The effects of nadolol on various cardiac tissues in normoxia, and on atrial muscle in simulated ischaemia

Neuropsychiatric symptoms of fragile X syndrome: pathophysiology and pharmacotherapy

Fragile X syndrome is the leading inherited form of mental retardation, and second only to Down's syndrome as a cause of mental retardation attributable to an identifiable genetic abnormality. Fragile X syndrome is caused by a defect in the fragile X mental retardation 1 gene (FMR1), located near the end of the long arm of the X chromosome. FMR1 normally synthesises the fragile X protein (FMRP), but mutations in FMR1 lead to a lack of FMRP synthesis, resulting in fragile X syndrome. While the specific function of FMRP is not yet fully understood, the protein is known to be important for normal brain development. The physical, cognitive and behavioural features of individuals with fragile X syndrome depend on gender (females have two X chromosomes, one active and one inactive) and the molecular status of the mutation (premutation, full mutation or mosaic). Features of the behavioural profile of individuals with fragile X syndrome include hypersensitivity to stimuli, overarousability, inattention, hyperactivity and (mostly in men) explosive and aggressive behaviour to others or self. Social anxiety, other anxiety disorders, depression, impulse control disorder and mood disorders are the most common psychiatric disorders diagnosed in individuals with fragile X syndrome, although no formal studies have been undertaken. There have been very few psychopharmacological studies of the treatment of behaviours associated with fragile X syndrome. These limited studies and surveys of psychotropic drugs used in individuals with fragile X syndrome suggest that stimulants are helpful for hyperactivity, that alpha(2)-adrenoceptor agonists and beta-adrenoceptor antagonists help to control overarousability, impulsivity and aggressiveness, and that SSRIs can control anxiety, impulsivity and irritability, alleviate depressive symptoms and decrease aggressive and self-injurious behaviour. Typical and atypical antipsychotics in combination with other psychotropics have been used for control of psychotic disorders and severe aggressive behaviours. Mood stabilisers have been found to be useful when mood dysregulation or mood disorders are present with or without aggressive behaviour. Folic acid and L-acetylcarnitine (levacecarnine) have not been found to improve deficits or behaviours. As there is no specific psychotropic drug for any of the deficits or behaviours associated with fragile X syndrome, clinicians are advised to diagnose any psychiatric syndromes or disorders present and treat them with the appropriate psychotropic drug. If no psychiatric disorder can be diagnosed and the patient's challenging behaviours cannot be controlled with environmental manipulation or behaviour modification techniques, the most benign psychotropic drug should be used. Antipsychotics should be reserved for psychotic disorders, for impulse control disorders (used in combination with other psychotropics), or when challenging behaviours constitute an emergency. In the future, new medications targeting molecules implicated in the modulation of anxiety, fear and fear responding will be useful for treating the social anxiety and overarousability exhibited by individuals with fragile X syndrome.

Mechanism of prevention of sudden death by nadolol: differential actions on arrhythmia triggers and substrate after myocardial infarction in the dog

Electrocardiographic monitoring and provocative ventricular pacing were used to evaluate control and nadolol treatment groups 6 to 24 hours after left anterior descending coronary artery ligation in the dog. During the 6 to 24 hour period, the control group (n = 20) developed ventricular triplets at rates exceeding 270/min. Seven dogs spontaneously developed sustained monomorphic ventricular tachycardia (421 +/- 12 beats/min) at 13 +/- 2 hours. Sustained monomorphic ventricular tachycardia was present for 38 +/- 8 seconds before ventricular fibrillation developed. One dog developed recurrent monomorphic ventricular tachycardia, with six episodes lasting from 8 to 72 seconds (375 to 425 beats/min). At 24 hours, ventricular pacing produced sustained monomorphic ventricular tachycardia (378 +/- 12 beats/min) in 9 of 13 surviving animals. Nadolol administration 6 hours after coronary artery ligation (n = 19) lowered both the rate (241 +/- 8 versus 328 +/- 8 beats/min; p = 0.001) and the incidence (8 +/- 6 versus 198 +/- 61 per hour; p = 0.004) of rapid ventricular triplets and prevented sudden arrhythmic death (0%; p = 0.005). Nadolol failed to prevent sustained monomorphic ventricular tachycardia (88%; 365 +/- 12 beats/min) produced by ventricular pacing. The data suggest that nadolol prevents spontaneous sustained monomorphic ventricular tachycardia by selectively suppressing the arrhythmia trigger (rapid ventricular triplets) without altering the underlying arrhythmia substrate.

Effects of bucumolol, nadolol and nifenalol on maximum upstroke velocity of action potential in guinea pig papillary muscles

The effects of bucumolol (BUC), nadolol (NAD) and nifenalol (NIF) on contractile forces and on action potentials (APs) were investigated in isolated guinea pig atrial and papillary muscles, respectively. Log 1/ED40 values for the negative inotropic effects of these drugs were 0.097, 10 and 0.74 mmol/l in this order. BUC (50 mumol/l), NAD (0.5 mmol/l) and NIF (0.2 mmol/l) produced about 60, 20 and 20% reduction of Vmax at 1 Hz. The frequency-dependent reductions at these and higher concentrations were greatest for BUC, intermediate for NAD and least for NIF. These potencies at certain frequencies were, as a whole, consistent with log P-potency relationship established in our previous papers (Harada et al. 1981; Ban et al. 1985). The reductions of Vmax in APs in response to premature stimuli during basic stimuli at the rate of 0.25 or 0.027 Hz decayed exponentially during diastolic intervals (DI). The time constants of these decay process (tau) estimated by linear and nonlinear regression analyses and by eye were 12.2-9.6 s for BUC (50-100 mumol/l) and 2.9-4.8 s for NAD (1-2 mmol/l) and 57-87 ms for NIF (0.2-1 mmol/l). In terms of the molecular weight (MW)-log tau relationship (Ban et al. 1985), these tau values are within the 95% fiducial limit for BUC and NAD and deviated from the lower fiducial limit for NIF. The frequency-dependent reductions of Vmax by these drugs were explained in terms of a function of tau and the intercept Ao. Based on the study made by Cohen et al.(ABSTRACT TRUNCATED AT 250 WORDS)