The use of invertebrate peptide toxins to establish Ca2+ channel identity of CA3-CA1 neurotransmission in rat hippocampal slices

Mature hippocampal astrocytes exhibit functional metabotropic and ionotropic glutamate receptors in situ

“…AMPA was applied after perfusion for 6-8 min while loaded cells were marked and baseline measurements taken. Figure 4C shows that the 5 µM conotoxin treatment inhibited fEPSPs even 1.5 h after its removal, confirming the observation of others that the effects of conotoxin MVIIC on fEPSPs are not quickly reversed (Wheeler et al, 1994;Nooney and Lodge, 1996).…”

“…Reports conflict as to whether AMPA applied with CTZ directly stimulates basal neurotransmitter release in the absence of action potentials (Barnes et al, 1994;Desai et al, 1994). To examine astrocyte AMPA responses without this possible contribution, we applied AMPA after treatment with -conotoxin MVIIC (conotoxin) which blocks the N-, P-, and Q-type Ca 2ϩ channels that are responsible for Ca 2ϩ -mediated neurotransmitter release from CA3 neurons that innervate CA1 (Hillyard et al, 1992;Sather et al, 1993;Grantham et al, 1994;Wheeler et al, 1994;Wu and Saggau, 1994;Nooney and Lodge, 1996). Slices were immersed in oxygenated aCSF containing 5 µM conotoxin and 0.5 mM ascorbic acid for 50 min, and then immersed in the same solution with 100 µM cyclothiazide and 1 µM tetrodotoxin for an additional 10 min.…”

Calcium influx is required for endocytotic membrane retrieval

“…We conclude that voltage-gated calcium channels (possibly P-type calcium channels), in addition to their role in signaling for exocytosis at synapses (41)(42)(43)(44)(45), are required for endocytotic membrane retrieval after fertilization. This result reveals a new functional role for this class of ion channel and predicts that membrane retrieval will be voltage-dependent, emphasizing the need to assay endocytosis under conditions that do not perturb membrane potential (46,47).…”

Pharmacological characterization of ionic currents that regulate the pacemaker rhythm in a weakly electric fish

“…CTX GVIA, which specifically blocks mammalian N-type calcium currents at concentrations of 1 M or less (Olivera et al, 1994;Randall and Tsien, 1995), had no significant effect on Pn firing rate at concentrations up to 5 M. CTX MVIIC, which blocks mammalian N-, P-, and Q-type calcium currents at concentrations of 0.3-5.0 M (Hillyard et al, 1992;Olivera et al, 1994;Randall and Tsien, 1995;Nooney and Lodge, 1996), did not affect Pn firing rate at concentrations of 2 M. -Agatoxin (AGA) IVA, which completely blocks mammalian P-and Q-type calcium currents at concentrations of 100 -200 nM , failed to significantly influence Pn firing rate at concentrations of up to 5 M. These results suggest that the pacemaker rhythm is not regulated by L-, N-, P-, or Q-type calcium currents and implicate T-or R-type calcium currents, both of which are sensitive to nickel and cadmium, but resistant to the specific blockers used in this study.…”