Neural Control of Heart Beat in the African Giant Snail, Achatina Fulica Ferussac I. Identification of the Heart Regulatory Neurones

Seven heart regulatory neurones (PON, TAN, TAN-2, TAN-3, d-RCDN, d-LCDN and VG1) were identified in the central nervous system of the African giant snail, Achatina fulica Ferussac. Among these neurones, the periodically oscillating neurone (PON) was the most effective heart excitor, producing heart excitation at rather low firing frequencies. The tonically autoactive neurones (TAN, TAN-2 and TAN-3) were tonically firing neurones and their spontaneous activity was found to produce tonic heart excitation which supplemented the myogenic heart activity. There was some evidence that two cerebral ganglion cells (the dorsal right and left cerebral distinct neurones, d-RCDN and d-LCDN) were also likely to be heart excitors although the direct connection to the heart was somewhat doubtful in some specimens. No direct inhibitory neurone was found, but the high firing frequency of the visceral ganglion neurone (VG1) usually produced heart inhibition.