Measurement of [3H]PN200-110 and [125I]-Conotoxin MVIIA Binding

Intracellular Ca²⁺ ([Ca²⁺ ]_i ) can rise primarily via release from intracellular storage sites (e.g., the endoplasmic reticulum) or via entry across the membrane down the steep concentration gradient (1 –3 ). Ca²⁺ can enter through two main classes of plasma membrane-located Ca²⁺ channels: receptor operated and voltage sensitive (4 –7 ). Voltage-sensitive Ca²⁺ channels are involved in a wide and diverse array of physiological responses including neurotransmitter release (8 ). In addition, many guanine nucleotide protein (G) coupled receptors couple to voltage-sensitive Ca²⁺ channels to reduce Ca²⁺ influx (9 ,10 ).