Catecholamines may stimulate ACTH secretion during stress. To investigate the nature and site of such an action, plasma ACTH was measured in four groups of unanesthetized adult female rats with an indwelling carotid cannula. Sequential 300-microliter blood samples were taken 60 min, 30 min, and immediately before an intracerebroventricular (icv) infusion of 2.5 microliter adrenaline or noradrenaline and 5, 15, 45, 60, and 120 min after the infusion. The four groups were: 1) intact rats; 2) rats infused 7 days after undergoing a discrete bilateral lesion of the ventral noradrenergic ascending bundle caused by 6-hydroxydopamine, which depleted their hypothalamic adrenaline and noradrenaline levels by 90% and 80%, respectively; 3) rats infused 30 min after pretreatment via the icv route with either prazosin or propranolol; and 4) rats infused 16 and 2 h after two successive intracarotid injections of an anti-rCRH-41 serum. In another group, the effects of icv catecholamine administration were compared with those of an intracerebral (ic) microinfusion close to a single paraventricular nucleus (PVN). Finally, in two additional groups blood was sampled at the above-mentioned times before and after a 2-min ether inhalation by intact rats or prazosin- and/or propranolol-pretreated rats. In the intact rats (group 1), a stress-like stimulatory dose response was noted after both adrenaline and noradrenaline infusions, with a half-maximal effect at concentrations of about 0.6 nmol and a maximal effect at 2.7 nmol or more. At maximally effective doses, adrenaline was significantly more active than noradrenaline. In the rats with ventral noradrenergic ascending bundle lesions (group 2), 2.7 nM adrenaline or noradrenaline stimulated ACTH release as in the controls without lesions. In group 3, prazosin blocked the ACTH responses to both adrenaline and noradrenaline, whereas propranolol only blocked the response to adrenaline. In group 4, i.e. rats pretreated with an anti-rCRH-41 serum, the amplitude of the ACTH surge after icv adrenaline or noradrenaline infusion was halved. A unilateral ic catecholamine microinfusion next to the PVN (half the icv dose given in group 1) led to a rapid ACTH release that peaked at half the response measured in the icv infused rats. Ether stress-induced ACTH release was decreased by 50-60% after icv pretreatment with 1 or 10 micrograms prazosin, 1 or 6.5 micrograms propranolol, or a combined dose comprising 1 microgram of both. The following conclusions were reached.(ABSTRACT TRUNCATED AT 400 WORDS)

Pb-Zn deposits and specifically Sedimentary-Exhalative (SEDEX) deposits are frequently found in deformed and/or metamorphosed geological terranes. Ore bodies structure is generally difficult to observe and its relationships to the regional structural framework is often lacking. In the Pyrenean Axial Zone (PAZ), the main Pb-Zn mineralizations are commonly considered as Ordovician SEDEX deposits in the literature. New structural field analyzes focusing on the relations between mineralization and regional structures allowed us to classify these Pb-Zn mineralizations into three types: (I) Type 1 corresponds to minor disseminated mineralization, probably syngenetic and from an exhalative source. (II) Type 2a is a stratabound mineralization, epigenetic and synchronous to the Variscan D1 regional deformation event and (III) Type 2b is a vein mineralization, epigenetic and synchronous to the late Variscan D2 regional deformation event. Structural control appears to be a key parameter in concentrating Pb-Zn in the PAZ, as mineralizations occur associated to fold hinges, cleavage, and/or faults. Here we show that the main exploited type 2a and type 2b Pb-Zn mineralizations are intimately controlled by Variscan tectonics. This study demonstrates the predominant role of structural study for unraveling the formation of Pb-Zn deposits especially in deformed/metamorphosed terranes.