Early postnatal exposure to isoflurane causes cognitive deficits and disrupts development of newborn hippocampal neurons via activation of the mTOR pathway.

Clinical and preclinical studies indicate that early postnatal exposure to anesthetics can lead to lasting deficits in learning and other cognitive processes. The mechanism underlying this phenomenon has not been clarified and there is no treatment currently available. Recent evidence suggests that anesthetics might cause persistent deficits in cognitive function by disrupting key events in brain development. The hippocampus, a brain region that is critical for learning and memory, contains a large number of neurons that develop in the early postnatal period, which are thus vulnerable to perturbation by anesthetic exposure. Using an in vivo mouse model we demonstrate abnormal development of dendrite arbors and dendritic spines in newly generated dentate gyrus granule cell neurons of the hippocampus after a clinically relevant isoflurane anesthesia exposure conducted at an early postnatal age. Furthermore, we find that isoflurane causes a sustained increase in activity in the mechanistic target of rapamycin pathway, and that inhibition of this pathway with rapamycin not only reverses the observed changes in neuronal development, but also substantially improves performance on behavioral tasks of spatial learning and memory that are impaired by isoflurane exposure. We conclude that isoflurane disrupts the development of hippocampal neurons generated in the early postnatal period by activating a well-defined neurodevelopmental disease pathway and that this phenotype can be reversed by pharmacologic inhibition.

Low-dose Induction of Buprenorphine in Pregnancy: A Case Series.

BACKGROUND: Because of a risk of precipitated withdrawal occurring from buprenorphine induction in people who use fentanyl, low-dose inductions are becoming increasingly common. However, little evidence exists on the use of this method in pregnant people. METHODS: We conducted a case series of all pregnant people treated for opioid use disorder with low-dose buprenorphine induction at the University of Maryland Medical Center between January 1, 2021, and August 22, 2022. Primary outcome was completion of induction regimen. Secondary outcomes were self-report of withdrawal, continuation of buprenorphine until delivery, and return to or continuation of illicit opioid use. RESULTS: Six pregnant people were prescribed a total of 10 buprenorphine inductions. Five of the 6 pregnant people (83.3%) completed at least 1 induction, none of whom experienced precipitated withdrawal. Two of 6 (33.3%) continued buprenorphine until the time of delivery, and 1 of 6 (16.7%) abstained from illicit opioid use. CONCLUSIONS: The low-dose buprenorphine induction regimen described was successful in 5 of 6 pregnant individuals. Further research, particularly regarding continuation rates, is needed.

Baltimore pediatric ocular trauma study: Health disparities and outcomes in pediatric and adolescent open globe trauma.

Purpose Children represent approximately one-third of patients with serious ocular injuries. Our study evaluates associations between race and socioeconomic status in presentation and outcomes of pediatric and adolescent traumatic open globe injuries. Methods We conducted a retrospective chart review of traumatic open globe injuries in pediatric and adolescent patients presenting to Johns Hopkins Hospital and University of Maryland Medical Center between 2006 and 2020. Variables assessed included age, gender, parent-identified race, median household income, mechanism of injury, initial and final visual acuity (VA), and length of follow-up. Results Eighty patients ranging from 4 months to 17.7 years (mean 9.3 years) presented with traumatic open globe injury. Identifications were 28 White (35%), 38 Black (48%), and 5 Hispanic (6%). Initial presenting and final VA, pediatric ocular trauma score (POTS), and length of follow-up did not differ significantly among race, gender, or income. Black patients had higher rates of blunt trauma (odds ratio (OR) 3.81; 95% confidence interval (CI) 0.95-15.24, p = 0.07), uveal prolapse (OR 3.58; 95% CI 1.03-12.43; p = 0.049), and enucleation (OR 10.55; 95% CI 1.26-88.31). Hispanic patients presented at a younger age of 2.8 years mean age vs. 9.9 years (p = 0.004) for others. Conclusion Visual outcomes following traumatic open globe injury were independent of race, gender, or income. However, blunt trauma, uveal prolapse, and enucleation rates were higher in Black patients, and ocular trauma occurred at a younger age in Hispanic patients.

Sensorimotor Outcomes in Pediatric Patients With Ocular Trauma in Baltimore.

