Oxytocin and Steroid Actions.

Biosynthesis and secretion of the hypothalamic nonapeptide oxytocin largely depends on steroid hormones. Estradiol, corticosterone, and vitamin D seem to be the most prominent actors. Due to their lipophilic nature, systemic steroids are thought to be capable of crossing the blood-brain barrier, thus mediating central functions including neuroendocrine and behavioral control. The actual mode of action of steroids in hypothalamic circuitry is still unknown: Most of the oxytocinergic perikarya lack nuclear steroid receptors but express proteins suspected to be membrane receptors for steroids. Oxytocin expressing neurons contain enzymes important for intrinsic steroid metabolism. Furthermore, they produce and probably liberate specific steroid-binding globulins. Rapid responses to steroid hormones may involve these binding proteins and membrane-associated receptors, rather than classic nuclear receptors and genomic pathways. Neuroendocrine regulation, reproductive behaviors, and stress response seem to depend on these mechanisms.

The separation and quantification of aminochromes using high-pressure liquid chromatography with electrochemical detection.

There is increasing evidence that oxidative stress plays an important role in the pathogenesis of many neurodegenerative diseases including Parkinson's disease (PD). In particular there is support for the participation of oxidized catecholamines in PD. Catecholamines are highly reactive and are readily oxidized to aminochromes. While aminochromes have been shown to be toxic, their formation in oxidative stress and subsequent participation in disease has yet to be confirmed. We propose that the characterization of aminochromes, specifically dopaminochrome, is important in clarifying the role that oxidized catecholamines play in PD. We have developed a novel method for the separation and quantification of aminochromes using high-pressure liquid chromatography with electrochemical detection (HPLC-ED). Our method utilizes the separation principles employed in measuring catecholamines by HPLC except that the electrochemical detection of aminochromes is achieved by reversing the detector's electrode. We have used this method to separate and quantify aminochrome standards, prepared by oxidizing catecholamines with sodium periodate (NaIO(4)) and we have also shown that aminochromes can be measured in plasma and cell lysates. Furthermore, we have characterized aminochromes to facilitate forthcoming studies on aminochromes and the role oxidized catecholamines may play in neurodegenerative disease.