Electrophysiologival Actions of Norepinephrine in Rat Lateral Hypothalamus. I. Norepinphrine-Induced Modulation of LH Neuronal Responsiveness to Afferent Synaptic Inputs and Putative Neurotransmitters

摘要

The present studies were conducted as part of an ongoing investigation of the effects of norepinephrine (NE) in neuronal circuits of the mammalian brain. In this report, we describe noradrenergic actions in the lateral hypothalamus (LH), an area which has been implicated in the central integration of cardiovascular regulatory mechanisms, fluid balance and ingestive behaviors. Microiontophoretically applied NE was interacted with extracellularly recorded responses of LH neurons to iontophoretically applied putative neurotransmitters - aminobutyric acid (GABA), acetylcholine (ACh) and glutamate (Glu); and activation of known input pathways from the reticular thalamus (RT) and the lateral preoptic area (LPO). Peri-event histograms of cell responses were computed before, during and after NE microiontophoresis and used to quantitatively evaluate monoamine-induced effects on spontaneous and stimulus evoked activity of LH neurons. The findings indicate that, as in other noradrenergic target regions of the CNS, NE can facilitate synaptically mediated responses of LH neurons. Taken together these observations suggest that NE may play an important regulatory role in the synaptic transfer of information within LH circuits, and consequently exert considerable influence over the influence over the homeostatic functions mediated by this structure. Keywords: Cerebral cortex, Cerebellum hypothalmus. (kt)