Synthetic scotophobin: analysis of behavioral effects on mice

Serotonin-kynurenine hypothesis of depression: historical overview and recent developments

This mini-review focuses on the studies of late Prof. IP Lapin (1903 - 2012) and his research team on the role of methoxyindole and kynurenine (KYN) pathways of tryptophan (TRP) metabolism in the pathogenesis of depression and action mechanisms of antidepressant effect. In the late 60s of the last century Prof. IP Lapin suggested that "intensification of central serotoninergic processes is a determinant of the thymoleptic (mood elevating) component" while "activation of noradrenergic processes is responsible for psychoenergetic and motor-stimulating component of the clinical antidepressant effect". The cause of serotonin deficiency in depression was attributed to the shunt of TRP "metabolism away from serotonin production towards KYN production" due to cortisol-induced activation of liver enzyme, tryptophan 2,3- dioxygenase, the rate-limiting enzyme of TRP - KYN pathway. Prof. Lapin suggested and discovered that KYN and its metabolites affect brain functions, and proposed the role of neurokynurenines in pathogenesis of depression and action mechanisms of antidepressant effect (kynurenine hypothesis). Further research suggested the antidepressant and cognition- enhancing effects of post-serotonin metabolite, N-acetylserotonin (NAS), an agonist to tyrosine kinase B (TrkB) receptor; and link between depression and chronic inflammation-associated disorders (e.g., insulin resistance, hepatitis C virus) via inflammation-induced activation of indoleamine 2,3- dioxygenase, brain located rate-limiting enzyme of TRY - KYN metabolism. NAS and kynurenines might be the targets for prevention and treatment of depression and associated conditions.

Effects of methimepip and JNJ-5207852 in Wistar rats exposed to an open-field with and without object and in Balb/c mice exposed to a radial-arm maze

The role of the histamine H₃ receptor (H₃R) in anxiety is controversial, due to limitations in drug selectivity and limited validity of behavioral tests used in previous studies. In the present report, we describe two experiments. In the first one, Wistar rats were treated with an H₃R agonist (methimepip), and exposed to an open-field. In the second one, Balb/c mice were treated with H₃R agonist (methimepip) or antagonist (JNJ-5207852), and exposed to an open space 3D maze which is a modified version of the radial-arm maze. C57BL/6J saline treated mice were included for comparisons. When exposed to an empty open field, Wistar rats spent more time in the outer area and made very low number of brief crossings in the central area. However, when an object occupied the central area, rats crossed frequently into and spent a long time in the central area. Administration of a range of different doses of methimepip (selective H₃R agonist) reduced the entries into the central area with a novel object, indicating enhanced avoidance response. In the 3D maze, both Balb/c and C57BL/6J saline-treated mice crossed frequently onto the bridges that radiate from the central platform but only C57BL/6J mice crossed onto the arms which extend the bridges. This suggests that Balb/c mice are more anxious than C57BL/6J mice. Neither methimepip nor JNJ-5207852 (selective H₃R antagonist/inverse agonist) induced entry into the arms of the maze, indicative of lack of anxiolytic effects.

Georges Ungar and memory transfer

The idea that memories could be transferred from one organism to another by administration of a "trained" donor brain to a naive recipient seized both scientific and public attention in the 1960's and early 1970's. Georges Ungar was one of the earliest and strongest proponents of this idea, and he provided it extensive theoretical and experimental support. This paper reviews Ungar's work on memory transfer (and in particular on the scotophobin molecule), with an analysis of its successes and failures.

Interanimal transferability of taste aversion learning for 0.1% saccharin

Three experiments were performed to assess the interanimal transferability of conditioned taste aversion to 0.1% saccharin. Two experiments used an intracerebrospinal fluid (subdural) route for administering brain extracts and a third used an intraperitoneal (IP) route. As assessed by repeated measurements ANOVA, saccharin consumption was significantly lower during extinction of conditioned aversion for experimental recipients (ER) receiving extracts from aversively conditioned donors, than that of control recipients (CR), receiving extracts from unconditioned donors in one subdural experiment, F(21, 189) = 1.61, p less than 0.05. In the IP experiment the results were in the same direction, though not significant, F(34, 238) = 1.39, p less than 0.1. Results of the other subdural experiment are discussed. It is concluded that these experiments with the conditioned taste aversion paradigm have potential as a model for investigations of behavioral interanimal transfer (BIT) and for neuromolecular research aimed at identification of associated putative neurochemical(s) and the elaboration of their mechanism of action.

Isolation and identification of two learning-induced brain peptides

Goldfish were trained either to avoid the blue compartment of a tank and swim into the green compartment or, conversely, to avoid green and prefer blue. Preliminary experiments indicated that acquisition of the avoidance behavior was associated with the presence in the brain of two peptides, one found in blue avoiding (BA), another in green avoiding (GA) fish. With the help of behavioral bioassays, the peptides were isolated and purified, and their structure was determined by ultrasmicroanalytical techniques. The sequence of the BA peptide, pglu-ile-gly-ala-val-phe-pro-leu-lys-tyr-gly-ser-lys-OH was reproduced by synthesis. Sequential analysis of the GA peptide gave two alternative structures, NAc-lys-gly-gln-ile-ala-val-phe-pro-leu-lys-tyr-gly-ser-OH or NAc-lys-gly-ala-val-gln-ile-phe-pro-lys-tyr-gly-ser-OH, both of which are being synthetized to be compared with the natural compound. Overlapping sequences between the BA and GA peptides suggest the existence of a family of peptides associated with behavior based on color discrimination.

Stimulus specific effect of scotophobin on mouse plasma corticoids

Scotophobin is a peptide previously extracted from brains of rodents shocked in the dark compartment of a white/dark apparatus and identified as the behaviorally active dark avoidance-inducing factor. This study attempted to ascertain whether a stable synthetic analog of scotophobin induced no adrenocortical stress reaction, a generalized, unconditioned stress reaction, or a stress reaction selectively triggered by the dark compartment of the apparatus. Twenty eight mice were injected IP with the synthetic substance and 28 with placebo. A day later half of each group was placed in the dark compartment and the other half in the light compartment. Fifteen min afterward, the animals were bled, and serum samples were obtained. Plasma corticoid levels were determined by radioassay. Only the animals injected with scotophobin analog and exposed to the dark box had elevated levels. The interaction effect between drug treatment and light or dark environment was highly significant.