Cholinergic mechanisms in Gilles de la Tourette's syndrome

Lack of association between SLC5A7 polymorphisms and Tourette syndrome in a Chinese Han population

Although Tourette syndrome (TS) is a chronic neuropsychiatric disorder whose pathogenesis remains unclear, genetic factors play an important role in the occurrence and development. A variety of studies have been shown that the candidate genes related to cholinergic neurons may be associated with the onset of TS. To investigate the association between the SLC5A7 polymorphisms and Tourette syndrome (TS) in the Chinese Han population, the SNP rs1013940, rs2433718, and rs4676169 were genotyped in 401 TS trios and 400 controls. The transmission disequilibrium test (TDT) and haplotype relative risk (HRR) compared genetic distributions of trios, while the chi-square test compared patients and controls. However, no transmission disequilibrium was found between the three SLC5A7 SNPs and TS. Therefore, we think that this gene may not be the main risk factor on the onset of TS. However, these results should be further validated in different populations.

Yawning and stretching induced by transcranial application of AC pulsed electromagnetic fields in Parkinson's disease

Yawning is considered a brainstem regulated behavior which is associated with changes in arousal and activity levels. Yawning and stretching are dopamine (DA) mediated behaviors and pharmacological studies indicate that these behaviors are associated with increased DA release coupled with stimulation of postsynaptic DA-D2 receptors. Despite their relation to the dopaminergic system, yawning and stretching are poorly documented in untreated or treated patients with Parkinson's disease (PD). A 49 year old fully medicated female patient with juvenile onset PD is presented in whom recurrent episodes of yawning and stretching developed during transcranial administration of AC pulsed electromagnetic fields (EM Fs) of picotesla flux density. These episodes have not been observed previously in this or other patients during treatment with levodopa or DA receptor agonists or in unmedicated PD patients during treatment with AC pulsed EMFs. It is suggested that yawning and stretching behavior resulted in this patient from a synergistic interaction between EMFs and DA derived from levodopa supplementation with EMFs possibly facilitating the release of DA and simultaneously activating postsynaptic DA-D2 receptors in the nigrostriatal dopaminergic pathways. In addition, it is postulated that the release of ACTH/MSH peptides from peptidergic neurons in the brain upon stimulation of the DA-D2 receptors reinforced the yawning and stretching behavior.

Self-mutilation in the Lesch-Nyhan syndrome: a corporal consciousness problem?--a new hypothesis

The Lesch-Nyhan syndrome (LNS) has been extensively studied from the genetic and biochemical point of view. The main characteristic of the syndrome is the self-mutilation feature, which has been poorly studied and understood. We propose a new hypothesis about the self-mutilation physiopathology, which is related to the supersensitivity of the dopaminergic D1 receptors in the neuromatrix found in the cingulum cortex region. The LNS shows an increase of uric acid levels as a result of the deficiency of hypoxanthine phosphoribosyltransferase enzyme. This increase could induce damage to dopaminergic neurons. As a consequence, a decrease in dopamine synthesis during gestation and the early postnatal period could occur, producing a functional dopaminergic denervation of the D1 receptors, located on the prefrontal cortex, specifically in the cingulum bundle projections. This phenomenon could induce a codification disturbance in the 'genetic body' of the neuromatrix, that could be expressed functionally as anosognosia, giving rise to self-mutilation. We suggest that this self-mutilation is a pain consciousness problem.

Effects of REM sleep deprivation on the d-amphetamine-induced self-mutilating behavior

It is well known that self-mutilating behavior (SMB) is developed in rats and humans during the daily treatment with d-amphetamine. Accordingly, in this work it was found that the daily treatment with 7.5 mg/kg d-amphetamine induced in rats a progressive appearance of SMB. Lower doses (5.0 mg/kg) were uneffective and higher doses (10 mg/kg) produced a pattern of SMB in which the mutilation induced at the beginning of the d-amphetamine administration disappears completely as the treatment progresses. Interestingly, it was also found that REM sleep deprivation (48 h) potentiated significantly the SMB induced by the daily administration of 7.5 mg/kg d-amphetamine, and to lesser extent, the SMB induced by the daily treatment with 10 mg/kg d-amphetamine. R(+)-SCH-23390 a D1 dopamine (DA) receptor antagonist blocked completely or abolished the SMB induced by 7.5 mg/kg d-amphetamine in REM sleep deprived rats while (+/-)-sulpiride a D2 DA receptor antagonist had only a partial blocking effect. Haloperidol a D1/D2 DA receptor antagonist behaved as a D1 antagonist. Our results indicate that REM sleep deprivation enhances the SMB induced by the daily administration of d-amphetamine and suggest the involvement of D1 DA receptors in the mechanism underlying the SMB. A role of REM sleep deprivation is also suggested in the appearance of self-mutilating episodes in d-amphetamine addicts.

