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CYCLIC AMP-INDUCED CURRENT IN ISOLATED OLFACTORY RECEPTORS OF THE NEWT.

TAKASHI KURAHASHI' AND AKIMICHI KANEKO, National Institute for Physiological Sciences,

Okazaki 444, Japan.

To examine the hypothesis that olfactory t ransduct ion is mediated by a G protein-adenylate cyclase system, we

analyzed responses of solitary receptor cells induced by intracellular injection of cyclic nucleotides under the whole-

cell voltage-clamp using a patch pipette. Cyclic nucleotides were applied into the cell by diffusion from the pipette. Introduction of either cAMP or cGMP (effective concentration in the pipette, > 0.1 raM) evoked an inward current

in cells held at their resting potentials. Response amplitude diminished with time due to desensitization. When

injected close to the ciliated apical dendrite, the nucleotide evoked a large response with a short latency. Injection

to the soma evoked a small response with a long latency. Cells lacking cilia did not respond to intracellularly

injected nucleotides. Thus, it is highly likely tha t the response was generated in the ciliary membrane. The cAMP-

induced or cGMP-induced currents and the odorant-induced response had very close reversal potentials, similar

sensitivity distribution and both showed desensitization dependent on extracellular Ca ions. These similarities strongly support the notion that cAMP or cGMP is the internal messenger mediating olfactory t ransduction.

TIME SERIES ANALYSIS OF SPONTANEOUS ACTIVITY OF SINGLE NEURONS IN THE CAT OLFAC- TORY BULB. YOICHI OGAWA AND FUMIAKI MOTOKIZAWA r Department of physiology r Nara Medical College¢ Kashihara t Nara 634 r Japan.

We previously classified the patterns of spontaneous discharge in olfactory bulb neurons into three types by visual or auditory inspection: continuous type, burst type and mixed type. In the present study, the spontaneous discharge of the neurons was quantitatively analyzed by a digital computer, and the comparison of classification between inspection and time series analysis was performed. A total of 63 units were recorded in 17 cats anesthetized with sodium pentobarbital or urethane-chloralose. They respired spontaneously through the nose or a tracheotomy tube. In each neuron, 512 inter-spike interval data were sampled and transformed into interval histogram, joint interval histogram, serial correlogram and pulse auto-correlogram. Of these analyses, interval histogram and joint in- terval histogram were especially useful for describing the discharge patterns. Interval histogram revealed at least three different types of distribution: unimodal nearly symmetric type, unimodal asymmetric type and bimodal asymmetric type. Joint interval histogram allowed the recognition of bursting discharge. The bimodal asymmetric type of neurons showed bursting discharge. The result obtained by visual or auditory inspection was not always consistent with the result of joint interval histogram. Therefore, it is suggested that quantitative analyses are necessary for the classification of spontaneous discharge.

GUSTATORY INFORMATION PROCESSING IN THE MEDULLARY AND PONTINE RELAY STATIONS IN RATS. SHIGERU YAMADA*, MORIYASU ADACHI*, TOSHIHIRO OHSHIMA*~ HAJIME ODA*, AND TOYOHIKO SATOH~ Department of Physiology, Aichi-Gakuin University Dental School~ I-I00 Kusumoto, Chlkusa~ Nagoya 464, Japan.

The mode of information processing of taste quality was investigated in the lower brainstem of anesthetized rats. The activity of two neurons was recorded simultaneously during stimulation with the four basic tastes. Correlation coefficients of two-neuron activities were computed to see whether peaks appear in the cross-correlogr~ms. In the solitary tract nucleus, narrow peaks (about 1 msec) appeared around the origin of the cross-correlogram. The stimulus to give the highest peak was usually NaCI or less frequently HCI. The best-stimulus for the partner neurons of these pairs with peaks was either NaCI/NaCI or NaCI/HCI. In the parabrachial nucleus most of the peaks were much broader (5-8 msec). The best- stimulus for the partner neurons and for the highest peak was identical; usually NaCI and less frequently HCI. The proportion of the correlated discharges to the total output of these parabrachial NaCl-best neurons was about ten times greater than that of the solitary tract neurons. It is suggested that the salt taste signals ascend along labeled lines, and that synchronization of these lines is enhanced by the feedback control of higher NaCl-best neurons.