Factors influencing frontal cortex development and recovery from early frontal injury

Ongoing effects of preterm birth on the dopaminergic and noradrenergic pathways in the frontal cortex and hippocampus of guinea pigs

Children born preterm have an increased likelihood of developing neurobehavioral disorders such as attention-deficit hyperactivity disorder (ADHD) and anxiety. These disorders have a sex bias, with males having a higher incidence of ADHD, whereas anxiety disorder tends to be more prevalent in females. Both disorders are underpinned by imbalances to key neurotransmitter systems, with dopamine and noradrenaline in particular having major roles in attention regulation and stress modulation. Preterm birth disturbances to neurodevelopment may affect this neurotransmission in a sexually dimorphic manner. Time-mated guinea pig dams were allocated to deliver by preterm induction of labor (gestational age 62 [GA62]) or spontaneously at term (GA69). The resultant offspring were randomized to endpoints as neonates (24 h after term-equivalence age) or juveniles (corrected postnatal day 40, childhood equivalence). Relative mRNA expressions of key dopamine and noradrenaline pathway genes were examined in the frontal cortex and hippocampus and quantified with real-time PCR. Myelin basic protein and neuronal nuclei immunostaining were performed to characterize the impact of preterm birth. Within the frontal cortex, there were persisting reductions in the expression of dopaminergic pathway components that occurred in preterm males only. Conversely, preterm-born females had increased expression of key noradrenergic receptors and a reduction of the noradrenergic transporter within the hippocampus. This study demonstrated that preterm birth results in major changes in dopaminergic and noradrenergic receptor, transporter, and synthesis enzyme gene expression in a sex- and region-based manner that may contribute to the sex differences in susceptibility to neurobehavioral disorders. These findings highlight the need for the development of sex-based treatments for improving these conditions.

Concussion History and Cognitive Function in a Large Cohort of Adolescent Athletes

BACKGROUND

The incidence of reported concussions in the adolescent population is increasing, yet research on the effects of concussions in this population is minimal and inconclusive.

PURPOSE

To assess the association between concussion and performance on a cognitive test battery.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Using multivariate models, the authors assessed the association between concussion and performance on a cognitive test battery among 5616 high school and junior high school athletes. The researchers utilized a global cognitive score and scores for 5 domains: verbal memory, visual memory, visual motor, reaction time, and impulse control. Each cognitive score was converted to a z score with the mean and SD of the nonconcussed population. Results from each model were then interpreted as change in the standardized unit score. In the models, concussion was evaluated as ever having a concussion, number of concussions, time since last concussion, and age at first concussion.

RESULTS

Ever having a concussion was associated with a mean decrease of 0.11 standardized units (95% CI, -0.20 to -0.01) on the global cognitive score and lower scores in all cognitive domains. Each additional concussion was associated with lower scores on global cognitive function (effect estimate, -0.06; 95% CI, -0.11 to -0.02), verbal memory, visual memory, and impulse control. Concussion in early childhood was associated with lower global cognition (effect estimate, -0.05; 95% CI, -0.08 to -0.01), visual memory, and motor visual scores as compared with concussions in later childhood. The associations between time since last concussion and cognitive test scores were nonlinear, and on all tests, lower scores were observed even ≥1 year after the concussion.

CONCLUSION

On the basis of objective performance metrics for cognitive function, concussions had a more persistent effect on cognitive function than previously thought. The age at which an individual has his or her first concussion may be an important factor in determining long-lasting cognitive effects.

Progesterone Treatment Shows Benefit in Female Rats in a Pediatric Model of Controlled Cortical Impact Injury

Purpose

We recently showed that progesterone treatment can reduce lesion size and behavioral deficits after moderate-to-severe bilateral injury to the medial prefrontal cortex in immature male rats. Whether there are important sex differences in response to injury and progesterone treatment in very young subjects has not been given sufficient attention. Here we investigated progesterone’s effects in the same model of brain injury but with pre-pubescent females.

