Head Bobs Research Articles

Meta-Analysis Reveals Behavioral Plasticity, Not Agonistic Behavior, Facilitates Invasion of Brown Anoles (Anolis sagrei) and Replacement of Green Anoles (Anolis carolinensis)

In a meta-analysis, we examined the behavioral portfolio of invasive brown anoles (Anolis sagrei) and native green anoles (Anolis carolinensis) in urban and non-urban environments. We hypothesized that invasive anoles would display more agonistic and bold signals (head bobbing, dewlap extensions, and pushups) than their native-range counterparts and their native competitors. We found that in urban settings, anoles of both species signaled more with dewlap extensions than with head bobs. Brown anoles displayed significantly more in non-urban habitats and their native range compared to urban habitats and invasive ranges. The outcome of our analysis suggests that brown anoles have plastic behavioral portfolios, whereas green anoles have relatively balanced preferences for head bobbing, irrespective of the habitat in which the populations were collected. We attribute the success of the brown anole invasion to the flexible strategy in the face of higher mate competition, higher predation risks, and less resource competition in both urban and invasive ranges. Lastly, we observed publication biases. More studies were conducted with urban and invasive brown anoles and specifically in manipulative mesocosm experimental settings—transplanting populations from native field settings. We show this altered the display rates across all studied signals.

The geometry of interpersonal synchrony in human dance

Collective synchronized behavior has powerful social-communicative functions observed across several animal taxa.1,2,3,4,5,6,7 Operationally, synchronized behavior can be explained by individuals responding to shared external cues (e.g., light, sound, or food) as well as by inter-individual adaptation.3,8,9,10,11 We contrasted these accounts in the context of a universal human practice-collective dance-by recording full-body kinematics from dyads of laypersons freely dancing to music in a "silent disco" setting. We orthogonally manipulated musical input (whether participants were dancing to the same, synchronous music) and visual contact (whether participants could see their dancing partner). Using a data-driven method, we decomposed full-body kinematics of 70 participants into 15 principal movement patterns, reminiscent of common dance moves, explaining over 95% of kinematic variance. We find that both music and partners drive synchrony, but through distinct dance moves. This leads to distinct kinds of synchrony that occur in parallel by virtue of a geometric organization: anteroposterior movements such as head bobs synchronize through music, while hand gestures and full-body lateral movements synchronize through visual contact. One specific dance move-vertical bounce-emerged as a supramodal pacesetter of coordination, synchronizing through both music and visual contact, and at the pace of the musical beat. These findings reveal that synchrony in human dance is independently supported by shared musical input and inter-individual adaptation. The independence between these drivers of synchrony hinges on a geometric organization, enabling dancers to synchronize to music and partners simultaneously by allocating distinct synchronies to distinct spatial axes and body parts.

PSII-7 Feed Intake and Behavioral Responses of Mature Rams Provided Feed Containing Phenylthiocarbamide

Abstract Bitter taste perception has been studied in various species, including humans, using the synthetic compound phenylthiocarbamide (PTC). Human perception of PTC is linked to the ability to taste bitter foods. Sheep express varying levels of aversion to PTC delivered in drinking water. The objective of this study was to determine the effects of PTC delivered in feed on dietary intake and behavior in mature rams. We hypothesized that rams previously classified into PTC-taster categories using PTC-spiked drinking water would rank similarly when PTC was added to feed. Mature Targhee, Rambouillet, Polypay, and composite-breed rams, previously classified as either super- (n = 3), intermediate- (n = 5), or non-PTC tasters (n = 4), were subjected to 4-d acclimation and 6-d test phases. Alfalfa (70%), corn (15%), and beat pulp (15%) meal were mixed with ethanol (150 g/kg, as fed) only (control) or PTC solubilized in ethanol (150 g/kg, as fed) to create three pelleted (6.3 mm) test diets (110, 220 and 330 mg PTC/kg feed, as fed). Rams received control and PTC diets (0.87% BW) daily for 30 min in a side-by-side presentation, which was replicated for each PTC concentration. Feeding duration, number of bucket approaches and switches, sniffs, drinks, lip smacks and licks, and head bobs, jerks, and shakes were recorded throughout the trial using video surveillance. For each PTC concentration, consumption of PTC and control diets was similar (P = 0.22) when measured as a percentage of total diet (control + PTC) consumed. Individual PTC diet intakes ranged from 1.5 to 89.8% of total diet consumed. The CV for intake of 110, 220 and 330 mg/kg diets increased from 22.4 to 34.1 to 36.1%, respectively. Intake of total diet offered decreased (P = 0.01) between 110 mg/kg (80.9 ± 3.2%) and 330 mg/kg (72.3 ± 3.2%), while 220 mg/kg (78.4 ± 3.2%) was intermediate (P ≥ 0.06). Rams were classified by average PTC diet consumption relative to ± 1.0 SD of the population mean (50.2 ± 7.5%). Using this method, only 7 of the 12 rams were classified similarly to the former classification established when PTC was added to drinking water. Total feeding duration was less (P ≤ 0.03) when rams were offered 330 mg/kg (805.4 ± 18.2 s) compared with 110 (858.1 ± 19.3 s) and 220 mg/kg (862.7 ± 19.5 s). Rams switched between the control and PTC diets more (P ≤ 0.02) when offered 110 mg/kg (21.2 ± 10.0) than the 220 (16.4 ± 7.8) and 330 mg/kg (18.4 ± 8.4). These results suggest that sheep perceive and exhibit variable responses to PTC when incorporated into a pelleted feed. More research is needed to identify mechanisms by which sheep perceive bitter-tasting feeds.

