Differential effects of monoaminergic agonists on alcohol intake in rats fed a tryptophan-enhanced diet.
The goal of the present study was to determine if enhancement of tryptophan levels in a nutritionally balanced liquid diet would affect alcohol intake in a two-bottle choice procedure. Furthermore. the monoaminergic agonists amphetamine, phentermine (dopaminergic- and noradrenergic-releasing drugs), and fenfluramine (a serotonin releaser) were administered to determine if these drugs reduced alcohol intake in animals fed the tryptophan-enhanced diet compared to those fed an alcohol-containing diet without added tryptophan. Amphetamine 0.5 and 2 mg/kg and phentermine 4 mg/kg selectively reduced alcohol intake in animals fed the tryptophan-enhanced diet; higher doses also reduced alcohol intake in animals fed the control alcohol diet. Three hours after drug administration, phentermine 2 and 4 mg/kg produced increases in consumption of the nonalcoholic diet in animals fed the control diet without affecting consumption in animals fed the tryptophan-enhanced diet. Finally, animals in the tryptophan-enhanced group gained less weight than those animals fed an identical diet without the added tryptophan. Neurochemical analysis revealed that the tryptophan-fed groups showed increased 5-HIAA concentrations and serotonin turnover in the striatum. hypothalamus, and frontal cortex compared to animals fed the control diet. The tryptophan-alcohol group also showed almost double the tryptophan levels in the hypothalamus compared to the tryptophan-isocaloric group. These results indicate that, whereas increasing tryptophan levels by itself was not sufficient to alter consumption of an alcohol-containing diet, the administration of monoaminergic agonists significantly interacted with tryptophan in a dose-dependent manner to reduce intake of an alcohol-containing diet without reducing intake of an isocaloric diet.
Halladay
A K
AK
Department of Psychology, Rutgers University, New Brunswick, NJ 08904, USA.
Wagner
G C
GC
Hsu
T
T
Sekowski
A
A
Fisher
H
H
D000428:Alcohol Drinking / Q000188:drug therapy*; D000661:Amphetamine / Q000627:therapeutic use; D000818:Animals; D001067:Appetite Depressants / Q000627:therapeutic use*; D002540:Cerebral Cortex / Q000737:chemistry; D003342:Corpus Striatum / Q000737:chemistry; D004298:Dopamine / Q000032:analysis / Q000378:metabolism*; D005277:Fenfluramine / Q000627:therapeutic use; D005526:Food, Formulated; D007031:Hypothalamus / Q000737:chemistry; D010645:Phentermine / Q000627:therapeutic use; D051381:Rats; D020318:Rats, Long-Evans; D012701:Serotonin / Q000032:analysis / Q000378:metabolism*; D013375:Substance Withdrawal Syndrome / Q000378:metabolism*; D014364:Tryptophan / Q000627:therapeutic use*
D001067:Appetite Depressants; D005277:Fenfluramine; D012701:Serotonin; D014364:Tryptophan; D010645:Phentermine; D000661:Amphetamine; D004298:Dopamine