LEAD (PB2-ADRENERGIC STIMULATION BY ISOPROTERENOL() AND CADMIUM (CD2+) INHIBIT THE DIPSOGENIC ACTION OF CENTRAL BETA)

We have previously demonstrated that acute third ventricle injections of both Pb2+ and Cd2+ impair the dipsogenic response elicited by three different situations: dehydration and central cholinergic or angioten sinergic stimulation. D-Adrenergic activation is part of the multifact orial integrated systems operating in drinking behavior control in the central nervous system. In the present study acute third ventricle in jections of Pb2+ (3, 30 and 300 pmol/rat) or Cd2+ (0.3, 3 and 30 pmol/ rat) blocked the dipsogenic response induced by third ventricle injec tions of isoproterenol (ISO; 160 nmol/rat) in a dose-dependent manner. Normohydrated animals receiving ISO + NaAc (sodium acetate) or saline (controls) displayed a high water intake after 120 min (ISO + saline = 5.78 +/- 0.54 ml/100 g; ISO + NaAc = 6.00 +/- 0.6 ml/100 g). After t he same period, animals receiving ISO but pretreated with PbAc at the highest dose employed (300 pmol/rat) drank 0.78 +/- 0.23 ml/100 g whil e those receiving ISO and pretreated with the highest dose of CdCl2(30 pmol/rat) presented a water intake of 0.7 +/- 0.30 ml/100 g. Third ve ntricle injections of CdCl2 (3 nmol/rat) or PbAc (3 nmol/rat) did not modify food intake in rats deprived of food for 24 h. Thus, general ce ntral nervous system depression explaining the antidipsogenic action o f the metals can be safely excluded, It is concluded that both Pb2+ an d Cd2+ inhibit water intake induced by central beta-adrenergic stimula tion.