Intracerebral administration of Mycoplasma fermentans produces sickness behavior: Role of prostaglandins

Mycoplasmas are small microorganisms, which cause various diseases in animals and in humans, activate the immune system, and induce the release of various cytokines. Some of the effects of mycoplasmas are mediated by the CNS. Moreover, Mycoplasma fermentans (MF) has recently been found in the brain, as well as other tissues of some AIDS patients, who usually display severe neurobehavioral disturbances. The present study was designed to examine the behavioral effects of central administration of MF, and the role of prostaglandins in mediating these effects. In one set of experiments, rats were injected intracerebroventricularly (i.c.v.) with either saline or a dose of MF (5.1-36 μg per rat), and several behavioral parameters were measured. In addition, body temperature and locomotor activity were continuously monitored by a biotelemetric system. MF induced a significant elevation in body temperature and suppression of motor activity levels. MF also significantly reduced the time spent in social exploration, decreased locomotor and exploratory activity in the open field test, suppressed the consumption of food and saccharine solution, and reduced body weight. In a second set of experiments, i.c.v. administration of MF (7.2 μg) was found to produce a significant increase in the production of prostaglandin E₂ (PGE₂) in hypothalamic, hippocampal, and cortical tissues. This effect was blocked by indomethacin, a prostaglandin synthesis inhibitor, Indomethacin also attenuated the effects of MF on body temperature, motor activity and body weight, suggesting the involvement of prostaglandins in mediating some of the effects of MF. Together, these findings suggest that the presence of MF in the brain may be responsible for some of the neurobehavioral abnormalities in HIV-infected patients.