A. Zahorodna1, G. Hess1,2 Imipramine and Citalopram Reverse Corticosterone-induced Alterations in the Effects of the Activation of 5-ht1a and 5-ht2 Receptors in Rat Frontal Cortex

Using extracellular recording we studied changes in the reactivity of rat frontal cortical slices to the 5-HT1A, 5-HT2 and 5-HT4 receptor agonists, (±)-2dipropyloamino-8-hydroxy-1,2,3,4-tetrahydronaphtalene hydrobromide (8-OHDPAT), (±)-2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI) and zacopride, respectively, induced by an earlier treatment of animals with corticosterone lasting 1 or 3 weeks. Spontaneous bursting activity was recorded in ex vivo slices incubated in a medium devoid of Mg2+ ions and containing picrotoxin (30 μM). Repetitive, but not single, corticosterone administration resulted in an attenuation of the effect of the activation of 5-HT1A receptors and in an enhancement of the effect related to 5-HT2 receptors. The effect of 5-HT4 receptor activation remained unchanged. In separate two sets of experiments rats were treated with corticosterone for 3 weeks and additionally with imipramine or citalopram, beginning on the eighth day of corticosterone administration. In the corticosterone plus imipramine as well as corticosterone plus citalopram groups the effects of 8-OH-DPAT and DOI were not different from control indicating that corticosterone-induced functional modifications in the reactivity of 5-HT1A and 5-HT2 receptors were reversed by antidepressant treatments.