Repeated treatment with imipramine enhances the excitatory response of hippocampal neurons to dopamine.

The effect of imipramine on the responsiveness of CA1 pyramidal neurons to dopamine was studied in hippocampal slices, obtained from rats treated acutely or repeatedly with imipramine (10 mg/kg, 14 days, twice a day p.o.).

Excitatory and inhibitory action of dopamine on hippocampal neurons in vitro. Involvement of D2 and D1 receptors.

The study examined the effects of dopaminergic agonists on the extracellularly recorded spontaneous activity of CA1 neurons in hippocampal slices of the rat. Dopamine evoked excitation or inhibition of the neuronal firing rate, the first reaction being more sensitive to the substance. Having used selective dopaminergic agonists (pergolide and 2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepines) and selective antagonists (haloperidol, spiperone, sulpiride and (R)-(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3- benzazepine-7-ol), it was concluded that the excitation evoked by dopamine was due to activation of D2 dopamine receptors, while the inhibition was the result of D1 receptor activation.

Repeated imipramine treatment increases the responsivity of the rat hippocampus to dopamine. An in vitro study.

The sensitivity of hippocampal neurons to dopamine was studied in hippocampal slices obtained from rats treated acutely (10 mg/kg) or repeatedly (10 mg/kg, 14 days, twice a day) with imipramine. In non-treated rats dopamine induced a slight excitation or depression of the firing rate of CA 1 pyramidal neurons in slice preparations. Hippocampal slices prepared from the imipramine-treated rats displayed greater changes in the firing rate after dopamine application.