Context dependence of head bobs in gerbils and potential neural contributions

Headbobs are up-down movements of the cranium associated with the use of motion parallax for depth perception. Mongolian gerbils (aka jirds; Meriones unguiculatus) often execute a series of headbobs prior to jumping between surfaces. Gerbils were tested in a jumping stand task and headbobs videotaped under three light levels approximating low daylight, dawn/dusk, and moonlight across a range of distances to target. Headbobs per trial increased linearly with increasing distance to the target platform, whereas headbob frequency (rate of headbobbing pre-jump on the start platform) increased with gap distance up to an intermediate level and then decreased. Overall, gerbils made the most headbobs per trial under the darkest conditions, whereas their headbobbing rate was highest for medium illumination, especially for medium-long gap distances. There was a positive correlation between headbob frequency and volume of the superior colliculus (SC), but no relationship between headbobs and relative size of the temporo-posterior (TP) visual cortex. The results suggest that gerbils employ a specific visuomotor strategy for depth perception differentially under different conditions. We suggest that the deployment of headbobs under specific conditions may be part of an SC-driven vigilant state, of which more rapid sampling of the visual environment using headbobs for depth estimation is one component. Moreover, the findings highlight the importance of considering ecological factors in designing studies of visual behavior and its underpinnings in rodents.

Head bobbing gives pigeons a sense of perspective

Having your eyes stuck on the side of your head is great to avoid turning up on someone else's menu. Providing almost 360 deg vision, wide-set eyes give pigeons the best chance of escape. But they also have lousy stereo vision. With little overlap between the views of both eyes, no one knew whether the birds are able to perceive depth or are trapped in a flat panorama: cue the comical walk. Pigeons are easily recognised from their eccentric gait, bobbing their heads to and fro. The head movement allows the goofy birds to stabilise their vision when strutting forward, by essentially holding the head still when the head bobs back. The question was, could the birds take advantage of the rapid rebound, when the head bobs forward, to help them to gauge the depth and distance of objects? To find out, Yuya Hataji, Hika Kuroshima and Kazuo Fujita, from Kyoto University, Japan, played some sleight of hand on the birds to find out whether their ungainly deportment allows them to distinguish near from far.But first the team had to train the pigeons to peck at a dot on a TV screen to tell the researchers whether it was small or large. After showing each pigeon five static individual dots on a grid, each the same size, the team then provided the bird with a choice of squares that they could peck to tell the researchers whether the dot was small (selecting the left square) or large (right square). ‘The pigeons learned to do this in a few sessions since we have a lot of experience training pigeons on similar perceptual tasks’, says Hataji. Once the discs had got the birds’ attention and the animals were reliably distinguishing between the small (14.9–20.5 mm) and large (21.7–29.7 mm) dots, Hataji turned up the pressure. Now the discs began roving across the screen, so that the pigeons had to move their heads to keep track of them. Hataji rigged two cameras to monitor the birds’ head motion, and adjusted the movement of the dots depending on whether he wanted the dot to jump out of the screen – moving it in the opposite direction from the pigeon's head – or slide behind the screen – moving the dot in the same direction as the pigeon's head. Then he filmed each pigeon to find out how close it got to the screen before pecking at the dot. ‘Pigeons hold their head at a constant distance before pecking’, says Hataji, so if the bobbing head movements were helping the pigeons judge distance, then they would crowd the screen when the dot appeared farther away and stand well back when the dot jumped out at them.Impressively, the pigeons could tell when the dots were in front of or behind the screen. The resourceful birds are able to determine how near or far objects are, thanks to their goofy head movements. Objects in the foreground seem to move differently from farther back objects as the pigeons move their heads, telling the birds which objects are near and which are distant. In addition, the birds were still able to differentiate between small and large dots, so head movements don't contribute to the bird's ability to determine size, although they did ponder longer before landing a peck when presented with intermediate-sized dots that were more difficult to categorise.Despite their bird-brained reputation, pigeons take advantage of their unconventional gait to overcome their wide-eyed disadvantage. Bobbing their heads to and fro gives the birds a sense of perspective, allowing them to land pecks whether the target is near or far.

