No abstract

No abstract

Our observation that male rats innate fear response differed with hormonal status, as well as the higher prevalence of fear and anxiety disorders in human females led to the current investigation of the impact of phases of the estrous cycle on innate fear responding. Female rats in different phases of the cycle were exposed to an innate fear-inducing stimulus (2,5-dihydro- 2,4,5-trimethylthiazoline, TMT odor) and monitored for changes in behavior and brain activation. Behavioral data showed freezing responses to TMT were significantly enhanced during estrus as compared to other phases of the cycle. This data was supported by significant increases in pixel intensity in cortical and sub-cortical regions in estrus compared to proestrus and diestrus. Imaging results demonstrated significant increases in brain activation in the somatosensory and insular cortices when comparing estrus to diestrus. There were significant increases in neural activity in the BNST and septum in estrus as compared to proestrus. Additionally, the hippocampus, hypothalamus, olfactory system, and cingulate cortex show significant increases in the estrus phase when compared to both diestrus and proestrus. Taken together, these results suggest that the female's hormonal status may be correlated with alterations in both neuronal and behavioral indices of fear.

Oxytocinergic neurotransmission during lactation contributes to reduction of anxiety levels and fear. However, our knowledge of where oxytocin acts in the brain to achieve this effect, particularly to an unconditioned fear stimulus, is incomplete. We used blood oxygenation level dependent (BOLD) fMRI to test whether central administration of oxytocin 45–60 minutes before fMRI scanning alters maternal brain activation in response to a predator scent (TMT, trimethylthiazoline). Comparison behavioral experiments that examined maternal responses to this unconditioned fear -inducing odor were carried out in a separate cohort of lactating rats given similar treatments. Behavioral experiments confirmed the effectiveness of oxytocin at reducing freezing behavior as compared to vehicle controls. Our fMRI findings indicate that oxytocin modulated both positive and negative BOLD responses across several olfactory and forebrain nuclei. Significantly greater percent increases in BOLD signal in response to TMT were observed in the anterior cingulate, bed nucleus of stria terminalis and perirhinal area of oxytocin pretreated rats. These animals also showed significantly larger percent decreases in BOLD in mammillary bodies, secondary motor cortex, gustatory cortex, prelimbic prefrontal cortex, orbital cortex, and the anterior olfactory nucleus. The observed pattern of brain activity suggests that oxytocin enhances neural processing in emotion and cognition driven brain areas such as the cingulate cortex, while dramatically reducing activity in areas also controlling autonomic, visceromotor and skeletomotor responses. The present data contribute to the growing literature suggesting the oxytocin modulate the integration of emotional and cognitive information through myriad brain regions to facilitate decreases in anxiety (even to an unconditioned stimulus) while potentially promoting pair-bonding, social memory and parental care.

OBJECTIVEThe need for anterior column reconstruction after thoracolumbar burst fractures remains controversial. Here, the authors present their experience with minimally invasive lateral thoracolumbar corpectomies for traumatic fractures.METHODSBetween 2012 and 2019, 59 patients with 65 thoracolumbar fractures underwent 65 minimally invasive lateral corpectomies (MIS group). This group was compared to 16 patients with single-level thoracolumbar fractures who had undergone open lateral corpectomies with the assistance of general surgery between 2007 and 2011 (open control group). Comparisons of the two groups were made with regard to operative time, estimated blood loss, time to ambulation, and fusion rates at 1 year postoperatively. The authors further analyzed the MIS group with regard to injury mechanism, fracture characteristics, neurological outcome, and complications.RESULTSPatients in the MIS group had a significantly shorter mean operative time (228.3 ± 27.9 vs 255.6 ± 34.1 minutes, p = 0.001) and significantly shorter mean time to ambulation after surgery (1.8 ± 1.1 vs 5.0 ± 0.8 days, p < 0.001) than the open corpectomy group. Mean estimated blood loss did not differ significantly between the two groups, though the MIS group did trend toward a lower mean blood loss. There was no significant difference in fusion status at 1 year between the MIS and open groups; however, this comparison was limited by poor follow-up, with only 32 of 59 patients (54.2%) in the MIS group and 8 of 16 (50%) in the open group having available imaging at 1 year. Complications in the MIS group included 1 screw misplacement requiring revision, 2 postoperative femoral neuropathies (one of which improved), 1 return to surgery for inadequate posterior decompression, 4 pneumothoraces requiring chest tube placement, and 1 posterior wound infection. The rate of revision surgery for the failure of fusion in the MIS group was 1.7% (1 of 59 patients).CONCLUSIONSThe minimally invasive lateral thoracolumbar corpectomy approach for traumatic fractures appears to be relatively safe and may result in shorter operative times and quicker mobilization as compared to those with open techniques. This should be considered as a treatment option for thoracolumbar spine fractures.