Noxious stimulation excites serotonergic neurons: A comparison between the lateral paragigantocellular reticular and the raphe magnus nuclei

摘要: The present study was designed to record electrophysiological responses graded noxious thermal stimuli of serotonergic and nonserotonergic neurons in the lateral paragigantocellular reticular (LPGi) raphe magnus (RMg) nuclei rats. All recorded were juxtacellularly filled with neurobiotin identified double immunofluorescent labeling for both serotonin. Under halothane anesthesia (0.75%), ⩾48°C activated almost all (88%) located within LPGi (n=16). increase firing clear (3.4±0.3spike/s: mean above population median) sustained during whole application strong stimuli, a high threshold (48.3±0.3°C) large receptive fields. Recording RMg (n=21) demonstrated that proportion strongly (>2spike/s) (19% vs 59% LPGi) as well magnitude activation (2.1±0.4spike/s: significantly lower than (P<.05). Within boundaries (B3 group), also predominantly excited (75%) by resulting (7.9±1.2spike/s) even greater neurons. Thermal stimuli-induced cells probably plays key role serotonin-mediated modulations cardiac baroreflex transmission nociceptive messages occurring under such intense conditions.