Delta-sleep inducing peptide (DSIP) and ACTH (4-10) analogue influence fos-induction in the limbic structures of the rat brain under emotional stress

Emotional Stress Induces Adaptive Response in Rat Lymphocytes to Subsequent Ionizing Radiation Exposure

We studied the molecular mechanisms of cross-adaptation to ionizing radiation (1 Gy) of lymphocytes isolated from rats subjected to emotional stress. The effects of chronic (CES; various types of stress exposure) and acute (AES; forced swimming) emotional stress in rats on indicators of oxidative stress, cell death, and levels of NRF2 and NOX4 proteins involved in the development of the adaptive response were analyzed in isolated lymphocytes. It was found that stress induced an adaptive response in rat lymphocytes and triggered processes similar to the adaptive response induced by low doses of ionizing radiation: an increase in the level of oxidized DNA and cell death, as well as an increase in the content of NOX4 and NRF2 proteins. In animals subjected to emotional stress, suppressed DNA oxidation in response to irradiation, reduced levels of protective factor NRF2, as well as lymphocyte death were observed.

Oxidized Cell-Free DNA Role in the Antioxidant Defense Mechanisms under Stress

The present study focuses on the investigation of the oxidized cell-free DNA (cfDNA) properties in several experimental models, including cultured cerebellum cells, peripheral blood lymphocytes (PBL), plasma, and hippocampus under an acute and chronic unpredictable stress model in rats. Firstly, our study shows that Spectrum Green fluorescence-labeled oxidized cfDNA fragments were transferred into the cytoplasm of 80% of the cerebellum culture cells; meanwhile, the nonoxidized cfDNA fragments do not pass into the cells. Oxidized cfDNA stimulates the antioxidant mechanisms and induction of transcription factor NRF2 expression, followed by an activation of NRF2 signaling pathway genes-rise of Nrf2 and Hmox1 gene expression and consequently NRF2 protein synthesis. Secondly, we showed that stress increases plasma cfDNA concentration in rats corresponding with the duration of the stress exposure. At the same time, our study did not reveal any significant changes of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) level in PBL of rats under acute or chronic stress, probably due to the significantly increased Nrf2 expression, that we found in such conditions. 8-oxodG is one of the most reliable markers of DNA oxidation. We also found an increased level of 8-oxodG in the hippocampal homogenates and hippocampal dentate gyrus in rats subjected to acute and chronic stress. Taken together, our data shows that oxidized cfDNA may play a significant role in systemic and neuronal physiological mechanisms of stress and adaptation.

Neuronal activity in the dorsal hippocampus after lateral hypothalamus stimulation: effects of delta-sleep-inducing peptide

We studied central effects of delta-sleep-inducing peptide in the mechanisms of positive emotional state formation in rats. In Wistar rats preliminary tested in an open field, the reactions of 57 neurons of the dorsal hippocampus were analyzed during lateral hypothalamus stimulation and microionophoretic application of delta-sleep-inducing peptide. It was found that the number of neurons not responding to stimulation in the lateral hypothalamus surpassed the number of sensitive neurons (63 and 37%, respectively). Hippocampal neurons in active animals were less sensitive to stimulation of the lateral hypothalamus than in passive rats (33 vs. 42%) After application of delta-sleep-inducing peptide, only 28% neurons responded to stimulation. Thus, delta-sleep-inducing peptide reduced the sensitivity of hippocampal neurons to stimulation of the lateral hypothalamus.

Dizocilpine and cycloheximide prevent inhibition of c-Fos gene expression by delta sleep-inducing peptide in the paraventricular nucleus of the hypothalamus in rats with different resistance to emotional stress

The effects of the non-competitive NMDA-receptor blocker MK-801 (dizocilpine) and the protein synthesis inhibitor cycloheximide on the delta sleep-inducing peptide (DSIP) inhibition of c-Fos immediate early gene expression were studied in the parvocellular subdivision of the hypothalamic paraventricular nucleus (pPVN) of male Wistar rats with either high or low resistance to emotional stress, predicted from differences in their open-field behaviour. The experiments show that intraperitoneal (i.p.) DSIP injection (60 nmol/kg) decreased the number of Fos-immunoreactive (Fos-IR) cells in the pPVN, activated by immobilization. The NMDA-receptor antagonist dizocilpine (MK-801) (90 nmol i.c.v.) prevented the inhibition of c-Fos expression by DSIP in the pPVN of rats predisposed to emotional stress. The protein synthesis inhibitor cycloheximide (210 nmol i.c.v.) prevented the inhibition of c-Fos expression by DSIP in the pPVN of rats that were resistant to emotional stress. The experiments indicate that the DSIP effect on c-Fos gene expression might be mediated by NMDA-receptors. DSIP may induce production of some protein transcription factors, transmitting a signal from membrane NMDA-receptors to the nucleus.

Delta-sleep inducing peptide and neuronal activity after glutamate microiontophoresis: the role of NMDA-receptors

The influence of microiontophoretic application of delta-sleep inducing peptide (DSIP) on a neuronal activity of sensorimotor brain cortex, dorsal hippocampus, ventral anterior thalamic nucleus and lateral hypothalamus was studied under the effects of glutamate and MK-801, a N-methyl-d-aspartate non-competitive antagonist, on male Wistar rats. DSIP microiontophoresis predominantly activated neurons of various brain regions, in particular, dorsal hippocampus and ventral anterior thalamic nucleus. A preliminary DSIP microiontophoresis prevented the augmentation of a neuronal activity in the studied structures under glutamate microiontophoresis. After MK-801 microiontophoresis the number of neurons activated by the DSIP significantly decreased. It is suggested that DSIP effects on the neuronal activity in the sensorimotor brain cortex, dorsal hippocampus, ventral anterior thalamic nucleus and lateral hypothalamus might be mediated by the NMDA-receptors.

Dizocilpine blocks the effects of delta sleep-inducing peptide-induced suppression of c-fos gene expression in the paraventricular nucleus of the hypothalamus in rats

The characteristics of the actions of the non-competitive blocker of NMDA receptors dizocilpine on the expression of the early c-fos gene in the paraventricular nuclei of the hypothalamus were studied in rats with different predicted susceptibilities to emotional stress in conditions of treatment with delta sleep-inducing peptide. The results showed that prior treatment with dizocilpine blocked reductions in c-fos expression induced by delta sleep peptide.