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E C Azmitia

Publications and source records attributed to E C Azmitia.

At least 127 records · Page 7Linked to original sources
PubMed1981

The visualization and characterization of 5HT reuptake sites in the rodent and primate hippocampus. A preliminary study.

The (re)uptake of 3H-5-HT was similar in hippocampal slices and synaptosomes from mice (C57BL/6), rats (Sprague DAwley), and macaque monkeys (Macaca fascicularis). In all species, the specific uptake was both saturable and showed high affinity for 5HT. However, the reuptake capacity was higher in rodents than in monkey. In a parallel series, radioautography was performed on hippocampal slices from the 3 species. The distribution of the reuptake sites extended into all hippocampal subfields, and a preferential relationship with pyramidal and granule cells was apparent. The innervation density followed mouse greater than rat greater than monkey. The innervation of the monkey Ammon's horn was the lowest of all fields examined. This anatomical observation of a decreased density in primate Ammon's horn was biochemically tested. Dissection of hippocampus into Ammon's horn and dentate gyrus showed much lower 3H-5-HT reuptake in the former. These results suggest a progressive decline in the serotonin innervation of the vertebrate hippocampus, with Ammon's horn more vulnerable than the dentate gyrus.

Animals↗
PubMed1980

Septal elicitation of hippocampal theta rhythm after localized de-afferentation of serotoninergic fibers.

Previous experiments using serotonin antagonists and electrolytic raphe lesions suggest that the serotonergic input to the hippocampus inhibits low frequencey (< Hz) theta rhythm in the rat, whereas experiments using raphe stimulation suggest facilitation. The present experiments employed neurotoxic lesions of the serotonergic input to the hippocampus in an attempt to reproduce the effects of systemically administered antagonists. If the septal area is stimulated at frequencies between 6 and 10 Hz in the rat, the threshold current for driving hippocampal theta is minimum at 7.7 Hz. Systemic blockage of serotonergic synapses has been shown to shift this minimum to 6.9 Hz. In the present experiments, neurotoxic lesions were made with injections of 5,7-dihydroxytryptamine into the cingulum bundle, fornix or both. The observed effect depended on the loss of serotonin in the hippocampus, rather than the site of injection, and extensive depletion shifted the minimum to 6.9 Hz. These results indicate that the fornix and cingulum serotonergic inputs to the hippocampus are functionally homogenous, at least with respect to this response; and that the effects of systemic manipulation of serotonin systems on the septal elicitation of hippocampal theta rhythm may be attributed to changes in these two inputs.

Afferent Pathways↗
PubMed1980

Specific uptake of tritiated serotonin in the adult rat pancreas: evidence for the presence of serotonergic fibers.

Fragments of adult rat pancreas were incubated in vitro with tritiated serotonin at concentrations from 10(-8) to 10(-7) M. The pancreas exhibited an uptake of serotonin which was saturable, with an uptake constant (Km) of 8.75 x 10(-7) M, and a Vmax of 873 pmoles per gram. Specificity was determined by the addition of fluoxetine or norepinephrine to the reaction mixture, both at 10(-5) M. Fluoxetine significantly reduced the 3H-5HT uptake, whereas norepinephrine was without effect. Metergoline (10(-6) M), a specific 5-HT postsynaptic receptor blocker, similarly had no effect on the serotonin uptake in the pancreas. Radioautography of the fragments following uptake of tritiated serotonin (5 x 10(-8) M) revealed silver- grain aggregates dispersed along blood vessels in the interstitial spaces of the exocrine and endocrine pancreas, areas known to be traversed by nerve fibers. There were no silver- grain aggregates over the exocrine or islet parenchymal cells. These data support the hypothesis that the pancreas is innervated by serotonergic fibers. Further evidence for this hypothesis was provided by a preliminary study demonstrating the presence of tryptophan hydroxylase in pancreatic homogenates. These serotonergic fibers may be involved in the regulation of pancreatic secretion.

Animals↗
PubMed1980

Age related changes in NGF, EGF and protease in the granular convoluted tubules of the mouse submandibular gland. A morphological and immunocytochemical study.

Granular convoluted tubule (GCT) cells in the submandibular glands of male mice were studied at 1.5, 6, 12 and 29 months of age by morphometric and immunocytochemical means. The relative proportion of GCT's was established by determining a tubule to acini (T/A) ratio. The T/A ratios were significantly increased between 1.5 months (0.76) and 6 months (1.34), and between 6 months and 12 months (1.96). However, a marked decrease was found at 29 months (0.59). The functional capacity of GCT cells was estimated by immunocytochemical staining for nerve growth factor (NGF), epidermal growth factor (EGF), protease and renin. The number of GCT cells immunoreactive for NGF, EGF and protease increased between 1.5 months and 6 months. No further change was noted at 12 months. However, once again at 29 months a decrease occurred in a number of cells reactive for all three substances. Renin was not detected in any cell at any age.

Age Factors↗
PubMed1980

In vitro hippocampal uptake of tritiated serotonin (3H-5HT): A morphological, biochemical, and pharmacological approach to specificity.

