Psychostimulants that generally

N06B E Psychostimulants that generally increase the physical capacity The medicinal plants that are considered to have this effect and which are described here are Schizandra chinensis, Panax finsen, Eleutherococcus senticosus, (Acanthopanax senticosus), Rhodiola rosea, and Pollen. 

In summary, caffeine is a known psychostimulant that exerts positive effects on physical endurance, alertness, and vigilance. The effects on reaction time and EEG activity are debatable. Caffeine may cause small, but inconsequential, increases in blood pressure, particularly in people who do not habitually use this compound. Although the effects on mood are generally positive, increased anxiety may result from doses of 300 mg or more. Caffeine s most reliable effects appear to occur in sleep-deprived personnel in whom doses ranging from 250 to 600 mg (including sustained-release caffeine doses of 300-600 mg) have been shown to improve wakefulness, mood, and various aspects of performance. 

There are differences in vulnerability to addiction in general, and there is growing evidence that this difference is particularly pronounced in psychostimulant abuse (e.g., Brady and Randall 1999 Brecht et al. 2004). In human subjects, although the dissimilar influence of social and environmental pressures on males and females cannot be overlooked, biological factors are also evident and suggest similarities to the differences observed in animal models of addiction. 

Aman (1996) postulated that focus of attention, IQ, and mental age may be useful predictors of psychostimulant response. In his theory, children with narrow attentional focus are generally expected to respond more poorly than those with broader attentional focus, and those with lower IQ and lower mental age are predicted to respond more poorly. Castellanos et al. (1992) reported that in 72 normally developing children, the 13 with IQ above 120 responded better to dextroamphetamine, while those with IQ below 120 responded equally well to either dextroamphetamine or methylphenidate, but they could not replicate this in a prospective study (personal communication). 

In recent years the psychostimulant male/female ratio appears to have narrowed to 1 6, in contrast to the 1 12 ratio in the mid-1980s (Safer, 1994). Similarly, Zito et al. (2000) noted that the male/female ratio for prescription frequency has also narrowed among preschoolers in two of three data sets (roughly 4-7 1 to 3-4 1). One interesting exception to this general male female ratio has been noted, however. Zito et al. (1998b) report that for children under the age of 15 years, males are more likely to receive psychotropic treatments (specifically methylphenidate, desipramine, and imipramine) than females. But in youth ages 15 years and older, females received the majority of psychotropic prescriptions. 

In Chapter 1 of this book, psychopharmaceuticals were introduced as effective medicines that primarily have a symptomatic action but are problematic in several respects. Antipsvchotics can cause serious side effects and antidepressants often exert their therapeutic effects only after a delay of weeks and in many cases have unpleasant side effects. With anxiolytics, hypnotics and, in particular, psychostimulants, there are problems with habituation and the potential of dependency. It is therefore not surprising that psychopharmaceuticals do not enjoy a very high reputation among many doctors and the general public (see Box 8.1) and have been given names such as chemical strait-jackets for the older neuroleptics (Szasz, 1957) or chemical blinkers for the mind for tranquillizers. Elomaa (1993) even posed the question of whether the long-tom use of conventional antipsychotics should be considered a crime against humanity. 

SSRIs reduce dopamine cell firing in the substantia nigra through their effects on serotonin input to this nucleus. The net result is that they can cause generally mild extrapyramidal side effects (EPS) (500). The most common are restlessness and tremors. The same mechanism is probably responsible for their interaction with other agents that affect central motor systems. Thus, the SSRIs can potentiate the tremor seen with lithium, as well as EPS caused by antipsychotics, bupropion, and psychostimulants (376, 500). 

Use in Obesity. As noted earlier, many of the psychostimulants have also been used as anorectics (anorexics anorexigenics), that is, as appetite suppressants. A few of them are still useful in this regard, but the high abuse potential of psychostimulants, coupled with the development of tolerance to their anorectic effects, has meant that prescribing psychostimulants for weight control has generally fallen into disfavor. 

Caffeine. The psychostimulant action of caffeine generally is accepted as well established. Caffeine quickens reaction time and enhances vigilance, increases self-rated alertness, and improves mood. There is, however, little unequivocal evidence to show that regular caffeine use is likely to benefit substantially either mood or performance. Indeed, one of the significant factors motivating caffeine consumption appears to be "withdrawal relief (49). 

A Rde for Norepinephrine. Although the vast majority of studies of psychostimulants have focused on the role of dopamine and/or serotonin, the importance of norepinephrine (thought to be paramount 30 years ago) is generally now overlooked. Details of the mechanism of action of psychostimulants have been developed primarily through the use of animal models, in which dopamine seems to be the key player, and these results then have been extrapolated to humans. Yet, cocaine also is a potent NE uptake inhibitor, and the potency of amphetamine for norepinephrine release is similar to that for dopamine release. Indeed, in the rat prefrontal cortex, amphetamine and cocaine increased extracellularnorepinephrine to an extent that was quantitatively similar to that of dopamine (116).Further, it appeared that the increase in prefrontal cortical norepinephrine was actually attributable to the blockade of the norepinephrine transporter by both drugs. Recently, Rothman et al. (117) reported that the oral doses of several stimulants required to produce amphetamine-like subjective effects in humans were most closely correlated with... 

This chapter makes no attempt to review all the literature that focuses on the role of norepinephrine and serotonin in the actions of psychostimulants. At the time of this writing, the general consensus seems to be that effects on dopamine systems are necessary, but perhaps not sufficient, conditions to explain all the different actions of stimulants. There appears to be increasing awareness, spurred initially by studies of cocaine, that serotonin may be a much more important player than was heretofore recognized. In the next few years this role likely will be studied and elucidated in much greater detail. 

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