The reduction in CD68
immunoreactivity between sedentary and exercised Grn − / − mice is consistent with the general anti-inflammatory effects of exercise, including those found in other mouse models of neurodegenerative disease (Gleeson et al., 2011; Stranahan et al., 2012).
The most recent study report described in these same regions decreased tissue levels of 5 - HT and tryptophan hydroxylase, the synthesizing enzyme for serotonin, and no evidence of excessive serotonin degradation as assessed by levels of 5 - hydroxyindoleacetic acid (the main metabolite of serotonin) or ratios of 5 - hydroxyindoleacetic acid to serotonin.30 A recent article described a significant association
between a decrease in medullary 5 - HT1A receptor
immunoreactivity and specific SIDS risk factors, including tobacco smoking.40 These data confirm results from earlier studies in humans39, 41 and are also consistent with studies in piglets that revealed that postnatal exposure to nicotine decreases medullary 5 - HT1A receptor
immunoreactivity.42 Animal studies have revealed that serotonergic neurons located in the medullary raphe and adjacent paragigantocellularis lateralis play important roles in many autonomic functions including the control of respiration, blood pressure, heart rate, thermoregulation, sleep and arousal, and upper airway patency.