PURPOSE: To evaluate sensorimotor outcomes following traumatic open globe injuries in the pediatric population. METHODS: A retrospective cohort of 80 pediatric patients aged 0.4 to 17.7 years (mean age: 9.3 years, median age: 8.3 years) presenting with traumatic open globe injury to the Johns Hopkins and University of Maryland Medical Centers was evaluated between January 2006 and January 2020. Parameters included the mechanism of injury, length of time of visual deprivation, initial and final visual acuity, additional eye pathologies, and demographic factors such as age and sex. RESULTS: Among children with more than 6 months of follow-up, 77.4% developed poor stereopsis and 50% developed strabismus. Children who developed strabismus had a lower Pediatric Ocular Trauma Score (POTS), indicating greater severity of injury, than children who did not develop strabismus (P = .005, chi-square test). A higher POTS, indicating less severe ocular injury, significantly correlated to a better stereoacuity (P = .001, chi-square test). CONCLUSIONS: The findings indicate that strabismus and poor stereopsis are common in pediatric open globe injuries, occurring in more than half of children with pediatric open globe trauma. These outcomes are associated with poor presenting visual acuity, more severe ocular trauma, and a lower presenting POTS. [J Pediatr Ophthalmol & Strabismus. 2022;59(5):303-309.].

Medial prefrontal cortex and anteromedial thalamus interaction regulates goal-directed behavior and dopaminergic neuron activity.

The prefrontal cortex is involved in goal-directed behavior. Here, we investigate circuits of the PFC regulating motivation, reinforcement, and its relationship to dopamine neuron activity. Stimulation of medial PFC (mPFC) neurons in mice activated many downstream regions, as shown by fMRI. Axonal terminal stimulation of mPFC neurons in downstream regions, including the anteromedial thalamic nucleus (AM), reinforced behavior and activated midbrain dopaminergic neurons. The stimulation of AM neurons projecting to the mPFC also reinforced behavior and activated dopamine neurons, and mPFC and AM showed a positive-feedback loop organization. We also found using fMRI in human participants watching reinforcing video clips that there is reciprocal excitatory functional connectivity, as well as co-activation of the two regions. Our results suggest that this cortico-thalamic loop regulates motivation, reinforcement, and dopaminergic neuron activity.

Supramammillary neurons projecting to the septum regulate dopamine and motivation for environmental interaction in mice.

The supramammillary region (SuM) is a posterior hypothalamic structure, known to regulate hippocampal theta oscillations and arousal. However, recent studies reported that the stimulation of SuM neurons with neuroactive chemicals, including substances of abuse, is reinforcing. We conducted experiments to elucidate how SuM neurons mediate such effects. Using optogenetics, we found that the excitation of SuM glutamatergic (GLU) neurons was reinforcing in mice; this effect was relayed by their projections to septal GLU neurons. SuM neurons were active during exploration and approach behavior and diminished activity during sucrose consumption. Consistently, inhibition of SuM neurons disrupted approach responses, but not sucrose consumption. Such functions are similar to those of mesolimbic dopamine neurons. Indeed, the stimulation of SuM-to-septum GLU neurons and septum-to-ventral tegmental area (VTA) GLU neurons activated mesolimbic dopamine neurons. We propose that the supramammillo-septo-VTA pathway regulates arousal that reinforces and energizes behavioral interaction with the environment.

Early Developmental Exposure to Repetitive Long Duration of Midazolam Sedation Causes Behavioral and Synaptic Alterations in a Rodent Model of Neurodevelopment.

There is a large body of preclinical literature suggesting that exposure to general anesthetic agents during early life may have harmful effects on brain development. Patients in intensive care settings are often treated for prolonged periods with sedative medications, many of which have mechanisms of action that are similar to general anesthetics. Using in vivo studies of the mouse hippocampus and an in vitro rat cortical neuron model we asked whether there is evidence that repeated, long duration exposure to midazolam, a commonly used sedative in pediatric intensive care practice, has the potential to cause lasting harm to the developing brain. We found that mice that underwent midazolam sedation in early postnatal life exhibited deficits in the performance on Y-maze and fear-conditioning testing at young adult ages. Labeling with a nucleoside analog revealed a reduction in the rate of adult neurogenesis in the hippocampal dentate gyrus, a brain region that has been shown to be vulnerable to developmental anesthetic neurotoxicity. In addition, using immunohistochemistry for synaptic markers we found that the number of presynaptic terminals in the dentate gyrus was reduced, while the number of excitatory postsynaptic terminals was increased. These findings were replicated in a midazolam sedation exposure model in neurons in culture. We conclude that repeated, long duration exposure to midazolam during early development has the potential to result in persistent alterations in the structure and function of the brain.