Disrupted social development enhances the motivation for cocaine in rats

for behavioural development. In particular, social play behaviour during post-weaning development is thought to facilitate the attainment of social, emotional and cognitive capacities. Conversely, social insults during development can cause longlasting behavioural impairments and increase the vulnerability for psychiatric disorders, such as drug addiction. Objectives The aim of this study was to investigate whether a lack of social experiences during the juvenile and early adolescent stage, when social play behaviour is highly abundant, alters cocaine self-administration in rats. Methods Rats were socially isolated from postnatal days 21 to 42 followed by re-socialization until adulthood. Cocaine selfadministration was then assessed under a fixed ratio and progressive ratio schedule of reinforcement. Next, cue, cocaine and stress-induced reinstatement of cocaine seeking was determined following extinction of self-administration. Results Early social isolation resulted in an enhanced acquisition of self-administration of a low dose (0.083mg/infusion) of cocaine, but the sensitivity to cocaine reinforcement, assessed using a dose–response analysis, was not altered in isolated rats. Moreover, isolated rats displayed an increased motivation for cocaine under a progressive ratio schedule of reinforcement. Extinction and reinstatement of cocaine seeking was not affected by early social isolation. Conclusions Early social isolation causes a long-lasting increase in the motivation to self-administer cocaine. Thus, aberrations in post-weaning social development, such as the absence of social play, enhance the vulnerability for drug addiction later in life

Male Wistar rats show individual differences in an animal model of conformity

Conformity refers to the act of changing one’s behaviour to match that of others. Recent studies in humans have shown that individual differences exist in conformity and that these differences are related to differences in neuronal activity. To understand the neuronal mechanisms in more detail, animal tests to assess conformity are needed. Here, we used a test of conformity in rats that has previously been evaluated in female, but not male, rats and assessed the nature of individual differences in conformity. Male Wistar rats were given the opportunity to learn that two diets differed in palatability. They were subsequently exposed to a demonstrator that had consumed the less palatable food. Thereafter, they were exposed to the same diets again. Just like female rats, male rats decreased their preference for the more palatable food after interaction with demonstrator rats that had eaten the less palatable food. Individual differences existed for this shift, which were only weakly related to an interaction between their own initial preference and the amount consumed by the demonstrator rat. The data show that this conformity test in rats is a promising tool to study the neurobiology of conformity

Hond met hernia

Mens en dier delen dezelfde ziektes. Daarom werken dierenartsen en mensendokters wereldwijd steeds meer samen. Beide specialisten kunnen veel van elkaar leren

Use of epidurally derived evoked potentials for quantification of caudal nociception in ponies

Am J Vet Res. 2009 Jul;70(7):813-9. Use of epidurally derived evoked potentials for quantification of caudal nociception in ponies. van Loon JP, Stienen PJ, Doornenbal A, Hellebrekers LJ. Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, 3508 TD Utrecht, The Netherlands. OBJECTIVE: To determine whether epidurally derived evoked potentials (EPs) can be used to reliably assess nociception and antinociception in ponies. ANIMALS: 7 ponies. PROCEDURES: EPs and electromyograms (EMGs) from the quadriceps femoris muscles were recorded simultaneously, following electrical stimulation applied to the distal portion of the hind limb. The effect of increasing stimulus intensity, conduction velocities of the stimulated nerves, effect of epidurally applied methadone, and effect of systemically administered propofol were evaluated. RESULTS: In the EP and EMG waveforms, 2 distinct complexes, the EP N25 and P50 and the EMG P27 and N62, respectively, were identified. On the basis of their latency and calculated conduction velocities, the EP P50 and EMG N62 were considered to be related to nociception (AD-mediated). All complexes increased significantly in amplitude with increasing stimulus intensity and decreased significantly following epidural administration of methadone or systemic administration of propofol. CONCLUSIONS AND CLINICAL RELEVANCE: Although the experimental setup allowed successful discrimination between tactile- and nociceptive-associated responses, the identified EPs, considered to reflect activity in the spinal cord, could not be definitively differentiated from activity in the lumbosacral epaxial musculature. Further research is required to refine measurement techniques to allow for discrimination between these 2 signals. Similar to other species, neurophysiologic variables such as EPs could potentially become a useful additional tool in quantifying nociception in equidae. PMID: 19566465 [PubMed - indexed for MEDLINE