Norepinephrine inhibits Afferent activation of NTS Catecholamine Neurons in Mice
The nucleus tractus solitarius (NTS) integrates visceral sensory input to regulate feeding behavior, with catecholaminergic (CA) and neuropeptide Y (NPY)-expressing neurons playing key roles in energy homeostasis. Recent evidence suggests functional heterogeneity among CA-NTS neurons, including distinct subpopulations that either suppress or promote feeding. In this study, we investigated how…
Norepinephrine, a neurotransmitter, plays a crucial role in modulating the excitatory synaptic transmission from solitary tract afferents to tyrosine hydroxylase-positive neurons in mice. Researchers investigated this mechanism using patch-clamp electrophysiology in horizontal brainstem slices. They discovered that norepinephrine inhibits the excitatory postsynaptic currents in a dose-dependent manner, with the maximum effect observed at a concentration of 10 microM and an effective concentration (EC50) of approximately 3.4 microM.
This inhibition was found to be mediated by alpha-adrenergic receptors and was not influenced by GABAA receptor activity. Furthermore, norepinephrine suppressed asynchronous glutamate release and attenuated the increase in spontaneous EPSC frequency induced by cholecystokinin (CCK), indicating a presynaptic mechanism. Interestingly, neuropeptide Y (NPY) also reduced the excitatory postsynaptic currents via Y2 receptor activation.
When applied together at subthreshold concentrations, norepinephrine and NPY showed additive or synergistic effects. The findings shed light on the novel interaction between noradrenergic and peptidergic systems in regulating visceral sensory processing within the brainstem.
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