Comparison of the effects of two anesthetics, isoflurane and urethane, on bladder function in rats

Integrated assessment of continuous uroflow cystometry and visceromotor responses to bladder distension in urethane-anesthetized mice

Bladder-related disorders, such as underactive or overactive bladder and chronic pelvic pain syndromes, are typically studied by recording cystometrogram and visceromotor responses (VMRs) to urinary bladder distension (UBD) in anesthetized rats. Recently, similar studies have been conducted in mice due to their suitability for genetic manipulation. However, assessing bladder physiology and pain in aged mice remains challenging due to inconsistencies in anesthesia. Here, we optimized a urethane anesthesia protocol to enable robust cystometrogram (CMG) recordings and VMR in female mice of 2 different age groups: mature (10-12 months) and aged (18-22 months). Mice were first anesthetized with 1.75% isoflurane inhalation for the surgical implantation of a bladder catheter and stainless-steel wire electrodes to the external oblique musculature for delivering bladder distension and recording muscular response respectively. Another catheter was placed intraperitoneally for continuous delivery of urethane (0.15-0.23 g/kg per hour for 2 hours). CMG was measured by delivering slow bladder filling (1.5 mL/h) through the catheter while recording intravesical pressure, VMR responses from external oblique musculature, and micturition volume. Afterwards, VMR response to UBD was recorded. In another cohort, both CMG and VMR response to UBD were assessed before and after intravesical infusion of 0.5% acetic acid and 0.1% lidocaine. Intravesical infusion of acetic acid significantly enhanced the VMR to grader bladder distension and disrupted the regular micturition cycles, which were normalized by intravesical lidocaine. This anesthesia protocol produced robust CMG and VMR recordings for 2 hours in mice of both age groups, enabling focused studies to advance mechanistic understanding of bladder-related disorders. SIGNIFICANCE STATEMENT: A urethane anesthesia protocol was optimized for robust cystometrogram and visceromotor response recordings in mature and aged mice. This model allows assessment of bladder physiology and pain, demonstrating that acetic acid disrupts micturition and enhances pain responses, which lidocaine normalizes.

Cardiac Vagal Nerve Activity During Exercise: New insights and future directions

A new paradigm is emerging in which cardiac vagal nerve activity is maintained and increases during exercise. This paradigm challenges decades of studies that have quoted a withdrawal of cardiac vagal activity during exercise. Here, we outline the existing evidence for increased cardiac vagal activity. We also explain why previous indirect methods used to measure vagal activity might have indirectly led to incorrect conclusions about the role of the cardiac vagus during exercise. We will review evidence that vagal control of the sinoatrial node and the ventricles differs and how vagal neurotransmitters other than acetylcholine may regulate cardiac function during exercise. We will also suggest future directions for research to uncover how the cardiac vagus influences cardiac function and the mechanisms behind the increase in cardiac vagal nerve activity during exercise.

Urinary dysfunction after spinal cord injury: Comparing outcomes after thoracic spinal transection and contusion in the rat

Spinal cord injury (SCI) above the lumbosacral spinal cord induces loss of voluntary control over micturition. Spinal cord transection (SCT) was the gold standard method to reproduce SCI in rodents, but its translational value is arguable and other experimental SCI methods need to be better investigated, including spinal cord contusion (SCC). At present, it is not fully investigated if urinary impairments arising after transection and contusion are comparable. To explore this, we studied bladder-reflex activity and lower urinary tract (LUT) and spinal cord innervation after SCT and different severities of SCC. Severe-contusion animals presented a longer spinal shock period and the tendency for higher residual volumes, followed by SCT and mild-contusion animals. Urodynamics showed that SCT animals presented higher basal and peak bladder pressures. Immunostaining against growth-associated protein-43 (GAP43) and calcitonin gene-related peptide (CGRP) at the lumbosacral spinal cord demonstrated that afferent sprouting is dependent on the injury model, reflecting the severity of the lesion, with a higher expression in SCT animals. In LUT organs, the expression of GAP43, CGRP cholinergic (vesicular acetylcholine transporter (VAChT)) and noradrenergic (tyrosine hydroxylase (TH)) markers was reduced after SCI in the LUT and lumbosacral cord, but only the lumbosacral expression of VAChT was dependent on the injury model. Overall, our findings demonstrate that changes in LUT innervation and function after contusion and transection are similar but result from distinct neuroplastic processes at the lumbosacral spinal cord. This may impact the development of new therapeutic options for urinary impairment arising after spinal cord insult.

