Pharmacological investigations on cross adaptation in mice subjected to stress immobilization

Trimethoxyflavones from Ocimum basilicum L. leaves improve long term memory in mice by modulating multiple pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Traditionally, Ocimum basilicum L. leaves (OB) are recommended for various brain disorders.

AIM OF THE STUDY

Scientific evidence highlights the cognition improvement capacity of Ocimum basilicum L. leave extract (OBE), however, the compound(s) responsible for this effect and the associated mechanism was not reported. The present study was, thus, designed to isolate and identify the compound responsible for memory improvement effects of OB and to delineate the associated mechanism of action.

MATERIALS AND METHODS

In-vitro acetylcholinesterase (AChE) inhibitory (Ellman method) and antioxidant (DPPH scavenging) assays guided fractionation was employed to isolate the bioactive compounds from OBE. The isolated compounds were characterised using spectroscopic techniques (FTIR, NMR and MS). In-silico and in-vivo [mouse model of scopolamine (SCOP) induced amnesia] investigations were used to substantiate the memory improvement effects of isolated compounds and to understand their mechanism of action.

RESULTS

AChE and DPPH assays guided fractionation of OBE lead to isolation of two pure compounds namely, 5,7-dihydroxy-3',4',5'-trimethoxyflavone (S1) and 3-hydroxy-3',4',5'-trimethoxyflavone (S2). Both S1 and S2 mitigated the cognitive impairment due to SCOP in mice by reducing brain AChE activity, TBARS, TNF-α, IL-1β, IL-6 and caspase-3 concentrations and elevating reduced glutathione and IL-10 levels; together with amelioration of brain hippocampus histopathological aberration (H and E staining). Moreover, the molecular docking of S1 and S2 at the active pockets of AChE and caspase-3 has shown good interactions with vital amino acid residues.

CONCLUSIONS

Our findings show that trimethoxy flavones are responsible for the memory improvement effect of OBE due to their anticholinergic, antioxidant, anti-inflammatory and anti-apoptotic properties. These maybe developed as valuable alternatives for management of cognitive disorders.

Beneficial role of central anticholinergic agent in preventing the development of symptoms in mouse model of post-traumatic stress disorder

Objectives The present study was designed to investigate the effectiveness of trihexyphenidyl, a central anticholinergic drug, in preventing the post-traumatic stress disorder (PTSD) symptoms in a mouse model. Methods Mice were subjected to underwater trauma stress for 30 s on day 1 followed by three situational reminders (3rd, 7th and 14th day). Thereafter, the behavioral alterations including freezing behavior were noted on 21st day. The serum corticosterone levels were measured as a biochemical marker of trauma. Elevated plus maze test was done on day 1 and day 2 to assess the memory formation following exposure to trauma. Results Trauma and situational reminders were associated with a significant development of behavioral changes and freezing behavior on the 21st day. Moreover, there was also a significant decrease in the serum corticosterone levels. A single administration of trihexyphenidyl (2 and 5 mg/kg) significantly restored trauma associated-behavioral changes and serum corticosterone levels. Moreover, it significantly increased the transfer latency time on day 2 following stress exposure in comparison to normal mice suggesting the inhibition of memory formation during trauma exposure. Trihexyphenidyl also led to significant reduction in freezing behavior in response to situational reminders again suggesting the inhibition of formation of aversive fear memory. Conclusion The blockade of central muscarinic receptors may block the formation of aversive memory during the traumatic event, which may be manifested in form of decreased contextual fear response during situational reminders. Central anticholinergic agents may be potentially useful as prophylactic agents in preventing the development of PTSD symptoms.

Investigating the role of nitric oxide in stress adaptive process in electric foot shock stress-subjected mice

AIM

The present study was designed to investigate the role of nitric oxide (NO) in the non-development of stress adaptation in high-intensity foot-shock stress (HIFS) subjected mice.

METHODS

Mice were subjected to low-intensity shocks (LIFS i.e. 0.5 mA) or HIFS (1.5 mA) for 5 days. Stress-induced behavioral changes were assessed by actophotometer, hole board, open field and social interaction tests. Biochemically, the serum corticosterone levels were measured as a marker of stress. L-arginine (100 mg/kg and 300 mg/kg), as NO donor, and L-NAME (10 mg/kg and 30 mg/kg), as nitric oxide synthase (NOS) inhibitor, were employed as pharmacological agents.

RESULTS

A single exposure of LIFS and HIFS produced behavioral and biochemical alterations. However, there was the restoration of behavioral and biochemical alterations on 5^th day in response to repeated LIFS exposure suggesting the development of stress adaptation. However, no stress adaptation was observed in HIFS subjected mice. Administration of L-arginine (300 mg/kg) abolished the stress adaptive response in LIFS-subjected mice, while L-NAME (30 mg/kg) induced the development of stress adaptation in HIFS subjected mice.

CONCLUSION

It is concluded that an increase in the NO release may possibly impede the process of stress adaptation in HIFS-subjected mice.

Anti-stress effects of a GSK-3β inhibitor, AR-A014418, in immobilization stress of variable duration in mice

BACKGROUND

The present study was designed to explore the anti-stress role of AR-A014418, a selective glycogen synthase kinase-3β inhibitor (GSK-3β), on changes provoked by immobilization stress of varying duration.

METHODS

Acute stress of varying degree was induced by subjecting mice to immobilization stress of short duration (30 min) or long duration (120 min). Thereafter, these animals were exposed to the same stressor for 5 days to induce stress adaptation. The behavioral alterations were assessed using an actophotometer, a hole-board, and the open field and social interaction tests. The serum corticosterone levels were assessed as markers of the hypothalamic-pituitary-adrenal (HPA) axis activity. The levels of total GSK-3β and p-GSK-3β-S9 were determined in the prefrontal cortex.

RESULTS

A single exposure to short or long immobilization stress produced behavioral and biochemical changes and the levels of p-GSK-3β-S9 decreased without affecting the total GSK-3β levels in the brain. However, repeated exposure to both short and long stress reversed the behavioral and biochemical changes along with the normalization of p-GSK-3β-S9 levels. The administration of AR-A014418, a selective GSK-3β inhibitor, diminished acute stress-induced behavioral and biochemical changes. Furthermore, AR-A014418 normalized acute stress-induced alterations in p-GSK-3β-S9 levels without changing total GSK-3β levels.

CONCLUSIONS

Our study suggests that acute stress-induced decrease in p-GSK-3β-S9 levels in the brain contributes to the development of behavioral and biochemical alterations and the normalization of GSK-3β signaling may contribute to stress adaptive behavior in mice which have been subjected to repeated immobilization stress.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Cross stress adaptation: Phenomenon of interactions between homotypic and heterotypic stressors

Individuals have an inherent capacity to cope with stressors in the form of stress adaptation. Apart from stress adaptation there is another well documented phenomenon known as cross stress adaptation. In this, there is a reduction in stress responsiveness to a novel stressor (in which the adapted organism had never encountered previously) in previously exposed organisms with another stressor given in either continuous or intermittent. However, regarding the existence of cross stress adaptation, there are mixed reports revealing that the positive cross stress adaptation exists between altitude and heat stress; swim and inescapable shock stress, hypoxia and cold stress, psychosocial stressor and exercise. However, there are other reports which reveal the non-existence of cross adaptation between forced swim and noise stress and cold and immobilized stress. The exact mechanisms responsible for cross stress adaptation are not defined and need to be investigated.