Activity-Based Training Alters Penile Reflex Responses in a Rat Model of Spinal Cord Injury

Sex Differences in Pubertal Circadian and Ultradian Rhythmic Development Under Semi-naturalistic Conditions

Biological rhythms in core body temperature (CBT) provide informative markers of adolescent development under controlled laboratory conditions. However, it is unknown whether these markers are preserved under more variable, semi-naturalistic conditions, and whether CBT may therefore prove useful in a real-world setting. To evaluate this possibility, we examined fecal steroid concentrations and CBT rhythms from pre-adolescence (p26) through early adulthood (p76) in intact male and female Wistar rats under natural light and climate at the Stephen Glickman Field Station for the Study of Behavior, Ecology and Reproduction. Despite greater environmental variability, CBT markers of pubertal onset and its rhythmic progression were comparable with those previously reported in laboratory conditions in female rats and extend actigraphy-based findings in males. Specifically, sex differences emerged in CBT circadian rhythm (CR) power and amplitude prior to pubertal onset and persisted into early adulthood, with females exhibiting elevated CBT and decreased CR power compared with males. Within-day (ultradian rhythm [UR]) patterns also exhibited a pronounced sex difference associated with estrous cyclicity. Pubertal onset, defined by vaginal opening, preputial separation, and sex steroid concentrations, occurred later than previously reported under lab conditions for both sexes. Vaginal opening and increased fecal estradiol concentrations were closely tied to the commencement of 4-day oscillations in CBT and UR power. By contrast, preputial separation and the first rise in testosterone concentration were not associated with adolescent changes to CBT rhythms in male rats. Together, males and females exhibited unique temporal patterning of CBT and sex steroids across pubertal development, with tractable associations between hormonal concentrations, external development, and temporal structure in females. The preservation of these features outside the laboratory supports CBT as a strong candidate for translational pubertal monitoring under semi-naturalistic conditions in females.

Developing Peri-Operative Rehabilitation in Degenerative Cervical Myelopathy [AO Spine RECODE-DCM Research Priority Number 6]: An Unexplored Opportunity?

STUDY DESIGN

Narrative review.

OBJECTIVE

Degenerative cervical myelopathy is one of the most frequent impairments of the spinal cord encountered internationally in adults. Currently, surgical decompression is the recommended treatment for people with DCM (PwCM) presenting with moderate to severe symptoms or neurological deficits. However, despite surgical intervention, not all patients make a complete recovery due to the irreversible tissue damage within the spinal cord. The objective of this review is to describe the state and gaps in the current literature on rehabilitation for PwCM and possible innovative rehabilitation strategies.

METHODS

Literature search.

RESULTS

In other neurological disorders such as stroke and acute traumatic spinal cord injury (SCI), timely and strategic rehabilitation has been shown to be indispensable for maximizing functional outcomes, and it is imperative that appropriate perioperative rehabilitative interventions accompany surgical approaches in order to enable the best outcomes. In this review, the current state of knowledge regarding rehabilitation for PwCM is described. Additionally, various therapies that have shown to improve outcomes in comparable neurological conditions such as stroke and SCI which may be translated to DCM will be reviewed.

CONCLUSIONS

We conclude that locomotor training and arm/hand therapy may benefit PwCM. Further, we conclude that body weight support, robotic assistance, and virtual/augmented reality therapies may be beneficial therapeutic analogs to locomotor and hand therapies.

Timeline of Changes in Biomarkers Associated with Spinal Cord Injury-Induced Polyuria

Deficits in upper and lower urinary tract function, which include detrusor overactivity, urinary incontinence, detrusor-sphincter dyssynergia, and polyuria, are among the leading issues that arise after spinal cord injury (SCI) affecting quality of life. Given that overproduction of urine (polyuria) has been shown to be associated with an imbalance in key regulators of body fluid homeostasis, the current study examined the timing of changes in levels of various relevant hormones, peptides, receptors, and channels post-contusion injury in adult male Wistar rats. The results show significant up- or downregulation at various time points, beginning at 7 days post-injury, in levels of urinary atrial natriuretic peptide, serum arginine vasopressin (AVP), kidney natriuretic peptide receptor-A, kidney vasopressin-2 receptor, kidney aquaporin-2 channels, and kidney epithelial sodium channels (β- and γ-, but not α-, subunits). The number of AVP-labeled neurons in the hypothalamus (supraoptic and -chiasmatic, but not paraventricular, nuclei) was also significantly altered at one or more time points. These data show significant fluctuations in key biomarkers involved in body fluid homeostasis during the post-SCI secondary injury phase, suggesting that therapeutic interventions (e.g., desmopressin, a synthetic analogue of AVP) should be considered early post-SCI.

