Spontaneous Behavioral Responses Research Articles

A possible role for reactive oxygen species in the regulation of an ultradian rhythm in Paramecium

ABSTRACTReactive oxygen species (ROS) are essential for the viability of cells, while excess levels can be lethal by damaging proteins and nucleic acids. It is imperative to identify and elucidate the various cellular functions for which ROS molecules have a role. In this paper, the role of ROS in the regulation of ultradian rhythms in the ciliated protozoan Paramecium tetraurelia is examined. The frequency of spontaneous behavioral responses in Parameciun display a well-established ultradian rhythm with a periodicity of approximately 50–60 min. The artificial elevation of cytoplasmic ROS concentrations is shown to completely eliminate the rhythm in a reversible manner. Furthermore, the use of RNA interference techniques to knockdown the expression of superoxide dismutase, an enzyme that scavenges excess cytoplasmic ROS, also eliminates the ultradian rhythm. These data indicate that the concentration of ROS plays a role in the generation of the ultradian rhythm. A hypothesis is proposed for the generation of this ultradian rhythm that incorporates a role for ROS.

Differences in Neural Circuitry Guiding Behavioral Responses to Polarized light Presented to Either the Dorsal or Ventral Retina in Drosophila

Linearly polarized light (POL) serves as an important cue for many animals, providing navigational information, as well as directing them toward food sources and reproduction sites. Many insects detect the celestial polarization pattern, or the linearly polarized reflections off of surfaces, such as water. Much progress has been made toward characterizing both retinal detectors and downstream circuit elements responsible for celestial POL vision in different insect species, yet much less is known about the neural basis of how polarized reflections are detected. We previously established a novel, fully automated behavioral assay for studying the spontaneous orientation response of Drosophila melanogaster populations to POL stimuli presented to either the dorsal, or the ventral halves of the retina. We identified separate retinal detectors mediating these responses: the ‘Dorsal Rim Area’ (DRA), which had long been implicated in celestial POL vision, as well as a previously uncharacterized ‘ventral polarization area’ (VPA). In this study, we investigate whether DRA and VPA use the same or different downstream circuitry, for mediating spontaneous behavioral responses. We use homozygous mutants, or molecular genetic circuit-breaking tools (silencing, as well as rescue of synaptic activity), in combination with our behavioral paradigm. We show that responses to dorsal versus ventral stimulation involve previously characterized optic lobe neurons, like lamina monopolar cell L2 and medulla cell types Dm8/Tm5c. However, using different experimental conditions, we show that important differences exist between the requirement of these cell types downstream of DRA versus VPA. Therefore, while the neural circuits underlying behavioral responses to celestial and reflected POL cues share important building blocks, these elements play different functional roles within the network.

The frequency of the spontaneous behavioral response in Paramecium tetraurelia is simultaneously modulated by both ultradian and circadian rhythms

The behavioral response of Paramecium tetraurelia is due to changes in the direction of swimming, which is initiated by the generation of an action potential that causes the re-orientation of the ciliary beat. The frequency of spontaneous behavioral responses displays an ultradian rhythm, with a periodicity of approximately 50 min. Furthermore, this rhythm is disrupted by the addition of LiCl, due to the interruption of the inositol signaling pathway. The present work is an observation of the frequency of the behavioral response for a 72-h period. The frequency of the behavioral response is influenced by a circadian clock, in that the frequency of behavioral responses changes during a 24-h period, while the periodicity of the ultradian clock remains unchanged. The addition of LiCl also disrupts the circadian rhythm, lengthening the circadian period from 24 h to 27.4 h. However, unlike the ultradian rhythm, where the addition of myo-inositol inhibits the LiCl effect, myo-inositol has no effect on the disruption of the circadian rhythm. In order to ascertain the effect of LiCl on the circadian clock, cells were grown in the presence of indirubin, a compound known to inhibit glycogen synthase kinase 3β (GSK3β); this enzyme is also inhibited by LiCl. When cells are incubated with indirubin for several hours, the circadian rhythm is lengthened to approximately 27 h, while the ultradian rhythm is unaffected. Furthermore, a decrease in GSK3β by RNA interference gives similar results. Therefore, the frequency of the behavioral response in Paramecium appears to be controlled by two different biological rhythms.

On the existence of a threshold for preventive behavioral responses to suppress epidemic spreading

The spontaneous behavioral responses of individuals to the progress of an epidemic are recognized to have a significant impact on how the infection spreads. One observation is that, even if the infection strength is larger than the classical epidemic threshold, the initially growing infection can diminish as the result of preventive behavioral patterns adopted by the individuals. In order to investigate such dynamics of the epidemic spreading, we use a simple behavioral model coupled with the individual-based SIS epidemic model where susceptible individuals adopt a preventive behavior when sensing infection. We show that, given any infection strength and contact topology, there exists a region in the behavior-related parameter space such that infection cannot survive in long run and is completely contained. Several simulation results, including a spreading scenario in a realistic contact network from a rural district in the State of Kansas, are presented to support our analytical arguments.

