Distinct binding sites for substance P and neurokinin A (substance K): co-transmitters in rat brain.

The distribution of binding sites in rat brain for iodinated neurokinin A and iodinated substance P were compared using autoradiography. Distinct patterns of binding for the two iodinated tachykinins were noted. Binding sites for iodinated neurokinin A were noted in the olfactory bulb, cortex, supraoptic n., paraventricular n., certain amygdaloid n., hippocampus, medial habenula, interpeduncular n., n. of the tractus solitarius, and dorsal horn of the spinal cord. This pattern was in contrast to low levels of binding of iodinated substance P to the cortex, supraoptic n., paraventricular n., and the interpeduncular n., but substantial density of binding sites in numerous other regions.