Autoradiographic localization of substance P ligand binding sites and distribution of immunoreactive neurons in the periaqueductal gray of the rat.
The autoradiographic localization of substance P (SP) binding sites and the distribution of SP immunoreactive (SP-ir) neurons in the periaqueductal gray (PAG) of the rat were studied. The autoradiograms revealed an uneven distribution of specific SP binding sites in the PAG. Throughout the rostrocaudal extent, the densest ligand binding sites were observed in the medial PAG adjacent to the aqueduct, and extended into the dorsal medullary region and to the dorsal raphe nucleus midline region. The distribution of binding sites were denser in the dorsal PAG than the ventral half. In the cuneiform nucleus, a lesser and a denser binding site were observed in the medial and lateral halves respectively. Optical density readings of autoradiograms also supported the differences between these areas. The distribution of SP-ir neurons was also found uneven. In the rostral PAG, SP-ir neurons were found in the entire dorsoventral region. In the caudal PAG, SP-ir neurons were found as 3 clusters: in the dorsomedial, dorsolateral and ventrolateral regions. The present study revealed more SP-ir neurons in the PAG than previously reported.
Liu
R P
RP
Department of Anatomy and Cell Biology, Georgetown University, Washington, DC.
Swenberg
M L
ML
D000818:Animals; D001345:Autoradiography; D007150:Immunohistochemistry; D008297:Male; D010487:Periaqueductal Gray / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D018040:Receptors, Neurokinin-1; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D013373:Substance P / Q000378:metabolism*
D018040:Receptors, Neurokinin-1; D017981:Receptors, Neurotransmitter; D013373:Substance P