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Pharmacological Research, Vol. 26, Supplement 2, 1992
NITRIC OXIDE (NO) MEDIATES ANTIDIPSOGENIC ACTION OF ESCHERICHIA COLI ENDOTOXIN (LPS) AND TUMOR NECROSIS FACTOR (TNF-a) IN THE RAT . Gioacchino Calapai, Domenica Altavilla*, Maria C . Marciano, Giampiero Mazzaglia, Marcello Cilia, Francesco Squadrito, Achille P . Caputi . Institute of Pharmacology, School of Medicine, Chair* of Pharmacology, School of Biological Sciences, University of Messina (Italy) . Key words : endotoxin, nitric oxide, TNF-a, drinking behaviour INTRODUCTION Intravenous (iv) or intracerebroventricularly (icv) injected LPS produces a dose-dependent inhibition of thirst in the rat . In previous works we showed that this effect is mediated by arachidonic acid metabolism activation and TNF-a formation in the central nervous system (CNS)
(1) .
Since both LPS and TNF-a stimulate several cellular types to release nitric oxide
(NO),
a L-arginine derived molecule, we
evaluated the effects of L-arginine, and of an inhibitor of NOsynthase, N n-nitro-l-arginina methyl-ester (L-NAME), on inhibition of thirst induced by i .c .v . LPS or TNF-a . MATERIALS AND METHODS Drinking behaviour was induced by 24 h water deprivation in male Sprague-Dawley rats weighing 280-320 g . Water intake was monitored for 1 hour and expressed as ml/rat . Drugs were administered at following times before water presentation : LPS (1 µg/icv) 180 min ; TNF-a (10 or 40 ng/icv) 25 min ; L-NAME (5 µg/icv) 10 min ; L-NAME (5 sg/iv) 10 min ; L-arginine
(2 .5,
5, 10
ig/icv) 10 min . I .c .v . LPS (1 µg) and TNF-a (40 ng) abolished water intake induced by water deprivation . I .c .v . L-NAME antagonized the
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© 1992 The Italian Pharmacological Society
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Pharmacological Research, Vol . 26, Supplement 2, 1992
antidipsogenic action of LPS and TNF-a in a percentage of 50 % and 70%, respectively . Instead, i .v . injected L-NAME at the same intracranially injected dose, failed to modify inhibition of thirst induced by LPS or TNF-a (data not shown) . Finally, i .c .v . L-arginine
(2 .5,
5, 10 µg) was antidipsogenic by itself and
caused to be antidipsogenic LPS and TNF-a doses which alone did not modify drinking behaviour (Fig .
1) .
CONCLUSIONS Our results suggest that : 1) brain L-arginine/NO pathway activation in CNS modulates thirst ; 2) LPS and more TNF-a stimulate in CNS release of NO which acts on mechanisms or sites regulating drinking behaviour . Table 1 . Effects of icv saline, LPS, TNF-a, L-arginine, L-NAME + LPS or TNF-a, L-arginine + LPS or TNF-a, on water intake induced by 24 h water deprivation . Treatment
Water intake ml/rat
Saline (5 µl/icv) LPS (0 .25 µg/icv) LPS (0 .25 µg/icv)+L-arginine (5 µg/icv) LPS (1 µg/icv) LPS (1 pg/icv)+L-NAME (5 µg/icv) TNF-a (10 ng/icv) TNF-a (10 ng/icv)+L-arginine (5 gg/icv) TNF-a (40 ng/icv) TNF-a (40 ng/icv)+L-NAME (5 gg/icv) L-arginine (2,5 µg/icv) L-arginine (5 µg/icv) L-arginine (10 µg/icv)
13 .5 13 .0 3 .4 0 .2 6 .7 12 .8 5 .2 0 .8 9 .1 12 .5 8 .9 4 .1
± ± ± ± ± ± ± ± ± ± ± ±
1 .0 1 .0 0 .7* 0 .08* 0 .8° 1 .0 1 .2* 0 .09* 0 .6# 0 .9 1 .1* 0 .7*
* = p < 0 .01 vs saline ; ° = p < 0 .01 vs LPS (1 µg/icv) ; # = p < 0 .01 vs TNF-a (40 ng/icv) . Each value is the mean of six experiments . REFERENCES 1) Calapai, G ., Squadrito, F ., Altavilla, D ., Zingarelli, B ., Campo, G .M ., Saitta, A ., Ioculano, M ., Urna, G ., Sardella, A . and Caputi A .P . (1991) Tumor necrosis factor involvement in lipopolysaccharide-induced inhibition of drinking in the rat . Neurosci . Res . Comm . 9 : 53-61 .
