Lack of desensitization to neurokinin A due to partial agonist property of this peptide at parotid substance P receptors.
Effects of substance P (SP) and neurokinin A (NKA) on intracellular free calcium concentration (Cai) were compared in Fura2-loaded parotid acinar cells. SP produced a pronounced increase in Cai which rapidly desensitized. In contrast, NKA produced a smaller increase which was well maintained. Cells desensitized to SP were cross-desensitized to NKA. The absence of NKA-induced desensitization reflects the inability of NKA to fully activate parotid SP receptors; NKA is a partial agonist in the parotid. Similarly, the action of NKA as a partial agonist in other systems may explain findings that SP responses desensitize while NKA responses do not.
McMillian
M K
MK
Neurosciences Program, Tufts University, Boston, MA 02111.
Talamo
B R
BR
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D005456:Fluorescent Dyes; D008297:Male; D015288:Neurokinin A / Q000494:pharmacology*; D010306:Parotid Gland / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D018040:Receptors, Neurokinin-1; D017981:Receptors, Neurotransmitter / Q000187:drug effects* / Q000502:physiology; D013373:Substance P / Q000494:pharmacology*
D005456:Fluorescent Dyes; D018040:Receptors, Neurokinin-1; D017981:Receptors, Neurotransmitter; D013373:Substance P; D015288:Neurokinin A; D002118:Calcium