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Rosa Maria Facciolo,¹ Raffaella Alò,¹ Maria Madeo,¹ Marcello Canonaco,¹ and Francesco Dessì-Fulgheri²

¹Comparative Anatomy Laboratory of the Ecology Department, University of Calabria, Cosenza, Italy; ²Animal Biology Department, University of Florence, Florence, Italy

Abstract

Recently, considerable interest has been aroused by the specific actions of bisphenol A (BPA) . The present investigation represents a first study dealing with the interaction of BPA with the biologically more active somatostatin receptor subtype (sst₂) in the rat limbic circuit. After treating pregnant female Sprague-Dawley rats with two doses (400 µg/kg/day ; 40 µg/kg/day) of BPA, the binding activity of the above receptor subtype was evaluated in some limbic regions of the offspring. The higher dose proved to be the more effective one, as demonstrated by the elevated affinity of sst₂ with its specific radioligand, [¹²⁵I]-Tyr⁰somatostatin-14. The most dramatic effects of BPA on sst₂ levels occurred at the low-affinity states of such a subtype in some telencephalic limbic areas of postnatal rats (10 days of age ; postnatal day [PND] 10) . These included lower (p < 0.05) sst₂ levels in the gyrus dentate of the hippocampus and basomedial nucleus of the amygdala ; significantly higher (p < 0.01) levels were observed only for the high-affinity states of the periventricular nucleus of the hypothalamus. A similar trend was maintained in PND 23 rats with the exception of much lower levels of the high-affinity sst₂ receptor subtype in the amygdala nucleus and ventromedial hypothalamic nucleus. However, greater changes produced by this environmental estrogen were reported when the binding activity of sst₂ was checked in the presence of the two more important selective agonists (zolpidem and Ro 15-4513) specific for the -containing -aminobutyric acid (GABA) type A receptor complex. In this case, an even greater potentiating effect (p < 0.001) was mainly obtained for the low-affinity sst₂ receptor subtype in PND 10 animals, with the exception of the high-affinity type in the ventromedial hypothalamic nucleus and gyrus dentate. These results support the contention that an sst₂ subtype -containing GABA type A receptor system might represent an important neuromediating station capable of promoting estrogenlike mechanisms of BPA, especially during the early developmental phases. Key words: autoradiography, brain, development, GABA, rats, somatostatin receptors, xenoestrogen. Environ Health Perspect 110(suppl 3) :397-402 (2002) .

http://ehpnet1.niehs.nih.gov/docs/2002/suppl-3/397-402facciolo/abstract.html