Evidence for altered α2-adrenoceptor function following isolation-rearing in the rat
- 1 October 1994
- journal article
- Published by Springer Nature in Psychopharmacology
- Vol. 116 (2) , 183-190
- https://doi.org/10.1007/bf02245061
Abstract
This study investigated central α2-adrenoceptor function in differentially reared rats. Rats reared from weaning were either housed singly or in groups of five. Measurements of spontaneous ambulatory activity at 4 weeks postweaning showed that isolates were more hyperactive on exposure to a novel environment than grouped rats. α2-Adrenoceptors were investigated using α2-adrenoceptor agonist-induced behaviours, [3H]-idazoxan binding and measurement of forskolin-stimulated cyclic AMP accumulation. Clonidine (0.001–1.0 mg/kg IP) induced mydriasis in both groups with no difference observed in the response between the isolation and group-reared animals. Clonidine (0.01–0.5 mg/kg IP) induced hypoactivity in both groups, with the effect significantly greater in the isolation-reared rats. Idazoxan markedly attenuated both responses, confirming their induction by α2-adrenoceptor stimulation. Clonidine-induced hypoactivity and mydriasis are mediated by pre- and postsynaptic α2-adrenoceptors, respectively; therefore the results suggest rats reared in isolation have enhanced presynaptic but unchanged postsynaptic α2-adrenoceptor function. Saturation binding experiments using [3H]-idazoxan were undertaken to determine α2-adrenoceptor number (Bmax) and affinity (Kd) in membranes prepared from the frontal cortex and hippocampus. Analysis of binding data revealed an increase in receptor number in the hippocampus of isolates. Cyclic AMP accumulation was measured in hippocampal slices from differentially reared rats. Isolation-rearing did not affect cyclic AMP accumulation in response to stimulation by forskolin (30 µM). However, the selective α2-adrenoceptor agonist, UK14304, produced a significantly greater inhibition of cyclic AMP accumulation in slices from isolated rats, confirming changes in α2-adrenoceptor function following isolation rearing.Keywords
This publication has 58 references indexed in Scilit:
- Endogenous Noradrenaline Activates α2‐Adrenoceptors on Serotonergic Nerve Endings in Human and Rat NeocortexJournal of Neurochemistry, 1993
- On the Role of Adenylate Cyclase in Presynaptic Modulation of Neurotransmitter Release Mediated by Monoamine and Opioid Receptors in the BrainAnnals of the New York Academy of Sciences, 1990
- Deficits in exploratory behaviour in socially isolated rats are not accompanied by changes in cerebral cortical adrenoceptor bindingJournal of Affective Disorders, 1988
- Analysis of radioligand binding experimentsJournal of Pharmacological Methods, 1985
- CNS adrenergic inhibition of parasympathetic oculomotor toneJournal of the Autonomic Nervous System, 1984
- Individually reared rats: Alteration in noradrenergic brain functionsJournal Of Neural Transmission-Parkinsons Disease and Dementia Section, 1981
- II. New evidence for a locus coeruleus-norepinephrine connection with anxietyLife Sciences, 1979
- Changes in brain catecholamine turnover and receptor sensitivity induced by social deprivation in ratsPsychopharmacology, 1978
- Incentive motivation and behavioral inhibition in socially-isolated ratsPhysiology & Behavior, 1975
- Incentive motivation and behavioral inhibition in socially-isolated ratsPhysiology & Behavior, 1975