New neostigmine-based behavioral mouse model of abdominal pain

BackgroundAnimal models of visceral pain have gained much attention as an important tool to elucidate the possible mechanisms underlying functional gastrointestinal (GI) disorders. Here we report the development of a new, minimally invasive behavioral model of abdominal pain induced by ip administration of neostigmine in mice. MethodsSpontaneous behavioral responses evoked by ip injection of neostigmine were compared to pain-related behaviors induced by acetic acid solution (ip), mustard oil (MO) and capsaicin (both ic). Pain behaviors were quantified by assessment of defined postures (licking of the abdomen, stretching, squashing of the abdomen and abdominal contractions). Neuronal activation of spinal cord was measured by determining the number of c-Fos-positive cells. ResultsNeostigmine (2.5μg/kg, ip), acetic acid solution (ip), MO and capsaicin (both ic) induced spontaneous behavioral responses in mice, which were blocked by morphine (3mg/kg, ip), suggesting the involvement of pain signaling pathways. Injection of neostigmine enhanced c-Fos expression in spinal cord neurons. ConclusionThe neostigmine model represents a new minimally invasive mouse model to study visceral pain. Based on the neuronal activation pattern in the spinal cord we suggest that this model may be used to study abdominal pain signaling pathways in the GI tract.

Spontaneous behavioral responses in the orofacial region: a model of trigeminal pain in mouse.

To develop a translational mouse model for the study and measurement of non-evoked pain in the orofacial region by establishing markers of nociceptive-specific grooming behaviors in the mouse. Some of the most prevalent and debilitating conditions involve pain in the trigeminal distribution. Although there are current therapies for these pain conditions, for many patients, they are far from optimal. Understanding the pathophysiology of pain disorders arising from structures innervated by the trigeminal nerve is still limited, and most animal behavioral models focus on the measurement of evoked pain. In patients, spontaneous (non-evoked) pain responses provide a more accurate representation of the pain experience than do responses that are evoked by an artificial stimulus. Therefore, the development of animal models that measure spontaneous nociceptive behaviors may provide a significant translational tool for a better understanding of pain neurobiology. C57BL/6 mice received either an injection of 0.9% saline solution or complete Freund's adjuvant into the right masseter muscle. Animals were video-recorded and then analyzed by an observer blind to the experiment group. The duration of different facial grooming patterns performed in the area of injection were measured. After 2 hours, mice were euthanized and perfused, and the brainstem was removed. Fos protein expression in the trigeminal nucleus caudalis was quantified using immunohistochemistry to investigate nociceptive-specific neuronal activation. A separate group of animals was treated with morphine sulfate to determine the nociceptive-specific nature of their behaviors. We characterized and quantified 3 distinct patterns of acute grooming behaviors: forepaw rubbing, lower lip skin/cheek rubbing against enclosure floor, and hindpaw scratching. These behaviors occurred with a reproducible frequency and time course, and were inhibited by the analgesic morphine. Complete Freund's adjuvant-injected animals also showed Fos labeling consistent with neuronal activation in nociceptive-specific pathways of the trigeminal nucleus after 2 hours. These behaviors and their correlated cellular responses represent a model of trigeminal pain that can be used to better understand basic mechanisms of orofacial pain and identify new therapeutic approaches to this common and challenging condition.

Behavioral Effects of Thyroxine in a Lizard (Ameiva undulata: Teiidae)

We investigated the effects of supplemental thyroxine (T₄) and thyroid deficiency on evoked and spontaneous behavioral responses in a lizard (Ameiva undulata). We quantified spontaneous behavior as distance walked without external stimulation and evoked behavior as organismal excitability during the first minute of forced activity on a treadmill, as running time to exhaustion during graded-intensity exercise, and as the outcome of staged competition for prey. Plasma T₄ was reduced to nondetectable levels by surgical thyroidectomy and was increased from 6.4 ± 0.59 to 22.0 ± 3.33 ng/mL (mean ± SE; P < 0.001) by intraperitoneal T₄-pellet implantation. Standard metabolic rate (SMR) was reduced by thyroid deficiency (P = 0.008) but was not stimulated by T₄ supplementation (P = 0.665). Excitability was increased by T₄ (P < 0.025) but was unaffected by thyroid deficiency. Spontaneous behavior was replicable between duplicate trials (r² = 0.47, P < 0.001) but did not differ among hormone treatment groups (P = 0.780) or among excitability categories (P = 0.881). Neither running endurance (P = 0.646) nor the outcome of staged competition for prey (0.05 < P < 0.10) were significantly affected by hormone treatment, and endurance was not correlated with spontaneous behavior (P = 0.148). However, running endurance was significantly lower in lizards of high than low excitability (P = 0.018), and winners in competition trials were usually more excitable than losers (P = 0.057). Physiologically realistic increments in plasma T₄ can increase evoked organismal excitability without being reflected in spontaneous behavior and without stimulating SMR. Excitability is reflected in rapid fatigue during activity and in success during competition for prey. Thyroxine can induce significant behavioral responses without an obligate energetic cost.

Recovery of functions after neonatal or adult hemispherectomy in cats. III. Complex functions: Open field exploration, social interactions, maze and holeboard performances

Complex behavioral patterns were studied in cats with removal of the entire left cerebral hemisphere either as neonates ( n = 10) or adults ( n = 11), and in intact control cats ( n = 24). Adult-lesioned cats showed decreased open field activity in locomotion, rearing and sniffing. Lesioned kittens showed similar deficits at 100 days of age, but by 150 days of age they resembled normal littermates in all 3 measures. In the presence of another cat, adult-hemispherectomized cats violated species-typical body-buffer space, approaching and attacking other cats. By comparison, normal cats never attacked and seldom approached in the open field. Neonatal-lesioned adults showed only occasional approach and a tendency to sit or stiff-walk in the presence of other cats; attacks were rare. Adult-lesioned cats responded poorly to reversal training for preferred arm of a T-maze, whereas neonatal-lesioned adults were significantly more trainable. Similarly, adult-lesioned cats exhibited a search deficit in a baited holeboard, while neonatal-lesioned adults searched normally. Overall, these results demonstrate that in this animal model, enhanced recovery following early vs adult lesions can also be found in relatively complex, spontaneous behavioral responses not previously studied in this regard.