L-thyroxine and L-triiodothyronine in the cerebral tissues of the adult rat. Effect of hypothyroidism]

The L-thyroxine and L-triiodothyronine concentrations in several brain areas (cerebral cortex, brain stem, hypothalamus, total brain and hypophysis) in normal and hypothyroid rats have been studied. Results show that L-thyroxine values at tissue level are inferior in the hypothyroid group, although non-significant with respect to the control group, whereas L-triiodothyronine presents values similar to the hypothyroid group and its control in all the brain regions studied with the exception of hypophysis. These results show that in hypothyroid situations exist a compensatory mechanism for maintaining the adequate L-triiodothyronine levels in several brain areas, although the serum levels are strongly decreased in hypothyroid animals.     

Effect of strontium and magnesium on blood calcium]

Twenty four male Wistar rats weighing 250 +/- 10 g, in three groups of 8 rats each, were used. Group A was used as control and the content of its drinking water was 6.5 mg/l Ca; 2.4 mg/l Mg. The drinking water of groups B and C was supplemented with 20 mM (SrCl2) and 20 mM (MgCl2), respectively. Once the 20 days of mineral supplementation had passed, arterial blood was extracted by puncture in the abdominal aorta. In the serum obtained after centrifugation, Ca, Mg, Sr and the total proteins (TP) were determined. Afterwards the serum was subjected to ultrafiltration. Concentrations of Ca, Mg and TP were measured in the obtained ultrafiltrates (u), with the above described techniques. The pH was measured before and after the ultrafiltration. The TP decreased significantly both in group B (supplemented with Sr), and in group C (supplement with Mg). Increases in Ca were found in group B and in Mg in group C. The Mg/Ca ratio increased 10% after the supplementation with Mg. At the ultrafiltrate a significant increase in Cau after supplementation with Sr and with Mg was observed. The Mgu/Cau ratio decreased 14% in the group supplemented with Sr and 38% after the supplementation with Mg. In conclusion, the supplementation with Sr (20 mM) in rats increases the Cau and could have the effect of reducing protein synthesis. These facts should be borne in mind when Sr is used for therapeutical purposes.     

Spectrofluorimetric determination of biogenic amines (serotonin, dopamine) in Metechinorhynchus salmonis (Acanthocephala)

Identification of serotonin and dopamine in M. salmonis was conducted by means of some fluorometric methods. The presence of negligible amount of a serotonin-like component and substance close in its spectral characteristics to dopamine was shown.     

The effect of administering corticoliberin into the striatum on the open-field and shuttle-box behaviors of KHA and KLA strain rats]

The effects of corticotropin-releasing hormone (CRH) injected into the dorsal neostriatum on the open-field and shuttle-box behavior were studied in rats with high (Koltushi high avoidance, KHA) and low (Koltushi low avoidance, KLA) capability for avoidance learning. The effects of this hormone on the behavior of these rat strains were different. In KLA rats with passive strategy of behavior the CRH injection led to a rapid locomotor activation in the open field, while the rats with active behavioral strategy (KHA) reacted to the injection by a significant decrease in locomotion and change for the passive mode of behavior. The same CRH effects on locomotion were obtained in the shuttle-box experiments. Moreover, in the KLA rats the neurohormone injection resulted in an improvement of avoidance learning in contrast to the KHA rats, in which CRH substantially impaired avoidance learning. The obtained evidence is discussed in terms of the important role of striatal CRH in the choice of behavioral strategy in stress.