Aggression, color signaling, and performance of the male color morphs of a Brazilian lizard (Tropidurus semitaeniatus)

Behavior can help to establish dominance in intrasexual interactions, preventing more costly aggressive interactions and improving access to mates. Distinct color morphs often correlate with behavior, driving differential reproductive success between them. The lizard Tropidurus semitaeniatus usually expresses two male color morphs, Yellow or Black. It is likely that morphs play a role in reproduction, which is still unexplored. Here, we test whether there is morph-related dominance during intrasexual interactions. We used ex situ behavioral trials to test whether a particular morph shows dominance, gathering dominance by attributing scores to aggressive/evasive behaviors. We also tested whether winner individuals show higher performance (sprint speed), and whether spectrophotometric measures of body coloration predict winners of male encounters. Morphs showed differences in behaviors suggesting alternative behavioral tactics: Black males behave more aggressively and less evasively while Yellow males show the opposite sets of behavior. Black males also tend to be dominant, but dominants do not show higher sprint speeds than submissive males. Chest coloration, often displayed during encounters, highly predicts winnings (particularly high yellow chroma and low lightness and UV). Our results show that lizards signal competitive condition by behaviorally exposing their chest. Males displaying more head bobs and with darker chests are more likely to win encounters. Our results suggest that Yellow males might undertake a sneaker tactic, preventing aggression costs by evasiveness even though they might perform similarly to Black males. Further studies should address whether female preference is biased in relation to male morphs and its colorations, which would suggest selective processes towards costly signals and morph maintenance. In the struggle for survival and reproduction, often, there is no single best strategy and multiple distinct tactics may evolve. Behavior, color signaling, and performance are frequently correlated with distinct color morphs, which can coexist as alternative mating tactics. However, studies that are able to integrate all these traits are scarce. Here, we test whether different color morphs of the lizard Tropidurus semitaeniatus show different behaviors and dominance patterns. We also test whether these color morphs differ in their performances (sprint speed) and visual signaling (behavioral displays and intensity of coloration). We demonstrate that Black and Yellow-morph males adopt distinct behavioral tactics: an aggressive (Black-morph) and an evasive (Yellow-morph) tactic. We also show that dominance is highly correlated to chest’s intensity of dark yellow colorations and that lizards signal their dominance status through displays of head bob bouts.

Maternal behaviour in response to predation threats in a vulnerable lizard from Patagonia, Argentina

AbstractClimatic and ecological conditions can determine the existence and degree of parental care. In species that live in cold‐temperate environments and exhibit high reproductive effort it is expected that parental care would have greater selective value. In this study, we aimed to detect maternal behavioural responses to predation threats in the lizard Phymaturus spectabilis from cold‐climate environments of Patagonia, Argentina. Seventeen females with their offspring each were exposed to four treatments in the laboratory: first a treatment with no stimulus, and then in a random order a carnivorous sympatric lizard, a conspecific male and a simulated flight of a museum mount of a raptor. We analysed the occurrence of 11 specific behaviours. Two clearly different parental responses occurred. In the presence of the raptor, mothers stayed near the offspring and remained motionless longer than in the other treatments. Their freezing response is consistent with their cryptic coloration and this species may rely on this strategy to avoid raptor predation. In contrast, in the presence of the predator lizard, mothers presented higher frequencies of flights, tail waves and head bobs. Head bobs are commonly interpreted as dissuasive signals to the predator to discourage attack. The behaviours observed in P. spectabilis together with similar behaviours observed in congeneric species would suggest the existence of a common pattern of parental care related to the high reproductive investment in Phymaturus.

