Effects of chronic oral administration of the antidepressants, desmethylimipramine and zimelidine on rat cortical GABAB binding sites: a comparison with 5‐HT2 binding site changes

Abstract

The effects of chronic oral administration of desmethylimipramine (DMI) or zimelidine (1.25 and 5 mg kg⁻¹ twice daily for 21 days) were studied on rat whole cortical γ‐aminobutyric acid_B (GABA_B) binding sites. No changes in receptor affinity or number were found with either drug. A subsequent study of GABA_B binding sites using higher doses of these drugs (5 and 10 mg kg⁻¹) and rat frontal cortex was also without effect, when investigated 24 h after termination of drug administration or 72 h after DMI administration (5 mg kg⁻¹). The number of frontal cortical 5‐hydroxytryptamine₂ (5‐HT₂) binding sites was significantly and dose‐dependently decreased after both drugs, whereas the number of hippocampal 5‐HT₂ binding sites was not significantly altered after either drug. As the number of frontal cortical GABA_B binding sites was unaltered whereas the number of 5‐HT₂ binding sites was significantly decreased under identical study conditions, it may be concluded that the effects of antidepressant administration upon GABA_B binding sites is a less consistent observation than their effects on 5‐HT₂ binding sites.