Pain syndrome in adenomyosis. finding new pathogenesis links and non-hormonal correction opportunities. Literature review

Adenomyosis is characterized by polymorphism of clinical manifestations and is the cause of chronic pelvic pain associated with endometriosis in 53–80% of cases. Heavy dysmenorrhea in adenomyosis is a key factor that reduces the quality of life and, moreover chronic pain reduces stress resistance and launches the rehabilitation cytokines cascade, which causes exacerbation of endometriosis. Formation of painful syndrome with adenomyosis may be due to: changes in neurohumoral regulation, stimulation of nerves and blood vessels growth and myometrium inflammatory remodeling against the background of circulatory disorders and vascular sclerosis. These processes lead to violation of neuroimmune relationships that determine the increase in the number and sensitivity of nociceptors against the background of the chronic immuno-inflammatory process in endometrials and myometry.Experimental studies have shown that the supraspinal role of the nitric oxide (NO) is to indirect mechanical nociceptive reflexes. The dose-dependent L-arginine role in the pain syndrome formation also was shown; it was found that small doses of L-arginine lead to the activation of nNO-synthase and analgesic effect. Large doses are activated by cotorphine synthase to form a dipeptide of cortorphine (L-tyrosine-L-arginine), which induces the met-enkephalin release and analgesic effect. Individual studies have demonstrated a decrease in the symptoms of urinary pain syndrome during L-arginine treatment, which made it possible to include it into the European Association of Urologists recommendations on the chronic pelvic pain treatment in 2017.Clinical comparative study (2013) of the NO donator (L-arginine) effectiveness in the treatment of endometriosis-associated intermenstrual pelvic pain and dysmenorrhea showed a high efficiency of a 3-month course of combination therapy (dienogest 2 mg + Tivortin 4.2 g). Supplement of basic therapy by NO donator (L-аrginine) has shown a faster reaching the clinical effect on reducing endometriosis-associated symptoms and sustainable maintenance of the result achieved. The multifaceted pharmacological effects of L-arginine directly affect a number of essential factors for the adenomyosis development and progression, which allows using this drug in clinical practice.

Electrocution as an alternative euthanasia method to blunt force trauma to the head followed by exsanguination for non-viable piglets

Background On farms, the currently approved and most widely practised method of euthanising non-viable piglets is blunt force trauma to the head followed by exsanguination. However, the use of this method is criticised due to public perceptions and aversion to the methodology by caretakers. Therefore, electrocution after electrical stunning was examined as an alternative approach in 80 hybrid piglets. Initially, electrocution was simulated with finite element analysis using a computer piglet-model, where current density in the heart was visualised and size and position of the electrodes were defined. The following step investigated electrical parameters for electrocution in anaesthetised piglets; first, with a constant voltage power source and then with a constant current power source. The electrical stunning was examined using the constant current supply. Finally, the results of electrical stunning and electrocution were verified in 25 healthy piglets with a body weight between 1 and 2 kg. Unconsciousness was proven by testing palpebral, corneal and nociceptive reflexes. Time of death was confirmed by electroencephalography (EEG) and electrocardiography (ECG) records. Results Stunning succeeded with the preset of 1.3 A and 50 Hz, placing the electrodes on both sides of the head between the eyes and ears using different timespans between 8 and 20 s. Prolonged electrical flow resulted in reduced paddling movements after the epileptic seizure, and allowed undisturbed reflex tests and installation of electrodes for EEG and ECG recording during electrocution. Using 0.75 A and 400 Hz, pin-shaped electrodes were first positioned on both sides of the chest for 5 s, followed by a break of 20–30 s and a second current flow, whereby the electrodes were placed above the withers and the sternum for 5 s. Cardiac arrest and an isoelectric EEG were induced within 3 min after the onset of the electrical flow through the chest. The most obvious indicator of effective stunning and electrocution was termination of rhythmic breathing. Piglets with cardiac arrest showed only single gasps lasting up to 3 min after electrocution. Conclusions The evaluated stunning and electrocution protocol might ease concerns about timely piglet euthanasia. However, this should be verified in non-viable piglets to exclude influencing factors like dehydration and diseases.

A brainstem circuit for coordinated pain-control

Supraspinal brain regions are involved in modifying nociceptive signals in response to environmental stimuli and stressors including mechanisms that elevate thresholds to noxious stimuli (pain suppression). However, details such as the cells, the circuits, and the molecular mechanisms, by which nociceptive responses are suppressed are incompletely understood. Therefore, we searched for unrecognized brain nuclei involved in these processes. Examination of neurons activated by noxious stimuli revealed catecholaminergic neurons in the caudal ventrolateral medulla that were stimulated by multiple noxious challenges. We found that, upon activation, these neurons operate in a diffuse feed-forward inhibitory loop to attenuate nociceptive reflexes via a descending locus coeruleus to spinal cord pathway. Importantly, this circuit is sufficient to attenuate injury induced allodynia and inhibit glucoprivation induced analgesia and is required for counter-stimulus induced analgesia. Our findings molecularly define a component of the brain pain modulatory system which can coordinate antinociceptive responses.