Methods

Twenty-eight-day-old female Sprague-Dawley rats received sham (n = 14) or controlled cortical impact (CCI) (n = 21) injury, were given progesterone (8 mg/kg body weight) or vehicle injections on post-injury days (PID) 1–7, and underwent behavioral testing from PID 9–27. Brains were evaluated for lesion size at PID 28.

Results

Lesion size in vehicle-treated female rats with CCI injury was smaller than that previously reported for similarly treated age-matched male rats. Treatment with progesterone reduced the effect of CCI on extent of damage and behavioral deficits.

Conclusion

Pre-pubescent female rats with midline CCI injury to the frontal cortex have reduced morphological and functional deficits following progesterone treatment. While gender differences in susceptibility to this injury were observed, progesterone treatment produced beneficial effects in young rats of both sexes following CCI.

Sex-related differences in effects of progesterone following neonatal hypoxic brain injury

There is no satisfactory therapeutic intervention for neonatal hypoxic-ischemic (HI) encephalopathy. Progesterone is known to be effective in treating traumatic brain injury in adult animals but its effects in neonatal brains have not been reported. Brain injuries were induced by a unilateral common carotid artery ligation plus hypoxia exposure. Progesterone was administered immediately after hypoxia and daily for 5 days at 8 mg/kg, followed by a tapered dose for two days. At six weeks post-injury, lesion size and inflammatory factors were evaluated. Progesterone-treated, HI-injured male animals, but not females, showed significant long-term tissue protection compared to vehicle, suggesting an important sex difference in neuroprotection. Progesterone-treated, HI-injured male rats had fewer activated microglia in the cortex and hippocampus compared to controls. The rats were tested for neurological reflexes, motor asymmetry, and cognitive performance at multiple time points. The injured animals exhibited few detectable motor deficits, suggesting a high level of age- and injury-related neuroplasticity. There were substantial sex differences on several behavioral tests, indicating that immature males and females should be analyzed separately. Progesterone-treated animals showed modest beneficial effects in both sexes compared to vehicle-treated injured animals. Sham animals given progesterone did not behave differently from vehicle-treated sham animals on any measures.

Single-micronutrient and broad-spectrum micronutrient approaches for treating mood disorders in youth and adults

Several different vitamins and minerals appear to be effective augmenting agents for mood-modifying drugs, but are not potent monotherapies in themselves for treating psychiatric disorders. In contrast, broad-spectrum micronutrient interventions appear in early trials to be as effective as psychiatric medications with fewer adverse effects for treating mood disorders, ADHD, aggressivity, and misconduct in youth and adults. Broad-spectrum treatments also may improve stress responses, cognition, and sense of well-being in healthy adults, but have been less well studied in youth. Current clinical data justify an extensive expansion of research on micronutrient mechanisms and treatments in psychiatry.

Status epilepticus during early development disrupts sexual behavior in adult female rats: recovery with sexual experience

Female sexual behavior is sensitive to stress and diseases. Some studies have shown that status epilepticus (SE) can affect sexual proceptivity and receptivity in female rats and also increases reject responses towards males. However, epidemiologic studies indicate that SE is more frequent in young individuals. Herein, we assessed the effects of SE in infant females on their sexual behavior during adulthood. Thirteen-day-old (P13) rat pups received intraperitoneal injections of lithium chloride (3 mEq/kg). Twenty hours later, at P14, SE was induced by subcutaneous injection of pilocarpine hydrochloride (100 mg/kg s.c.). Control animals were given an equal volume of saline subcutaneously. The animals were weaned at P21 and, later in adulthood, were ovariectomized and hormone-primed with estradiol+progesterone, and their sexual behavior assessed during 4 separate trials of 30 min each with a stud male. Our results indicate that proceptive behaviors (solicitations and hops and darts) were impaired during the first trial, but no alterations were observed for receptivity and attractivity. By trial 3, all SE females displayed normal proceptivity. These results indicate that SE in infancy readily affects proceptivity in a reversible manner. We discuss the role of sexual experience in recovery.

