Neuroanatomical systems

Accordingly, several of the neurochemical and neuroanatomical systems considered to be involved in arousal and consciousness, i.e. Meynert nucleus, pontine reticular formation, locus coeruleus and raphe nucleus with their cholinergic, noradrenergic and serotonergic afferents (Delacourt, 1995) are affected in PD. In addition, the dopamine system, in particular the mesolim-bocortical system, is involved in cognition and motivation, and possibly in the emergence of positive psychotic symptoms such as hallucinations and delusions. 

Unipolar and bipolar depressive disorders in children and adolescents are serious conditions. The pathophysiology of these disorders is poorly understood. The new tools available through neuroimaging techniques will help to unravel the neuroanatomical systems involved in the onset and recurrence of these disorders. There is a need for more developmentally informed predinical research and more studies of the normal development of the neural systems implicated in emotional regulation. 

MCEWEN B s (1999) Clinical review 108 The molecular and neuroanatomical basis for estrogen effects in the central nervous system. J Clin Endocrinol Metab. 84 1790-97. 

Neuroanatomical and neurochemical basis of wakefulness and REM sleep systems... 

Despite the advent of molecular genetics in neurobiology, our understanding of the functional relationships of the components of the CNS remains in its infancy, particularly in the areas of cellular interaction and synaptic modulation. Nevertheless, the fine structural relationships of most elements of nervous system tissue have been described well [1-5]. The excellent neuroanatomical atlases of Peters et al. [3] and Palay and Chan-Palay [1]... 

Golgi, in early neuroanatomical studies (1898) staining neurones by silver impregnation, observed a reticular apparatus which was crescent shaped and appeared to be linked through canaliculi. The structure was also seen in secretory cells. Between 1949 and 1954, Baker reported the presence of similar systems in unfixed cells examined by phase contrast. The structures could be stained by osmium tetroxide and probably contained lipid. They also stained for glycoprotein and alkaline phosphatase. Baker s confirmation of the existence of the... 

A detailed description of the neuroanatomical structures involved in sleep is provided in the excellent reviews, of Jones (1989) and Hobson et al. (1998). Alertness and sleep are dependent on the activity of the brain as a whole, although different levels of consciousness are determined primarily by areas of the brain stem. Lesion and stimulation studies have been used to identify specific regions and delineate relevant neuronal systems (reviewed by Parkes, 1985). 

The neuroanatomical data collected so far indicate that the CRH system is clearly in the position to modulate serotoninergic neurotransmission at the level of the raphe nuclei, not only directly but also indirectly via effects targeted to GABAergic interneurones. More detailed studies, however, will be needed... 

Because neuropeptides have a more discrete neuroanatomical localization than classical neurotransmitters, it is expected that they produce less disturbances of physiological processes if modulated by drugs and antagonists are suggested to be less likely to produce tolerance or dependency. Additionally, these drugs are not expected to disrupt normal physiology in the absence of neuropeptide release, i.e., activation of the system. 

Further evidence concerning anxiolytic effects of neurosteroids involves its action on the prefrontal cortical dopamine system. This system has been identified as one of the neuroanatomically involved CNS areas in stress and anxiety responses, where increases in dopamine metabolism are observed following a variety of stressors [A. Y. Deutch and Roth 1990]. Grobin et al. [1992] demonstrated that intracerebroventricularly administered allo-THDOC effectively reduced dopamine metabolism in rats, thereby antagonizing stress-induced activation of the prefrontal cortical dopamine innervation. 

Finally, neuroanatomical distribution of steroid-sensitive GABA, receptors in the CNS needs to be further correlated with CNS areas involved in anxiety responses as well as their interaction with other transmitter systems, for example, CRH or dopamine [Grobin et al. 1992 Zhang and Jackson 1994). Such characterization may result in the development of more specific compounds, possibly also involving concomitant antidepres-sive effects. 

The working assumption that the striatal system is only involved with extrapyramidal function (e.g., parkinsonian side effects, dystonias, and TD) and that the mesolimbic or mesocortical systems are only involved with psychosis may be an oversimplification. Many of the neuroanatomical studies on the identified dopaminergic tracts are done with rats. In the monkey, by contrast, there are many more DA tracts that are either absent in the rat or at least markedly different human systems could be different from the rat s or monkey s. Understanding the neuropharmacology of the antipsychotics is further complicated, given that neither the mesolimbic-mesocortical nor the striatal systems are homogeneous but may also include various subsystems. 

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