Biomedical subjects

M Taglialatela

Publications and source records attributed to M Taglialatela.

79 records · Page 5Linked to original sources

PubMed1987

Plasma prolactin levels in the inferior petrosal sinuses in various pituitary disorders during perihypophyseal phlebography.

The use of intercavernous sinus phlebography for the diagnosis and neurosurgical treatment of pituitary adenomas has enabled the collection of selective venous samplings of the inferior petrosal sinuses (IPSs), where prolactin (PRL) levels can be measured before the hormone becomes excessively diluted in the systemic circulation. In the present study, plasma PRL levels were studied in the right and/or left IPS and, simultaneously, in the peripheral circulation of: (1) normoprolactinemic patients affected with various pituitary disorders which required phlebographic procedures; (2) hyperprolactinemic patients with negative radiological and computed tomographic (CT) signs of pituitary adenomas and (3) adenomatous hyperprolactinemic patients. In the 17 normoprolactinemic patients, the plasma PRL concentration in the IPSs was significantly higher (3.5 times; p less than 0.01) than in the peripheral circulation. In the 11 hyperprolactinemic patients with negative radiological and CT signs of pituitary adenomas, the central gradient for PRL was significantly higher (2.8 times; p less than 0.05) than in the peripheral circulation. No significant difference was detected between PRL concentrations in the left and right IPSs. In the 11 adenomatous hyperprolactinemic patients, there was a significant (p less than 0.01) central gradient for PRL 3.8 times higher than in the peripheral circulation on the ipsilateral side of the tumor. Furthermore, the plasma PRL concentration in the ipsilateral IPS was significantly higher (3.4 times; p less than 0.05) than that in the contralateral sinus. In conclusion, the present study shows that a clear-cut concentration gradient exists between plasma PRL levels in the IPSs and in the peripheral circulation of normoprolactinemic and hyperprolactinemic patients with negative radiological and CT signs of pituitary adenomas.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗

PubMed1986

Maitotoxin and Bay-K-8644: two putative calcium channel activators with different effects on endogenous dopamine release from tuberoinfundibular neurons.

In the present study we report on the effects of two putative calcium channel activators, maitotoxin and the dihydropyridine BAY-K-8644, on endogenous dopamine release from tuberoinfundibular dopaminergic neurons. Maitotoxin stimulated basal dopamine release and this effect was calcium-dependent. By contrast BAY-K-8644 failed to produce any modification of basal or high potassium-induced dopamine release. These results suggest that maitotoxin, unlike BAY-K-8644, represents a suitable tool to investigate the functional role of calcium channels in central dopaminergic neurons.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1986

Reduced tuberoinfundibular dopaminergic neuronal function in rats after long-term withdrawal of estrogen treatment.

Hypothalamic fragments from female rats treated repeatedly with estradiol valerate (EV) and bearing prolactin (PRL)-secreting tumors contained, seven months after the last EV injection, lower concentrations of dopamine (DA) than age-matched controls. Depolarizing concentrations of K+ (35 mM) and amphetamine (50 microM) evoked in PRL-secreting tumor bearing rats an endogenous DA release significantly lower than in controls.

Animals↗

PubMed1986

Endogenous dopamine release from tuberoinfundibular neurons: does calmodulin play any role?

