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Summary. 1. A pair of chemoreceptor neurons sensitive to lactic acid (LA) was identified in the grooved-peg (A3) sensilla on the antennae of the mosquito, Aedes aegypti.2. One chemoreceptor responded to LA with an increase in spike frequency, whereas the other chemoreceptor exhibited a decrease in spike frequency when presented with LA.3. CO2, either alone or in combination with LA, elicited no change in spike frequency of either LA-sensitive neuron, indicating that the behavioral synergism of CO2 and LA occurs centrally and not at the primary receptor level.4. Water vapor induced such a weak excitatory response in both LAsensitive neurons that their involvement in the detection of water vapor is questioned.5. The insect repellent, DEET, inhibited both LA-sensitive neurons. DEET plus LA was additive in the LA-inhibited cell, whereas the LA response of the LA-excited cell was attenuated by DEET.6. The reaction spectra of the LA-sensitive neurons were determined using pure compounds (Table 1).7. The importance of LA in the host-finding behavior of the mosquito is discussed.

Our goals in this study were to explore the type of written questions students ask after reading one or more chapters from their textbook, and to investigate the ability of students to improve their questions during the course of a single semester. In order to classify student's questions we used a taxonomy that we have developed specifically for this purpose. Two comparable populations were examined: Undergraduate students in a large, introductory biology class who were taught in traditional lecture format, and students in a similar class who were taught in cooperative/active learning style. After the taxonomy was presented to the active learning class, more students were able to pose better, written questions. Their questions became more insightful, thoughtful, and content‐related, and were not easily answered by consulting the textbook or another readily available source. The best questions could be recast as scientific research questions (i.e., hypotheses). In contrast, when the taxonomy was presented to students in the traditionally taught class, the quality of student‐posed questions was largely unchanged. Various explanations for the difference in outcomes are discussed, and methods are suggested about how generally to encourage students' questions and to improve their question‐asking skills regardless of overall teaching style. © 2000 John Wiley & Sons, Inc. J Res Sci Teach 37: 854–870, 2000

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The crayfish tonic stretch receptor neuron manifests three phenomena: (a) Impulse frequency in response to a depolarizing current decays exponentially to half the initial rate with a time constant of about 4 sec. (b) One or more extra impulses superimposed on steady activity result in a lengthening of the interspike interval immediately following the last extra impulse which is proportional to the number of extra impulses. However, above a "threshold' number of impulses the proportionality constant becomes abruptly larger. (c) Following trains of impulses, the resting potential of the cell is hyperpolarized by an amount proportional to impulse number. Such posttetanic hyperpolarization (PTH) decays approximately exponentially with a time constant of 11 sec, but this varies with membrane potential. These effects are attributed to the incremental increase of an inhibitory (hyperpolarizing) current with a long (relative to interspike interval) decay constant. We suggest that this inhibitory current is the result of increased electrogenic Na pumping stimulated by Na entering with each impulse. Evidence is presented that the three effects are reversibly inhibited by conditions which depress active Na transport: (a) Li substituted for Na in the bath; (b) application of strophanthidin; (c) K removal; (d) treatment with cyanide; (e) cooling. We conclude that a single process is responsible for the three responses described above and identify that process as electrogenic Na pumping. Our observations also indicate that electrogenic pumping contributes to this neuron's resting potential.