PRESUMPTIVE GABAERGIC FEEDBACK INPUT TO THE FROG OLFACTORY-BULB - A DOUBLE LABELING STUDY WITH RETROGRADE AXONAL TRACING AND GABA IMMUNOHISTOCHEMISTRY

The localization of gamma-aminobutyric acid (GABA)-immunoreactive neurons that project to the main olfactory bulb in the frog was studied by combining GABA immunohistochemistry with retrograde axonal tracing. Double-labelled neurons were observed in the dorsal, medial and lateral pallial areas involved in reciprocal connections with the main olfactory bulb. GABA-immunoreactive cell bodies constituted only a part of the population of bulbopetal neurons in each pallial region. This suggests that bulbopetal neurons in the frog pallium belong to neuronal populations which differ in their neurotransmitter specificities. The bulbopetal GABA-immunoreactive pallial neurons may be the source of GABAergic feedback input to the frog main olfactory bulb.