A possible synaptic configuration underlying coeruleospinal inhibition of visceral nociceptive transmission in the rat

作者：Hayashi Bunsho; Tsuruoka Masayoshi^*; Maeda Masako; Tamaki Junichiro; Inoue Tomio

来源：Neurological Sciences, 2012, 33(2): 463-468.

DOI：10.1007/s10072-011-0739-5

• Locus coeruleus
• Subcoeruleus
• Inhibition
• Visceral pain
• Spinal cord

A synaptic arrangement underlying descending inhibition from the locus coeruleus/subcoeruleus (LC/SC) on visceral nociceptive transmission in the spinal cord was investigated in the anesthetized rat. Extracellular recordings were made from the L-6-S-2 segmental level using a carbon filament glass microelectrode (4-6 M Omega). Colorectal distention (CRD) was produced by inflating a balloon inside the descending colon and rectum. All neurons tested responded to both CRD and to cutaneous pinch (a force of 613 g/mm(2)), indicating that nociceptive signals from visceral organs and nociceptive signals from the cutaneous receptive field converge on a single neuron. These neurons were divided into two groups based on their response to CRD: short latency-abrupt and short latency-sustained neurons. Electrical stimulation of the LC/SC (30 or 50 mu A, 100 Hz, 0.1 ms pulses) inhibited both CRD-evoked and cutaneous pinch-evoked responses in short latency-abrupt and short latency-sustained neurons. When graded CRD (20, 40, 60, and 80 mmHg) was delivered, LC/SC stimulation produced a reduction in slope of the linear CRD intensity-response magnitude curve without a change in the response threshold in both short latency-abrupt (n = 42) and short latency-sustained neurons (n = 11). This result suggests that coeruleospinal inhibition of visceral nociceptive transmission is due to a synaptic configuration in which inhibitory and excitatory terminals are in close spatial proximity, including presynaptic inhibition.

• 出版日期2012-4