Fig. 9.

Involvement of muscarinic receptors in neuronal transmission in guinea-pig AM. A–C: amperometric records of catecholamine secretion in response to electrical stimulation. A and B were obtained from the same adrenal gland. Guinea-pig adrenal gland was retrogradely perfused through the adrenal vein with saline. Perfusate was exchanged with saline containing 1 or 3 μM atropine or 3 μM atropine and 500 μM hexamethonium (C6). The nerve fibers in the adrenal gland were electrically stimulated with 50-V pulses of 1.5-ms duration for 30 s at 5 (double lines) and 10 Hz (bars). Catecholamines were measured using the amperometric method. Records were interrupted for 6 min. D: summary of effects of 1 and 3 μM atropine on catecholamine secretion in response to electrical stimulation at 10 Hz (9 adrenal glands) and at 5 (6 adrenal glands) and 10 Hz (6 adrenal glands), respectively. Amounts of secreted catecholamines during application of atropine were expressed relative to averages of those before and after it. *P < 0.05 and **P < 0.01, statistically significant decrease.