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Noradrenergic effects in rat sacral autonomic nucleus using in vitro slice patch-clamp recordings
Masahiro Kawatani1, Nozomi Akimoto2, Akihiro Yamada2
1Department of Neurophysiology, Akita University, School of Medicine.
Biomedical Research (Tokyo, Japan)
|December 12, 2017
Summary
Noradrenaline (NA) has complex effects on sacral preganglionic nucleus (SPN) neurons controlling pelvic organs. NA differentially modulates neuronal activity and synaptic transmission via alpha-1 and alpha-2 receptors, suggesting distinct SPN neuron functions.
Area of Science:
- Neuroscience
- Neurophysiology
- Autonomic Nervous System Research
Background:
- Noradrenergic modulation is implicated in pelvic organ neural control.
- The sacral preganglionic nucleus (SPN) contains parasympathetic neurons innervating pelvic organs.
- The precise role of noradrenaline (NA) within the SPN remains unclear despite abundant noradrenergic innervation.
Purpose of the Study:
- To investigate the electrophysiological effects of noradrenaline (NA) on parasympathetic preganglionic neurons in the sacral preganglionic nucleus (SPN).
- To determine the subtypes of adrenergic receptors involved in NA's action within the SPN.
- To elucidate how NA influences synaptic transmission in different SPN neuronal populations.
Main Methods:
- Whole-cell patch clamp recordings were performed on DiI-labeled SPN neurons.
- Application of noradrenaline (NA), phenylephrine (α1 agonist), and clonidine (α2 agonist) to assess neuronal responses.
- Analysis of spontaneous excitatory and inhibitory postsynaptic currents (sEPSCs and sIPSCs) to evaluate synaptic modulation.
- Classification of SPN neurons based on their firing patterns (delayed and regular).
Main Results:
- NA induced inward or outward currents in SPN neurons, independent of firing pattern.
- Phenylephrine (α1 agonist) caused inward currents, while clonidine (α2 agonist) induced outward currents, confirming α1 and α2 adrenoreceptor presence.
- NA differentially modulated synaptic transmission: inhibiting sEPSCs and sIPSCs in delayed-firing neurons, but facilitating them in regular-firing neurons.
- α1 and α2 receptor activation mimicked and opposed the effects of NA on synaptic currents, respectively.
Conclusions:
- Noradrenaline exerts multiple, complex effects on sacral preganglionic nucleus (SPN) neurons.
- The distinct actions of NA on synaptic transmission suggest functional heterogeneity among SPN neurons.
- Adrenergic receptor signaling plays a significant role in regulating the activity of parasympathetic preganglionic neurons controlling pelvic organs.
