Mapping of 5-HT1a receptor binding sites in the feline brain: A quantitative autoradiographic study using [³H]8-OH-DPAT

The distribution of high affinity [³H]8-OH-DPAT binding, a 5-HT1a receptor agonist, was investigated by quantitative autoradiography in coronal sections of cat brain. High levels of binding sites were found in the raphe nuclei and the interpeduncular nucleus. Additionally, a strong radiosignal was detected in the septum, the amygdala and the hippocampal formation. In the cerebral cortex, binding sites displayed a striking laminar pattern of distribution, the superficial and deep layers being generally more intensely labeled than the intermediate layers. Other brain areas showing high to moderate densities in [³H]8-OH-DPAT binding sites included the central, laterodorsal and paraventricular nuclei of the thalamus, the medial preoptic area, paraventricular and supramammillary nuclei of the hypothalamus, the outer layers of the superior colliculus, the parabigeminal nucleus, the dorsal and laterodorsal tegmental nuclei, the solitary complex and the laminar spinal trigeminal nucleus. In contrast, some areas also known to receive massive serotonergic projections such as the caudate-putamen, substantia nigra and inferior olivary complex were virtually devoid of labeling. These anatomical findings suggest that mediation of serotonergic neurotransmission via 5-HT1a receptors could play a major role in limbic and several other discrete brain areas.