Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology 

About: Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology is an academic journal published by Springer Science+Business Media. The journal publishes majorly in the area(s): Circadian rhythm & Compound eye. It has an ISSN identifier of 0340-7594. Over the lifetime, 8473 publications have been published receiving 346750 citations. The journal is also known as: Journal of comparative physiology. A, Sensory, neural, and behavioral physiology (Internet) & Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology (Print).

A Functional Analysis of Circadian Pacemakers in Nocturnal Rodents. I. The Stability and Lability of Spontaneous Frequency

Abstract: 1. In the first part of the paper, the model of non-parametric entrainment of circadian pacemakers is tested for the case of nocturnal rodents. The model makes use of the available data on freerunning period (τ) in constant darkness and on phase response curves (PRC) for short light pulses. It is tested in experiments using 1 or 2 light pulses per cycle. 2. Mesocricetus auratus and Peromyscus leucopus entrain to Zeitgebers involving 1 pulse (15' or 60') per cycle. The phase angle differences between rhythm and light cycle depends on the periods (τ and T) as predicted by the model. Entrainment of P. leucopus is unstable due to the after effects on τ created by the light pulse. 3. The limiting values of Zeitgeber period to which the animals entrain are much closer to 24 h than in Drosophila pseudoobscura, as the model predicts. However, frequent failures to entrain to T = 23 and T = 25 h are only explained if we take considerable interindividual variation in both τ and PRC into account. 4. With 2 pulses per cycle, the model predicts that entrainment will be more stable when activity is in the longer interval between the pulses than when it is in the shorter interval. This is true in the experimental data, where the phase relationships match predictions for skeleton photoperiods up to ca. 14 h. Increasing asymmetry forces animals into a "phase jump", so that activity shifts from the shorter to the longer interval. These ψ-jumps are accurately predicted in the hamster, but they occur at much longer photoperiods than predicted in P. leucopus. 5. Thus, the unqualified model, using a rigidly fixed species τ and PRC, is surely inadequate to explain entrainment. The extent to which variations in τ and PRC-shape, both "spontaneous" and induced by the entrainment process, can be known or inferred restricts the validity of the predictions. Yet we conclude, from a good deal of agreement between experiment and prediction (i), from the close correspondence between complete and skeleton photoperiods (ii), and on behavioural grounds (iii), that non-parametric entrainment by short light signals has a major share in the entrainment of nocturnal rodent rhythms in nature. 6. With these restrictions in mind, we analyse in the second part of the paper how the empirical regularities concerning τ and PRC contribute to the stabilization of the phase angle difference (ψ) between the pacemaker and the external world. Use is made of computer simulations of artificial pacemakers with variable τ and PRC. 7. ψ is most sensitive to instabilities in τ when ¯τ is close to 24 h. Thus the very circadian nature of these pacemakers helps to conserve ψ. Selection pressure for homeostasis of τ has been large in a species (M. auratus) where ¯τ = 24 h. The effect of ψ-instability is further reduced by entrainment with 2 pulses (dawn and dusk), made possible by the PRC's having both an advance and a delay section. 8. To analyze the contributions to ψ-conservation with seasonally changing photoperiod, we have assumed that it is of functional significance to conserve the phase of activity with respect to dusk (nocturnal animals) or to dawn (diurnal animals). We distinguish three contributions of nocturnal pacemaker behaviour to this type of ψ-conservation: increased amplitude of the PRC (i), asymmetry in the PRC, such that the slope of the delay-part is steeper than the slope of the advance-part (ii), and a short freerunning period in DD (iii). 9. A further contribution must derive from parametric effects of light, which are not traceable by the model, but certainly effective in preventing in complete photoperiods the ψ-jump which is seen in skeleton photoperiods. The existence of parametric effects is further demonstrated by the change of τ with light intensity in LL, described by Aschoffs Rule, which presumably reflects differences in PRC-shape between nocturnal and diurnal animals. 10. The paper concludes with an attempt to distinguish the features of circadian clocks that are analytically necessary for entrainment to occur (i), or have functional meaning, either in the measurement of the lapse of time (ii) or in the identification of local time (iii).

A functional analysis of circadian pacemakers in nocturnal rodents

Abstract: 1 Phase response curves for 15′ bright light pulses of four species of nocturnal rodents are described. All show delay phase shifts early in the subjective night, advance shifts in the late subjective night, and relative insensitivity during the subjective day. 2 The broad scatter in measured phase-shifts is largely due to error of measurement: the response of the pacemakers to light stimuli is more accurate than we observe. 3. Indications are found that the response to a resetting stimulus at a given phase of the rhythm is correlated with the individual\(\bar \tau \) (freerunning period). Fast pacemakers (short\(\bar \tau \)) tend to be more delayed or less advanced by the light than slow pacemakers (long\(\bar \tau \)). 4. Within individual mice (Mus musculus) the circadian pacemaker adjusts its resetting response to variations in its frequency: when τ is long (induced as after-effect of prior light treatment) light pulses at a defined phase of the oscillation (ct 15) produce smaller delay phase shifts than when τ is short. 5. Among species there are conspicuous differences in the shape of the phase response curve: where\(\bar \tau \) is long, advance phase shifts are large and delay phase shifts small (Mesocricetus auratus); where\(\bar \tau \) is short, advance shifts are small, and delay shifts are large (Mus musculus;Peromyscus maniculatus). 6. The functional meaning of the interrelationships of τ and PRC is briefly discussed.

Classical conditioning and retention in normal and mutant Drosophila melanogaster.

Abstract: By changing the conditioned discrimination paradigm of Quinn et al. (1974) from an instrumental procedure to a classical (Pavlovian) one, we have demonstrated strong learning in type flies. About 150 flies were sequestered in a closed chamber and trained by explosing them sequentially to two odors in air currents. Flies received twelve electric shock pulses in the presence of the first odor (CS+) but not in the presence of the second odor (CS−). To test for conditioned avoidance responses, flies were transported to a Tmaze choice point, between converging currents of the two odors. Typically, 95% of trained flies avoided the shock-associated odor (CS+).

Improved stability of Drosophila larval neuromuscular preparations in haemolymph-like physiological solutions.

Abstract: Neuromuscular preparations from third instar larvae of Drosophila are not well-maintained in commonly used physiological solutions: vacuoles form in the muscle fibers, and membrane potential declines. These problems may result from the Na:K ratio and total divalent cation content of these physiological solutions being quite different from those of haemolymph. Accordingly haemolymph-like solutions, based upon ion measurements of major cations, were developed and tested. Haemolymph-like solutions maintained the membrane potential at a relatively constant level, and prolonged the physiological life of the preparations. Synaptic transmission was well-maintained in haemolymph-like solutions, but the excitatory synaptic potentials had a slower time course and summated more effectively with repetitive stimulation, than in standard Drosophila solutions. Voltage-clamp experiments suggest that these effects are linked to more pronounced activation of muscle fiber membrane conductances in standard solutions, rather than to differences in passive muscle membrane properties or changes in postsynaptic receptor channel kinetics. Calcium dependence of transmitter release was steep in both standard and haemolymph-like solutions, but higher external calcium concentrations were required for a given level of release in haemolymph-like solutions. Thus, haemolymph-like solutions allow for prolonged, stable recording of synaptic transmission.