Pharmacological Research, Vol. 26, Supplement 2, 1992
NITRIC OXIDE (NO) MEDIATES ANTIDIPSOGENIC ACTION OF ESCHERICHIA COLI ENDOTOXIN (LPS) AND TUMOR NECROSIS FACTOR (TNF-a) IN THE RAT . Gioacchino Calapai, Domenica Altavilla*, Maria C . Marciano, Giampiero Mazzaglia, Marcello Cilia, Francesco Squadrito, Achille P . Caputi . Institute of Pharmacology, School of Medicine, Chair* of Pharmacology, School of Biological Sciences, University of Messina (Italy) . Key words : endotoxin, nitric oxide, TNF-a, drinking behaviour INTRODUCTION Intravenous (iv) or intracerebroventricularly (icv) injected LPS produces a dose-dependent inhibition of thirst in the rat . In previous works we showed that this effect is mediated by arachidonic acid metabolism activation and TNF-a formation in the central nervous system (CNS)
(1) .
Since both LPS and TNF-a stimulate several cellular types to release nitric oxide
(NO),
a L-arginine derived molecule, we
evaluated the effects of L-arginine, and of an inhibitor of NOsynthase, N n-nitro-l-arginina methyl-ester (L-NAME), on inhibition of thirst induced by i .c .v . LPS or TNF-a . MATERIALS AND METHODS Drinking behaviour was induced by 24 h water deprivation in male Sprague-Dawley rats weighing 280-320 g . Water intake was monitored for 1 hour and expressed as ml/rat . Drugs were administered at following times before water presentation : LPS (1 µg/icv) 180 min ; TNF-a (10 or 40 ng/icv) 25 min ; L-NAME (5 µg/icv) 10 min ; L-NAME (5 sg/iv) 10 min ; L-arginine
(2 .5,
5, 10
ig/icv) 10 min . I .c .v . LPS (1 µg) and TNF-a (40 ng) abolished water intake induced by water deprivation . I .c .v . L-NAME antagonized the
1043-6618/92/26I10166-02/$03 .00/0
© 1992 The Italian Pharmacological Society
1 67
Pharmacological Research, Vol . 26, Supplement 2, 1992
antidipsogenic action of LPS and TNF-a in a percentage of 50 % and 70%, respectively . Instead, i .v . injected L-NAME at the same intracranially injected dose, failed to modify inhibition of thirst induced by LPS or TNF-a (data not shown) . Finally, i .c .v . L-arginine
(2 .5,
5, 10 µg) was antidipsogenic by itself and
caused to be antidipsogenic LPS and TNF-a doses which alone did not modify drinking behaviour (Fig .
1) .
CONCLUSIONS Our results suggest that : 1) brain L-arginine/NO pathway activation in CNS modulates thirst ; 2) LPS and more TNF-a stimulate in CNS release of NO which acts on mechanisms or sites regulating drinking behaviour . Table 1 . Effects of icv saline, LPS, TNF-a, L-arginine, L-NAME + LPS or TNF-a, L-arginine + LPS or TNF-a, on water intake induced by 24 h water deprivation . Treatment
Water intake ml/rat
Saline (5 µl/icv) LPS (0 .25 µg/icv) LPS (0 .25 µg/icv)+L-arginine (5 µg/icv) LPS (1 µg/icv) LPS (1 pg/icv)+L-NAME (5 µg/icv) TNF-a (10 ng/icv) TNF-a (10 ng/icv)+L-arginine (5 gg/icv) TNF-a (40 ng/icv) TNF-a (40 ng/icv)+L-NAME (5 gg/icv) L-arginine (2,5 µg/icv) L-arginine (5 µg/icv) L-arginine (10 µg/icv)
13 .5 13 .0 3 .4 0 .2 6 .7 12 .8 5 .2 0 .8 9 .1 12 .5 8 .9 4 .1
± ± ± ± ± ± ± ± ± ± ± ±
1 .0 1 .0 0 .7* 0 .08* 0 .8° 1 .0 1 .2* 0 .09* 0 .6# 0 .9 1 .1* 0 .7*
* = p < 0 .01 vs saline ; ° = p < 0 .01 vs LPS (1 µg/icv) ; # = p < 0 .01 vs TNF-a (40 ng/icv) . Each value is the mean of six experiments . REFERENCES 1) Calapai, G ., Squadrito, F ., Altavilla, D ., Zingarelli, B ., Campo, G .M ., Saitta, A ., Ioculano, M ., Urna, G ., Sardella, A . and Caputi A .P . (1991) Tumor necrosis factor involvement in lipopolysaccharide-induced inhibition of drinking in the rat . Neurosci . Res . Comm . 9 : 53-61 .
