The effects of subacute noise stress on the noradrenergic pattern and receptor-mediated responses were examined in aorta and atria of young and aged rats. Noise exposure increased the density of noradrenergic fibres and responses to the beta-adrenergic agonist isoprenaline in the cardiac tissue of young animals. In aged rats, the stressing stimulus markedly increased the maximal response to the alpha-agonist on the aortic musculature; on the contrary, a reduced responsiveness to the beta-agonist was observed at the cardiac level, without any noteworthy changes in the noradrenergic pattern in comparison to aged controls. The present results indicate that subacute noise stress induces both morphological and functional modifications of the noradrenergic nervous system and also that after subacute noise stress, morphological changes do not necessarily correspond exactly to functional data; the latter show responses that are more widely differentiated than the morphological ones.

One, six and twelve hs of exposure to acoustic stress showed different influences on the noradrenergic pattern and receptor function of the rat atria and aorta. Moreover, the lipid content of the adrenal cortex and hepatic glycogen were histochemically evaluated in the same animals to correlate these observations with the previous results. The increase in exposure time induced a corresponding increase in sympathetic innervation, which was more evident at cardiac level. The functional results showed that the potency of the agonists on the alpha- and beta-adrenoceptors does not vary, with the exception of 6-h treatment, which affected beta-receptors. By contrast, the M.R.R. of beta-receptors proved to be modified in all treatments, suggesting that noise stress affected mainly postreceptorial mechanisms linked to beta-adrenoceptors rather than their density or affinity; no significant functional modifications were observed when alpha-receptors were considered.

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The two linear diterpenes from Cystoseira brachycarpa var. balearica isolated following the method previously described, were tested on guinea-pig intestinal prepara-Abstract Eleganolone (1) and elegandiol (2), two linear diterpenes isolated from Cystoseira brachycarpa var. balearica, were tested on guinea-pig intestinal pre-10 M). Tetraethylammonium (TEA), furosemide, Ne,nitro L-arginine methyl ester (i.-NAME), indomethacin, a-chymotrypsin, and metoprolol were unable to block the eleganolone and elegandiol relaxing action on colonic musculature, but rather potentiated this response. On the contrary, the /32-blocker butoxamine partially inhibited the diterpenes activity. These results suggest that Cystoseira diterpenes act at a second messenger cyclase system rather than at a receptor level.

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