Interspike interval patterns of taste neurons in the hamster solitary nucleus

The central nervous system first processes taste informationin the solitary nucleus, which has been almost exclusively studiedin terms of average firing rate. We analyzed interspike intervals(ISI's) of 25 taste-responsive single units in the hamster (Mesocricetusauratus) solitary nucleus. ISI's were measured during spontaneousactivity and during stimulation with NaCl, KCl, sucrose, ora mixture of the three, and graphed on semi-logarithmic plots.Two different ISI patterns were evident: simple (13 units) andcomplex (12 units). Simple ISI patterns had a single broad peakat 284.7 ± 70.4 ms spontaneous and 78.8 ± 12.8ms stimulated. All complex ISI patterns had one distinct, sharppeak for an interval about 10 ms (11.3 ± 0.4 ms: spontaneous,9.3 ± 0.5 ms: stimulated), and a second, broader peakat 273.9 ± 45.9 ms spontaneous and 71.5 ± 14.6ms stimulated. As rate of firing increased peaks in ISI patternspredictably moved towards lower intervals, but ISI pattern-typedid not change. This constancy of ISI pattern held for responsesof a unit across all stimuli and did not depend upon the stimulusspecificity or location of the unit within the rostral poleof the solitary nucleus. Apparently, the pattern that a tasteneuron generates is intrinsic to the neuron and may relate tothe way it processes tast information.