Endogenous cholinergic inputs and local circuit mechanisms govern the phasic mesolimbic dopamine response to nicotine

Nicotine exerts its reinforcing action by stimulating nicotinic acetylcholine receptors (nAChRs) and boosting dopamine (DA) output from the ventral tegmental area (VTA). Recent data have led to a debate about the principal pathway of nicotine action: direct stimulation of the DAergic cells through nAChR activation, or disinhibition mediated through desensitization of nAChRs on GABAergic interneurons. We use a computational model of the VTA circuitry and nAChR function to shed light on this issue. Our model illustrates that the α4β2-containing nAChRs either on DA or GABA cells can mediate the acute effects of nicotine. We account for in vitro as well as in vivo data, and predict the conditions necessary for either direct stimulation or disinhibition to be at the origin of DA activity increases. We propose key experiments to disentangle the contribution of both mechanisms. We show that the rate of endogenous acetylcholine input crucially determines the evoked DA response for both mechanisms. Together our results delineate the mechanisms by which the VTA mediates the acute rewarding properties of nicotine and suggest an acetylcholine dependence hypothesis for nicotine reinforcement.Peer reviewe

The nest-holding grass goby (Zosterisessor ophiocephalus) male adjusts the spawning activity in relation to parasitic nest intrusions.

This study examines the temporal pattern of spawning behavior by the territorial (i.e. nest-holding) grass goby male, Zosterisessor ophiocephalus, in response to sneak intrusions by the small parasitic male under controlled laboratory conditions. The spawning activity of the territorial male consists of a sequence of upside-down movements on the ceiling of the nest accompanied by undulations of the body and sperm release. Five pairs of one territorial male and one parasitic male, each kept inside a large tank provided with an artificial buried nest (always occupied by the territorial male) and one small tunnel-shaped shelter (always occupied by the small male), were observed during one-female spawning taking place in the innermost part of the nest (i.e. the nest chamber). During the spawning, the presence of the small male nearby the nest openings elicited aggressive behavior and increased nest patrolling by the territorial male. In one spawn the small male never attempted to enter the nest. In four spawns the small male entered one to three times the nest chamber (sneaks), staying there from 2 to 203 s until the large male chased him away. The temporal patterning of the spawning activity by the territorial male (bouts of upside-down, U-D), and its changes following a sneak by the small male, were investigated using bout analysis and correlative tests. Results showed the length of bouts U-D did not change significantly after a sneak intrusion. whereas gap length (i.e. the period between subsequent bouts U-D) decreased significantly after each sneak intrusion. The mean duty cycle of bouts U-D tended to be positively correlated to the number of sneaker intrusions of each replicate. Results are discussed in the light of current knowledge on sperm competition among externally fertilizing teleosts

Fostering appropriate behaviour in rehabilitant orangutans (Pongo pygmaeus)

Rehabilitation centres in Indonesia and Malaysia accommodate displaced orangutans (Pongo pygmaeus and P. abelii) and aim to facilitate their release into the wild by developing in them the skills that are necessary for survival. Regular forest excursions are provided but their efficacy in improving learning of appropriate behaviours is unknown. We observed forty rehabilitating orangutans from the Orangutan Care and Quarantine Centre during three forest excursions each to determine whether their behaviour fostered the development of survival skills. In total 38% of their time was spent in locomotion, particularly quadrupedal arboreal travel (13%), walking (8%), climbing (7%) and vine-swinging (4%). 26.5% of their time was spent 5 m or more from the ground, at heights up to 25 m. Arboreal activities were more 2 common early in the excursions and interaction with c are-givers more common later (hour 1: 0.3% of time; hour 5: 0.9% of time). Animals of lower body weight were significantly more likely to engage in arboreal movement, locomotion in general, eating of bark and leaves, and social play, and less likely to eat insects. Those that had been at the Centre the longest were less likely to perform arboreal activities and significantly more likely to be found standing and at ground level, than those that were there for a shorter time. During this study, many forest food items were consumed, particularly leaves and fruit, but also invertebrates and bark. Little time was spent in sexual behaviour, tool use, nest building or socially-mediated learning, but social play occupied almost 6% of their time. We conclude that regular excursions into the forest are likely to assist in the development of locomotion and feeding skills for survival in rehabilitating orangutans, but special attention is needed to encourage nest building, social activities and arboreal activity. Animals least likely to benefit are heavy animals and those that have been captive for a long time

Neonatal imitation predicts infant rhesus macaque (Macaca mulatta) social and anxiety-related behaviours at one year

The identification of early markers that predict the development of specific social trajectories is critical to understand the developmental and neurobiological underpinnings of healthy social development. We investigated, in infant rhesus macaques (Macaca mulatta), whether newborns’ capacity to imitate facial gestures is a valid predictive marker for the emergence of social competencies later in development, at one year of age. Here we first assessed whether infant macaques (N = 126) imitate lipsmacking gestures (a macaque affiliative expression) performed by a human experimenter in their first week of life. We then collected data on infants’ social interactions (aggression, grooming, and play) and self-scratching (a proxy indicator of anxiety) at 11–14 months when infants were transferred into a new enclosure with a large social group. Our results show that neonatal imitators exhibit more dominant behaviours, are less anxious, and, for males only, spend more time in play at one year old. These findings suggest that neonatal imitation may be an early predictor of infant sociality and may help identify infants at risk of neurodevelopmental social deficits