Behavioural persistence during an agonistic encounter differentiates winners from losers in green anole lizards

Agonistic encounters featuring ritualized displays precede the establishment of dominance relationships in many animals. We investigated the predictive value of the amount of display behaviour (number and duration of displays) vs. quickness to display (latency to express a display behaviour) in determining the outcome of aggressive interactions and establishment of dominant vs. subordinate status in male green anole lizards, Anolis carolinensis. Similar-sized males were paired and observed for ninety minutes as they established social status. We recorded the number, duration (where appropriate) and latencies to first expression for multiple behavioural display components (head bob A, B and C, dewlap displays, open mouth displays, pushups, lateral displays) and colour changes (eyespot presence and body colour changes). Males that eventually won and became the dominant male had significantly higher counts and durations with the exception of Bob C counts, pushup counts and open mouth duration. Future dominants also maintained a green body colour longer than future subordinates, which had brown shades more often and for longer durations. Latency to first express a display component was shorter in future dominants for head bobs A and C, dewlap and open mouth displays when all data were considered. However, all significant latency differences disappeared when data only from pairs in which both males displayed a behaviour were included in the analysis. Counts, durations, and latencies were highly correlated with each other within individuals. The results indicate that behavioural display patterns during an initial display contest predict the outcome of the interaction, with the amount of display behaviour being the best predictor of whether a male will win or lose the contest and hence become dominant or subordinate. These results are consistent with the idea that displays are honest signals of a male’s physiological capacity or stamina, and hence fighting and resource holding ability.

Rival assessment and comparison of morphological and performance-based predictors of fighting ability in Lake Eyre dragon lizards, Ctenophorus maculosus

Although the outcome of contests is often critical to fitness, we still have much to learn regarding the reliability of different predictors of fighting ability (e.g. morphological traits versus performance measures) and the strategies individuals use to decide when to withdraw. We examined predictors of contest success and assessment strategies in staged contests between male Lake Eyre dragon lizards, Ctenophorus maculosus, in which males engage in escalated contests. Bite force was the only significant predictor of contest success. Although head width and depth predicted the number and duration of bites during contests, neither of these traits predicted contest outcome, nor did body size or experience in the prior two contests. These results support the view that measures of physical performance may be more reliable indicators of male fighting ability in escalated contests than morphological traits, because performance is more directly linked to the quality being signalled (i.e. fighting ability). Contest intensity was positively associated with the resource holding potential (RHP) of the loser, but not that of the winner or RHP asymmetry, indicating that individuals base their decision to withdraw on assessment of their own cost threshold (self-assessment) rather than assessment of their opponent’s ability (mutual assessment). Lastly, the number of displays (head bobs and push-ups) was also correlated with the RHP of losers (but not winners or RHP asymmetry), consistent with the recently proposed ‘information conflict hypothesis’, which predicts that weaker individuals should limit information transfer about their ability by performing fewer displays.

Predation reduces visual communication distance in an Anolis lizard.

In his book Descent of Man and Selection in Relation to Sex, Darwin (1) made a compelling argument that evolution could not be explained solely on the basis of differential survival (natural selection). In particular, traits that enhance an individual’s reproductive success (sexual selection) often decrease its chances of survival. For example, the risks of injury and death can be high for males that fight for direct access to females or for territories that contain resources needed by females. Courtship ornaments and displays, which often determine territorial ownership or mating success, are not only energetically costly but frequently result in increased chances of predation. Some of the most striking and well-documented examples of the latter phenomenon involve reductions in sexual ornaments and modifications of behavior that reduce the conspicuousness of courting individuals in areas where predation is high compared with areas where predators are absent or uncommon (2, 3). These changes almost certainly increase survivorship at the expense of less effective territorial defense and lower mating success. In PNAS, Steinberg et al. (4) found that males of a semiarboreal lizard, the brown anole (Anolis sagrei), on islands in the Bahamas where a predator was introduced show a significant reduction in the amplitude of head bobs compared with lizards from predator-free islands. This behavioral change reduces the communication range of these visual signals, thus lowering the chances of being detected by a predator. By the same token, such signals are likely to be less effective in repelling more distant territorial rivals and attracting potential mates. Whereas a common response to predation is to reduce the duration or frequency of their displays (5), the main change in A. sagrei on islands with predators was head-bob amplitude, a display component used in territorial defense and mate attraction.

