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Galanin positively modulates prolactin secretion in normal women

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Abstract

It is widely accepted that, in man, galanin, a neuropeptide, has a clear GH releasing effect while its stimulatory influence on PRL secretion is matter of debate. To clarify this point, in 6 normal young women (23–35 yr) in their early follicular phase, we studied the effect of galanin (pGAL, 80 pmol/kg. min infused iv over 60 min) on both basal and arginine (ARG, 0.5 g/kg iv in 30 min), TRH (400 μg iv as a bolus at 0 min) or metoclopramide (MCP, 10 mg iv as a bolus at 0 min)-stimulated PRL secretion. GAL infusion failed to significantly increase basal PRL levels (peak vs baseline: 12.2±3.6 vs 8.7±1.2 μg/L) but counteracted the spontaneous PRL decrease observed during saline infusion (AUG: 1216.6±282.1 vs 672.0±94.5 μg.min/L; p<0.05). GAL infusion clearly enhanced the PRL response to TRH (AUC: 5806.3±743.0 vs 3952.1 ±423.9 μg.min/L, p<0.05) and ARG (AUC: 3676.8±382.6 us 2638.9 ± 287.0 μg.min/L, p<0.05), respectively. On the other hand, GAL failed to modify the MCP-induced PRL response (AUC: 15409.5±2085.3 vs 14787.9±2045.5 μg.min/L). The PRL response to MCP was higher than that to TRH (p<0.01 ) which, in turn, was higher than that to ARG (p<0.01). During GAL infusion, the PRL response to TRH or ARG remained lower (p<0.01) than that after MCP administration. Thus, in conclusion, present data demonstrate that in normal women galanin enhances the PRL response to ARG and TRH but fails to modify that induced by dopamine receptor blockade with metoclopramide. Based on evidence that the inhibition of central dopaminergic activity inhibits the lactotrope responsiveness to dopaminergic antagonists or TRH, it is unlikely that galanin influences PRL secretion via inhibition of dopaminergic tone.

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Authors and Affiliations

  1. Divisione di Endocrinologia, Dipartimento di Medicina Interna, University of Torino, C.so Dogliotti 14, 10126, Torino, Italy

    S. Grottoli, E. Arvat, L. Gianotti, J. Ramunni, L. Di Vito, B. Maccagno, E. Ciccarelli, F. Camanni & E. Ghigo M.D.

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  1. S. Grottoli
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  2. E. Arvat
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  3. L. Gianotti
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  4. J. Ramunni
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  5. L. Di Vito
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  6. B. Maccagno
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  7. E. Ciccarelli
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  8. F. Camanni
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  9. E. Ghigo M.D.
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Grottoli, S., Arvat, E., Gianotti, L. et al. Galanin positively modulates prolactin secretion in normal women. J Endocrinol Invest 19, 739–744 (1996). https://doi.org/10.1007/BF03347877

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