Pharmacological analysis of slow potentials recorded in frog olfactory bulb during natural stimulation.

Pharmacological agents (strychnine, picrotoxin, pentobarbital, chloralose, GABA, penicillin, morphine) were used to investigate the nature of the slow potential recorded in the frog olfactory bulb in response to natural stimulation. Three possible hypotheses were tested: 1) The slow potential is neuroglial in nature; 2) it is the analog of the dorsal-root potential of the spinal cord and reflects depolarization of primary afferents arising in the terminals of the olfactory nerve and responsible for presynaptic inhibition in the frog olfactory bulb; 3) the slow potential reflects postsynaptic processes. The results showed great similarity between changes in the slow and dorsal-root potentials of the spinal cord in response to the action of pharmacological agents. However, the slow potential is evidently a complex response and incorporates at least one other component - depolarization of the dendrites of unknown nature.

[Electrical characteristics of the granular neurons of the carp olfactory bulb]. / Elektricheskie kharakteristiki granuliarnykh neironov oboniatel'noi lukovitsy karpa

Using the intracellular recording technique the electrical activity of the carp olfactory bulb granular cells and secondary neurons was studied. Early and late EPSP and IPSP were the synaptic responses of granular cells both to the olfactory nerve and olfactory tract electrical stimulation. The comparison of responses of the granular cells and secondary neurons led to the conclusion that the granular cells are interneurons producing post-synaptic inhibition of the secondary neurons. It was supposed that the granular neurons are excited by dendro-dendritic and reccurent-collateral pathways and that the inhibitory synapses are located on the dendrites of secondary neurons which are in contact with the olfactory nerve terminals.

[A pharmacologic analysis of the slow potential arising in response to adequate stimulation of the frog olfactory bulb]. / Farmakologicheskii analiz medlennogo potentsiala, voznikaiushchego v otvet na adekvatnoe razdrazhenie v oboniatel'noi lukovitse liagushki

The nature of slow potential recorded in the frog olfactory bulb in response to natural stimulation was studied using application of different pharmacological substances. Three suppositions were checked up: 1) if the slow potential is of neuro-glial nature; 2) whether it reflects the primary afferent depolarization in the terminations of olfactory fibres which is responsible for the presynaptic inhibition in the olfactory bulb (as the dorsal root potential in the spinal cord); 3) if it reflects postsynaptic potentials. The slow potential was found to have many pharmacological properties similar to those of the dorsal root potential in the spinal cord. However, the slow potential appears to be more a complicated response and includes at least one more component--a depolarization of dendrites of unknown nature.