Push–pull perfusion

Abstract: A diverse array of neurotransmitters and neuromodulators control and affect brain function A profound understanding of the signaling pathways and the neural circuits underlying behavior is therefore likely to require the tracking of concentration changes of active neurochemicals In the present study, we demonstrate the feasibility of a method allowing the simultaneous determination of the concentrations of six neurotransmitters: acetylcholine, serotonin, dopamine, gamma-aminobutyric acid (GABA), glutamate and aspartate, in the extracellular brain fluid (EBF) We used hydrophilic interaction chromatography (HILIC) coupled to tandem mass spectrometry (MS/MS) to analyze the EBF from the monkey brain A push-pull sampling method was used to collect EBF from the prefrontal cortex (PFC) of conscious monkeys at flow rates in the range of low nL/min The detection limits of acetylcholine, serotonin, dopamine, GABA, glutamate and aspartate were 0015,015,03,12, 6 and 15 femtomoles, respectively, allowing us to quantitatively determine the concentrations of these six neurotransmitters simultaneously from 500 nL in vivo samples We conclude that HILIC/MS/MS combined with the push-pull sampling method represents a sensitive technique for simultaneous monitoring of neurotransmitters from EBF samples Copyright (C) 2007 John Wiley & Sons, Ltd

Abstract: Oxytocin (0T)-containing neurons are localized predominantly in the compact magnocellular and parvocellular divisions of the paraventricular nucleus (PVN) and in the supraoptic nucleus (SON). Unlike arginine vasopressin (AVP) neurons, OT-producing cell bodies appear to be absent in extrahypothalamic brain areas. Magnocellular hypothalamic neurons project to the neurohypophysis. Following peripheral release, OT is primarily associated with smooth muscle contraction of the female reproductive system, and AVP with water reabsorption by the kidney, vasoconstriction in certain vascular beds, and glycogenolysis in the liver. Additionally, parvocellular neurons of the PVN (OT, AVP) and of extrahypothalamic sources (AVP) project to central targets, especially limbic areasZ known to be involved in learning, memory, and behavioral performance. Since the transport of endogenous nonapeptides across the blood-brain barrier is severely re~tricted,~ central effects should be the result of centrally released rather than peripherally circulating OT and AVP, respectively. Such central effects include defervescence (AVP)4 and selective behavioral regulation (OT, AVP).5,6 The fact that different cell populations project peripherally to the neurohypophysis and centrally to limbic brain targets implies that a stimulus which provokes a release of OT and AVP into the bloodstream does not necessarily provoke a release within the

Abstract: Utilizing the push-pull perfusion technique, we examined the effect of an intravenous bolus injection of recombinant human interleukin (IL)-1 beta on the release of prostaglandin E2 (PGE2), CRF, and AVP in several hypothalamic areas of freely moving rats, simultaneously monitoring plasma ACTH levels. Perfused hypothalamic areas were the median eminence (ME), the paraventricular nucleus (PVN), and the medial preoptic area (MPOA). During the period 12:00-15:00 h, perfusates and blood samples were collected every 10 min (between 13:00 and 13:40 h) or 20 min (between 12:00 and 13:00 h, and between 13:40 and 15:00 h). IL-1 beta (1.0 micrograms/rat) or vehicle only (in control groups) was injected at 13:00 h. In both the ME and the PVN but not in the MPOA, the outputs of CRF and AVP were significantly stimulated by IL-1 beta, prior to the rise in plasma ACTH. A significant stimulation of PGE2 by IL-1 beta was observed only in the PVN, and its temporal profile was very similar to those of CRF and AVP in the PVN. These results suggest that PGE2 may be a trigger in the PVN for the activation of CRF and AVP neurons, and thereby ACTH secretion, which follows IL-1 beta injection.