Expression and characterization of the substance P (NK1) receptor in the rat pituitary and AtT20 mouse pituitary tumor cells

Although substance P is known to take part in the regulation of the anterior pituitary, no conclusive evidence for the expression of the tachykinin NK₁ receptor has been found yet in the pituitary or pituitary derived cells. With the reverse transcription-polymerase chain reaction (RT-PCR) method we could detect the low abundant transcripts of the NK₁ receptor in the rat pituitary and in the AtT20 cell line (clone D16v). Furthermore, the functional expression of the NK₁ receptor in AtT20 cells was confirmed by activation of the phosphatidylinositol-calcium second messenger system when the cells were treated with substance P. In addition, binding studies also indicated the functional expression of this receptor in AtT20 cells. Thus we provide the first evidence that the NK₁ receptor is expressed in AtT20 cells and the rat pituitary.