The response of juxtacellular labeled GABA interneurons in the basolateral amygdaloid nucleus anterior part to 5-HT2A/2C receptor activation is decreased in rats with 6-hydroxydopamine lesions.

ABSTRACT

Here we report that juxtacellular labeled GABA interneurons in the basolateral amygdaloid nucleus anterior part (BLA) of rats with 6-hydroxydopamine lesions of the substantia nigra pars compacta (SNc) showed a more burst-firing pattern, while having no change in the firing rate. In sham-operated and the lesioned rats, systemic administration of 5-HT(2A/2C) receptor agonist DOI produced excitation, inhibition and unchanged in the firing rate of the interneurons, and the mean response of DOI was excitatory. However, cumulative dose producing excitation in the lesioned rats was higher than that of sham-operated rats. The local administration of DOI in the BLA also produced three types of responses in two groups of rats. Furthermore, the local administration of DOI excited the interneurons in sham-operated rats, whereas the mean firing rate of the interneurons in the lesioned rats was not affected at the same dose. The excitatory effect of the majority of the interneurons after systemic and local administration of DOI was not reversed by the selective 5-HT(2C) receptor antagonist SB242084, and the inhibitory effect of DOI in all the interneurons examined was reversed by GABA(A) receptor antagonist picrotoxinin. The SNc lesion in rats did not change the density of GAD67/5-HT(2A) receptor co-expressing neurons in the BLA. These results indicate that the SNc lesion changes the firing activity of BLA GABA interneurons. Moreover, DOI regulated the firing activity of the interneurons mainly through activation of 5-HT(2A) receptor, and the lesion led to a decreased response of the interneurons to DOI, which attributes to dysfunction of 5-HT(2A) receptor on these interneurons.