Bidirectional effect of electromagnetic fields on ketanserin-induced yawning in patients with multiple sclerosis: the role of melatonin

5-HT2 receptors regulate sleep including yawning behavior. Ritanserin, a selective 5-HT2A receptor antagonist, increases the duration of slow wave in rats and humans. This effect is more pronounced during the light period when melatonin plasma levels are low; melatonin inhibits the sleep effects of ritanserin. These findings indicate that melatonin co-determines the effects of ritanserin on sleep. In a cohort of multiple sclerosis (MS) patients ketanserin, a selective 5-HT2A receptor antagonist, induces recurrent yawning particularly when administered in daytime. The frequency of yawning induced by the drug was modified by AC pulsed picotesla flux electromagnetic fields (EMFs) which affect melatonin secretion. Two MS patients are presented in whom the frequency of ketanserin-induced yawning was altered in opposite directions by these EMFs. The first patient, a 50 year old woman with a remitting-relapsing course, developed recurrent yawning and sleepiness after administration of ketanserin (10 mg, PO). Yawning was decreased dramatically during application of EMFs but was unaffected by a placebo EMFs treatment. The second patient, a 35 year old man with a chronic progressive course, manifested a single and brief yawn after administration of an equal dose of ketanserin. Yawning was increased dramatically during application of EMFs while remaining unchanged during a placebo EMFs treatment. These observations demonstrate a bidirectional effect of picotesla flux EMFs on ketanserin-induced yawning which may be related to differences in daytime melatonin plasma levels among MS patients. If validated by estimations of melatonin plasma levels in a larger cohort of patients the information derived from the effects of picotesla EMFs on ketanserin-induced yawning could be used to: (a) assess pineal melatonin functions in patients with MS; (b) indicate differences in pineal functions between male and female MS patients; and (c) indicate a relationship between plasma melatonin levels and the fatigue of MS.

Effects of picotesla flux electromagnetic fields on dopaminergic transmission in Tourette's syndrome

Tourette's syndrome (TS), a chronic familial neuropsychiatric disorder of unknown etiology, is characterized clinically by the presence of motor and vocal tics that wax and wane in severity over the time and by the occurrence of a variety of neurobehavioral disorders. It is believed that the tics of TS result from increased dopamine (DA) activity caused by postsynaptic DA receptor supersensitivity. The synthesis and release of DA is regulated presynaptically by a specific class of DA D2 receptors, termed autoreceptors activation of which causes inhibition of DA synthesis and release. In experimental animals and humans administration of small doses of apomorphine, a DA D2 autoreceptor agonist, produces yawning. Recurrent episodes of yawning followed by increased motor tic activity was observed in two patients with TS during exposure to brief, extracranial applications of picotesla flux electromagnetic fields (EMFs). On the basis of these observations it is suggested that recurrent episodes of yawning in response to application of EMFs was induced by activation of presynaptic DA D2 autoreceptors while further exposure to these EMFs caused excessive stimulation of postsynaptic DA D2 receptors resulting in exacerbation of the tics. Thus, the dual effects of picotesla flux EMFs on the DA D2 autoreceptor and the postsynaptic receptor resemble the biphasic pharmacological and behavioral properties of apomorphine, a DA agonist which activates the autoreceptors in low doses while in higher doses causes stimulation of the postsynaptic receptors producing exacerbation of symptoms of TS. These findings demonstrate that picotesla flux EMFs applied extracerebrally may influence nigrostriatal DA transmission at pre- and postsynaptic DA D2 receptor sites.