The possible involvement of calmodulin in the process of endogenous dopamine (DA) release from arcuate-periventricular nuclei-median eminence fragments, containing tuberoinfundibular dopaminergic (TIDA) neurons, has been investigated in an in vitro incubation system. For this purpose the basal and K+-stimulated DA release was examined in the presence and in the absence of the different putative calmodulin antagonists, pimozide, trifluoperazine, penfluridol and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7). Trifluoperazine and pimozide in concentrations up to 100 microM were both uneffective in blocking K+-evoked DA release. Penfluridol in doses of 5 and 10 microM, did not prevent 35 mM K+-induced endogenous DA release. It was able to reduce K+-stimulated DA release only at the very large concentration of 100 microM. W-7 added in vitro to the hypothalamic fragments, prevented endogenous DA release evoked by 35 mM K+ in a dose-dependent manner. W-5, a chlorine deficient analogue of W-7, that interacts only weakly with calmodulin, failed to modify K+-stimulated endogenous DA release in doses up to 200 microM. All the putative calmodulin antagonists used in the present study did not induce any change of basal DA release. In conclusion the fact that most of the agents, except W-7, known to antagonize calmodulin-dependent processes in many biological systems failed to interfere with the release of endogenous DA from TIDA neurons seems to suggest that calmodulin does not play a crucial role in the process of DA release and that the inhibitory effect of W-7 on endogenous DA release may be better attributed to other mechanisms different from its anticalmodulin action.

Animals↗

PubMed1986

Effect of different organic and inorganic blockers of calcium entry on the release of endogenous dopamine from tuberoinfundibular neurones.

In the present study the effect of different blockers of calcium entry belonging to different chemical classes on basal and K+-elicited release of endogenous dopamine (DA) from tuberoinfundibular dopaminergic neurones was studied in vitro. For this purpose fragments of hypothalamus containing arcuate-periventricular nuclei and median eminence were incubated in vitro and endogenous DA released into the medium was assayed by radioenzymatic assay. The organic blockers of calcium entry, nitrendipine, nimodipine, nifedipine, diltiazem and flunarizine did not modify basal or K+-evoked release of endogenous DA, unless very large concentrations (100 microM) of nifedipine or diltiazem were used. The phenylalkylamine methoxyverapamil (D-600) consistently inhibited K+-stimulated release of endogenous DA in concentrations of 50 and 100 microM. Cobalt and lanthanum, two ions with an ionic radius similar to that of calcium and which are known to inhibit calcium fluxes through nerve membranes, significantly blocked release of endogenous DA elicited by 35 mM K+. In summary, the results of the present study showed that calcium channels in the tuberoinfundibular dopaminergic system displayed a different sensitivity to various classes of blockers of calcium entry. Inorganic blockers of calcium entry, like lanthanum and cobalt, appeared to be the most effective in blocking Ca2+-dependent release of endogenous DA, whereas, among the organic calcium antagonists, phenylalkylamines seemed to possess a certain degree of effectiveness.

Animals↗

PubMed1984

Dual effect of verapamil on K+-evoked release of endogenous dopamine from arcuate nucleus-median eminence complex.

The effect of verapamil, a calcium-entrance blocker, on K+-evoked release of endogenous dopamine from tuberoinfundibular neurons incubated in vitro was studied. This compound, added to the incubation medium, at the dose of 10(-6) M, significantly reinforced K+-induced dopamine release, whereas, at higher doses (10(-5), 5 X 10(-5) and 10(-4) M), it completely prevented the stimulated dopamine release. The results obtained with the higher doses showed the calcium dependence of K+-evoked release of endogenous dopamine from central neurons. The opposite effect, seen with the lower dose of verapamil, could be due to different pharmacological properties of the drug.

Animals↗

PubMedDate not supplied

Lack of evidence for an impairment of tuberoinfundibolar dopaminergic neurons in aged male rats of the Sprague-Dawley strain.

Circulating prolactin (PRL) levels, dopamine (DA) content, in vitro basal and stimulus-evoked endogenous DA release from arcuate-periventricular nuclei median-eminence fragments were studied in young (4 months) and old (24-25 months) male rats of Sprague-Dawley strain. Serum PRL levels did not differ in young and aged animals. In addition DA tissue content, basal and K+- or d-amphetamine evoked endogenous DA release did not show age-related differences. These results suggest that in male rats of the Sprague-Dawley strain the activity of tuberoinfundibular dopaminergic (TIDA) neurons does not change during senescence, unlike what happens in other strains of rats.

Aging↗