Dissimilar responses of cortical neurons to chronic trazodone or desipramine treatment

Effects of trazodone treatment on alpha-2 adrenoceptor function in depressed patients

Tricyclic antidepressant drugs reduce the sensitivity of alpha 2 adrenoceptors during long-term treatment. In the present study, the alpha 2 adrenergic agonist clonidine was administered to 11 depressed patients before and during treatment with the triazolopyridine antidepressant trazodone (TRZ). Clonidine's ability to decrease blood pressure (BP) and plasma levels of the norepinephrine metabolite 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG), and to increase sedation and plasma growth hormone (GH), were measured. TRZ had little effect on these indices of pre- and postsynaptic alpha 2 receptor function, suggesting that the antidepressant properties of TRZ are not related to changes in alpha 2 adrenoceptor sensitivity.

Frequency-dependent block of field potentials in the rat hippocampal slice caused by tricyclic antidepressants

The effect of the tricyclic antidepressants imipramine and desipramine were studied on field potentials in the rat hippocampal slice. The electrically evoked stratum radiatum nerve volley, excitatory postsynaptic potential (e.p.s.p.) and pyramidal cell layer population spike (PS) were recorded in the CA1 region. At concentrations of 10(-6)M to 10(-5)M, impramine did not affect the amplitude of the nerve volley, e.p.s.p. or PS at low frequencies of stimulation (0.01 Hz). At higher frequencies of stimulation (1-100 Hz), imipramine caused a frequency-dependent block of the nerve volley, e.p.s.p. and PS. The time course of onset of the frequency-dependent block in the presence of imipramine was very slow. Maximum inhibition was reached after 3-4 h treatment with imipramine. Desipramine (10(-6)-10(-5)M) also caused a frequency-dependent block of the hippocampal field potentials. Only slight frequency-dependent block was observed in slices from rats injected in vivo with desipramine (10 mg kg-1) for 14 days.