Peripheral amitriptyline suppresses formalin-induced Fos expression in the rat spinal cord

Modulation of nociception by amitriptyline hydrochloride in the Speke's hinge-back tortoise (Kiniskys spekii)

BACKGROUND

There are limited studies on the utilization of analgesics in testudines. Management of pain in reptiles is by use of analgesics generally used in other vertebrate species. Evidently, some analgesics considered to be generally effective in reptiles are not effective in certain reptile species.

OBJECTIVE

The purpose of this study was to examine the effect of amitriptyline hydrochloride on nociceptive behaviour in Speke's hinge-back tortoise.

METHODS

Twenty-four adult Speke-hinged tortoises weighing 500-700 g were used. The effects of amitriptyline hydrochloride on nociception were evaluated using the formalin, capsaicin and hot plate nociceptive tests. Amitriptyline was administered intracoelomically at doses of 0.5, 1.0 and 3.0 mg/kg.

RESULTS

The higher doses of amitriptyline hydrochloride caused an increase in nociceptive behaviour (time spent in hindlimb withdrawal) on the formalin and capsaicin nociceptive tests, suggesting a potentiating effect. However, the doses used had no significant change in nociceptive behaviour on withdrawal response in the hot plate test.

CONCLUSIONS

The study showed that amitriptyline hydrochloride which is widely used in management of neuropathic pain potentiates nociceptive effects in the formalin and capsaicin nociceptive tests in the Speke's hinge-back tortoise. The hot plate test, which previously has not been reported in these animals, gave results not in line with the other tests and therefore more testing and validation of the test is required. Amitriptyline modulates chemical and thermal pain differently.

Administration of Wasabia koreana Ameliorates Irritable Bowel Syndrome-Like Symptoms in a Zymosan-Induced Mouse Model

Irritable bowel syndrome (IBS) is a functional gastrointestinal disease with complex pathophysiology involving the brain-gut axis. To assess the effects of Wasabia koreana (WK) on IBS, we employed a mouse model of colonic zymosan injection presenting with diarrhea-predominant IBS-like symptoms. Oral WK administration significantly diminished stool score, suppressed colon length and weight change, and minimized body weight loss without affecting food intake. In WK-treated mice, the submucosal thickening and epithelial lining of the colon were inhibited and were similar to those of naïve mice. Infiltration of mast cells into the colon and serum tumor necrosis factor-α levels were markedly suppressed. These effects were comparable to those of sulfasalazine, an anti-inflammatory drug. Furthermore, the number of visceral pain-related behaviors was significantly decreased, and locomotion activities measured in the elevated plus maze and open field tests were significantly increased by WK in a dose-dependent manner compared with amitriptyline, an antidepressant. These changes were accompanied by reduced FosB2 expression in the brain. Taken together, these data suggest that WK may have potential as a medicinal food for IBS by acting on inflammatory diarrhea and neural activity.

Alterations of c-Fos mRNA expression in hypothalamic-pituitary-adrenal axis and various brain regions induced by intrathecal single and repeated substance P administrations in mice

The effect of substance P (Sub P) injected intrathecally (i.t.) on c-fos mRNA expression in various tissues was examined in the present study. We found that a single administration of Sub P (0.5 nM) caused an increase of the c-fos mRNA level in the hypothalamic-pituitary-adrenal (HPA) axis, hippocampus, and spinal cord. The time-course study showed that c-fos mRNA level was maximal at 10 min and began to decrease 30 min after the Sub P injection in all tissues, and the Sub P-induced increase of the c-fos mRNA level was returned to the control level 1 h after the injection. The kinetics of the c-fos mRNA expression in mice that were repeatedly injected with Sub P (every 30 min interval up to 4 times) were different in the HPA axis, hippocampus, and spinal cord. The increased c-fos mRNA level in the hypothalamus and the spinal cord induced by i.t. injected Sub P remained at a high level. In the pituitary gland, adrenal gland, and hippocampus, the increased level of c-fos mRNA expression gradually returned to the control level during the repeated substance P injections up to 4 times. Our results suggest that spinally injected Sub P-induced pain stress increases c-fos mRNA expression in the spinal cord, hippocampus, and HPA axis. In mice repeatedly injected with Sub P, the kinetics of c-fos mRNA appear to be different varied from tissue to tissue.

Topical application of the tricyclic antidepressant doxepin can reduce dysuria and frequency

The aim of this article is to highlight a novel treatment for the symptoms of chronic urethral and trigonal irritation. A patient with severe urethral hyperaesthesia who derived almost complete alleviation of symptoms with topical application of a tricyclic antidepressant cream is described. The possible modes of action of tricyclics when used via the topical route of administration are described. Topical application of a tricyclic antidepressant cream may alleviate the symptoms of urethral hyperaesthesia.

Antidepressants for chronic neuropathic pain

Tricyclic antidepressants have been used to manage pain for several decades, and are superior treatments for some patients suffering from neuropathic pain. Unfortunately, older antidepressants have dose-limiting side effects that can lead to drug intolerance. The most common are anticholinergic side effects, although some patients experience sexual dysfunction. Cognitive impairment, sedation, and orthostatic hypotension also are relatively common. Taking an overdose of tricyclic antidepressants can be lethal in overdose. Several weeks of therapy may be required before antinociception occurs, but tricyclic antidepressants in optimal doses appear to be the most effective treatment for neuropathic pain; this is supported by systematic reviews comparing them with other agents. Newer medications such as atypical antidepressants and anticonvulsants may be overtaking older antidepressants, but they should not be overlooked as important options for the management of pain.