Anja H. Tissari

Radioimmunoassay of oxytocin in amniotic fluid, fetal urine, and meconium during late pregnancy and delivery

Abstract Oxytocin concentrations, determined by radioimmunoassay, in amniotic fluid of 12 women during late pregnancy with no labor contractions varied from 150 to 800 pg. (median 275 pg. or 138 μU) per milliliter. In 18 women in labor, concentrations were 110 to 1,600 pg. (median 695 pg. or 350 μU) per milliliter. The difference between the oxytocin concentrations in these two groups is statistically significant (p

Reduction of dopamine synthesis inhibition by dopamine autoreceptor activation in striatal synaptosomes with in vivo reserpine administration.

Abstract: In an attempt to clarify the mechanisms by which dopamine (DA) autoreceptor activation inhibits DA synthesis, the efficacy and potency of the D2 DA agonists bromocriptine, lisuride, and pergolide, and the D1,‐D2 DA agonist apomorphine were studied in rat striatal synapto‐ somes, in which the rate of DA synthesis (formation of 14CO2 from l‐[1–14C]tyrosine) was increased 103% by treating the animals from which the synaptosomes were obtained with reserpine (5 mg/kg i.p. twice, 24 and 2 h before they were killed), using the striatal total homogenate as the standard synaptosomal preparation. The increase in DA synthesis evoked by reserpine was additive with that produced by treatment of the synaptosomes with dibutyryl cyclic AMP, suggesting that, not a cyclic AMP‐dependent, but possibly a Ca2+‐dependent mechanism was involved. The DA agonists showed a concentration‐dependent inhibition of DA synthesis in the control synaptosomes, which was antagonized by the selective D2 DA antagonist (‐)‐sulpiride. In the synaptosomes with increased rate of DA synthesis obtained from the rats treated with reserpine, the concentration‐response curves of DA synthesis inhibition for the other DA agonists were shifted to the right, and the effect of bromocriptine was completely eliminated, whereas bromocriptine antagonized the effect of apomorphine. The increased rate of DA synthesis was not preserved in the striatal P1+ P2 fraction obtained from the reserpine‐treated rats, but the effects of the DA agonists were still reduced to the same degree as those in the total homogenate. (‐)‐Sulpiride did not enhance DA synthesis in synaptosomes from the reserpine‐ treated rats. The results presented indicate that the reduced effect of the DA agonists in synaptosomes from the reserpine‐treated rats was not due to endogenous DA occupying the DA autoreceptors. Because it is known from the literature that reserpine in vivo increases impulse activity in DA neurons and, as a result, increases the Ca2+ concentration, these results suggest that the effect of DA agonists was reduced because DA autoreceptors may normally control DA synthesis by decreasing the free intraneuronal Ca2+ concentration, and consequently, the Ca2+‐dependent phosphorylation of tyrosine hydroxylase.

SUBCELLULAR DISTRIBUTION OF 5-HYDROXYTRYPTAMINE IN RAT BRAIN DURING DEVELOPMENT: EFFECT OF DRUGS AND FASTING

Abstract— Distribution of brain 5‐HT content between the high‐speed supernatant and particulate fractions under normal and experimental conditions was studied in postnatal and adult rats. In adult and 35‐day‐old rats the 5‐HT content of the supernatant fraction was about 25% of that of the total homogenate and significantly higher than that in 1, 7 and 21‐day‐old rats. In 1‐day‐old rats fasting caused an increase of 100% in the turnover, 50% in the content and no alteration in the subcellular distribution of brain 5‐HT, which suggests that under normal conditions 5‐HT stores may be filled near to capacity. After 5‐hydroxytryptophan administration, the 5‐HT content of the adult rat brain increased 3‐fold and that of the supernatant fraction to 35% of 5‐HT content of the total homogenate. In postnatal rats, the brain 5‐HT content rose to an adult level and the supernatant 5‐HT percentage to a markedly higher than adult level, probably because of the known higher than adult 5‐hydroxytryptophan decarboxylase activity of brain capillaries. Administration of tranylcypromine to adult rats caused a 2.6‐fold increase of brain 5‐HT content and a slight increase of the supernatant 5‐HT percentage. At various times after the administration of the MAO inhibitors (tranylcypromine or pargyline) and fasting to the 1‐day‐old rats, brain 5‐HT content increased 4, 5 and 7‐fold, respectively, and the supernatant 5‐HT rose consistently and, as in the adult, to about 30% of the 5‐HT content of the total homogenate. After pargyline following reserpine pretreatment, the 5‐HT content of the adult and 1‐day‐old rat brain increased to 2–3 times the control level and that of the supernatant fraction to about 40% of the 5‐HT content of the total homogenate. The adult values for 5‐HT in the particulate fraction of the 1‐day‐old rats after the drug treatments are in sharp contradiction to the low endogenous 5‐HT content and known lack of nerve terminals and synaptic vesicles in their brains, and suggest that after MAO inhibition brain 5‐HT neurons may bind the amine by some other mechanism than the Mg2+‐ATP‐dependent, reserpine‐sensitive granular storage.

