Localization of ARG-vasopressin-like material in central neurones and mechanism of action of ARG-vasotocin on identified neurones of the snail Helix aspersa.
Immunocytochemical and electrophysiological studies were made on neurones in the suboesophageal ganglia of Helix aspersa. A group of neurones in the anterior dorsal surface of each parietal ganglion showed positive immunoreactivity to an antibody to arginine vasopressin (AVP), as did the neuropile and the nerves associated with the parietal and visceral ganglia. The only peripheral tissue to exhibit positive immunoreactivity to AVP was the optic tentacle, where positive immunoreactive fibres were present in the optic nerve and cell bodies below the retinal cell layer. Two central neurones, F1 and E13 were excited by arginine vasotocin (AVT), threshold 1-10 nM, and the ionic mechanism associated with this response was investigated. This excitation involved both sodium and calcium ions with an overall increase in resistance. In low sodium Ringer, the AVT response was greatly reduced, while in calcium-free 3 mM cobalt Ringer, the response was potentiated. Changing the external concentrations of potassium and chloride ions had no apparent effect on the response. The amplitude of the excitation induced by AVT was enhanced when the cells were hyperpolarized. Most of the other neurones tested failed to respond to AVT though the excitatory response of certain cells to acetylcholine was enhanced by 0.1 microM AVT. Excitation by 5-hydroxytryptamine was unaffected in the cells tested. This study provides further evidence for a role for an AVT-like peptide in the nervous system of Helix.
Department of Neurophysiology, University of Southampton, U.K.
P J
PJ
Boyd
N N
NN
Osborne
R J
RJ
Walker
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004594:Electrophysiology; D006372:Helix, Snails; D007150:Immunohistochemistry; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D011312:Pressure; D012701:Serotonin / Q000378:metabolism; D014668:Vasotocin / Q000494:pharmacology*
D002121:Calcium Channel Blockers; D001127:Arginine Vasopressin; D012701:Serotonin; D000109:Acetylcholine; D014668:Vasotocin