GABA_C receptors are expressed in GABAergic and non-GABAergic neurons of the rat superior colliculus and visual cortex

摘要

GABA_C receptors are enriched in the upper grey layers of the mammalian superior colliculus and contribute to synaptic processing. Electrophysiological data suggested that the GABA_C receptor p subunits are expressed by GABAergic interneurons which represent about half of the neurons in the stratum griseum superfici-ale (SGS). Combining in situ hybridization for p2 receptor mRNA and the glutamic acid decarboxylase GAD-65 mRNA confirmed this assumption. A majority of p-labeled neurons in SGS and pretectum are GABAergic. Combining in situ hybridization with immunohistochemistry for the two projection neuron markers calbindin and parvalbumin revealed that a few p2 mRNA expressing cells coexpressed calbindin, but not parvalbumin. In visual cortex, p2 mRNA was present in pyramidal neurons and parvalbumin-con-taining interneurons. The results show that in the SGS primarily GABAergic neurons express GABA_C receptors whereas the majority of tectothalamic calbindin neurons and intrinsically projecting parvalbumin neurons do not.