Further evidence against using sorbitans in the brain mechanisms investigation.

In both experimental groups an intraperitoneal injection of a single dose of 450 mg/kg p-Chlorophenylalanine (p-CPA) containing 1.0% arabic gum and 450 mg/kg p-CPA containing 0.1% Tween 80 resulted in a similar drop of the serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) level in the anterior (HA) and posterior (HP) hypothalamus, midbrain (GC) and amygdala (AM). Despite the fact that just the same decrease in the 5-HT turnover occurred in both groups, only in the group treated with p-CPA containing arabic gum a rise in postcarbachol emotional-defensive response was observed. The level of dopamine (DA) did not change in both groups. The level of noradrenaline (NA) in the p-CPA with arabic gum treated group was not subject to any change, whereas in the p-CPA with Tween 80 treated group its considerable decrease was noticed, though no essential statistical differences appeared: in HA by 26%, in HP by 38%, in GC by 23% and in AM by 62% as compared to control group (NaCl treated) and in HA by 35%, in HP by 41%, in GC by 33% and in AM by 50% as compared to the p-CPA with arabic gum treated group. In all groups of animals there occurred neither spontaneous aggressive behavior nor changes in spontaneous motility. The results obtained make it clear that Tween 80 exerts its effect both on biochemical and behavioral processes. Thus, it should be acknowledged that using sorbitans in the investigation of brain mechanisms is inadvisable.