1905 Synaptic plasticity in the olfactory bulb of salmonid fish

S229

1903 Laboratory

MORPHOLOGY AND GLUTAMATE RESPONSES OF THE PROCEREBRAL RONS OF TERRESTRIAL SLUG LIMAX MARGINATUS of Neurobiophysics, School of Pharmaceutical Sciences, The University of Tokyo

SATOSHI WATANABE,

SHIGENORI

KAWAHARA,

YUTAKA

NEU-

KIRINO

Morphology and glutamate responses of the procerebral (PC) neurons in Limuz marginatus were examined by perforated patch recording and injection of sulforhodamine B. PC neurons were classified into bursting and nonbursting neurons as in previous reports. The bursting neurons had larger somata than t,he nonbursting neurons. Neurites of the bursting neurons are confined in the cell layer and oriented to the dorsal-ventral axis, which is the direction of synchronization of the membrane potential oscillation. In contrast, neurites of the nonbursting neurons extended to the neuropil layers. These results suggest that nonbursting neurons interact with input or output pathways and that the bursting neurons are related to local interaction of PC neurons. Glutamate evoked different responses from the two types of neurons: transient Cl- current in bursting neurons and sustained K’ current in nonbursting neurons. These results imply significance of glutamatergic transmission in the PC.

1904

Transduction

Biological Institute,

mechanism of taste receptor cell of the fly

Graduate School of Science, Tohoku University

Masayuki Koganezawa, Ichiro Shimada We previously suggested that the response of labellar taste receptor cells of the fleshfly to some taste stimuli were mediated by G protein-coupled transduction cascade. In this study, the effects of IPs, neomycin (an inhibitor of IPs production) and ruthenium red (a blocker of the IPs-gated channel) were investigated on the taste receptor cell of the fly. To introduce IPs or neomycin into the receptor cells, the tip of a chemosensory hair was treated with IPs or neomycin in 0.03% DOC. After treatment with IPs + DOC, the responses of the sugar receptor cell to sugars and amino acids were enhanced. After treatment with neomycin + DOC, the responses of the sugar receptor cell were depressed compared with those after treatment with deoxycholate alone. When the taste stimuli mixed with ruthenium red, the responses to the sugars and amino acids were inhibited. These results suggested that the response of sugar receptor cell of fleshfly was mediated by IPS.

1905

SYNAPTIC

PLASTICITY

IN THE OLFACTORY

BULB OF SALMONID

Grad. Sch. Integr. Sci., Yokohama City Univ., Yokohama 236, Japan’, Nikko Branch, Nikko321-16, Japan2

Natl.

Res. Inst.

FISH Aquacult.,

MASAHIKO SATOU’, SHIN SUGIYAMAI, TAMAMI INADOMI’, SHOJI KITAMURA’ Dentro-dendritic mitral-to-granule cell synapse in the carp olfactory bulb shows both long-term and short-term plasticity (LTP and STP) after low frequency tetanic stimulation (5-lOHz, 200 pulses) applied to the olfactory tract (OT) (Anzai et al. 1995; Anzai and Satou, 1996). As the index of the synaptic transmission OT-evoked field potentials were used. In the present study we tested whether or not field potentials with similar property can be evoked also in the olfactory bulb of the salmonid fish. As the results we found that (1) electrical stimuli applied to the ventral part of the rostral telencephalon evoked field potentials with components similar to those in the carp and (2) low frequency tetanic stimulation (8Hz, 500 pulses) induced a plastic change (LTP and STP) in the field potentials. Anzai et al. (1995) Zool. Sci., Suppl. 12, ~117; Anzai and Satou (1996) Neurosci. Res., Suppl. 20, S223.