A simplified method for selecting a carbon-fiber electrode in pulse voltammetry

Fabrication optimisation of carbon fiber electrode with Taguchi method

In this study, we describe an optimised procedure for fabricating carbon fiber electrodes using Taguchi quality engineering method (TQEM). The preliminary results show a S/N ratio improvement from 22 to 30 db (decibel). The optimised parameter was tested by using a glass micropipette (0.3 mm outer/2.5 mm inner length of carbon fiber) dipped into PBS solution under 2.9 V triangle-wave electrochemical processing for 15 s, followed by coating treatment of micropipette on 2.6 V DC for 45 s in 5% Nafion solution. It is thus shown that Taguchi process optimisation can improve cost, manufacture time and quality of carbon fiber electrodes.

Melatonin potentiates 5-HT(1A) receptor activation in rat hypothalamus and results in hypothermia

Effects of melatonin on both thermoregulatory responses and hypothalamic serotonin release were assessed in unanesthetized rats at three different ambient temperatures (Ta). Systemic administration of melatonin (30-120 mg/kg, i.p) caused a decrease in both colonic temperature and hypothalamic serotonin (5-HT) release in rats at both Ta 8 and 22 degrees C. The hypothermia was brought about by a decrease in metabolic rate at Ta 8 degrees C, whereas at Ta 22 degrees C the hypothermia was produced by both a decrease in metabolic rate and an increase in cutaneous temperature. However, in the heat (Ta 31 degrees C), neither thermoregulatory responses nor hypothalamic 5-HT release was affected by the same amount of administered melatonin. The melatonin-induced hypothermia and decreased 5-HT release in the hypothalamus were attenuated by selective depletion of brain 5-HT produced by intracerebroventricular injection of 5,7-dihydroxytryptamine. Furthermore, the melatonin-induced hypothermia was almost completely abolished by treatment with a 5-HT2A receptor agonist (DOI) or a 5-HT1A receptor antagonist [(-)-pindolol]. The data indicate that melatonin potentiates the 5-HT1A receptor activation in the hypothalamus and results in hypothermic effects which can be antagonized by the expected hyperthermic effect of DOI.

Brain serotonin depletion attenuates diabetogenic effects of streptozotocin

The diabetogenic effects of streptozotocin (STZ) were studied on blood glucose, plasma insulin, feeding and drinking, body weight, islet morphology, and hypothalamic serotonin (5-HT) release in vehicle-pretreated rats and in rats pretreated with either intracerebroventricular injection of 5,7-dihydroxytryptamine (5,7-DHT; a 5-HT nerve fiber depletor), intraperitoneal injection of p-chlorophenylalanine (PCPA; a tryptophan hydroxylase inhibitor), or intraperitoneal injection of p-chloroamphetamine (PCA; a neurotoxin for 5-HT nerve fiber). At four days after STZ administration, vehicle-treated rats displayed hyperglycemia, polydipsia, polyphagia, decreased plasma insulin level, derangement of islet morphology (few insulin cells, accumulation of glucagon cells), and elevated 5-HT release in the hypothalamus. The above diabetogenic effects of STZ were attenuated by brain serotonin depletion induced by 5,7-DHT, PCPA, or PCA. Furthermore, the STZ-induced hyperglycemia or derangement of islet morphology was attenuated by peripheral sympathectomy or adrenalectomy. It is concluded that brain serotonin depletion attenuates diabetogenic effects of STZ by reducing sympathetic efferent activity in rats.

Nigrostriatal dopamine system mediates baroreflex sensitivity in rats

Both sham-operated rats and rats with lesions of the nigrostriatal dopamine (DA) pathway were subjected to increasing or decreasing carotid sinus pressure (respectively produced by phenylephrine injection or bilateral carotid occlusion) and their striatal DA release and baroreflex responses were compared. In sham-operated rats, phenylephrine produced both increased striatal DA release and decreased heart rate, while bilateral carotid occlusion produced the opposite effects. Both the striatal DA release and baroreflex responses produced by phenylephrine or carotid occlusion were attenuated by lesions of the nigrostriatal DA pathway induced by intramedial forebrain bundle injection of 6-hydroxydopamine. The data indicate that the nigrostriatal DA pathway mediates baroreflex sensitivity in rats.