Bladder and bowel responses to lumbosacral epidural stimulation in uninjured and transected anesthetized rats

Spinal cord epidural stimulation (scES) mapping at L5-S1 was performed to identify parameters for bladder and bowel inhibition and/or contraction. Using spinally intact and chronic transected rats of both sexes in acute urethane-anesthetized terminal preparations, scES was systematically applied using a modified Specify 5-6-5 (Medtronic) electrode during bladder filling/emptying cycles while recording bladder and colorectal pressures and external urethral and anal sphincter electromyography activity. The results indicate frequency-dependent effects on void volume, micturition, bowel peristalsis, and sphincter activity just above visualized movement threshold intensities that differed depending upon neurological intactness, with some sex-dependent differences. Thereafter, a custom-designed miniature 15-electrode array designed for greater selectivity was tested and exhibited the same frequency-dependent urinary effects over a much smaller surface area without any concurrent movements. Thus, select activation of autonomic nervous system circuitries with scES is a promising neuromodulation approach for expedient translation to individuals with SCI and potentially other neurologic disorders.

Kinematic analysis of penile reflexes in a rat model of spinal cord injury

The ex-copula penile dorsiflexion reflex (PDFR) is an established measure of sexual dysfunction in male rat models of spinal cord injury. Although the PDFR after complete spinal transection is well described, information regarding the more clinically relevant incomplete spinal contusion injury model is limited. This study examined, using two-dimensional (2D) kinematic analysis, the relationship between the PDFR and degree of white matter sparing (WMS). Male Wistar rats received a T9 contusion with varying degrees of impactor forces. Weekly kinematic recordings of the PDFR were made 3–8 weeks postinjury. Sexual reflex components examined included maximum angle of penile dorsiflexion, total penile event duration, and penile ascent speed. Post hoc comparison between animals grouped based upon injury severity (moderate–severe: 13.33%–17.15% WMS vs moderate: 20.85%–33.50% WMS) indicated PDFR effects. Specifically, the numbers of animals with more moderate contusions having data points above the median in both maximum angle of penile dorsiflexion and penile ascent speed were significantly lower than animals with more severe injuries. Total penile event duration was also affected but only at more chronic time points (6–8 weeks). Thus, 2D kinematic analysis of the PDFR allows for more consistent and quantifiable analysis of the subtle differences that can occur between injury severity groups in the rat contusion model.

Telemetric monitoring of penile pressure during mating in rats after chronic spinal cord injury

In men with a spinal cord injury (SCI), erectile function, ejaculation, and fertility are severely impaired. The present study utilized a telemetric pressure transducer implanted into the corpus cavernosum of the penis to examine sexual function during awake mating behavior in a rat contusion model with a range of Infinite Horizon Impactor forces distributed between 150 and 215 kdyn. The mating behavior paradigm included examination of the counts, average pressure, and average duration for mounts, intromissions, and ejaculations. Male Wistar rats were mated with receptive females in 30-min sessions preinjury (sexual acclimation) and once per week for 6 wk beginning after a 2-wk recovery period post-SCI. All SCI animals had significant deficits in sexual function in the parameters measured. These deficiencies were more prevalent in a subset having less than 20% white matter sparing, likely a reflection of the extent of bilateral spino-bulbo-spinal sexual circuitry disruption at the lesion epicenter. The resulting discoordination of the autonomic and somatic reflex control of erection and ejaculation recorded using telemetry devices in an awake, behaving animal model provides an effective means of gauging sexual function deficits after SCI and could have utility for quantifying recovery after a therapeutic intervention.