Tachykinin receptors in the equine pelvic flexure.
Tachykinins, of which substance P (SP) is the prototype, are neuropeptides which are widely distributed in the nervous systems. In the equine gut, SP is present in enteric nerves and is a powerful constrictor of enteric muscle; in other species, SP is also known to have potent vasodilatory and pro-inflammatory effects. The specific effects of SP are determined by the subtype of receptor present in the target tissue. There are 3 known subtypes of tachykinin receptors, distinguished by their relative affinities for SP and other tachykinins. The distribution of SP binding sites in the equine pelvic flexure was determined using 125I-Bolton Hunter SP (I-BHSP) autoradiography. Most I-BHSP binding sites were determined to be saturable and specific, therefore presumably representing tachykinin receptors. The greatest degree of I-BHSP binding occurred over very small vessels, and over the muscularis mucosae; I-BHSP binding was also intense over the circular muscle of the muscularis externa and mucosa, and present, although less intense, over the longitudinal muscle of the muscularis externa. Competition of I-BHSP with specific receptor agonists for binding sites in the equine pelvic flexure were used to determine the subtypes of tachykinin receptors present. The neurokinin-1 receptor subtype predominated in the equine pelvic flexure, followed by the neurokinin-3 receptor subtype.
Sonea
I M
IM
Department of Anatomy, Michigan State University, East Lansing, Michigan 48824, USA.
Wilson
D V
DV
Bowker
R M
RM
Robinson
N E
NE
D000818:Animals; D001345:Autoradiography / Q000662:veterinary; D001665:Binding Sites; D003106:Colon / Q000294:innervation* / Q000378:metabolism; D003720:Densitometry / Q000662:veterinary; D005260:Female; D006736:Horses / Q000378:metabolism* / Q000502:physiology; D007457:Iodine Radioisotopes; D008297:Male; D010388:Pelvis / Q000294:innervation; D018040:Receptors, Neurokinin-1 / Q000378:metabolism; D018039:Receptors, Tachykinin / Q000378:metabolism*; D013373:Substance P / Q000378:metabolism; D015320:Tachykinins / Q000378:metabolism*
D007457:Iodine Radioisotopes; D018040:Receptors, Neurokinin-1; D018039:Receptors, Tachykinin; D015320:Tachykinins; D013373:Substance P