Feeding responses to a high dose of 8-OH-DPAT in young and adult rats: influence of food texture

doi:10.1016/0014-2999(88)90807-2

European Journal of Pharmacology

Volume 151, Issue 2, 7 July 1988, Pages 267-273

https://doi.org/10.1016/0014-2999(88)90807-2 Get rights and content

Abstract

The present study was undertaken to investigate the hyperphagic responses to the 5-HT_1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), in young and adult rats fed either a powder diet or pellets. In the young rats, 8-OH-DPAT (500 μg/kg s.c.) increased the consumption of pellets - but not powder - during the 2 h following drug administration. On the other hand, 8-OH-DPAT did not promote hyperphagia in adult rats presented with either pellets or a powdered diet. The influence of the 5-HT_1A agonist on midbrain serotonin (5-hydroxytryptamine, 5-HT) turnover was examined. Administration of 8-OH-DPAT (500 μg/kg s.c.) induced similar decreases in 5-HT turnover, as reflected by the ratio of 5-hydroxyindoleacetic acid (5-HIAA) to 5-HT, in young and adult rath 1 h after administration. Nevertheless, some metabolic responses to 8-OH-DPAT were found to be influenced by age. Young and adult rats were injected with a low dose of 8-OH-DPAT (50 μg/kg s.c.) to specifically test the presynaptic regulation of 5-HT turnover. Again, midbrain 5-HIAA to 5-HT ratios were decreased to the same extent in both young and adult rats. The results suggest that (i) gnawing may be an important parameter in the food consumption that is triggered by a high dose of 8-OH-DPAT, (ii) analysis of the presynaptic effects of 8-OH-DPAT on 5-HT turnover cannot solely explain the influence of the agonist on feeding behavior.

References (26)

C. Bendotti et al.
8-Hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) elicits eating in free-feeding rats by acting on central serotonin neurons
European J. Pharmacol.
(1986)
C. Bendotti et al.
The role of putative 5-HT_1A and 5-HT_1B receptors in the control of feeding in rats
Life Sci.
(1987)
J.E. Blundell
Serotonin and appetite
Neuropharmacology
(1984)
J.E. Blundell
Serotonin manipulations and the structure of feeding behaviour
Appetite
(1986)
F. Chaouloff et al.
Tryptophan and serotonin turnover rate in the brain of genetically hyperammonemic mice
Neurochem. Int.
(1985)
c.T. Dourish et al.
Characteristics of feeding induced by the serotonin agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT)
Brain Res. Bull.
(1985)
M. Hamon et al.
Biochemical evidence for the 5-HT agonist property of PAT (8-hydroxy-2-(di-n-propylamino)tetralin) in the rat brain
European J. Pharmacol.
(1984)
P.H. Hutson et al.
Neurochemical and behavioral evidence for mediation of the hyperphagic action of 8-OH-DPAT by 5-HT cell body autoreceptors
European J. Pharmacol.
(1986)
D.N. Middlemiss et al.
8-Hydroxy-2-(di-n-propylamino)tetralin discriminates between subtypes of the 5-HT₁ recognition site
European J. Pharmacol.
(1983)
H. Schoemaker et al.
³H-8-OH-DPAT labels the serotonin transporter in the rat striatum
European J. Pharmacol.
(1986)

D. Vergé et al.

Presynaptic 5-HT autoreceptors on serotonergic cell bodies and/or dendrites but not terminals are of the 5-HT_1A subtype

European J. Pharmacol.

(1985)

F. Chaouloff et al.

5-HT_1A and alpha₂-adrenergic receptors mediate the hyperglycemic and hypoinsulinemic effects of 8-hydroxy-2-(di-n-propylamino)tetralin in the conscious rat

J. Pharmacol. Exp. Ther.

(1987)

Blasi A. De et al.

Selective changes of receptor binding in brain regions of aged rats

Life Sci.

(1982)

