Background Although the hypothalamic orexin system is known to regulate appetitive behaviors and promote wakefulness and arousal (Sakurai, 2007), this system may also be important in adaptive and pathological anxiety/stress responses (Suzuki et al., 2005). In a recent study, we demonstrated that CSF orexin levels were significantly higher in patients experiencing panic attacks compared to non-panicking depressed subjects (Johnson et al., 2010). Furthermore, genetically silencing orexin synthesis or blocking orexin 1 receptors attenuated lactate-induced panic in an animal model of panic disorder. Therefore, in the present study, we tested if orexin (ORX) modulates the panic responses and brain pathways activated by two different panicogenic drugs. Methods We conducted a series of pharmacological, behavioral, physiological and immunohistochemical experiments to study the modulation by the orexinergic inputs of anxiety behaviors, autonomic responses, and activation of brain pathways elicited by systemic injections of anxiogenic/panicogenic drugs in rats. Results We show that systemic injections of two different anxiogenic/panicogenic drugs (FG-7142, an inverse agonist at the benzodiazepine site of the GABAA receptor, and caffeine, a nonselective competitive adenosine receptor antagonist) increased c-Fos induction in a specific subset of orexin neurons located in the dorsomedial/ perifornical (DMH/PeF) but not the lateral hypothalamus. Pre-treating rats with an orexin 1 receptor antagonist attenuated the FG-7142-induced anxiety-like behaviors, increased heart rate, and neuronal activation in key panic pathways, including subregions of the central nucleus of the amygdala, bed nucleus of the stria terminalis, periaqueductal gray and in the rostroventrolateral medulla. Conclusion Overall, the data here suggest that the ORX neurons in the DMH/PeF region are critical to eliciting a coordinated panic responses and that ORX1 receptor antagonists constitute a potential novel treatment strategy for panic and related anxiety disorders. The neural pathways through which ORX1 receptor antagonists attenuate panic responses involve the extended amygdala, periaqueductal gray, and medullary autonomic centers.

Aggression, self-injurious behavior, and severe tantrums are impairing symptoms frequently experienced by individuals with autism spectrum disorders. Despite US Food and Drug Administration approval of two atypical antipsychotics targeting these symptoms in youth with autistic disorder, they remain frequently drug refractory. We define drug-refractory aggression, self-injurious behavior, and severe tantrums in people with autism spectrum disorders as behavioral symptoms requiring medication adjustment despite previous trials of risperidone and aripiprazole or previous trials of three psychotropic drugs targeting the symptom cluster, one of which was risperidone or aripiprazole. We reviewed the medical records of individuals of all ages referred to our clinic for autism spectrum disorder diagnostic evaluation, as well as pharmacotherapy follow-up notes for all people meeting autism spectrum disorder criteria, for drug-refractory symptoms. Among 250 consecutively referred individuals, 135 met autism spectrum disorder and enrollment criteria, and 53 of these individuals met drug-refractory symptom criteria. Factors associated with drug-refractory symptoms included age 12 years or older (p < 0.0001), diagnosis of autistic disorder (p = 0.0139), and presence of intellectual disability (p = 0.0273). This pilot report underscores the significance of drug-refractory aggression, self-injurious behavior, and severe tantrums; suggests the need for future study clarifying factors related to symptom development; and identifies the need for focused treatment study of this impairing symptom domain.

Acamprosate was generally safe and well tolerated and was associated with a significant improvement in social behavior and a reduction in inattention/hyperactivity. The increase in BDNF that occurred with treatment may be a useful pharmacodynamic marker in future acamprosate studies. Given these findings, a double-blind, placebo-controlled study of acamprosate in youth with FXS is warranted.