Vol 54, No 6 (2018)

The effects of hydroquinone (200 mg/kg) on spontaneous periodic motor activity (SPMA) and a number of biochemical markers were studied in 116-day-old rats. According to Laborit (1965), the mechanism of hydroquinone action is based on inhibition of the pentose phosphate pathway in excitable structures. Herein, we confirmed that intraperitoneal injection of hydroquinone drastically changes the SPMA pattern, inducing uninterrupted intense motor activity. To test the metabolic, redox and anticholinergic hypotheses, various feasible targets of hydroquinone were addressed. The experimental results revealed age-related changes in a number of biochemical markers. In erythrocytes (RBC), hydroquinone induced a slight increase in lactate and pyruvate levels but did not affect the glucose level, nor did it inhibit the activity of lactate dehydrogenase (LDH) and glucose-6-phosphate dehydrogenase (G6PDH) in vitro. Hydroquinone did not affect significantly RBS levels of reduced and oxidised glutathione (GSH and GSSG) and different types of hemoglobin as well as plasma levels of malonic dialdehyde (MDA). High doses of hydroquinone inhibited RBC acetylcholinesterase (AChE) in vitro. However, blockade of central and peripheral muscarinic and nicotinic acetylcholine receptors, induced both before and after hydroquinone injection, did not prevent SPMA potentiation and changes in its pattern. Thus, our results cast doubt both on the metabolic hypothesis of the hydroquinone action and the physiological relevance of its anticholinesterase effect to enhancing motor activity. The tasks for further investigation in this direction are outlined.

We report here the long-term effects of deep hypobaric hypoxia or dexamethasone administration (0.8 mg/kg) endured at the early prenatal period of gestation (days 14–16 or 17–19) on contextual and cued fear conditioning in postnatal ontogenesis of male rats. Fear responses conditioned to a context or a cue (tone) were comparatively evaluated in the male offspring of rats exposed to hypoxia or injected with dexamethasone at different gestational ages. Hypoxic exposures at any period of early prenatal ontogenesis were found to entail no statistically significant differences in the offspring relative to control. During contextual fear conditioning or extinction, the freezing time increased relative to control in animals born to females that were injected with dexamethasone on gestational days 17–19. In an analogous test on fear conditioning to a tone, the freezing time decreased relative to control in rats born to females injected with dexamethasone on gestational days 14–16 and increased in those whose mothers were injected with dexamethasone on days 17–19. We suggest that effects induced by dexamethasone administration at both gestation periods were mainly due to the involvement of the amygdala nuclei. The effect of dexamethasone on contextual fear conditioning, which seems to be due to functional changes in the hippocampus, was only detected upon its injection on gestational days 17–19.

To evaluate the effects of photobiomodulation, we used laser devices with wavelengths of 662 nm (ALOD-01; Alcom Medica, Russia) and 808 nm (ALPH-01 Diolan; NPP VOLO, Russia) and an energy density of 1–15 J/cm². The experiments were carried out on the infusoria Paramecium caudatum (Alveolata: Ciliophora: Oligohymenophora: Peniculia). The results were evaluated before as well as 5, 10, 30, 60 min and 24 h after irradiation. 5 min after exposure to red light (662 nm), motor activity of P. caudatum increased vs. control and then decreased within 60 minutes. 24 h after irradiation at an energy density of 15 J/cm², the speed of P. caudatum was 52% of the initial (73% in the control) (p < 0.05). Immediately since exposure to infrared radiation (808 nm) and during the first hour, motor activity tended to decrease. 24 h later, the speed decrement was significantly less than in the control. The data obtained indicate that changes in the functional state of P. caudatum arise immediately after irradiation and persist for a long time, leading either to an increased (808 nm) or a decreased (662 nm) resistance at the same values of a radiation energy density. The peculiarities of the P. caudatum response to red vs. infrared radiation appear to be due to the differences between primary photoacceptors and appropriate signaling pathways, which come into action immediately upon their excitation.

The number, location and morphology of intersegmental descending interneurons, which connect pro- and mesothoracic ganglia with the matathoracic ganglion in the cockroach Periplaneta americana, were investigated herein using a retrograde nickel chloride tracing through one of the connectives that link meso- and metathoracic ganglia. The bodies of stained neurons were aggregated into clusters lying ether ipsilaterally or contralaterally to the axon through which the dye was delivered. Differences in size, architecture and dendrite ramification of ipsi- and contralateral neurons were described. Ipsilateral neurons ramified also ipsilaterally, whereas contralateral neurons formed ramifications on the both sides of the ganglion. The data obtained suggest that adjustment of the walking pattern generator by sensory input from legs is mainly achieved through ipsilateral descending neurons, while adaptation to the environment and brain commands is accomplished through contralateral neurons.