd/¹⁴⁴Nd. Across the region, there is no correlation between SiO₂ content and Sr–Nd isotope ratios, revealing a lack of crustal contamination. Instead, ‘spiky’ mid-ocean ridge basalt normalized trace element patterns are the result of derivation from a subduction-modified mantle source, which probably inherited its subduction component from subduction of the Tethys Ocean prior to the onset of continent–continent collision in the late Miocene. In addition to the more isotopically enriched mantle source, modelling of non-modal batch melting suggests lower degrees of melting and the involvement of garnet as a residual phase in the SE. Melt thermobarometry calculations based on bulk-rock major elements confirm that melting in the SE must occur at greater depths in the mantle. Temperatures of melting below 1200°C, along with the subduction-modified source, suggest that melting occurred within the lithosphere. It is proposed that in the northern Lesser Caucasus this melting occurs close to the base of the very thin lithosphere (at a depth of ∼45 km) as a result of small-scale delamination. A striking similarity between the conditions of melting in NW Iran and the southern Lesser Caucasus (two regions between which the difference in lithosphere thickness is ∼100 km) suggests a common mechanism of melt generation in the mid-lithosphere (∼75 km). The southern Lesser Caucasus magmas result from mixing between partial melts of deep lithosphere (∼120 km in the south) and mid-lithosphere sources to give a composition intermediate between magmas from the northern Lesser Caucasus and NW Iran. The mid-lithosphere magma source has a distinct composition compared with the base of the lithosphere, which is argued to be the result of the increased retention of metasomatic components in phases such as apatite and amphibole, which are stabilized by lower temperatures prior to magma generation