Distinct promoters direct neuronal and nonneuronal expression of rat aromatic L-amino acid decarboxylase.

Aromatic L-amino acid decarboxylase (AADC, EC 4.1.1.28) catalyzes the decarboxylation of L-dopa to dopamine in catecholamine cells and 5-hydroxytryptophan to serotonin in serotonin-producing neurons. This enzyme is also expressed in relatively large quantities in nonneuronal tissues such as liver and kidney, where its function is unknown. Neuronal and nonneuronal tissues express AADC mRNAs with distinct 5' untranslated regions. To understand how this is accomplished at the genomic level, we have isolated rat genomic DNA encoding AADC. The organization of the AADC gene suggests that there are two separate promoters specific for the transcription of neuronal and nonneuronal forms of the AADC message. A small exon containing 68 bases of the neuronal-specific 5' end is located approximately 9.5 kilobases upstream of the translation start site, which is contained in the third exon. Approximately 7 kilobases upstream from the neuron-specific promoter is another small exon containing 71 bases of the 5' end of the nonneuronal AADC message. These data suggest that transcription initiating at distinct promoters, followed by alternative splicing, is responsible for the expression of the neuronal and nonneuronal forms of the AADC message.

The pharmacokinetics of naloxone in the premature newborn.

We examined the pharmacokinetic properties of naloxone in a group of premature infants infused with an intravenous bolus of the drug. Ten infants with a mean birth weight of 1,328 +/- 402 g and a gestational age of 29.4 +/- 2.8 weeks were studied at an age of 4.5 +/- 3.2 days of life. Following administration of 0.4 mg/kg of naloxone, we obtained blood samples at specific time intervals, and stored the serum for later analysis by a radioimmunoassay method. Calculations from the serum concentration versus time relationship resulted in an elimination rate constant of 0.75 +/- 0.39/h, a half-life of 70.5 +/- 35.2 min, a systemic clearance of 39.13 +/- 14.53 ml/min/kg, and an apparent volume of distribution of 3.52 +/- 1.20 liters/kg.

Melatonin in serum and the pineal of spontaneously hypertensive rats.

Involvement of melatonin in the blood pressure regulation as an endogenous central hypotensive factor has been suggested in rats and in man. We studied the relationship between melatonin and the development of hypertension in 5- and 15-week-old spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats, by measuring serum and the pineal concentrations with a sensitive and specific radioimmunoassay coupled with a novel extraction method. Serum melatonin concentration at midnight in young SHR rats was significantly higher than that in age-matched WKY rats (P less than 0.01), whereas it was decreased in the adult SHR (P less than 0.01). No such differences were observed at noon. Pineal content of melatonin at midnight in 5-week-old SHR rats was lower than in age-matched WKY rats (P less than 0.01). These data demonstrate that melatonin in the nocturnal serum of SHR rats is elevated at prehypertensive stage while it is decreased after the development of hypertension. The role of melatonin in the hypertensive process in SHR rats requires further study.

Opioid polypeptides in guinea pig pancreas.

Extracts from guinea pig pancreas were found to contain high molecular weight enkephalin-containing polypeptides as well as free [Met]enkephalin and [Leu]enkephalin and the hexa-, hepta-, and octapeptides derived from proenkephalin. Within the limits of sensitivity of our assay (10 fmol/g of tissue), beta-endorphin and beta-lipotropin were undetectable.

A new radioimmunoassay for haloperidol: direct measurement of serum and striatal concentrations.

A sensitive and specific radioimmunoassay for haloperidol has been developed. Antibodies were elicited in rabbits immunized with haloperidol hemisuccinate coupled to bovine serum albumin. Optimum sensitivity was obtained with a 1:4000 dilution of the antisera, permitting the detection of as little as 2.6 ng/ml of haloperidol. Major metabolites of haloperidol did not cross-react in the assay. The method does not require an extraction procedure and can be performed using as little as a 5-microliter sample. Haloperidol levels in rat serum and striatum were determined with this method, after the i.v. administration of different dosages of the drug. The distribution and elimination of haloperidol was linear over the dose range to have an elimination half-life of approximately 2.6 hr at all three dosage levels.

Radioimmunoassay of atropine in plasma.

Antibodies, against atropine, were produced in rabbits immunized with atropine conjugated to bovine serum albumin. The antisera possessed a high binding affinity and were quite specific. The sensitivity of the method allowed detection of 6.25 ng of atropine per ml of plasma in a 10-microliter specimen. The method does not require an extraction procedure and can be performed using very small volumes of plasma. Plasma concentration-time profiles were determined by this method in dogs after rapid i.v. administration of atropine. Atropine declined from plasma in a biexponential fashion, exhibiting a terminal half-life of approximately 2.1 hours.

Correlation of chlorpromazine levels in rat brain and serum with its hypothermic effect.

The correlation between chlorpromazine (CPZ) levels in rat brain and serum with hypothermia was investigated. Even large differences between brain and serum concentrations of CPZ could be demonstrated at the two dosages of the drug investigated, the groups showed an identical hypothermic effect between 5 to 30 minutes, with maximum hypothermia being reached 1 hour. It also appears that when brain concentrations of CPZ were lower than 1 mug/g, body temperature returned to normal. We could not demonstrate any preferential uptake of CPZ into the hypothalamus, the proposed site at which CPZ acts to cause hypothermia.