In this autopsy series, only 2 of 12 patients with unexplained sudden death were observed to have a defect in HERG among five candidate genes tested. It is likely that elucidation of SCD mechanisms in such patients will await the discovery of multiple, novel arrhythmia-causing gene defects.

This chapter reviews the neurobiological effects of stress sensitivity and CIT treatment observed in our nonhuman primate model of Functional Hypothalamic Amenorrhea (FHA). This type of infertility, also known as stress-induced amenorrhea, is exhibited by cynomolgus macaques. In small populations, some individuals are stress sensitive (SS) and others are highly stress resilient (HSR). The SS macaques have suboptimal secretion of estrogen and progesterone during normal menstrual cycles. SS monkeys also have decreased serotonin gene expression and increased CRF expression compared to HSR monkeys. Recently, we found that s-citalopram (CIT) treatment improved ovarian steroid secretion in SS monkeys, but had no effect in HSR monkeys. Examination of the serotonin system revealed that SS monkeys had significantly lower Fev (fifth Ewing variant, rodent Pet1), TPH2 (tryptophan hydroxylase 2), 5HT1A autoreceptor and SERT (serotonin reuptake transporter) expression in the dorsal raphe than SR monkeys. However, CIT did not alter the expression of either Fev, TPH2, SERT or 5HT1A mRNAs. In contrast, SS monkeys tended to a higher density of CRF fiber innervation of the dorsal raphe than HSR monkeys, and CIT significantly decreased the CRF fiber density in SS animals. In addition, CIT increased CRF-R2 gene expression in the dorsal raphe. We speculate that in a 15-week time frame, the therapeutic effect of S-citalopram may be achieved through a mechanism involving extracellular serotonin inhibition of CRF and stimulation of CRF-R2, rather than alteration of serotonin-related gene expression.

We have demonstrated marked differences in the neurobiology of the serotonin system between stress-sensitive (SS) and stress-resilient (SR) cynomolgus macaques characterized in a model of stress-induced amenorrhea, also called functional hypothalamic amenorrhea (FHA). Dysfunction of the serotonin system in SS monkeys suggested that administration of a selective serotonin reuptake inhibitor (SSRI) might correct FHA. This study examines the effect of escitalopram (CIT) administration to SS and SR monkeys on corticotrophin-releasing factor (CRF) receptor 1 (CRF-R1) and CRF receptor 2 (CRF-R2) gene expression in the serotonin cell body region of the midbrain dorsal raphe. CRF-R1 was not significantly different between groups. There was a significant effect of treatment and a significant interaction between treatment and stress sensitivity on the average CRF-R2-positive pixel area (P < .004 and P < .006, respectively) and on the average number of CRF-R2-positive cells (P < .023 and P < .025, respectively). CIT significantly increased CRF-R2-positive pixel area and cell number in the SS group (pixel area P < .001; cell number P < .01; Bonferoni) but not in the SR group. In summary, CIT administration tended to decrease CRF-R1, but the small animal number precluded significance. CIT administration significantly increased CRF-R2 only in SS animals. These data suggest that the administration of CIT reduces anxiogenic components and increases anxiolytic components of the CRF system in the midbrain serotonin network, which in turn leads to improved ovarian function. Moreover, these data raise the possibility that SSRIs may be effective in the treatment of stress-induced infertility.

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