Serotonin<sub>2c</sub> Receptor Constitutive Activity: In vivo Direct and Indirect Evidence and Functional Significance

Serotonin2c (5-HT2c) receptors are widely expressed in the central nervous system where they play a pivotal role in the regulation of neuronal network excitability. Along with this fundamental physiological function, 5-HT2c receptors are thought to be implicated in the pathophysiology of several neuropsychiatric disorders and have become a major pharmacological target for the development of improved treatments of these disorders. In the past decade, many studies have focused on the constitutive activity of 5-HT2c receptors and the therapeutic potential of drugs acting as inverse agonists. Although the constitutive activity of the 5-HT2c receptor has been clearly described in vitro, the transposition of this concept to living animals is often difficult to ascertain. Nevertheless, cumulating evidence has demonstrated the functional relevance of such property in regulating physiological systems in vivo both at the level of the central and peripheral nervous systems. The present review provides an update of the growing number of studies that show, by means of pharmacological tools, the participation of the constitutive activity of 5-HT2c receptors in the control of various biochemical and behavioural functions in vivo and emphasizes the functional organization of this constitutive control together with the phasic and tonic (involving the spontaneous release of 5-HT) modalities of the 5-HT2c receptor in the brain.

Phospholipase C mediates (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI)-, but not lysergic acid diethylamide (LSD)-elicited head bobs in rabbit medial prefrontal cortex

The phenethylamine and indoleamine classes of hallucinogens demonstrate distinct pharmacological properties, although they share a serotonin2A (5-HT2A) receptor mechanism of action (MOA). The 5-HT2A receptor signals through phosphatidylinositol (PI) hydrolysis, which is initiated upon activation of phospholipase C (PLC). The role of PI hydrolysis in the effects of hallucinogens remains unclear. In order to better understand the role of PI hydrolysis in the MOA of hallucinogens, the PLC inhibitor, 1-[6-((17β-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-1H-pyrrole-2,5-dione (U73122), was used to study the effects of two hallucinogens, the phenethylamine, (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), and the indoleamine, lysergic acid diethylamide (LSD). PI hydrolysis was quantified through release of [3H]inositol-4-phosphate from living rabbit frontocortical tissue prisms. Head bobs were counted after hallucinogens were infused into the medial prefrontal cortex (mPFC) of rabbits. Both DOI and LSD stimulated PI hydrolysis in frontocortical tissue through activation of PLC. DOI-stimulated PI hydrolysis was blocked by 5-HT2A/2C receptor antagonist, ketanserin, whereas the LSD signal was blocked by 5-HT2B/2C receptor antagonist, SB206553. When infused into the mPFC, both DOI- and LSD-elicited head bobs. Pretreatment with U73122 blocked DOI-, but not LSD-elicited head bobs. The two hallucinogens investigated were distinct in their activation of the PI hydrolysis signaling pathway. The serotonergic receptors involved with DOI and LSD signals in frontocortical tissue were different. Furthermore, PLC activation in mPFC was necessary for DOI-elicited head bobs, whereas LSD-elicited head bobs were independent of this pathway. These novel findings urge closer investigation into the intracellular mechanism of action of these unique compounds.

Serotonergic and dopaminergic distinctions in the behavioral pharmacology of (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) and lysergic acid diethylamide (LSD)

RationaleAfter decades of social stigma, hallucinogens have reappeared in the clinical literature demonstrating unique benefits in medicine. The precise behavioral pharmacology of these compounds remains unclear, however. ObjectivesTwo commonly studied hallucinogens, (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) and lysergic acid diethylamide (LSD), were investigated both in vivo and in vitro to determine the pharmacology of their behavioral effects in an animal model. MethodRabbits were administered DOI or LSD and observed for head bob behavior after chronic drug treatment or after pretreatment with antagonist ligands. The receptor binding characteristics of DOI and LSD were studied in vitro in frontocortical homogenates from naïve rabbits or ex vivo in animals receiving an acute drug injection. ResultsBoth DOI- and LSD-elicited head bobs required serotonin2A (5-HT2A) and dopamine1 (D1) receptor activation. Serotonin2B/2C receptors were not implicated in these behaviors. In vitro studies demonstrated that LSD and the 5-HT2A/2C receptor antagonist, ritanserin, bound frontocortical 5-HT2A receptors in a pseudo-irreversible manner. In contrast, DOI and the 5-HT2A/2C receptor antagonist, ketanserin, bound reversibly. These binding properties were reflected in ex vivo binding studies. The two hallucinogens also differed in that LSD showed modest D1 receptor binding affinity whereas DOI had negligible binding affinity at this receptor. ConclusionAlthough DOI and LSD differed in their receptor binding properties, activation of 5-HT2A and D1 receptors was a common mechanism for eliciting head bob behavior. These findings implicate these two receptors in the mechanism of action of hallucinogens.