Mini-invasive methods of treatment of diabetic foot pain

Neuropathic pain occurs with diabetic polyneuropathy more often than with all polyneuropathies of another etiology. Because the cause of pain can rarely be cured, treatment is usually symptomatic. Neuropathic pain is usually poorly controlled by analgesics. Management of neuropathic pain is started with conservative pharmacotherapy before invasive pain management is applied. Although there are many drugs that can be used in patients with diabetic pain syndrome, pain syndrome can not be surely stoped with monotherapy. In addition, the patient may not tolerate the full therapeutic dose of the drug. All this dictates the need for combination therapy. It is believed that regional anesthesia as an independent type of analgesia or a component of combined anesthesia is the method of choice for the elderly and senile patients. The main reasons for this choice, when comparing regional anesthesia with narcosis, are less stressful response of the organism, absence of depression of the central nervous system, stable reliable analgesia with complete blockade of nociceptive reflexes with the provision of adequate muscle relaxation, prevention of neurovegetative reactions, which ultimately helps to reduce the incidence of postoperative complications and mortality. Clinicians have accumulated considerable experience demonstrating the need for regional analgesia in the management of diabetic foot pain.

Discrimination between nociceptive reflexes and more complex responses consistent with pain in crustaceans

Animals have quick-acting nociceptive reflexes that protect them from tissue damage. Some taxa have also evolved the capacity for pain. Pain appears to be linked to long-term changes in motivation brought about by the aversive nature of the experience. Pain presumably enhances long-term protection through behaviour modification based, in part, on memory. However, crustaceans have long been viewed as responding purely by reflex and thus not experiencing pain. This paper considers behavioural and physiological criteria that distinguish nociception from potential pain in this taxon. These include trade-offs with other motivational systems and prolonged motivational change. Complex, prolonged grooming or rubbing demonstrate the perception of the specific site of stimulus application. Recent evidence of fitness-enhancing, anxiety-like states is also consistent with the idea of pain. Physiological changes in response to noxious stimuli mediate some of the behavioural change. Rapid avoidance learning and prolonged memory indicate central processing rather than mere reflexes. Thus, available data go beyond the idea of just nociception. However, the impossibility of total proof of pain described in ways appropriate for our own species means that pain in crustaceans is still disputed. Pain in animals should be defined in ways that do not depend on human pain experience. This article is part of the Theo Murphy meeting issue ‘Evolution of mechanisms and behaviour important for pain’.

Temporal and spatial dynamics of spinal sensorimotor processing in an intersegmental cutaneous nociceptive reflex

The cutaneus trunci muscle (CTM) reflex produces a skin “shrug” in response to pinch on a rat’s back through a three-part neural circuit: 1) A-fiber and C-fiber afferents in segmental dorsal cutaneous nerves (DCNs) from lumbar to cervical levels, 2) ascending propriospinal interneurons, and 3) the CTM motoneuron pool located at the cervicothoracic junction. We recorded neurograms from a CTM nerve branch in response to electrical stimulation. The pulse trains were delivered at multiple DCNs (T6–L1), on both sides of the midline, at two stimulus strengths (0.5 or 5 mA, to activate Aδ fibers or Aδ and C fibers, respectively) and four stimulation frequencies (1, 2, 5, or 10 Hz) for 20 s. We quantified both the temporal dynamics (i.e., latency, sensitization, habituation, and frequency dependence) and the spatial dynamics (spinal level) of the reflex. The evoked responses were time-windowed into Early, Mid, Late, and Ongoing phases, of which the Mid phase, between the Early (Aδ fiber mediated) and Late (C fiber mediated) phases, has not been previously identified. All phases of the response varied with stimulus strength, frequency, history, and DCN level/side stimulated. In addition, we observed nociceptive characteristics like C fiber-mediated sensitization (wind-up) and habituation. Finally, the range of latencies in the ipsilateral responses were not very large rostrocaudally, suggesting a myelinated neural path within the ipsilateral spinal cord for at least the A fiber-mediated Early-phase response. Overall, these results demonstrate that the CTM reflex shares the temporal dynamics in other nociceptive reflexes and exhibits spatial (segmental and lateral) dynamics not seen in those reflexes. NEW & NOTEWORTHY We have physiologically studied an intersegmental reflex exploring detailed temporal, stimulus strength-based, stimulation history-dependent, lateral and segmental quantification of the reflex responses to cutaneous nociceptive stimulations. We found several physiological features in this reflex pathway, e.g., wind-up, latency changes, and somatotopic differences. These physiological observations allow us to understand how the anatomy of this reflex may be organized. We have also identified a new phase of this reflex, termed the “mid” response.