Plasma free MHPG and neuroendocrine responses to challenge doses of clonidine in Tourette's syndrome: preliminary report

Emerging drugs for the treatment of symptoms associated with autism spectrum disorders

IMPORTANCE OF THE FIELD

Autism spectrum disorders, or pervasive developmental disorders (PDDs), are neurodevelopmental disorders defined by qualitative impairment in social interaction, impaired communication and stereotyped patterns of behavior. The most common forms of PDD are autistic disorder (autism), Asperger's disorder and PDD not otherwise specified. Recent surveillance studies reveal an increase in the prevalence of autism and related PDDs. The use of pharmacologic agents in the treatment of these disorders can reduce the impact of interfering symptoms, providing relief for affected individuals and their families.

AREAS COVERED IN THIS REVIEW

This review examines results from neurobiologic research in an attempt to both elucidate the pathophysiology of autism and guide the development of pharmacologic agents for the treatment of associated symptoms. The safety and efficacy data of drugs currently in clinical use for the treatment of these symptoms, as well as pharmaceuticals currently under development, are discussed.

WHAT THE READER WILL GAIN

This comprehensive review will deepen the reader's current understanding of the research guiding the pharmacologic treatment of symptoms associated with autism and related PDDs. Areas of focus for future research are also discussed. The need for large-scale investigation of some commonly used pharmacologic agents, in addition to the development of drugs with improved efficacy and safety profiles, is made evident.

TAKE HOME MESSAGE

Despite progress in the development of pharmacologic treatments for a number of interfering symptom domains associated with autism and other PDDs, a great deal of work remains.

Examining cortisol rhythmicity and responsivity to stress in children with Tourette syndrome

BACKGROUND

Tourette syndrome (TS) is characterized by motor and vocal tics, which are often exacerbated by stress. The hypothalamic-pituitary-adrenocortical (HPA) axis, a major stress response system is thus of interest for understanding TS.

METHODS

Diurnal cortisol rhythms were estimated in medication-free children 7-13 years with TS (N=20) and healthy age-matched controls (N=16). Salivary samples were collected on 3 consecutive days from the home. HPA responsivity was assessed by examining cortisol in response to a mock and real MRI scan.

RESULTS

The results of diurnal rhythmicity revealed a trend showing marginally lower evening cortisol for the TS group. By contrast, the TS group had higher cortisol levels in response to the stressor. There were strong, negative correlations between evening cortisol and tic severity as well as diurnal cortisol and anxiety.

CONCLUSIONS

The children with TS showed increased cortisol in response to the MRI environment, supporting a model of enhanced HPA responsivity. The lower evening cortisol may be the result of chronic daily stress. Alternatively, the negative associations between cortisol and reported anxiety and tics may reflect biologically based anxiolytic properties of tic expression. Taken together, the results clearly implicate involvement of the HPA axis in the neuropathology of TS.

Plasma beta-endorphin, adrenocorticotropin hormone, and cortisol in autism

Plasma levels of the hypothalamo-pituitary-adrenal axis hormones beta-endorphin (BE), adrenocorticotropin hormone (ACTH), and cortisol were measured in autistic (N = 48), mentally retarded/cognitively impaired (MR/CI, N = 16), and normal control (N = 26) individuals. Comparison of log transformed data from the three groups revealed that levels of BE and ACTH were significantly higher (p < .05) in the autistic individuals than in normal controls. The higher means in the autistic group were due to significantly higher plasma levels of BE and ACTH, indices of acute stress response, in the more severely affected individuals. The data support the idea that individuals with severe autism have a heightened response to acute stressors rather than chronic hyperarousal or elevated basal stress response system functioning.

Predictors of clonidine response in Tourette syndrome: implications and inferences

Clonidine is an alpha-adrenergic agonist which may alleviate emerging symptoms in Tourette syndrome, an observation that has fueled speculation regarding involvement of stress-sensitive central noradrenergic systems in this disorder. We conducted a retrospective study of 53 juvenile patients with Tourette syndrome to assess predictors of short-term behavioral and tic response to oral clonidine and to examine the relationship, if any, among pretreatment blood pressure, tic severity, and clonidine response. When adverse effects were considered, older subjects experienced a better therapeutic response to clonidine, independent of dose. Improvement in symptoms of attention-deficit hyperactivity disorder was associated with a longer duration of vocal tics before treatment. Baseline sitting diastolic blood pressure was directly correlated with measures of tic severity but not with tic response to clonidine. The findings (1) provide indirect support for involvement of central noradrenergic systems in tic expression; (2) suggest that emergence of a tic-related neurophysiologic dysfunction may be necessary for optimal behavioral response to clonidine in Tourette syndrome; and (3) provide broad guidelines for the clinician considering clonidine therapy for pediatric patients with Tourette syndrome, particularly those with comorbid attention-deficit hyperactivity disorder.

Tourette's medications: effect on minor oxidative and reductive pathways of biogenic amines

The effect of acute treatment of two major Tourette's drugs, haloperidol and pimozide given 60 mg/kg, IP over 48 hr, on hepatic alcohol dehydrogenase (L-ADH) and aldehyde dehydrogenase was studied in the female mouse. The effect of these drugs on heart cytoplasmic lactate dehydrogenase (H-LDH) isoenzyme LDH1 (M) and LDH2 (H) was also measured. Both haloperidol and pimozide significantly inhibited cytoplasmic L-ADH and L-ALDH from controls. Conversely, the haloperidol treatment was associated with induction of both H-LDH isoenzymes studied. Injection of pimozide, 25 mg/kg, IP, to rats with preference to ethanol drinking, caused aversion to voluntary intake of 5% ethanol consumption. This suggests that pimozide produced inhibition of L-ADH in another species and thereby causing aversion to ethanol drinking or may be related to dopaminergic antagonist property. This inhibition of these drugs on the oxidative and reductive pathways of biogenic amine aldehydes may be implicated in and/or associated with the underlying mechanism(s) of action.