The Game of Life

The Game of Life Lisa Ohlen Harris (bio) 1 We’re always a little carsick when we crest that last hill in the coast range and the Pacific comes into view, sparkling in sunlight or gray and choppy on a stormy day. My girls stretch to see the water, while Todd reminds them to stay safely buckled in. I roll down the window. “Smell that salt air,” I say, and we breathe it in. After the last fifty or so miles twisting through the Siuslaw National Forest on U.S. Route 20, we’re relieved to reach the coast. Todd parks and we walk down to the beach, perching on driftwood logs at the base of the sea wall to remove our shoes. Twelve-year-old Ashley and I walk barefoot along the hard, wet sand left foamy by the outgoing tide. Ashley points to a place between the lines of waves. “Look, a seal!” A slick brown head bobs in the water, looking right at us with wide seal eyes. “We saw seals at Camp Westwind,” Ashley says. Her sixth-grade camp, two weeks ago, was just up the coast from here. “Mom, did you know people used to think seals were mermaids?” “I’ve heard that. You’d have to be out at sea for an awful long time to imagine a seal as a beautiful woman.” “Half woman, half fish, Mom. I can see why. It’s their eyes.” [End Page 27] I watch the seal, who meets my gaze. The seal’s eyes do look human, almost as if she knows things I don’t. Ashley bends to look more closely at shell fragments in the wet sand. The seal ducks under a wave and disappears. 2 Severed between the elbow and wrist. She’d caught it in some kind of machinery. “A tragedy,” Michael, my boss, said. “Keep José’s mother in your prayers.” “Where does she work?” I asked. “I’m not sure,” Michael answered. “They had just returned from a trip to Mexico, and now this.” José and I teach at a small Christian college in Oregon. We’re both adjunct instructors, both new to the department. I hardly know him, really. That evening I found more information online. It was a plant nursery. She’d been separating bulbs with some sort of hydraulic cutter. Coworkers rushed to her aid, recovered the severed arm, and gave it to the Life Flight paramedics. The reattachment surgery took more than ten hours. The article didn’t mention that she’d just come back from Mexico. Jet lag, I thought. She was too tired to safely operate the machinery. Except that Mexico is, of course, in the same time zones as the western U.S. She may have been tired, but no more so than someone who just returned to Portland from Dallas. Below the article was a space for comments. One reader, who sounded like a bossy older brother, said that machines such as this usually have safety features, which workers sometimes override in an effort to boost productivity. Through misspellings and poor grammar, most of the comments blamed the victim. As much as I knew I shouldn’t, I found myself nodding in agreement. Agreeing so I could distance myself from the possibility of the blade falling on my mother, my husband, my children. I want to believe if we never override safety features, if we don’t go to work jetlagged, we’ll be safe. I want to think these things only happen to people who don’t speak English, to those without training, to those who don’t take precautions. [End Page 28] 3 I place the tiny pink stick person into the plastic car that serves as my game piece. “I’m going to see what my life would have been like if I hadn’t gone to college,” I tell my girls. They’re shocked. “We always go to college when we play Life,” my eldest says. “It’s the game of Life,” I tell her. In this version of Life, from the eighties, higher education makes no difference. I select my occupation from the same set of cards as...

Intrahippocampal LSD accelerates learning and desensitizes the 5-HT2A receptor in the rabbit, Romano et al.

