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Physiological Recordings of High and Low Output NMJs on the Crayfish Leg Extensor Muscle
Published on: November 17, 2010
Serotonin potentiates sympathetic responses evoked by spinal NMDA
Christopher J Madden1, Shaun F Morrison
1Neurological Sciences Institute/OHSU, 505 NW 185th Avenue, Beaverton, OR 97006, USA. maddench@ohsu.edu
The Journal of Physiology
|September 16, 2006
Summary
Spinal NMDA and serotonin receptor activation significantly increases brown adipose tissue (BAT) sympathetic nerve activity and thermogenesis in rats. Simultaneous activation synergistically enhances these effects, highlighting their role in metabolic regulation.
Area of Science:
- Neuroscience
- Physiology
- Metabolism
Background:
- Brown adipose tissue (BAT) plays a crucial role in thermogenesis and metabolic regulation.
- The sympathetic nervous system (SNS) is a key regulator of BAT activity.
- Spinal cord pathways are involved in controlling sympathetic outflow to various organs, including BAT.
Purpose of the Study:
- To investigate the effects of N-methyl-D-aspartate (NMDA) and serotonin (5-HT) receptor activation within the spinal cord on BAT sympathetic nerve activity (SNA) and thermogenesis.
- To determine if NMDA and 5-HT receptors act synergistically in modulating BAT SNA and thermogenesis.
Main Methods:
- Experiments were conducted in urethane-chloralose anesthetized, ventilated, and neuromuscularly blocked rats.
- Separate and simultaneous microinjections of NMDA and 5-HT were administered into the T4 spinal intermediolateral nucleus (IML).
- Measurements included BAT sympathetic nerve activity (SNA), BAT temperature, and heart rate.
Main Results:
- Microinjection of NMDA (12 pmol) into the T4 IML rapidly increased BAT SNA, thermogenesis, and heart rate.
- Microinjection of 5-HT (2 nmol) into the T4 IML increased BAT SNA with a long latency, which was blocked by methysergide.
- Co-administration of 5-HT potentiated NMDA-induced increases in BAT SNA and thermogenesis, with 5-HT converting a subthreshold NMDA dose into an effective one.
Conclusions:
- Activation of spinal excitatory amino acid (NMDA) and serotonin (5-HT) receptors can independently drive BAT SNA and thermogenesis.
- Concomitant activation of spinal NMDA and 5-HT receptors exhibits synergistic effects, markedly increasing BAT SNA and thermogenesis.
- These findings suggest that spinal NMDA and 5-HT receptors are important targets for modulating BAT activity and energy expenditure.
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