Electromyographic activity of the vocal muscle was analysed in 10 subjects during the phonation of different vowels and with different voice pitches. Analysis of the firing pattern of single or a few motor units was performed with the aid of an amplitude discriminator on the computer. The firing rate increases with increasing voice pitch (in the region co-ho the decrease of mean interspike interval with the slope 30-40 msec/octave was found). In the firing pattern of several motor units the periodicity was observed to be correlated with the voice pitch. The period of 8 msec corresponding H, 123 Hz, decreased to about 6 msec during phonation of do, 147 Hz. The periodicity was present both in units with pure prephonatory activity and in units which were active during phonation. It seems possible that the activity in the vocal muscle changes characteristically during the phonation of different vowels.

Adult↗

PubMedDate not supplied

Comparison of response properties of neurons in the inferior colliculus of guinea pigs under different anesthetics.

Responses of the inferior colliculus (IC) neurons to acoustical stimulation were recorded in anesthetized guinea pigs. Three kinds of anesthesia were used: (1) urethane (8 ml/kg b.w. of 20 per cent solution i.p.); (2) ketamine-xylazine combination (1 ml/kg b.w. of mixture 2:1); and (3) pentobarbital (25 mg/kg i.p.) combined with intramuscular injection of fentanyl (0.5 ml) and droperidol (1 ml). The frequency tuning of neurons evaluated on the basis of Q10 values and the composite neural audiogram represented by points of lowest thresholds of individual IC neurons were similar for guinea pigs treated with any of the anesthetics. The number of spontaneously active IC neurons was significantly larger with ketamine than with urethane or pentobarbital. The response latencies to tone bursts at characteristic frequency (CF) were shortest in animals anesthetized with pentobarbital. Whereas with ketamine and urethane many neurons were recorded in which response latencies were longer than 40 ms, in pentobarbital-anesthetized animals the latencies usually did not exceed 25 ms. The occurrence of neurons with an onset type of response was significantly larger with pentobarbital than with the other two anesthetics. In ketamine and urethane anesthesia, thresholds of units with sustained response were significantly lower than thresholds of units with onset response. Our results suggest that in experiments where the level of spontaneous activity, latency and type of responses were important parameters, the kind of anesthesia should be taken into account.

Anesthetics↗

PubMedDate not supplied

Local effects of PAF in guinea-pig inner ear.

The effect of PAF-containing artificial perilymph at 10(-7) and 10(-8) M on the endocochlear potential (EP) was investigated in guinea-pigs. The inner ear was perfused and the EP recorded at the same time. The characteristic decline of the EP which is highly sensitive to all stimuli could be prevented by pretreating the animals with either ginkgolide B (BN 52,021) or BM 13,177 (Sulotraban). Less effective in preventing the EP decline was Daltroban (BM 13,505). The results are discussed with respect to an involvement of PAF in cochlear physiology and in the regulation of ion transport, respectively.

Animals↗