Olanzapine treatment of adolescent rats causes enduring specific memory impairments and alters cortical development and function

Antipsychotic drugs are increasingly used in children and adolescents to treat a variety of psychiatric disorders. However, little is known about the long-term effects of early life antipsychotic drug treatment. Most antipsychotic drugs are potent antagonists or partial agonists of dopamine D2 receptors; atypical antipsychotic drugs also antagonize type 2A serotonin receptors. Dopamine and serotonin regulate many neurodevelopmental processes. Thus, early life antipsychotic drug treatment can, potentially, perturb these processes, causing long-term behavioral- and neurobiological impairments. Here, we treated adolescent, male rats with olanzapine on post-natal days 28-49. As adults, they exhibited impaired working memory, but normal spatial memory, as compared to vehicle-treated control rats. They also showed a deficit in extinction of fear conditioning. Measures of motor activity and skill, habituation to an open field, and affect were normal. In the orbital- and medial prefrontal cortices, parietal cortex, nucleus accumbens core and dentate gyrus, adolescent olanzapine treatment altered the developmental dynamics and mature values of dendritic spine density in a region-specific manner. Measures of motor activity and skill, habituation to an open field, and affect were normal. In the orbital- and medial prefrontal cortices, D1 binding was reduced and binding of GABA(A) receptors with open Cl(-) channels was increased. In medial prefrontal cortex, D2 binding was also increased. The persistence of these changes underscores the importance of improved understanding of the enduring sequelae of pediatric APD treatment as a basis for weighing the benefits and risks of adolescent antipsychotic drug therapy, especially prophylactic treatment in high risk, asymptomatic patients. The long-term changes in neurotransmitter receptor binding and neural circuitry induced by adolescent APD treatment may also cause enduring changes in behavioral- and neurobiological responses to other therapeutic- or illicit psychotropic drugs.

Cortical development of AMPA receptor trafficking proteins

AMPA-receptor trafficking plays a central role in excitatory plasticity, especially during development. Changes in the number of AMPA receptors and time spent at the synaptic surface are important factors of plasticity that directly affect long-term potentiation (LTP), long-term depression (LTD), synaptic scaling, and the excitatory-inhibitory (E/I) balance in the developing cortex. Experience-dependent changes in synaptic strength in visual cortex (V1) use a molecularly distinct AMPA trafficking pathway that includes the GluA2 subunit. We studied developmental changes in AMPA receptor trafficking proteins by quantifying expression of GluA2, pGluA2 (GluA2serine880), GRIP1, and PICK1 in rat visual and frontal cortex. We used Western Blot analysis of synaptoneurosome preparations of rat visual and frontal cortex from animals ranging in age from P0 to P105. GluA2 and pGluA2 followed different developmental trajectories in visual and frontal cortex, with a brief period of over expression in frontal cortex. The over expression of GluA2 and pGluA2 in immature frontal cortex raises the possibility that there may be a period of GluA2-dependent vulnerability in frontal cortex that is not found in V1. In contrast, GRIP1 and PICK1 had the same developmental trajectories and were expressed very early in development of both cortical areas. This suggests that the AMPA-interacting proteins are available to begin trafficking receptors as soon as GluA2-containing receptors are expressed. Finally, we used all four proteins to analyze the surface-to-internalization balance and found that this balance was roughly equal across both cortical regions, and throughout development. Our finding of an exquisite surface-to-internalization balance highlights that these AMPA receptor trafficking proteins function as a tightly controlled system in the developing cortex.

Brain plasticity and recovery from early cortical injury

Neocortical development represents more than a simple unfolding of a genetic blueprint: rather, it represents a complex dance of genetic and environmental events that interact to adapt the brain to fit a particular environmental context. Most cortical regions are sensitive to a wide range of experiential factors during development and later in life, but the injured cortex appears to be unusually sensitive to perinatal experiences. This paper reviews the factors that influence how normal and injured brains (both focal and ischemic injuries) develop and adapt into adulthood. Such factors include prenatal experiences in utero as well as postnatal experiences throughout life. Examples include the effects of sensory and motor stimulation, psychoactive drugs (including illicit and prescription drugs), maternal and postnatal stress, neurotrophic factors, and pre- and postnatal diet. All these factors influence cerebral development and influence recovery from brain injury during development.