This paper presents the first evidence that some neurons in the octopu
s CNS contain delta-amino butyric acid (GABA). Using conventional immu
nohistochemical methods with appropriate controls, we obtained positiv
e staining with an antibody to GABA in fibres in the neuropil of many
lobes of the brain of the northern octopus Eledone cirrhosa. In severa
l lobes cell bodies were also stained. Staining was not uniformly dist
ributed in the brain nor within a particular lobe: some regions staine
d strongly, others not at all. These findings suggest that GABA should
be added to the already long fist of putative neurotransmitters in th
e cephalopod CNS.