Effects of acute and repeated administration of Staphylococcal enterotoxin A on Morris water maze learning, corticosterone and hippocampal IL-1β and TNFα

Simulated acute central Mycoplasma infections in rats induce fever, anorexia, body mass stunting and lethargy but spare memory

Despite the documented post-infectious neurological complications of a central nervous system (CNS) Mycoplasma infection in humans, very few studies have investigated the acute inflammatory responses and sickness behaviours induced by CNS Mycoplasma infections. We therefore determined the effect of acute central administration of fibroblast-stimulating lipopeptide-1 (FSL-1), derived from Mycoplasma salivarium, and FAM-20 from a more pathogenic species, namely Mycoplasma pneumoniae, on behavioural and inflammatory responses in rats. Male Sprague-Dawley rats had radiotransmitters implanted, intra-abdominally, to measure body temperature and cage activity continuously. After recovery from surgery, rats were conditioned in a fear conditioning task and then immediately received an intra-cisterna magna (i.c.m.) injection of either: (1) FSL-1 (10 or 100μg/5μl) or its vehicle (phosphate-buffered saline, 5μl), or (2) FAM-20 (10 or 100μg/5μl) or its vehicle (dimethyl sulfoxide, 5μl). Body mass and food intake were measured daily. Memory was assessed seven days after injection using fear conditioning tests. A single, i.c.m. injection of either FSL-1 or FAM-20 induced profound, dose-dependent fever, anorexia, lethargy and body mass stunting in rats. Moreover, rats that received an i.c.m. injection of 100μg/5μl FAM-20 had a significant increase in the concentration of IL-1β in both the hypothalamus and the hippocampus for ~27h after injection. Seven days after FSL-1 or FAM-20 injection, when body mass of rats still was stunted, they maintained their memory for fear of the context and for fear of the tone, despite the increase in hippocampal IL-1β concentration after FAM-20 administration. Thus, acute simulated CNS Mycoplasma infections caused pronounced sickness responses and brain inflammation in rats, but spared fear memory.

A review of the neuro- and systemic inflammatory responses in post concussion symptoms: Introduction of the "post-inflammatory brain syndrome" PIBS

Post-concussion syndrome is an aggregate of symptoms that commonly present together after head injury. These symptoms, depending on definition, include headaches, dizziness, neuropsychiatric symptoms, and cognitive impairment. However, these symptoms are common, occurring frequently in non-head injured controls, leading some to question the existence of post-concussion syndrome as a unique syndrome. Therefore, some have attempted to explain post-concussion symptoms as post-traumatic stress disorder, as they share many similar symptoms and post-traumatic stress disorder does not require head injury. This explanation falls short as patients with post-concussion syndrome do not necessarily experience many key symptoms of post-traumatic stress disorder. Therefore, other explanations must be sought to explain the prevalence of post-concussion like symptoms in non-head injury patients. Many of the situations in which post-concussion syndrome like symptoms may be experienced such as infection and post-surgery are associated with systemic inflammatory responses, and even neuroinflammation. Post-concussion syndrome itself has a significant neuroinflammatory component. In this review we examine the evidence of neuroinflammation in post-concussion syndrome and the potential role systemic inflammation plays in post-concussion syndrome like symptoms. We conclude that given the overlap between these conditions and the role of inflammation in their etiologies, a new term, post-inflammatory brain syndromes (PIBS), is necessary to describe the common outcomes of many different inflammatory insults. The concept of post-concussion syndrome is in its evolution therefore, the new term post-inflammatory brain syndromes provides a better understanding of etiology of its wide-array of symptoms and the wide array of conditions they can be seen in.

Dissociation between learning and memory impairment and other sickness behaviours during simulated Mycoplasma infection in rats

To investigate potential consequences for learning and memory, we have simulated the effects of Mycoplasma infection, in rats, by administering fibroblast-stimulating lipopepide-1 (FSL-1), a pyrogenic moiety of Mycoplasma salivarium. We measured the effects on body temperature, cage activity, food intake, and on spatial learning and memory in a Morris Water Maze. Male Sprague-Dawley rats had radio transponders implanted to measure abdominal temperature and cage activity. After recovery, rats were assigned randomly to receive intraperitoneal (I.P.) injections of FSL-1 (500 or 1000 μg kg(-1) in 1 ml kg(-1) phosphate-buffered saline; PBS) or vehicle (PBS, 1 ml kg(-1)). Body mass and food intake were measured daily. Training in the Maze commenced 18 h after injections and continued daily for four days. Spatial memory was assessed on the fifth day. In other rats, we measured concentrations of brain pro-inflammatory cytokines, interleukin (IL)-1β and IL-6, at 3 and 18 h after injections. FSL-1 administration induced a dose-dependent fever (∼1°C) for two days, lethargy (∼78%) for four days, anorexia (∼65%) for three days and body mass stunting (∼6%) for at least four days. Eighteen hours after FSL-1 administration, when concentrations of IL-1β, but not that of IL-6, were elevated in both the hypothalamus and the hippocampus, and when rats were febrile, lethargic and anorexic, learning in the Maze was unaffected. There also was no memory impairment. Our results support emerging evidence that impaired learning and memory is not inevitable during simulated infection.