The in vitro uptake of tritiated serotonin (3H-5HT) into hippocampal slices was measured in Ringer's solution (37 degrees C) containing pargyline, ascorbic acid, and dextrose. The specific uptake of 3H-5HT rose asymptotically as the 3H-5HT molarity was increased from 5 x 10(-10) to 1.5 x 10(-6) M. Linear regression analysis gave a Km value for the specific uptake of 1.4 x 10(-7) M. The nonspecific binding (NSB) was the amount of 3H-5HT retained by the slices following incubation in a medium with a very large excess of unlabeled 5-HT added to dilute the specific uptake of 3H-5HT. This NSB increased with increasing molarity of 3H-5HT, and was linearly related to 3H-5HT concentrations between 5 x 10(-9) and 1.5 x 10(-6) M. The ratio of specific uptake to NSB was highest at 5 x 10(-8) M (2.75) and lowest at 1.5 x 10(-6) M of 3H-5HT (0.54). Competition studies with noradrenaline, desipramine (a noradrenergic uptake blocker), fluoxetine (a 5-HT uptake blocker), and tryptophan confirmed the specificity of the 3H-5HT uptake mechanism. Radioautographic studies of in vitro incubated hippocampal slices showed silver grain aggregates at 3H-5HT specific uptake sites. Addition of an excess of unlabeled 5-HT to the slices, or the use of hippocampi from 5,7-dihydroxytryptamine intracerebral microinjected rats (5 microgram/400 nl into the fornix-fimbria and the cingulum bundle, 6 day survival) caused a dramatic decrease in these aggregates. The distribution of hippocampal 5-HT axons and terminals, inferred from the pattern of silver grain aggregates, is more widespread than previously described. 5-HT varicosities were clearly seen in all layers of Ammon's horn, dentate gyrus, and the subicular cortex. Innervation routes were seen to the stratum radiatum and stratum lacunosum from stratum oriens in Ammon's horn, and to the polymorphic layer of the dentate gyrus from the subicular cortex and from the fimbria. Semiquantitation of the occurrence of silver grain aggregates was done in the various hippocampal regions. The highest density in Ammon's horn was 119.5 boutons/10,000 micron2, in the dentate gyrus it was 67.4 boutons/10,000 micron2, and in the subicular cortex it was 79.2 boutons/10,000 micron2. These results are consistent with previous quantitative results.

5,7-Dihydroxytryptamine↗
PubMed1976

Temporal effects of fornix transection on brain tryptophan hydroxylase activity and plasma corticosterone levels.

The effect of fornix transection on plasma corticosterone and on midbrain (MID), septum/preoptic (S/POA) or hippocampal (HIP) tryptophan hydroxylase activity (THA) was studied in adult male rats. A mild stress resulted in higher levels of plasma corticosterone in operated as compared to sham-operated rats 6 and 40 h post-transection; however, at 30 days post-operation no difference was found. The response of THA to fornix transection was region-specific. No significant change in the S/POA region was found at any time. THA in the HIP, a terminal area of 5-HT fibers, showed a progressive fall over time to values 80% below normal levels. This result suggests that most of the 5-HT fibers to the HIP had been severed. A 28 h half-life for HIP THA was calculated. THA in the MID, an area known to contain the majority of 5-HT cell bodies with ascending fibers, was significantly reduced compared to sham controls at 6 h, 40 h, and 8 days post-transection. However, at 30 days post-operation no difference was found. The depression in MID THA by its rapid onset, the distance from the fornix transection site, and its return to normal after 30 days, is thought to be due to a transneuronal effect on the serotonin-containing neurons in MID raphe. The fall in MID THA at a time when plasma corticosterone levels are increased in fornix-transected rats may be compared with the situation in normal, stressed and adrenalectomized rats where MID THA andplasma corticosterone levels change in the same direction. The data suggest that the glucocorticoid effects on MID 5-HT containing neurons are mediated transneuronally through the hormone concentrating cells in the HIP.

Animals↗
PubMed1970

Amnesia produced by electroconvulsive shock or cycloheximide: conditions for recovery.

Retrograde amnesia for a passive avoidance response was produced in rats by electroconvulsive shock and in mice by cycloheximide, an inhibitor of protein synthesis. One day after training the memory could be restored if a "reminder" of the original foot shock was given after the retention test on which the amnesia was demonstrated. Memory did not return if the reminder was given without the prior retention test or if the reminder and the test were separated by 23 hours.

Amnesia↗
PubMed1970

In vivo conversion of 3H-L-tryptophan into 3H-serotonin in brain areas of adrenalectomized rats.

Rats were adrenalectomized 10 days before we estimated in vivo the conversion index of (3)H-tryptophan into radioactive serotonin in brainstem and telediencephalon. We found that the conversion index in the brainstem of adrenalectomized rats is smaller than in the same area of sham-operated rats. Conversely, the conversion index in the telediencephalon was similar in the two groups of rats. The serotonin concentrations were unchanged by adrenalectomy, which suggests that in brainstem the decrease of tryptophan hydroxylase is reflected by the conversion index estimation and not by measurement of serotonin steady-state concentrations.

Adrenalectomy↗
PubMed1969

Corticosterone regulation of tryptophan hydroxylase in midbrain of the rat.

The tryptophan hydroxylase activity in the rat midbrain decreases after adrenalectomy and is restored by treatment with corticosterone. Cycloheximide, adminiistered intracisternally, prevents the restoration of the enzyme activity by corticosterone. Cycloheximide administration to adrenalectomized rats resutlts in a further decrease in the enzyme activity. an indication that the enzyme has a rapid turnover even in the absence of corticosterone.

Adrenalectomy↗