RESUMEN
The relationship between CCK-and VP-neurons in the rat retrochiasmatic area was studied at ultrastructural level by means of pre-embedding(PAP) double immunoelectron microscopic labeling technique. First, the VP-immunoreactivity was demonstrated by DAB method. After thoroughly washing, the CCK-immuno- reactivity was revealed by ammonium molybdate-TMB method. Being stabili- zed by DAB-cobalt chloride, the sections were embedded in Epon 812. Under ele- ctron microscope, it was observed that in the retrochiasmatic area, the VP-LI products distributed diffusely as high electron dense granular or flocculent depo- sits, whereas the CCK-LI products distributed sparsely as needle-or mass-like deposits. VP-LI perikarya were small in size with oval shape and CCK-LI peri- karya were medium in size with polygonal shape. CCK-LI perikarya and dendri- tes received afferent synapses from non-CCK- and non-VP-axonal terminals VP- LI axons received afferent synapses from VP and non-VP-axonal terminals It was interesting that the VP-LI axonal terminals formed efferent axoaxonic syna- pses with CCK-LI axonal endings and, vice versa, the CCK-LI axonal terminals established also efferent axoaxonic synapses with VP-LI axonal endings. The above mentioned results identified for the first time that in the rat retrochiasma- tic area not only there were CCK- and VP-neurons, but also there were reciprocal synaptic regulations between above two kinds of peptidergic neuron, providing new ultrastructural basis for the regulatory mechanism of the neuroendocrine in hypothalamus.