Prescription for change: health supplement regulations and protecting the public interest.
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Biomedical subjects
Publications and source records attributed to M C Scally.
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Intracaudate injections of kainic acid destroy striatal neurons containing acetylcholine and gamma-aminobutyric acid but leave dopaminergic nerve terminals in this brain region intact. Rats injected with the drug are aphagic and adipsic, and have other behavioral abnormalities strikingly similar to those seen in animals with lesions in the dopaminergic nigrostriatal bundle.
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Treatments that increase the release of acetylcholine from the splanchnic nerve have previously been shown to induce the enzyme tyrosine hydroxylase in adrenal chromaffin cells. Such treatments include the systemic administration of the drugs phenoxybenzamine and 6-hydroxydopamine, insulin-induced hypoglycemia, and prolonged exposure to cold. We have reported that the administration of choline also induces the adrenal enzyme and have suggested that the mechanism of this induction involves an increase in the amount of acetylcholine released each time the splanchnic nerve fires. In the present studies, rats received both choline and one of the above treatments. Choline caused an augmentation of the adrenomedullary response to each of the treatments, but it had no apparent effect on a presynaptic enzyme, choline acetyltransferase. These observations strongly support the view that choline availability determines both the amount of acetylcholine present in nerve terminals and the amount liberated when cholinergic neurons fire.
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Animals received either haloperidol (2 mg/kg) or probenecid (200 mg/kg) in conjunction with tyrosine (100 mg/kg) or its diluent. Striatal homovanillic acid levels increased in probenecid-treated animals to the same range whether they were given tyrosine or not. In haloperidol-treated animals the levels of homovanillic acid were significantly elevated in animals receiving tyrosine. Tyrosine and homovanillic acid levels were highly correlated as determined by linear regression analysis.