Abstract
In Experiment 1, body weights of rats fed a powdered tryptophan-free (TF) diet decreased monotonically during a 13-day period. Control animals fed the same diet supplemented with 0.5% l-tryptophan gained weight. The groups did not differ significantly in acoustic startle amplitude measured at 2, 4, 6, 7, 9, 11, and 13 days despite a 28% decrease in whole-brain serotonin in the TF rats. In Experiment 2, daily intubation of rats with a syrup form of each diet maintained the two groups' body weights at comparable levels. TF diet intubation decreased whole-brain serotonin by 64% and produced significantly elevated startle amplitudes, which returned to control levels when 0.5% l-tryptophan was added to the diet. Changes in whole-brain serotonin level preceded changes in startle amplitude by several days. In Experiment 3, acute injections of 125 mg/kg l-tryptophan significantly reduced the startle amplitude of TF diet intubated rats and significantly raised their brain serotonin levels. The results show that acoustic startle reflex is increased by a TF diet, provided the animals receive adequate nourishment, and suggest that this facilitation may result from depletion of brain serotonin.
Similar content being viewed by others
References
Biggio, G., Fadda, F., Fanni, P., Tagliamonte, A., Gessa, G. L.: Rapid depletion of serum tryptophan, brain tryptophan, serotonin and 5-hydroxyindoleacetic acid by a tryptophan-free diet. Life Sci. 14, 1321–1329 (1974)
Bogdanski, D. F., Pletscher, A., Brodie, B. B., Undenfriend, S.: Identification and assay of serotonin in brain. J. Pharmacol. Exp. Ther. 117, 82–88 (1956)
Carlton, P. L., Advokat, C.: Attenuated habituation due to parachlorophenylalanine. Pharmacol. Biochem. Behav. 1, 657–663 (1973)
Carruba, M. O., Picotti, G. B., Genovese, E., Mantegazza, P.: Stimulatory effect of a maize diet on sexual behavior of male rats. Life Sci. 20, 159–164 (1977)
Conner, R. L., Stolk, J. M., Barchas, J. D., Levine, S.: Parachlorophenylalanine and habituation to repetitive auditory startle stimuli in rats. Physiol. Behav. 5, 1215–1219 (1970)
Davis, M., Sheard, M. H.: Habituation and sensitization of the rat startle response: effects of raphe lesions. Physiol. Behav. 12, 425–431 (1974)
Davis, M., Sheard, M. H.: p-Chloroamphetamine (PCA): acute and chronic effects on habituation and sensitization of the acoustic startle response in rats. Eur. J. Pharmacol. 35, 261–273 (1976)
Fechter, L. D., Ison, J. R.: The inhibition of the acoustic startle reaction in rats by food and water deprivation. Learn. Motiv. 3, 109–124 (1972)
Fernstrom, J. D., Lytle, L. D.: Corn malnutrition, brain serotonin and behavior. Nutr. Rev. 34, 257–262 (1976)
Fernstrom, J. D., Hirsch, M. J.: Rapid repletion of brain serotonin in malnourished corn-fed rats following l-tryptophan injection. Life Sci. 17, 455–464 (1975)
Fernstrom, J. D., Wurtman, R. J.: Brain serotonin content: physiological dependence on plasma tryptophan levels. Science 173, 149–152 (1971)
Fernstrom, J. D., Wurtman, R. J.: Brain serotonin content: physiological regulation by plasma neutral amino acids. Science 178, 414–416 (1972)
Gessa, G. L., Biggio, G., Corsini, G. U., Fratta, W., Mereu, G. P., Tagliamonte, A.: Tryptophan-free diets: a new means for effectively decreasing brain serotonin synthesis in animals and man. Agents Actions 5, 498 (abstract) (1975)
Geyer, M. A., Puerto, A., Menkes, D. B., Segal, D. S., Mandell, A. J.: Behavioral studies following lesions of the mesolimbic and mesostriatal serotonergic pathways. Brain Res. 106, 257–270 (1976)
Gibbons, J. L., Barr, G. A., Bridger, W. H., Liebowitz, S. F.: Effects of PCPA, tryptophan and a tryptophan-free diet on mouse-killing behavior of rats. Neurosci. Abstr. 2, 465 (1976)
Lytle, L. D., Messing, R. B., Fisher, L., Phebus, L.: Effects of long-term corn consumption on brain serotonin and the response to electric shock. Science 190, 692–694 (1975)
Majumdar, A. P., Nakhla, A. M.: Influence of tryptophan on the activity of acetylcholinesterase in the brain of well-fed normal and adrenalectomized rats. Biochem. Biophys. Res. Commun. 76, 71–77 (1977)
Messing, R. B., Fisher, L. A., Phebus, L., Lytle, L. D.: Interaction of diet and drugs in the regulation of brain 5-hydroxyindoles and the response to painful electric shock. Life Sci. 18, 707–714 (1976)
Overstreet, D. H.: Pharmacological approaches to habituation of the acoustic startle response in rats. Physiol. Psychol. 5, 230–238 (1977)
Perez-Cruet, J. A., Tagliamonte, A., Tagliamonte, P., Gessa, G. L.: Changes in brain serotonin metabolism associated with fasting and satiation in rats. Life Sci. 11, 31–39 (1972)
Rogers, Q. R., Leung, P. M. B.: The influence of amino acids on the neuroregulation of food intake. Fed. Proc. 32, 1709–1719 (1973)
Sheard, M. H.: The effect of p-chlorophenylalanine on behavior in rats: relation to brain 5-hydroxytryptamine and 5-hydroxyindoleacetic acid. Brain Res. 15, 524–528 (1969)
Weiss, G. T., Davis, M.: Automated system for acquisition and reduction of startle response data. Pharm. Biochem. Behav. 4, 713–720 (1976)
Wurtman, R. J., Fernstrom, J. D.: Effects of the diet on brain neurotransmitters. Nutr. Rev. 32, 193–200 (1974)
Wurtman, R. J., Fernstrom, J. D.: Control of brain monoamine synthesis by diet and plasma amino acids. Am. J. Clin. Nutr. 28, 638–647 (1975)
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Walters, J.K., Davis, M. & Sheard, M.H. Tryptophan-free diet: Effects on the acoustic startle reflex in rats. Psychopharmacology 62, 103–109 (1979). https://doi.org/10.1007/BF00427121
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00427121