Related Experiment Videos
Noxious thermal input from the rat tail: modulation by descending inhibitory influences
1National Institute for Medical Research, Mill Hill, London NW7 1AA Great Britain.
Pain
|February 1, 1978
Summary
Nerve fibers in rats respond to heat above 40°C. Descending control in the spinal cord modulates these heat-sensing neurons, suggesting inhibitory pathways influence pain perception.
Area of Science:
- Neuroscience
- Physiology
Background:
- Peripheral nerve fibers and dorsal horn neurons are involved in thermosensation.
- The role of descending control in modulating nociceptive signaling is not fully understood.
Purpose of the Study:
- To investigate the response of afferent nerve fibers and dorsal horn neurons to noxious heat in rats.
- To determine the influence of descending spinal cord pathways on the activity of heat-sensitive dorsal horn neurons.
Main Methods:
- Single nerve fibers from rat tail nerves were dissected and their responses to thermal stimuli recorded.
- Neuronal activity in the dorsal horn of the spinal cord was monitored.
- Reversible spinal cord blockade was induced by cooling the thoracic region.
Main Results:
- Afferent fibers from rat tail nerves exhibited excitation above 40°C, with firing rates increasing with temperature.
- Dorsal horn neurons responding to noxious heat had higher activation thresholds (42.5–45°C).
- Spinal cord blockade reduced dorsal horn neuron thresholds and increased their activity at supra-threshold temperatures.
Conclusions:
- Dorsal horn neurons responding to noxious heat are under tonic descending inhibitory control.
- These findings suggest a regulatory mechanism for pain and temperature signaling originating from the central nervous system.