Interactions between different antidepressants and morphine alter gastrointestinal transit in mice

Effects of serotonin transporter inhibition on gastrointestinal motility and colonic sensitivity in the mouse

Serotonin-selective reuptake transporter (SERT) expression is decreased in animal models of intestinal inflammation and in individuals with inflammatory bowel disease (IBD) or irritable bowel syndrome (IBS), and it is possible that resultant changes in intestinal serotonin signalling contribute to the manifestation of clinical features associated with these disorders. The objective of this investigation was to determine whether inhibition of SERT function leads to changes in gut motility and sensitivity. Mice underwent a 14-day treatment with the SERT inhibitor, paroxetine (20 mg kg(-1)), or vehicle (saline/propylene glycol). Gastrointestinal (GI) transit following charcoal gavage, colonic motility, stool frequency and visceromotor responses to colorectal distension were evaluated. In mice treated with paroxetine, stool output was decreased, upper GI transit was delayed, and colonic sensitivity to a nociceptive stimulus was attenuated. These results demonstrate that reduced SERT function (via pharmacological blockade) significantly alters GI motility and sensitivity in mice, and support the concept that altered SERT expression and function could contribute to symptoms associated with IBS and IBD.

Effects of fluvoxamine on morphine-induced inhibition of gastrointestinal transit, antinociception and hyperlocomotion in mice

In the present study, the effects of fluvoxamine on the inhibition of gastrointestinal transit, antinociception and hyperlocomotion induced by morphine were investigated in mice. Treatment with morphine (10 mg/kg, subcutaneously (s.c.)) inhibited gastrointestinal transit and hyperlocomotion. These effects were attenuated by fluvoxamine in a dose-dependent manner. On the other hand, morphine (1 mg/kg, s.c.)-induced antinociception was significantly potentiated by fluvoxamine. These results suggest that fluvoxamine combined with morphine may be useful for the treatment of not only depression but also pain in cancer patients without constipation or activation of the mesolimbic dopaminergic system. However, further understanding and clinical studies will be required to confirm this possibility.

Endogenous opiates: 1997

This paper is the twentieth installment of our annual review of research concerning the opiate system. It summarizes papers published during 1997 that studied the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress; tolerance and dependence; eating and drinking; alcohol; gastrointestinal, renal, and hepatic function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurologic disorders; electrical-related activity; general activity and locomotion; sex, pregnancy, and development; immunologic responses; and other behaviors.