Neural Mechanisms That Underlie Angina-Induced Referred Pain in the Trigeminal Nerve Territory: A c-Fos Study in Rats.

The present study was designed to determine whether the trigeminal sensory nuclear complex (TSNC) is involved in angina-induced referred pain in the trigeminal nerve territory and to identify the peripheral nerve conducting nociceptive signals that are input into the TSNC. Following application of the pain producing substance (PPS) infusion, the number of Fos-labeled cells increased significantly in the subnucleus caudalis (Sp5C) compared with other nuclei in the TSNC. The Fos-labeled cells in the Sp5C disappeared when the left and right cervical vagus nerves were sectioned.

Biological implications of coeruleospinal inhibition of nociceptive processing in the spinal cord.

The coeruleospinal inhibitory pathway (CSIP), the descending pathway from the nucleus locus coeruleus (LC) and the nucleus subcoeruleus (SC), is one of the centrifugal pain control systems. This review answers two questions regarding the role coeruleospinal inhibition plays in the mammalian brain. First is related to an abnormal pain state, such as inflammation.

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

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 MΩ). Colorectal distention (CRD) was produced by inflating a balloon inside the descending colon and rectum.

The nucleus locus coeruleus/subcoeruleus contributes to antinociception during freezing behavior following the air-puff startle in rats.

An air puff elicits a startle response in mammals. Following the startle response, rats react with a defensive-like, immobile posture (DIP) of approximately 2-5s in length. We have previously reported that air-puff stimulation (APS) activates the nucleus locus coeruleus/subcoeruleus (LC/SC) so that the DIP is induced.

Descending pathways from activated locus coeruleus/subcoeruleus following unilateral hindpaw inflammation in the rat.

We have previously shown that the descending pathways from the locus coeruleus (LC)/subcoeruleus (SC) to the spinal cord are activated during peripheral inflammation, and that activation of this coeruleospinal system decreases development of hyperalgesia. Anatomical evidence suggests that the descending modulation system from the LC/SC should be active bilaterally during inflammation when the LC/SC either ipsilateral or contralateral to the site of inflammation is activated. In the present study, the development of hyperalgesia following the induction of unilateral hindpaw inflammation was compared between rats with either bilateral or unilateral lesions of the LC/SC and rats with a sham operation.

Descending modulation of visceral nociceptive transmission from the locus coeruleus/subcoeruleus in the rat.

The purpose of the present investigation was to examine whether electrical stimulation in the locus coeruleus/subcoeruleus (LC/SC) could modulate visceral pain evoked by noxious colorectal distention (CRD). Experiments were performed on 40 pentobarbital anesthetized male Sprague-Dawley rats. Extracellular potentials of single L(6)-S(2) spinal neuron were recorded with a carbon filament electrode.

NSAID loxoprofen inhibits high threshold or wide dynamic range neuronal responses in the rat at different time-courses.

The onset of the antinociceptive effect with loxoprofen sodium (LOX), a non-steroidal anti-inflammatory drug, was examined electrophysiologically during carrageenan-induced hindpaw inflammation in the rat. Extracellular recordings were made from either wide dynamic range (WDR) or high threshold (HT) neurons in the dorsal horn. Recordings from the same neuron were continued for at least 3 h after the injection of carrageenan.

Coeruleospinal inhibition of visceral nociceptive processing in the rat spinal cord.

Visceral nociceptive information is transmitted in two different areas of the spinal cord gray matter, the dorsal horn and the area near the central canal. The present study was designed to examine whether visceral nociceptive transmission in the two different areas is under the control of the centrifugal pathways from the locus coeruleus/subcoeruleus (LC/SC). Extracellular recordings were made from the L(6)-S(2) segmental level using a carbon filament glass microelectrode (4-6 MOmega).