Vol 42, No 4 (2025): VOL 42, NO4 (2025) Diversity of Neuroregulatory Processes (on the 100th Anniversary of I. P. Ashmarin) (Special Issue, Part 2)

Gasotransmitters (gas-mediators) such as nitric oxide (NO), hydrogen sulfide (H₂S) and carbon monoxide (CO) are a promising group of endogenous signalling molecules to study. The physiological effects of gasotransmitters may contribute to the generation of nociceptive signal in various pain syndromes, including migraine. The basis of pain sensation in migraine is the activation of the trigeminovascular system (TVS), consisting of trigeminal ganglion (TG) afferents, blood vessels and mast cells in the dura mater. The involvement of NO in the nociceptive signalling process in headaches has been described in numerous studies, and injections of the NO donor, nitroglycerin, are a well-known method for modelling migraine in humans and laboratory animals. In TVS, NO interacts with various molecular targets such as TRPV1 and TRPA1 channels, as well as key migraine mediators, PACAP (pituitary adenylate cyclase-activating polypeptide) and CGRP (calcitonin gene-related peptide). H₂S exerts its own activating effect on trigeminal nerve activity and is also able to modulate the activity of TRP channels (transient receptor potential channels) and P2X receptors, exhibiting both pro- and antinociceptive effects. The result of the interaction between NO and H₂S, nitroxyl ion (HNO-) is able to activate TRPA1 channels. CO is a less studied gasotransmitter in the context of molecular mechanisms of migraine, but the involvement of its producing enzyme, haemoxygenase, in pro- and anti-nociceptive effects in models of inflammatory and neuropathic pain has been described. The molecular targets of CO action remain unidentified in TVS. This review provides information on the role of endogenous and exogenous gasotransmitters in TVS, in which the excitability of peripheral afferents determines the occurrence of action potentials that transmit the nociceptive signal to central structures, and sensitization is a factor in the development of chronic migraine. An in-depth study of the signalling role of gasotransmitters in the pathophysiology of migraine pain syndrome may contribute to the development of more effective therapies for this disease.

We have previously found that in mature mouse motor synapses calcitonin gene-related peptide (CGRP) causes an increase in the size of acetylcholine (ACh) quanta and described a complex molecular cascade leading to the release of endogenous CGRP and a subsequent increase in the amplitude of miniature end plate potentials (MEPPs) after long-term synaptic activity (i.e., in the post-tetanic period). In functionally immature motor synapses regenerating after nerve injury, mechanisms that facilitate synaptic transmission are of particular interest as a potential way of influencing the processes of skeletal muscle reinnervation. In this work, we tested how exogenous CGRP affects spontaneous and evoked activity of regenerating motor synapses. Also, using the stimulation mode developed for modeling tetanic activity (2 min, 30 Hz), we described the presence of a post-tetanic increase in the amplitude of MEPPs caused by the release of endogenous CGRP in such synapses. As a result, we are the first to discover an acute, receptor-specific, potentiating effect of exogenous CGRP, as well as the possibility of endogenous CGRP exocytosis followed by subsequent activation of a molecular cascade involving the release of stored calcium and activation of protein kinases A and C, which leads to an increase in the size of ACh quanta in regenerating mouse motor synapses.

In the course of the study, a new scheme for the synthesis of Ac-DMet-PRG-NH₂ (an analog of the C-terminal fragment of arginine vasopressin) by the method of condensation of peptide blocks was proposed.The effect of subchronic intranasal administration of this tetrapeptide on the zoosocial behavior of white Wistar rats of both sexes in the Social Behavior test was studied. As a result of the experiment, a complex dose-dependent effect of Ac-DMet-PRG-NH₂ on rats of different ages was revealed. A reliable effect of the tetrapeptide on the zoosocial behavior of rodents at a dose of 0.01 and 10 µg/kg was established, with pronounced gender differences in the nature of behavioral changes.

