Effects of catecholamines, monophenolamines and phenylamines on identifiable giant neurons of an African giant snail (Achatina fulica Férussac).

The effects of catecholamines, monophenolamines and phenylamines on eight identifiable giant neurons of an African giant snail (Achatina fulica Férussac) were examined to classify these neurons into several categories according to their sensitivities to the various substances. The five neurons, PON (periodically oscillating neuron), TAN (tonically autoactive neuron), 1-VMN (left-visceral multiple spike neuron), d-RPeAN (dorsal-right pedal autoactive neuron) and VIN (visceral intermittent firing neuron), were sensitive to catecholamines. Of these neurons, PON was excited most markedly by dopamine (dopamine-sensitive); TAN, 1-VMN and d-RPeAN were inhibited most markedly by epinine (epinine-sensitive); and VIN was excited equally by the four catecholamines, dopamine, epinine, L-noradrenaline and L-adrenaline (widely sensitive). The three other neurons, FAN (frequently autoactive neuron), d-LPeLN (dorsal-left pedal large neuron) and d-LCDN (dorsal-left cerebral distinct neuron) were sensitive to monophenolamines. DL-Octopamine was the most inhibitory on FAN and d-LCDN, but was the most excitatory on d-LPeLN. DL-Synephrine had the same but somewhat weaker effects on the three neurons as did DL-octopamine. The three phenylamines, L-phenylalanine, beta-phenylethylamine and DL-beta-phenylethanolamine, had no effect on any of the eight neurons examined.