Autoradiographic visualization of NK-3 tachykinin binding sites in the rat brain, utilizing [3H]senktide.

The autoradiographic distribution of the selective NK-3 tachykinin agonist [3H]senktide was investigated in rat brain. [3H]Senktide bound with high affinity (KD less than 2.5 nM) and high specificity (greater than 75%) to cerebral cortex and numerous subcortical sites, including the substantia nigra pars compacta. In addition, moderately dense binding was seen in the median but not the dorsal raphe nucleus, and this was disrupted by 5,7-dihydroxytryptamine (5,7-DHT)-induced destruction of 5-HT neurons. 5,7-DHT lesions did not affect the binding of [3H]senktide to forebrain regions, suggesting that 5-HT terminals are devoid of NK-3 receptors.