Current treatments for major depressive disorder (depression) have significant limitations and there is an urgent need to develop new approaches for antidepressant therapy. Stressful events and hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis play an important role in the pathogenesis of depression. HPA axis activity is self-regulated by negative feedback loops at several levels, including the negative feedback of the adrenocorticotropic hormone (ACTH). ACTH(6-9) is the amino acid sequence required for activation of ACTH receptors. Here in a chronic unpredictable stress (CUS) model of depression, we investigated the effects of a synthetic PGP-containing analog of this sequence, the peptide ACTH(6-9)-PGP. Adult male Sprague-Dawley rats were daily intraperitoneally injected with saline or ACTH(6-9)-PGP (60 nmol/kg body weight) during the CUS procedure. Administration of ACTH(6-9)-PGP significantly attenuated CUS-induced body weight gain decrease, prevented the decrease in sucrose preference and reduction in hippocampal BDNF levels. The results indicate that in the CUS model, systemically administered ACTH(6-9)-PGP exerts antidepressant-like effects and attenuates the metabolic marker of chronic stress. ACTH(6-9)-PGP can be considered as one of the promising candidates in the development of new pharmacological agents for the treatment and prevention of depression and other stress-related pathologies.

Type 2 diabetes is associated with the formation of features of Alzheimer's disease (AD). A common mechanism appears to be the impairment of autophagy, making its stimulation a potential target for AD treatment. A good opportunity to study the correction of diabetes and neurodegeneration is provided by db/db mice, a model of diabetes and obesity that develop signs of AD with age. In our previous work, we found that db/db mice are amenable to treatment with the disaccharide trehalose, which activates autophagy via an mTOR-independent pathway. In 3-month-old mice, trehalose reduced obesity, attenuated hyperglycaemia, significantly activated autophagy in the brain, weakened neuroinflammation and oxidative stress, and restored cognitive impairment. It remains unclear to what extent the therapeutic effect of trehalose depends on the age of mice and on the activation of autophagy gene transcription and ultrastructural changes in neurons and glia cells. The therapeutic effect of treatment with 3% trehalose in drinking was investigated on 5-month-old db/db mice. Trehalose did not induce a significant decrease in the body mass or blood glucose and cholesterol levels but it decreased the expression of the insulin receptor gene Insr. There was a visual increase in the lipofuscin levels in cortical neurons and glial cells, while trehalose did not attenuate the accumulation of the marker. Thus, a differential effect of trehalose was obtained for 5-month-old db/db mice, consisting in the absence of activation of autophagy gene transcription or attenuation of lipofuscin accumulation. Apparently, the therapeutic effect of trehalose on the disturbances in db/db line mice decreases with age and becomes ineffective at 5 months of age.

Periodic hypoxia is the episodic occurrence of hypoxia, which alternates with periods of reoxygenation and normoxia. Depending on the severity and duration of exposure, periodic hypoxia can lead to activation of both protective and pathological mechanisms. The aim of the study was to evaluate the dependence of the effects of periodic hypoxia on the age of rats. Male Wistar rats aged 2 and 4 months were used in the study. Half of the animals of each age were exposed to normobaric hypoxia (8% O₂, 2 hours) daily for 5 days. Subsequently, changes in body weight, anxiety levels, learning ability, and the activity of enzymes of the antioxidant system in the blood plasma were evaluated in rats. It has been shown that daily hypoxic exposure leads to a decrease in body weight and an increase in anxiety levels in male rats aged 2 and 4 months, as well as impaired learning ability in 4-month-old rats. In addition, age-dependent changes in the activity of enzymes of the glutathione antioxidant system in the blood were noted in rats exposed to hypoxia.

Glial cell line- derived neurotrophic factor (GDNF) is a protein belonging to a large group of proteins called neurotrophic factors. GDNF ensures the development of the nervous system during embryogenesis, supports the process of neuronal differentiation in the adult organism, and promotes the survival of neurons throughout their lifetime. Early experiments as well as clinical trials showed the possibility of using GDNF as a therapeutic factor for adjuvant therapy of a number of diseases of the nervous system: Parkinson's disease, ischaemic stroke, spinal cord disorders. Failures in clinical trials have led to a search for possible alternatives that would allow GDNF to be used effectively in therapy. One such option was the search for GDNF isoforms and the study of their possible neuroprotective and neuroinducer potential. A new splice variant of GDNF was discovered and named djGDNF47. In this work, we show the localisation of a novel GDNF isoform, djGDNF47, in the normal brain of healthy rats 10 days old from birth, as well as in adult individuals. We show that djGDNF47 is predominantly expressed in young neurons of the subventricular zone (SVZ). The expression of djGDNF47 was also evaluated in pathology cells (human glioblastoma cell culture), where its expression is detected by CD133⁺ conditional stemness cells.