ABSTRACT
Glutamate-induced cobalt uptake reveals that non-NMDA glutamate receptors (GluRs) are present in rat taste bud cells. Previous studies involving glutamate induced cobalt staining suggest this uptake mainly occurs via kainate type GluRs. It is not known which of the 4 types of taste bud cells express subunits of kainate GluR. Circumvallate and foliate papillae of Sprague-Dawley rats (45~60 days old) were used to search for the mRNAs of subunits of non-NMDA GluRs using RT-PCR with specific primers for GluR1-7, KA1 and KA2. We also performed RT-PCR for GluR5, KA1, PLCbeta2, and NCAM/SNAP 25 in isolated single cells from taste buds. Taste epithelium, including circumvallate or foliate papilla, express mRNAs of GluR5 and KA1. However, non-taste tongue epithelium expresses no subunits of non-NMDA GluRs. Isolated single cell RT-PCR reveals that the mRNAs of GluR5 and KA1 are preferentially expressed in Type II and Type III cells over Type I cells.
Subject(s)
Animals , Rats , Cobalt , Epithelium , Glutamic Acid , Kainic Acid , Rats, Sprague-Dawley , Receptors, Glutamate , Receptors, Kainic Acid , RNA, Messenger , Taste Buds , TongueABSTRACT
The glutaramic acid derivative cholecystokinin ( CCK ) receptor antagonist, CR1409 was tested for its ability to inhibit CCK induced increase in cytosolic calcium concentration in isolated rat pancreatic acinar cells using fura-2 as calcium probe. Preaddition of 10?mol/L CR1409 completely inhibited the increase of cytosolic calcium concertration induced with 1 nmol/L CCK, but had no antagonistic effect on carbacholine bombesin-induced increase in cytosolic calcium concentration. The half maximal inhibition was obtained for 0.37?mol/L, corresponding to a potency a hundred fold higher than that of db cGMP. In the presence of increasing concentrations of CR1409, the response curves of CCK concentrations were shifted to the right but the same maximum was achieved. Schild representation gave a straight line with a slope close to one ( n = 0.92 ) and pA2 value of 6.93. These findings therefore support that CR1409 is a powerful competitive and specific antagonist bf CCK-induced increase in cytosolic calcium Concentration in isolated rat pancreatic acinar cells and provide further evidence for the role of this ion as an intracellular mediator of pancreatic CCK receptor.