Effect of isolation rearing on 5-HT agonist-induced responses in the rat
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Rats were reared from weaning (21 days of age) either in isolation or in social groups of five for 30 days and were then tested for spontaneous locomotor activity and 7 days later for 5-hydroxytryptamine (5-HT) agonist-induced behaviour. Isolation-reared animals displayed locomotor hyperactivity when placed in a novel environment. 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) (2 mg/kg IP) and 8-hydroxy-2-(di-n-propyl-amino) tetralin (8-OH-DPAT) (0.32 mg/kg SC) elicited various components of the “5-HT behavioural syndrome” in both groups of animals, with forepaw treading and flat body posture being significantly more pronounced in isolation-reared animals. 1-(2,5-Dimethoxy-4-iodophenyl)-2-aminopropane (DOI) (2.5 mg/kg IP), a 5-HT2 selective agonist, produced a significantly greater number of back muscle contractions in isolation-reared animals but there was no difference between the two groups in the number of wet-dog shakes produced. Forepaw treading and flat body posture are thought to be mediated by 5-HT1A receptor activation, and stimulation of this receptor by either 5-MeODMT or 8-OH-DPAT produced greater responding in isolation-reared rats, suggesting supersensitivity of the post-synaptic 5-HT1A receptor. Wet-dog shakes are thought to be mediated by 5-HT2 and other (none-5-HT) receptors while back muscle contractions have been shown to be mediated by 5-HT2 receptors, indicating that there is also an increase in 5-HT2 receptor responsiveness in the socially-isolated animals. In general, the results indicate post-synaptic 5-HT receptor supersensitivity in isolation-reared rats and these receptor changes may be involved in the behavioural profile observed in such rats.
Key wordsIsolation rearing Spontaneous locomotor activity 5-HT behavioural syndrome Rat
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- Fone KCF, Bennett GW, Marsden CA (1987) Involvement of catecholaminergic neurones anda-adrenoceptors in the wet-dog shake and forepaw licking behaviours produced by the intrathecal injection of an analogue of thyrotrophin-releasing hormone (CG 3509). Neuropharmacology 26:1147–1155CrossRefPubMedGoogle Scholar
- Glennon RA (1987) Central serotonin receptors as targets for drug research. J Neurochem 30:1–12Google Scholar
- Green AR, Johnson P, Nimgaonkar VL (1983) Increased 5-HT2 receptor number in brain as a probable explanation for the enhanced 5-hydroxytryptamine-mediated behaviour following repeated electroconvulsive shock administration to rats. Br J Pharmacol 80:173–177Google Scholar
- Hjorth S, Carlsson A, Lindberg P, Sanchez D, Wikstrom H, Arvidsson L-E, Hacksell U, Nilsson JLG (1982) 8-Hydroxy-2-(di-n-propylamino) tetralin, 8-OH-DPAT, a potent and selective simplified ergot congener with central 5-HT-receptor stimulating activity. J Neural Transm 55:169–188CrossRefGoogle Scholar
- Jones GH, Hernandez TD, Robbins TW, Marsden CA (1988) Enhanced striatal response tod-amphetamine as revealed by intracerebral dialysis following social isolation in rats. Br J Pharmacol 94:249PGoogle Scholar
- Morgan MJ, Einon DF, Nicholas D (1975) The effects of isolation rearing on behavioural inhibition in the rat. Q J Exp Psychol 27:615–634Google Scholar
- Morinan A, Parker V (1985) Are socially-isolated rats anxious? Br J Pharmacol 86:460PGoogle Scholar
- Sahakian BJ, Robbins TW, Iversen SD (1977) The effects of isolation rearing on exploration in the rat. Anim Learn Behav 5:193–198Google Scholar
- Tricklebank MD (1984) Behavioural effects of 8-hydroxy-2-(di-n-propylamino) tetralin, a putative 5-HT1A receptor agonist. Br J Pharmacol 81:26PGoogle Scholar
- Wright IK, Crespi F, Marsden CA, Jones GH, Robbins TW (1989) Effect of isolation-rearing on 5-HT release in the frontal cortex. J Neurosci Methods 29:283Google Scholar
- Wright IK, Ismail H, Upton N, Marsden CA (1990) Effect of isolation-rearing on performance in the elevated plus-maze and open field behaviour. Br J Pharmacol 100:357PGoogle Scholar