Brain-stem development

CJ-Receptors are localized ia the brain stem and limbic stmcture, regions associated with endocrine function (76). In the periphery, CJ-receptors are found in the Hver, heart, ileum, vas deferens, and on lymphocytes and thymocytes. Although there is insufficient evidence to clearly define the functional role of CNS CJ-sites, based on the effects of PCP and the interaction of haloperidol with CJ-sites, CJ-receptor ligands may be antipsychotics or used for the treatment of substance abuse. Several CJ-receptor ligands have shown neuroprotective effects in vivo. Ifenprodil (315) and CNS 1102 (316) are being developed for treatment of stroke (Table 18). 

Brain metastasis is the most common neurologic complication seen in patients with cancer. Approximately 170,000 patients develop brain metastases in the United States each year.20 Many malignancies are frequently associated with brain metastases (Table 96-7). While melanoma is the tumor type most likely to metastasize to the brain, brain metastases owing to lung and breast cancers are seen more often because they are among the most common cancers. In addition, brain metastasis may be diagnosed at the same time as the primary malignancy in around 20% of cases.22 Around 80% of brain metastases occur in the cerebral hemispheres, 15% in the cerebellum, and 5% in the brain stem. 

When levodopa is given without a peripheral decarboxylase inhibitor, anorexia and nausea and vomiting occur in about 80% of patients. These adverse effects can be minimized by taking the drug in divided doses, with or immediately after meals, and by increasing the total daily dose very slowly antacids taken 30-60 minutes before levodopa may also be beneficial. The vomiting has been attributed to stimulation of the chemoreceptor trigger zone located in the brain stem but outside the blood-brain barrier. Fortunately, tolerance to this emetic effect develops in many patients. Antiemetics such as phenothiazines should be avoided because they reduce the antiparkinsonism effects of levodopa and may exacerbate the disease. 

The extracellular microelectrode recording technique developed by David Hubei for his epochal studies of the cat visual system and further perfected by Eduard Evarts for his pioneering work on the cat motor system was easily applied to exploring the brain stem. There were two major obstacles that needed to be overcome to guarantee success, however. The first was movement not only was head movement itself a problem, but body movement also had to be limited because the targets were deep and located on the major axis of lateral and vertical head-on-neck movement. The second problem was identification of the neurons of interest. At the onset, no one knew that the modulatory elements would identify themselves both by their distinctive spike-to-spike firing pattern, but also—and this is the main point of the discovery—by their dramatic state dependent alterations of firing propensity. 

Another important side effect of all opiates on the central nervous system is respiratory depression. This is caused by an inhibitory effect on the brain stem, which is the part of the brain that controls breathing and other involuntary bodily systems such as heart beat, etc. Like nausea and vomiting, people who take methadone and other opiates normally develop a tolerance to this side effect. However, even people who have taken methadone for a long period of time can develop major respiratory depression. 

Prevention alone is often not enough. Children still become jaundiced even after careful assessment. When this occurs.it is important to assess the risk of developing significant hyperbilirubinemia. The main concern is that the child will develop acute bilirubin encephalopathy, which is caused by the toxicity of bilirubin on the basal ganglia and other brain stem nuclei. There are early, middle, and late stages of acute bilirubin encephalopathy (Table 22-3). The term kernicterus is applied to chronic... 

Stimulates vomiting center in brain stem (tolerance to this effect develops quickly)... 

For the mammalian brain the most important period of life lasts from weaning until sexual maturity. At the time of weaning fully developed enhancer regulation in the brain stem starts working on a higher activity level. This state lasts until sexual maturity is reached (Knoll and Miklya, 1995). For details see Sect. 3.5.1.1. 

Grothe, C., Zachmann, K., and Unsicker, K., Basic FGF-like immunoreactivity in the developing and adult rat brain stem, J. Comp. Neurol., 305, 328, 1991. 

Suzuki H, Park S J, Tamura M, Ando S. Effect of the long-term feeding of dietary lipids on the learning ability, fatty acid composition of brain stem phospholipids and synaptic membrane fluidity in adult mice a comparison of sardine oil diet with palm oil diet. Meeh Ageing Develop 1998 101 119-128. 

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