A neuroprotective effect of pentoxifylline in rats with diabetic neuropathy: Mitigation of inflammatory and vascular alterations

BACKGROUND

Treatment of diabetic neuropathic pain does not change the natural history of neuropathy. Improved glycemic control is the recommended treatment in these cases, given that no specific treatment for the underlying nerve damage is available, so far. In the present study, the potential neuroprotective effect of pentoxifylline in streptozotocin (50 mg/kg) induced diabetic neuropathy in rats was investigated.

METHODS

Pentoxifylline was administered at doses equivalent to 50, 100 & 200 mg/kg, in drinking water, starting one week after streptozotocin injection and for 7 weeks. Mechanical allodynia, body weight and blood glucose level were assessed weekly. Epidermal thickness of the footpad skin, and neuroinflammation and vascular alterations markers were assessed.

RESULTS

Tactile allodynia was less in rats that received pentoxifylline at doses of 100 and 200 mg/kg (60 % mechanical threshold increased by 48 % and 60 %, respectively). The decrease in epidermal thickness of footpad skin was almost completely prevented by the same doses. This was associated with a decrease in spinal tumor necrosis factor alpha (TNFα) and nuclear factor kappa B levels and a decrease in microglial ionized calcium binding adaptor molecule 1 immunoreactivity, compared to the control diabetic group. In sciatic nerve, there was decrease in TNF-α and vascular endothelial growth factor levels and intercellular adhesion molecule immunoreactivity.

CONCLUSION

Pentoxifylline showed a neuroprotective effect in streptozotocin-induced diabetic neuropathy, which was associated with a suppression of both the inflammatory and vascular pathogenic pathways that was not associated with a hypoglycemic effect. Thus, it may represent a potential neuroprotective drug for diabetics.

Molecular mechanisms of cholinergic neurotransmission in visceral smooth muscles with a focus on receptor-operated TRPC4 channel and impairment of gastrointestinal motility by general anaesthetics and anxiolytics

Acetylcholine is the primary excitatory neurotransmitter in visceral smooth muscles, wherein it binds to and activates two muscarinic receptors subtypes, M2 and M3, thus causing smooth muscle excitation and contraction. The first part of this review focuses on the types of cells involved in cholinergic neurotransmission and on the molecular mechanisms underlying acetylcholine-induced membrane depolarisation, which is the central event of excitation-contraction coupling causing Ca2+ entry via L-type Ca2+ channels and smooth muscle contraction. Studies of the muscarinic cation current in intestinal myocytes (mICAT) revealed its main molecular counterpart, receptor-operated TRPC4 channel, which is activated in synergy by both M2 and M3 receptors. M3 receptors activation is of permissive nature, while activation of M2 receptors via Gi/o proteins that are coupled to them plays a direct role in TRPC4 opening. Our understanding of signalling pathways underlying mICAT generation has vastly expanded in recent years through studies of TRPC4 gating in native cells and its regulation in heterologous cells. Recent studies using muscarinic receptor knockout have established that at low agonist concentration activation of both M2 receptor and the M2/M3 receptor complex elicits smooth muscle contraction, while at high agonist concentration M3 receptor function becomes dominant. Based on this knowledge, in the second part of this review we discuss the cellular and molecular mechanisms underlying the numerous anticholinergic effects on neuroactive drugs, in particular general anaesthetics and anxiolytics, which can significantly impair gastrointestinal motility. This article is part of the Special Issue on "Ukrainian Neuroscience".