Plasma MHPG: within- and across-day stability in children and adults with Tourette's syndrome

Within- and across-day stability of unconjugated plasma 3-methoxy-4-hydroxyphenethyleneglycol (pMHPG, the major metabolite of norepinephrine) levels were assessed in several subgroups of 47 primarily child and adolescent subjects with Tourette's syndrome (TS). Mean morning pMHPG levels remained stable over a 20-min period from 8:30 to 8:50 AM at 3.5 +/- 0.8 ng/ml. However, the mean intraindividual fluctuation in pMHPG levels over 20 min was +/- 12%. Mean pMHPG levels remained stable in the morning from 8:00-8:30 AM to noon. However, an 11% decrease (p less than 0.01) in mean pMHPG levels was observed in the afternoon between noon and 3:00-4:00 PM. Monitored on consecutive days, mean morning pMHPG levels fell 12% (p less than 0.002). The afternoon and across-day falls in pMHPG levels observed in this study of primarily children and adolescents with TS have not been observed in studies of adult control subjects. The results suggest that the design of research protocols involving children and adolescents that use pMHPG should take into consideration the effects of time, both within- and across-day, in pMHPG levels.

Motor, behavioral and pharmacologic findings in Tourette's syndrome

We studied 112 patients with Tourette's syndrome (TS); the male-to-female ratio was 3.8, the mean age of onset was 7.3 years, and the average duration of symptoms prior to the initial evaluation was 15.2 years. Seventy-nine percent of the patients had at least one family member with motor or vocal tics, and an additional 10 percent had a family member with marked obsessive-compulsive behavior. Simple motor tics occurred as the presenting symptom in about one-third of patients; one-third had multiple motor tics at the onset, and another third started with vocal tics. During the course of the illness all patients developed multifocal motor tics and 86 percent had vocal tics. Verbal and mental coprolalia was present in 44 percent of the patients. Copropraxia was seen in 19 percent of patients, and both coprolalia and copropraxia were more frequent among the males than expected. Attentional deficit disorder was diagnosed in 36 percent of the patients and 32 percent had obsessive-compulsive personality. Sleep disturbances were reported by 62 percent of the patients and polysomnographs in 34 patients showed motor and vocal tics during all stage of sleep, sleep apnea, abnormal arousal pattern, and other sleep disturbances. Patients with mild symptoms improved with clonidine or clonazepam, but those with more advanced disorder required fluphenazine, pimozide, haloperidol or tetrabenazine.

The hypothalamus in Tourette's syndrome

Although a recent report by Devinsky (1983) has suggested that dysfunction at a midbrain levels is most likely to underlie the major symptoms of Tourette's syndrome, several features of the disease including alterations in the severity of the disease during puberty and premenstrually, disorders of appetite, amelioration of tics with rise in body temperature, and sleep point to hypothalamic involvement in the pathophysiology of the disease.

Behavioral and clinical profiles of Tourette's disease: a comprehensive overview

A brief review of Gilles de la Tourette's disease is presented. The initial part gives an overview of major signs, symptoms displayed, and diagnosis in addition to certain minor concomitant features. The latter conditions included appetite, adaptive function, learning disorders, sexual behavior, sleep disturbances, speech pathology, and tic-related injury. Neurological manifestations, infectious etiology, and genetics were discussed. Treatment modalities are outlined and description of various drug therapy is given in conjunction with rationale of pharmacotherapy and possible underlying mechanism of action. Drug-induced Tourette's-like syndrome was also summarized.

Determination of norepinephrine in brain perfusates using high-performance liquid chromatography with electrochemical detection

A procedure for determining catecholamine levels in brain perfusates is described. A single-step extraction on alumina followed by reversed-phase ion-pair chromatography and electrochemical detection was employed. Levels of norepinephrine are reported in push-pull perfusates of the rat hypothalamus under baseline and various ion substitution conditions. The resulting estimated norepinephrine release values are correlated with the behavior of the animal. The data are discussed in terms of the validity of the measures and the noradrenergic mediation of behavior.

Dopaminergic dsyfunction in Tourette syndrome

A prospective clinical and biochemical study on the effects of treatment with haloperidol has been performed in seven patients with Tourette syndrome. Pretreatment cerebrospinal fluid levels of homovanillic acid (CSF HVA) were significantly reduce in all patients, whereas 5-hydroxyindoleacetic acid was reduced in only two. With haloperidol treatment, symptoms decreased in all cases (21 to 88%) and clinical improvement was associated with an increased level of CSF HVA, often returning to the normal range. Optimal therapeutic response was found with serum levels of haloperidol between 1 and 4 ng/ml; however, disturbing side effects also occurred within this range. These results support the hypothesis that Tourette syndrome may result from a supersensitivity of dopaminergic receptors.

Clinical neurochemistry of autism and associated disorders

Advances in information concerning brain function in animals and advances in analytical neurochemical methods for determining extremely low levels of compounds in physiological fluids have opened great opportunities for clinical neurochemical studies of autism. Nevertheless, the behavioral deficits in autistic individuals are major obstacles to clarification of the relations between symptoms and biochemical dysfunction in the brain. The fundamental preclinical and clinical studies of serotonin, dopamine, and norepinephrine metabolism related to infantile autism are reviewed, and new studies are suggested as examples of the productive strategies that will illuminate features of the autistic syndrome in the next decade.