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Biomedical subjects

A Enjalbert

Publications and source records attributed to A Enjalbert.

At least 145 records · Page 8Linked to original sources
PubMed1977

Midbrain raphe lesion in the newborn rat: II. Biochemical alterations in serotoninergic innervation.

Electrolytic raphe lesion was performed in 4-6-day-old rats and the resulting changes of 5HT metabolism within the central nervous system were analyzed up to 9 months later. As soon as the 2nd day following the selective destruction of B7 and B8 nuclei, forebrain 5HT levels were decreased by more than 75%. This reduction persisted for at least 9 months with no sign of recovery. The time course of 5-HIAA decrease was parallel to that of the indoleamine so that the ratio of 5-HIAA over 5-HT levels in the forebrain of lesioned rats was similar to that estimated in controls, whatever their age. This result would suggest that the remaining serotoninergic neurons in the lesioned rats did not develop a compensatory hyperactivity. The raphe lesion induced no change in MAO activity and synaptosomal tryptophan uptake but a pronounce decrease in the Vmax of synaptosomal KHT uptake process in various forebrain areas occurred. The serotonin sensitive adenylate cyclase activity in colliculi homogenate was not altered by the lesion suggesting that this enzyme was probably located in postsynaptic membranes. In addition, this observation would indicate that 5-HT receptors which are linked to this adenylate cyclase did not become supersensitive following the selective degeneration of serotoninergic neurons. Animals without forebrain serotoninergic innervation might be of great interest to analyse the role of serotoninergic neurons in various functions (sleep, analgesia, thermoregulation).

Adenylyl Cyclases↗
PubMed1977

Prolactin inhibiting activity of dopamine-free subcellular fractions from rat mediobasal hypothalamus.

In order to check the hypothesis of an identity of dopamine (DA) and prolactin inhibiting activity (PIF), their subcellular distribution was studied in the mediobasal hypothalamus (MBH) and the striatum, which served as a control structure. PIF was tested both in vivo and on pituitary incubates. Fractions were also assayed after adsorption of their catecholamine content on alumina, as well as in presence of haloperidol or alpha-flupentixol, potent DA receptor inhibitors. In the MBH, PIF was evenly distributed in the 17,000 g supernatant (S2) and in the crude mitochondrial fraction (P2) which contains synaptosomes. PIF activity was completely removed by alumina adsorption of S2, but not of P2 in spite of an over 99.9% elimination of DA. In contrast, striatal PIF activity was detected only in P2, and disappeared completely upon alumina adsorption, thus indicating that, in this structure, it is entirely due to DA. Addition of haloperidol (10--5M) or alpha-flupentixol (10--6M) reduced PIF activity of crude MBH homogenates, but no longer affected it after alumina adsorption. Quantitative studies suggest that only half of the total MBH PIF activity is accounted for by DA. It is concluded that the MBH contains dopamine-free PIF, which, as already shown for several other neurohormones, is exclusively distributed in nerve-endings.

Animals↗