<p>Parietal Block Using Bupivacaine in the Rat: An Anatomical, Behavioral and Histological Study</p>

Abstract

Purpose: Animal models of regional anaesthesia are useful for studying the effects of blocks and improve their efficacy. The aim of our experiments was to validate a multi-site paravertebral block in the rat. Material and methods: Dissection and indigo carmine dye injection were performed in five rats (3 rats were dissected and 2 were dye injected). In other groups (n=7rats/group), after inflammation inductive carrageenan injection in the abdominal wall, bupivacaine or saline was injected laterally to the spinal column at the T5, T10, L1, L4 and S1 level. The efficacy of the block on mechanical nociception was measured using von Frey hairs. In addition, we measured c-Fos immunoreactive nuclei in the cord. Results: The multi-site injection showed a perinervous distribution of the injected solution without intra-thoracic, intra-abdominal or epidural diffusion. Bilateral block with a relatively small volume of bupivacaine (0.5 mL) significantly increased the threshold to mechanical pain as compared to control (p=0.007) and significantly decreased the number of c-Fos immunoreactive nuclei in the posterior horn of the spinal cord (p<0.0001). Conclusion: This study shows that a parietal abdominal wall block is easy to perform in the rat. This block allows investigators to explore the mechanisms of action of abdominal parietal wall blocks.

Acute Visceral Pain in Rats: Vagal Nerve Block Compared to Bupivacaine Administered Intramuscularly

“…Briefly, 1-mL 2.5% carrageenan or saline and 15-mg/kg 0.25% bupivacaine with 1:200,000 epinephrine or saline were injected in the wall or peritoneum. 3 An additional control group of 6 rats received the same volume of saline. Proto-oncogene c-Fos (c-Fos) reactive nuclei were counted in the dorsal horn 2 hours after inflammation induction.…”

“…Apart from traditional analgesics, local anesthetics and regional anesthesia may be helpful. Parietal blocks alone are able to relieve visceral pain both in experimental 3 and clinical conditions 4 but not in all studies. 5 Blocks acting on the paravertebral sympathetic ganglions (ie, celiac plexus block) combined with a parietal block (ie, transverse abdominis plane [TAP] block) could be effective to inhibit somatic and visceral afferences of postoperative pain.…”

“…11,12 In previous rat experiments, we showed that systemically administered local anesthetics were able to decrease visceral pain induced by different models. 3,13 In addition, treated animals had lower local and general inflammation as shown by a lower production of tumor necrosis factor alpha (TNF-α) in whole blood and peritoneal macrophage cultures stimulated by lypopolysaccharide (LPS).…”

Anatomical Differences in the Abdominal Wall Between Species with Implications for the Transversus Abdominis Plane Block

“…Yet, because the number of vertebrae shows high variability across species, the specific nerves that will travel and innervate the abdominal wall varies. In mammals, the abdominal wall is typically innervated by the lower thoracic nerves and the upper lumbar nerves, although in some species this can extend to include the sacral nerves as well [31][32][33]. In birds, the number of nerves innervating the musculature and overlying skin of the abdominal wall is reduced.…”

“…In humans, the abdominal wall is typically supplied by spinal nerves T6 to L1 [33], this differs in other mammals. For instance, in the rat, the abdominal wall is supplied by nerve roots T5 to S1 [32]. Similarly, in cats, the abdominal wall receives innervation from spinal nerves T6 to L5 [69,70].…”