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Postnatal treatment with NAN-190 but not with 5-HT1A receptor agonists retards growth of the rat brain
2005, International Journal of Developmental Neuroscience
Citation Excerpt :
Lack of influence of the 5-HT1A agonists on the body weight of rat pups is also an unexpected finding. In the adult rats injections of these agonists evoke hyperphagia (Chaouloff et al., 1988; Hutson et al., 1988; Ebenezer, 1992, 1996), while we did not observe any increase of the body weight in the injected pups or acceleration of their development. In fact, the growth curves of pups injected with either buspirone or 8-OHDPA were almost identical with those of their control littermates and there were no changes in all investigated anatomical and functional parameters of the brain development.
We investigated the influence of prolonged administration of the 5-HT1A receptor agonists (8-OH-DPAT or buspirone) or its antagonist, NAN-190 to rat pups on development of their cortical barrel field. Pups were injected daily with the drugs starting from the day of birth till either the 5th postnatal day or the 22–25th postnatal day and were perfused one day later. Square areas of their whisker barrel fields were measured on tangential sections of the cortex stained for cytochrome oxidase. Injections of 8-OH-DPAT or buspirone till the 5th postnatal day did not change any of the investigated parameters, while injections of NAN-190 resulted in 15% reduction of the pups’ body and brain weight and proportional reduction of the square area of their barrel fields. Groups treated till the 22–25th postnatal day showed similar results. Some of these pups were injected with [C¹⁴]2-deoxyglucose to investigate the strength of responses of their cortical barrels to stimulation of corresponding vibrissae. The cortical area labeled with 2-deoxyglucose after stimulation of vibrissae of the row C was narrower in the NAN-190 injected rats. This functional deficit was more pronounced than the anatomical one, which resembled the effects of neonatal serotonin depletion (Neuroreport, 1997). Therefore, the results of injecting NAN-190 to the rat pups point to a deficit of trophic developmental influences of serotonin, adding new arguments for the hypothesis of a trophic role of 5-HT1A receptors in the brain development.
Effects of the 5-HT(1A) receptor agonist 8-OH-DPAT on operant food intake in food-deprived pigs
1999, Physiology and Behavior
The effects of the 5-HT_1A agonist 8-hydroxy-2 (di-n-propylamino)tetralin (8-OH-DPAT) were investigated on operant food intake in food-deprived pigs. In Experiment 1, 8-OH-DPAT (5–20 μg/kg) administered intravenously (i.v.) 15 min prior to the occurrence of feeding produced a dose-related decrease in operant food intake in pigs that had been fasted overnight. The effects were mainly apparent during the first 30 min after the start of the feeding period. In Experiment 2, 8-OH-DPAT (25 and 50 μg/kg, i.v.) administered 60 min prior to the ocurrence of feeding in pigs that were fasted overnight also produced significant decreases in food intake. The effects were mainly apparent during the first 30–40 min after the start of the feeding period. In Experiment 3, 8-OH-DPAT (20 μg/kg, i.v.) significantly increased operant feeding in satiated pigs during the first 30 min after administration. These results show that 8-OH-DPAT has complex effects on feeding behaviour in pigs, increasing operant food intake in satiated pigs, while producing a reduction in food intake in food-deprived animals.
Modulation of the behavioral effects of 8-OH-DPAT by estrogen and DOI
1997, Pharmacology Biochemistry and Behavior
MASWOOD N., AND L. UPHOUSE. Modulation of the behavioral effects of 8-OH-DPAT by estrogen and DOI. PHARMACOL BIOCHEM BEHAV 58(4) 859–866, 1997.—The effects of female gonadal hormones on 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT)-induced flat body posture, hypothermia, and eating behavior were examined. Ovariectomized rats were injected with estradiol benzoate, estradiol benzoate, and progesterone, progesterone or vehicle on each of 2 consecutive weeks. On each week, the behavioral effects of the 5-HT_1A receptor agonist, 8-OH-DPAT, or the combination of both 8-OH-DPAT and 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI), a 5-HT₂ receptor agonist, were examined. 8-OH-DPAT produced flat body posture, hypothermia, and eating behavior on each week of the experiment. Female gonadal hormones modulated eating behavior (e.g., rats treated with estradiol benzoate showed less eating after 8-OH-DPAT), but had no effect on either flat body posture or hypothermia. The 5-HT₂ receptor agonist, DOI, attenuated 8-OH-DPAT’s effect on flat body posture and on hypothermia, but not on eating behavior. 8-OH-DPAT’s effect on all behaviors declined during the second week of the experiment.
5-HT<inf>1A</inf> behavioural models
1997, Pharmacochemistry Library
5-HT_1A receptor agonists have been tested in a wide variety of animal models indicative of CNS functions. These range from models for motion sickness and emesis to models predictive for antipsychotic drugs. In most of these tests, 5-HT_1A receptor agonists appear to be active, although the degree of specificity varies. 5-HT_1A receptor agonists influence the total serotonin neurotransmission by acting on the somatodendritic autoreceptor as well as by acting on postsynaptic receptors. From many behavioral effects of 5-HT_1A receptor agonists, the precise molecular mechanism of action remains elusive and it is quite conceivable that similar behavioral effects can be induced by various manipulations of the serotonin neurotransmission.
Effects of the 5-HT<inf>1A</inf> agonist 8-OH-DPAT on operant feeding in pigs
1995, Physiology and Behavior
The effect of intravenous (IV) injection of 8-OH-DPAT on operant food intake in pigs has been examined in animals with food available ad lib and in pigs feeding after 4 h deprivation of food. Operant methods were used to ascertain whether any increases in food intake were due to increased motivation to feed rather than stereotypic chewing movements. In nondeprived animals IV injection of 8-OH-DPAT at doses of 10, 30, and 50 μg/kg significantly increased food intake in the 45 min following injection. In pigs feeding after 4 h deprivation, IV injection of 8-OH-DPAT at doses of 30 and 50 μg/kg, given 5 min before feeding commenced, had no effect on food intake.
8-OH-DPAT induces a selective increase in protein intake in ageing overweight animals
1994, European Journal of Pharmacology
We have examined the effects of a 5-HT_1A receptor agonist (8-hydroxy-2-(di-n-propylamino)tetralin, 8-OH-DPAT) on food preference in ageing rats that had been given a ‘palatable’ meal 15 min before administration of the drug. Ageing rats consumed a greater amount of the ‘palatable’ pre-meal than the young rats. In young rats lipids were the predominant source of calories, but in old animals lipid and protein consumption was similar. Administration of 8-OH-DPAT resulted in an increase in total caloric intake in both groups. Concomitant with this there was a significant increase in protein intake in both groups, which was most important in ageing rats, where proteins became the predominant source of calories.

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Feeding responses to a high dose of 8-OH-DPAT in young and adult rats: influence of food texture

Abstract

European J. Pharmacol.

Life Sci.

Neuropharmacology

Appetite

Neurochem. Int.

Brain Res. Bull.

European J. Pharmacol.

European J. Pharmacol.

European J. Pharmacol.

European J. Pharmacol.

European J. Pharmacol.

5-HT1A and alpha2-adrenergic receptors mediate the hyperglycemic and hypoinsulinemic effects of 8-hydroxy-2-(di-n-propylamino)tetralin in the conscious rat

J. Pharmacol. Exp. Ther.

Selective changes of receptor binding in brain regions of aged rats

Life Sci.

5-HT_1A and alpha₂-adrenergic receptors mediate the hyperglycemic and hypoinsulinemic effects of 8-hydroxy-2-(di-n-propylamino)tetralin in the conscious rat