Ultrastructural identification of monoaminergic synaptosomes from one day old rat brain.

SummarySynaptosomes from one day old and adult rat brain were studied. Specific cytochemical methods for demonstrating monoaminergic (MA) nerve endings were used. Permanganate fixation after preincubation with 5-OHDA or α-methyl-NA demonstrated MA synaptosomes. Their number was small in the adult (less than 1%) and still smaller in the one day old rat brain. The MA synaptosomes from developing rats were different from the adult ones. The large amount of endoplasmic reticulum in developing synaptosomes suggests that granular vesicles are formed from endoplasmic reticulum in nerve endings.

Ultrastructure of synaptosomes from one-day old and adult rat brain stem

SummaryThe ultrastructure and protein content of the five subfractions of the crude mitochondrial fraction from the brain stem of the 1-day old and adult rat was examined. The morphological composition of the subfractions after fixation in glutaraldehyde and osmiumtetroxide in the adult rat brain stem resembled that previously reported for the whole brain; synaptosomes sedimented in a sucrose gradient in subfractions C and D. In the 1-day old rat, mature synaptosomes were found in subfractions A, B, C and D; E contained mainly free mitochondria. 80–95% of the processes in the adult and 10–30% in the 1-day old rat contained synaptic vesicles which were of four types: (1) small agranular vesicles (2) large dense core vesicles (3) large agranular vesicles (4) coated vesicles. Pre- and postsynaptic membrane thickenings were demonstrated in many nerve-ending particles. In the subfractions of the 1-day old rat the protein content was one half and the distribution resembled that in the adult. Evidently nerve endings develop faster in the brain stem than in cortical areas; a serotoninor adrenergic origin of the early synaptosomes is suggested.

Synaptosomal dopamine autoreceptors: Sensitivity changes after in vitro and in vivo treatments

Dopamine (DA) synthesis in rat striatal synaptosomes was approximately doubled either by treating the animals from which the synaptosomes were obtained with reserpine, or by treating the preparations in vitro with d-amphetamine, ouabain or dibutyryl cyclic AMP. The concentration-response curve of DA synthesis inhibition by apomorphine was shifted to the right after treatment with all these compounds. The inhibitory effect of bromocriptine on DA synthesis was reduced completely after treatment with all the above compounds with the exception of dibutyryl cyclic AMP. When the inhibitory effect of bromocriptine was eliminated by treatment with reserpine or d-amphetamine, bromocriptine antagonized the inhibitory effect of apomorphine. This indicates that bromocriptine could still be bound to the DA autoreceptors and that the reduced sensitivity was due to a reduced functioning of the DA autoreceptors. The reduced sensitivity to apomorphine observed after all the above treatments was possibly due both to a reduced function of and/or to a reduced binding to the DA autoreceptors. The increase in DA synthesis produced by treatment with reserpine in vivo or with d-amphetamine or ouabain in vitro was additive to that produced by a maximally effective concentration of dibutyryl cyclic AMP in vitro, and thus mediated by a presumably non-cyclic AMP-dependent mechanism. Our results obtained with bromocriptine suggest that stimulation of the DA autoreceptors may inhibit DA synthesis by diminishing Ca2+-dependent and not cyclic AMP-dependent phosphorylation of tyrosine hydroxylase.

Modulation of the Sensitivity of Synaptosomal Dopamine Autoreceptors to Bromocriptine by in vitro and in vivo Treatments

The presence and pharmacological profile of the dopamine (DA) autoreceptors which regulate DA synthesis have been succesfully determined in synaptosomal preparations from the striatum and other brain regions rich in dopaminergic nerve terminals. To clarify the intraneuronal mechanisms by which stimulation of the DA autoreceptors by DA agonists produces inhibition of DA synthesis, we studied the function and sensitivity of the DA autoreceptors to DA agonists in synaptosomal preparations in which DA synthesis was increased by various in vitro and in vivo treatments.

The appearance of intestinal and blood 5-hydroxytryptamine and the 5-hydroxytryptamine binding capacity of platelets in the developing guinea-pig

Abstract The generally accepted view (1) is that 5-hydroxytryptamine (5HT) in the blood originates in the enterochromaffine cells of the intestinal mucosa. For this reason, in studying the development of 5HT and the enzymes connected with its formation and inactivation in the early stages of life, we paid particular attention to the appearance of intestinal and blood 5HT. We found a certain discrepancy which necessitated a further study of the decarboxylation efficiency and the 5HT binding capacity of platelets during the time of development. Guinea-pigs were used. Preliminary communications on this work have been given earlier (2,3).