Parenteral injections of d-lysergic acid diethylamide (LSD), a serotonin 5-HT(2A) receptor agonist, enhance eyeblink conditioning. Another hallucinogen, (±)-1(2, 5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI), was shown to elicit a 5-HT(2A)-mediated behavior (head bobs) after injection into the hippocampus, a structure known to mediate trace eyeblink conditioning. This study aims to determine if parenteral injections of the hallucinogens LSD, d,l-2,5-dimethoxy-4-methylamphetamine, and 5-methoxy-dimethyltryptamine elicit the 5-HT(2A)-mediated behavior of head bobs and whether intrahippocampal injections of LSD would produce head bobs and enhance trace eyeblink conditioning. LSD was infused into the dorsal hippocampus just prior to each of eight conditioning sessions. One day after the last infusion of LSD, DOI was infused into the hippocampus to determine whether there had been a desensitization of the 5-HT(2A) receptor as measured by a decrease in DOI-elicited head bobs. Acute parenteral or intrahippocampal LSD elicited a 5-HT(2A) but not a 5-HT(2C)-mediated behavior, and chronic administration enhanced conditioned responding relative to vehicle controls. Rabbits that had been chronically infused with 3 or 10nmol per side of LSD during Pavlovian conditioning and then infused with DOI demonstrated a smaller increase in head bobs relative to controls. LSD produced its enhancement of Pavlovian conditioning through an effect on 5-HT(2A) receptors located in the dorsal hippocampus. The slight, short-lived enhancement of learning produced by LSD appears to be due to the development of desensitization of the 5-HT(2A) receptor within the hippocampus as a result of repeated administration of its agonist (LSD).

The role of serotonin-2 (5-HT2) and dopamine receptors in the behavioral actions of the 5-HT2A/2C agonist, DOI, and putative 5-HT2C inverse agonist, SR46349B

Atypical antipsychotic efficacy is often attributed to actions at serotonin-2 (5-HT(2)) and dopamine receptors, indicating a potential benefit of understanding the interplay between these systems. Currently, it is known that 5-HT(2) receptors modulate dopamine release, although the role of specific dopamine receptors in 5-HT(2)-mediated behavior is not well understood. We examined the role of 5-HT(2A), 5-HT(2C), and dopamine (D1 and D2) receptors in the behavioral response to a 5-HT(2A/2C) agonist (DOI) and 5-HT(2A/2C) antagonist (SR46349B). Effects were assessed by measuring rabbit head bobs (previously characterized as 5-HT(2A) receptor-mediated) and body shakes (5-HT(2C)-mediated). As expected, DOI produced head bobs and body shakes, and these DOI-elicited behaviors were attenuated by the SR46349B pretreatment. Unexpectedly, SR46349B also induced head bobs when administered alone. However, SR46349B-elicited head bobs are distinguishable from those produced by DOI since the 5-HT(2A) antagonist, ketanserin, only attenuated DOI-elicited head bobs. Conversely, 5-HT(2C) ligands (SB242084 and SB206553) inhibited SR46349B but not DOI-induced head bobs. Furthermore, when administered alone, SB206553 (a 5-HT(2C) inverse agonist) produced head bobs, indicating the behavior can be either 5-HT(2A) or 5-HT(2C) mediated. Next, it was revealed that D1 and D2 receptors play a role in DOI-elicited head bobs, but only D1 receptors are required for SR46349B-elicited head bobs. 5-HT(2A) receptor agonism and 5-HT(2C) inverse agonism produce the same behavior, likely due to similar downstream actions at D1 receptors. Consequently, 5-HT(2C) agonism or D1 agonism may be effective therapies for disorders, such as schizophrenia, currently being treated with 5-HT(2A) antagonists.

Serotonin 2C (5‐HT2C) receptor inverse agonists elicit head bob behavior through a dopamine D1 receptor dependent mechanism

Rabbit head bobs and rodent head twitches are behavioral assays of serotonin (5‐HT)2A receptor activation; each behavior can be elicited by DOI (a 5‐HT2A/2C agonist) and attenuated by ketanserin (a 5‐HT2A antagonist). 5‐HT2A receptor antagonists M100907 (M100) and MDL11939 (MDL) also elicit head bobs; however, these effects are distinguishable from DOI‐elicited responses as they are not blocked by ketanserin, suggesting a mechanism other than 5‐HT2A receptor activation. The current study examined the potential role of 5‐HT2C and dopamine (DA) receptors in inducing head bobs. Pre‐administration of the 5‐HT2C antagonist, SB242084 (1umol/kg, sc, 30 min) reduced head bobs elicited by both M100 (2.5umol/kg) and MDL (3umol/kg). Pretreatment of rabbits with the D1 antagonist SCH23390 (0.05umol/kg) also blocked M100 and MDL elicited head bobs. Moreover, administration of a D1 agonist, SKF38393 (9umol/kg) increased head bobs. To further characterize the role of 5‐HT2C receptors, we tested the response to a 5‐HT2C inverse agonist, SB206553. At a dose of 1umol/kg, we found no effect; however, a higher dose (3umol/kg) significantly increased head bobs. Consequently, head bobs may be considered an in vivo measure of 5‐HT2C inverse agonism. Finally, given the role of 5‐HT in DA release, we conclude that SB206553, M100, and MDL all induce the same behavior through 5‐HT2C inverse agonist‐mediated activation of D1 receptors.

