Fine structures of nerve fibers with corticotropin-releasing factor-like immunoreactivity in the rat lateral septum.

The fine structures of nerve fibers with corticotropin-releasing factor (CRF)-like immunoreactivity in the rat lateral septum were investigated by means preembedding immunoelectron microscopy. A number of CRF axon terminals formed synapses with cell bodies of non-immunoreactive septal neurons. They occasionally had broad terminal bulges whose subregions showed little or no immunoreactivity for CRF. CRF axon terminals were also in synaptic contact with non-immunoreactive dendrites or dendritic spines. Some dendrites with CRF were postsynaptic to non-immunoreactive axon terminals.