The benzodiazepine agonist diazepam inhibits basal and secretagogue-stimulated prolactin release in vitro

Benzodiazepines reduce basal and stimulated rat prolactin (PRL) serum levels in vivo. We investigated whether the inhibition of PRL secretion by the benzodiazepine receptor agonist, diazepam, occurs directly at the pituitary. At nanomolar concentrations diazepam did not affect PRL secretion, whereas at micromolar concentrations, diazepam dose-dependently inhibited basal and secretagogue-stimulated PRL release from hemipituitary glands and from primary cultures of rat anterior pituitary cells. The inhibitory effect of the highest concentration of diazepam (100 μM) was abolished when the pituitary tissue was incubated with the benzodiazepine receptor antagonist Ro 15–1788. Although nanomolar concentrations of diazepam alone did not affect PRL release, they did enhance the PRL inhibitory effect of muscimol, a γ-amino butyric acid (GABA) receptor agonist. Neither diazepam nor muscimol affected cellular adenosine 3′, 5′-monophosphate (cAMP) content. Since these effects do not appear to occur through an inhibition of the cAMP generating system, diazepam may inhibit PRL release via a cAMP-independent pathway.We suggest that diazepam inhibits PRL secretion either by enhancing the GABAergic inhibition of PRL release, or by inhibiting, at micromolar concentrations, a benzodiazepine-sensitive Ca²⁺-calmodulin dependent protein kinase.     

Longitudinal echocardiographic evaluation in children with thalassemia major

We report the results of a longitudinal echocardiographic survey on 15 children with thalassemia major, who had received multiple transfusions. The average interval between the two examinations was 2.9 +/- 0.7 years. At the second examination the mean hemoglobin (Hb) level for the group was higher because of the increased number of transfusions. During the same period of time the chelating treatment with desferrioxamine was administered subcutaneously instead of intramuscularly. The following echocardiographic parameters have been measured: left ventricular dimension, diastolic (LVDd); left ventricular dimension, systolic (LVDs); septal thickness, diastolic (STd); free wall, diastolic (FWd); left atrial dimension (LAD); aortic root (AoR); fractional shortening (FA); velocity of circumferential shortening (VCF). At the first examination 6 patients had abnormal values of LVDd, STd and AoR; 10 subjects had increased LAD; the mean Hb levels of the patients with abnormal STd and LAD was significantly lower than in normals (p less than 0.05 and less than 0.01 respectively). At the second examination 8 patients had abnormal LVDd values and 7 had increased LAD. Only the patients with increased LVDd had lower Hb values. Patients with increased LAD had received more transfusions. The following functional parameters were found to be decreased at the second study: FA (29 +/- 3.3 vs 32.6 +/- 7; p less than 0.05); VCF (1.16 +/- 0.25 vs 0.99 +/- 0.14; p less than 0.05). From the results it appears that the change of treatment improved some parameters (STd, AoR, LAD), but was unable to arrest the deterioration of the LV contractile efficiency.(ABSTRACT TRUNCATED AT 250 WORDS)