The stereotyped behavior syndrome: a new model and proposed therapy

Autism and Clostridium tetani

Autism is a severe developmental disability believed to have multiple etiologies. This paper outlines the possibility of a subacute, chronic tetanus infection of the intestinal tract as the underlying cause for symptoms of autism observed in some individuals. A significant percentage of individuals with autism have a history of extensive antibiotic use. Oral antibiotics significantly disrupt protective intestinal microbiota, creating a favorable environment for colonization by opportunistic pathogens. Clostridium tetani is an ubiquitous anaerobic bacillus that produces a potent neurotoxin. Intestinal colonization by C. tetani, and subsequent neurotoxin release, have been demonstrated in laboratory animals which were fed vegetative cells. The vagus nerve is capable of transporting tetanus neurotoxin (TeNT) and provides a route of ascent from the intestinal tract to the CNS. This route bypasses TeNT's normal preferential binding sites in the spinal cord, and therefore the symptoms of a typical tetanus infection are not evident. Once in the brain, TeNT disrupts the release of neurotransmitters by the proteolytic cleavage of synaptobrevin, a synaptic vesicle membrane protein. This inhibition of neurotransmitter release would explain a wide variety of behavioral deficits apparent in autism. Lab animals injected in the brain with TeNT have exhibited many of these behaviors. Some children with autism have also shown a significant reduction in stereotyped behaviors when treated with antimicrobials effective against intestinal clostridia. When viewed as sequelae to a subacute, chronic tetanus infection, many of the puzzling abnormalities of autism have a logical basis. A review of atypical tetanus cases, and strategies to test the validity of this paper's hypothesis, are included.

Tetanus: pathophysiology, management, and prophylaxis

As tetanus has become a rare disease in the developed world, physicians have become less comfortable with its diagnosis and management. The extent of adequate antitetanus immunity in the adult population, especially the elderly, is waning, in great measure because primary care physicians have not made prophylaxis a priority in their routine encounters with patients. Furthermore, as the population of immunocompromised hosts grows, an increasing percentage of our patients may not respond to standard active immunization routines. Unless these trends are reversed, we face a substantial increase in the incidence of this dread disorder. Tetanus is also of interest as a relatively simple model of disordered motor control that can instruct us in the management of the many more common causes of neurogenic muscular rigidity. The toxin produced by Clostridium tetani finds increasing use in laboratories investigating brain function as well. Clinical tetanus is divided into four symptomatic types: generalized tetanus, local tetanus, cephalic tetanus, and neonatal tetanus. This monograph discusses the diagnostic aspects of each type of tetanus, its pathophysiology, diagnosis, differential diagnosis, and treatment. Preventing tetanus should be a high priority for all primary care physicians. Active immunization with tetanus toxoid is remarkably effective and safe. Passive immunization with human tetanus immune globulin is indicated in certain circumstances, which are discussed below.

Self-injection of diazepam in naive rats: effects of dose, schedule and blockade of different receptors

The present series of experiments had two main objectives: The first was to determine the conditions under which self-injection of the benzodiazepine diazepam would be optimal; the second was to identify neurochemical substrates which underlie the maintenance of diazepam self-administration. Data from the first experiment indicated that rats maintained on an FI-1 (Fixed Interval of 1 min) schedule of food delivery self-injected significantly more diazepam than rats not maintained on this schedule. Results from the second experiment demonstrated that the benzodiazepine antagonist Ro 15-1788, and the GABA antagonist bicuculline, significantly reduced diazepam self-administration, but the opiate antagonist naloxone was without effect. Data from the third experiment showed that the dopamine antagonist haloperidol also significantly reduced the rate of diazepam self-injection. Thus, these findings indicate that the acquisition of diazepam self-injection occurs under an FI-1 schedule of food delivery, which has been shown to be middly stressful, while its maintenance depends upon the functional integrity of benzodiazepine and GABA receptors and upon the activity of dopaminergic pathways.