Daily Activity Budgets for Neonate and Adult Sceloporus jarrovii and Adult Sceloporus virgatus in Southeastern Arizona

Predators must balance their time between foraging (searching for and capturing food) and other necessary behaviors, such as courtship, mating, territoriality, and predator avoidance. The purpose of this study was to determine how much time two lizard species (Sceloporus jarrovii and Sceloporus virgatus) spent in foraging, aggressive, general maintenance, and basking behaviors. Two age classes of S. jarrovii were examined in this study, neonate and adult, whereas only adults of S. virgatus were studied. Lizards were observed for 30-min intervals from late May through July in 2004 and 2005 at two research sites in southeastern Arizona. Neonatal S. jarrovii spent more time running and foraging during observational intervals than did adults of either species, which may be a result of their higher metabolic needs. Adult S. virgatus spent more time doing head bobs than did either age class of S. jarrovii, possibly explained by the notion that this behavior is used for both aggression and courtship and both were occurring for S. virgatus during the study. In contrast, adult S. jarrovii spent little time in head bobs, because courtship and mating in this species were not occurring during the time of the study. Very little time was spent actively foraging by any subject lizard group, because the majority of time was spent immobile, likely basking or passively searching for prey. Differential amounts of time spent in the various measured behaviors can be explained by the reproductive or developmental state of the lizards involved.

SR46349B elicits head bobs in the rabbit via dopamine D1 receptors

Rabbit head bobs are analogous to rodent head twitches and are behavioral assays of serotonin (5HT)2A receptor activation. Both are elicited by the 5HT2A/2C receptor agonist DOI and this effect is attenuated by the 5HT2A antagonist ketanserin. We have demonstrated that the 5HT2A antagonist, SR46349B (SR; Sanofi‐Synthelabo Recherche) induces rabbit head bobs which are not blocked by ketanserin thus SR does not elicit head bobs as a partial agonist at 5HT2A receptors. The current study was designed to determine if SR elicits head bobs via interaction with dopamine D1 receptors. The D1 antagonist SCH 23390 (0.05μmol/kg) was administered to New Zealand rabbits 30 min prior to DOI (0.3μmol/kg) or SR (0.26μmol/kg). In confirmation to the results obtained in rats, SCH23390 significantly attenuated DOI elicited head bobs. Similarly, SCH23390 also significantly attenuated SR elicited head bobs. SCH23390 exhibits high affinity for the D1 receptor and 25 fold lower affinity for the 5HT2A receptor. Thus, it may act as a competitive antagonist to inhibit DOI elicited head bobs. However, since ketanserin does not attenuate SR elicited head bobs, the ability of SCH23390 to interact with 5HT2A receptors cannot account for the inhibition. These results suggest DOI mediates head bobs via the expected 5HT2A receptor mechanism, but SR induces the same behavior by increasing extracellular dopamine. (MH‐16841‐39; J. A. Harvey)

Behavioral response to emotional stress in rabbits: role of serotonin and serotonin2A receptors

Exposure to a novel environment is a stressor which modulates behavior, increases stress hormones and enhances the release of several neurotransmitters including serotonin (5-HT). Exposing rabbits to a novel environment significantly increases head-bob behavior but fails to alter either grooming or wet dog shakes compared with those observed in the home-cage. The goal of this study was to determine the role of 5-HT and its receptors in mediating novelty-elicited head-bob behavior. Reduction of central 5-HT levels after treatment with the serotonergic neurotoxin 5,7-DHT significantly decreased novelty-elicited head bobs by 40% compared with those in sham-lesioned rabbits, indicating that 5-HT mediates, in part, this behavior. Additionally, pretreatment with the 5-HT1A partial agonist and clinically used anxiolytic buspirone also significantly attenuated novelty-elicited head bobs. Pretreatment with the selective 5-HT2A antagonist M 100,907 significantly reduced novel environment-elicited head bobs by 40%. Furthermore, agonist-induced reduction of cortical 5-HT2A receptor density resulted in a significant 40% reduction in the number of head bobs elicited by the novel environment. These data demonstrate that rabbit head-bob behavior, an index of the response to novelty stress, is mediated, in part, by 5-HT activation of 5-HT2A receptors.