[I-125] GALANIN BINDING-SITES IN THE RAT FRONTAL-LOBE ARE GUANINE NUCLEOTIDE-SENSITIVE AND DISPLAY A LOW REGIONAL INDEX OF OCCUPANCY

As the neuropeptide galanin is possibly involved in spatial learning, we investigated both the precise location and the binding features of the receptors within the rat frontal cortex using quantitative autorad iography. Galanin receptors predominated in layers I and V of medial a nd lateral frontal cortex with a low regional index of occupancy by en dogenous galanin. These receptors might be of functional relevance sin ce the guanylnucleotide Gpp(NH)p inhibited [I-125]galanin specific bin ding in each labeled region in the frontal lobe. Nevertheless, the str iking areal difference of expression of this effect within the medial frontal cortex suggests that [I-125]galanin binding sites might be cou pled to one or more types of G-proteins related to the functionally di stinct cortical subareas.