and purpose: Methylamine is an endogenous aliphatic amine exhibiting anorexigenic properties in mice. the periventricular hypothalamic (PH) nucleus accounts for hyperphagic or hypophagic behaviour (Stanley Kv1.6 subtype potassium channels (Pirisino mice which lack the hypothalamic leptin receptor (Cioni Kv1.6 potassium channels as a PP2 result of specific antisense treatment. Following intracerebroventricular (i.c.v.) methylamine injection animal feeding was monitored and perfusates were analysed for their content of some mediators involved in feeding. Materials and methods Animals Male rats (150-200?g) from the Morini breeding farm (San Polo d’Enza Italy) were used. Five rats were housed per cage. The cages were placed in the experimental room 24?h before the test for adaptation and the rats fasted overnight before the experiment. The animals were kept at 23±1°C with a 12?h light-dark cycle (light on at 0700 h) and were fed a standard laboratory diet with water All experiments were carried out in accordance with the European Communities Council Directive of 24 November 1986 (86/609/EEC) for experimental animal care. All efforts were made to minimize animal suffering and to reduce the number of animals used. Unless otherwise indicated at least 10 animals per group were used in each behavioural protocol. Evaluation of food consumption Rats did not have access to food for 12?h but water was available A weighed amount of food (standard laboratory pellets) was given and the amount consumed (evaluated as the difference between the original amount and the food left in the PP2 cage including spillage) was measured 20 40 60 120 180 after i.c.v. administration of saline or methylamine with an accuracy of 0.1?g. An arbitrary cutoff time of 120?min was used and the total amount of food consumed was expressed in mg per rat 120?min?1. In some experiments food consumption was evaluated in rats pretreated i.c.v. (2?microdialysis procedures and i.c.v drug administration Male Wistar rats weighing 180-200?g were anaesthetized with chloral hydrate (400?mg?kg?1 i.p.) and placed in a stereotaxic apparatus with the upper incisor bar set to allow the bregma to be at the same height as experiments phosphorothioate-cappedphosphorodiester oligonucleotides associated with an artificial cationic lipid (DOTAP =comparison were used to verify significance between two means. Data were analysed using the PP2 StatView software. Results Food intake behaviour in methylamine-treated rats The 12-h PP2 starved saline-treated rats showed a time-dependent increase in food intake which reached Rabbit polyclonal to ING2. a plateau 120?min after food readministration (5539±31?mg per rat 120?min?1; orexigenic mediator we decided to analyse our samples for the presence of NO which might account for the activation of orexigenic pathways. Moreover we examined the release of dopamine and 5HT as they are the mediators most commonly involved in hypophagic responses (Ghelardini Kv1.6 channel subtype integrity is essential for the effects of PP2 methylamine as previously described in mice (Pirisino et al. 2004 The bell-shaped dose-response curves of methylamine-induced NO release might be explained by Ca2+-dependent desensitization of brain neurons following sustained reduction of potassium conductance. Similar biphasic responses have been reported after activation of voltage-dependent Ca2+ channels which depend on the functional status of channel domains including either the voltage-dependent activated or the voltage or Ca2+-dependent-inactivated gates (Fox 1981 Di Virgilio et al. 1987 Different stimulatory compounds have been described as inducing Ca2+-related desensitization processes on central PP2 neurotransmitter release including NO (Izumi et al. 1989..