ACTIVITY-DEPENDENT CHANGES IN INTRACELLULAR CALCIUM IN MYENTERIC NEURONS

The spatial distribution and changes in intracellular calcium concentr ation ([Ca2+](i)) in myenteric neurons were measured using fura 2 in t he longitudinal muscle-myenteric plexus preparation from the guinea pi g duodenum. These measurements were made simultaneously with intracell ular voltage recordings. The generation of action potentials in the ce ll bodies of both S-and AH-type neurons increased [Ca2+](i) in the pro cesses and cell bodies. There was no measurable delay between the [Ca2 +](i) changes in the somata and the processes, indicating that these c hanges were caused by the spread of electrical signals and not by diff usion. The rate of Ca2+ removal was faster in the processes than in th e somata, apparently due to the large surface-to-volume ratio in the f ormer. In AH neurons, the [Ca2+](i) transient was shorter than the dur ation of the after-spike hyperpolarization. It is concluded that the t wo main types of myenteric neurons possess voltage-gated Ca2+ channels in both somata and processes.