Aging associated changes in amygdalar corticotropin-releasing hormone (CRH) and CRH-binding protein in Fischer 344 rats.

Behavioral adaptation in aging may become impaired from abnormal expression of amygdalar corticotropin-releasing hormone (CRH) and/or CRH-binding protein (CRH-BP). In this study, we serially sectioned the amygdala in 4-, 12-, and 24-month-old Fischer 344 rats following perfusion with 4% paraformaldehyde. We determined the amount of CRH and CRH-BP containing cells as well as the density of fibers expressing CRH or CRH-BP utilizing densitometric methods. Images were digitized using Zeiss Axiovision software and densitometrically analyzed using Scion Image. Both sides were analyzed in sections cut at 30 mum thickness. Cell counts of CRH-BP containing cells in the basolateral and lateral nucleus of the amygdala were lower in 24-month-old rats vs. 4-month-old rats, respectively (mean cells/section +/- SE): 31 +/- 6 vs. 72 +/- 10 (n = 3; P < 0.05 via ANOVA and Fisher's PLSD). There was a trend for cell counts of CRH containing cells in the central nucleus of the amygdala to be lower in 24-month-old rats vs. 4-month-old rats, respectively 28 +/- 7 vs. 47 +/- 9 (n = 3; P = 0.07 via ANOVA). Densitometric analysis of the number of CRH-BP positive fibers revealed no age differences in CeA; however, with regards to CRH-positive fibers, both 4- and 12-month rats had greater CeA CRH immunoreactivity relative to 24-month-old rats (Ps < 0.05 via ANOVA and Fisher's PLSD). These changes may contribute to impaired adaptations to stress, cognitive decline, and other pathophysiological processes during aging.

Problem solving following neonatal exposure to cocaine, ethanol, or cocaine/ethanol in combination in rats.

This study examined the effects of neonatal drug exposure on performance in a digging maze. Subjects were Sprague-Dawley rats, artificially reared (AR) and fed through a gastrostomy tube from postnatal days (PND) 4-10. The AR groups included a cocaine group (20 mg/kg/day cocaine hydrochloride), an ethanol group (4 g/kg/day ethanol), a cocaine/ethanol group (20 mg/kg/day cocaine and 4 g/kg/day ethanol), and an AR control group. A suckled control raised by its dam was also included. At approximately PND 55, subjects were tested in a digging maze paradigm. The digging maze required subjects to use a species typical behavior (digging) to solve a novel problem (gaining access to water). While neonatal treatment had no effect on acquisition of a simple runway task for water reward, neonatal exposure to cocaine and ethanol in combination resulted in impaired performance on the digging maze task. None of the other neonatal treatment groups showed impairments on this task. These findings suggest that exposure to these doses of cocaine and ethanol during neonatal development may have more serious effects on problem solving tasks in rats than exposure to either drug alone.

The effects of neonatal ethanol and/or cocaine exposure on isolation-induced ultrasonic vocalizations.

Isolation-induced ultrasonic vocalizations (USVs) are emitted by young rat pups when isolated from their dam and conspecifics. These USVs play an important role in maternal/offspring interactions, and have been used as an indicator of response to stress and isolation. This study examined the effects of neonatal ethanol and/or cocaine exposure on USVs in neonatal rats. The neonatal exposure paradigm serves as a model for the "human third trimester of pregnancy" in terms of CNS development. There were five treatment groups including an artificially reared (AR) ethanol-exposed group (6 g/kg/day), an AR cocaine-exposed group (60 mg/kg/day), an AR ethanol- and cocaine-exposed group (6 g/kg/day+60 mg/kg/day), an AR isocaloric control, and a normally reared control. Both groups that received ethanol took longer to vocalize, and displayed fewer vocalizations than non-ethanol-exposed pups when tested on clean bedding (Experiment 1) or on chips from the nest of a lactating dam (Experiment 2). These results suggest that neonatal ethanol exposure alters the pup's immediate response to isolation. This could have direct effects on maternal/infant interactions, and might help explain some of the long-term effects of ethanol exposure on social behaviors.

The effects of neonatal cocaine exposure on a play-rewarded spatial discrimination task in juvenile rats.

This study examined the effects of neonatal cocaine exposure on the rewarding properties of play in a modified T-maze. Animals were artificially reared from postnatal day (PND) 4-9 with drug concentrated in four daily feeds. There were four treatment groups, 40 mg/kg/day cocaine, 20 mg/kg/day cocaine, an artificially reared control and a surgery control. From PND 38-42, subjects were tested with a food reward (EXP 1) or a play reward (EXP 2). No deficits in learning were seen when the reward was food. The 20 mg/kg/day cocaine group, however, showed impaired learning and altered play behavior when the reward was access to a play partner. Neonatal cocaine exposure thus appears to differentially affect learning based on the type of reward presented.

Neonatal cocaine and/or ethanol exposure: effects on a runway task with suckling reward.

This experiment employed a rodent model to examine the effects of neonatal exposure to cocaine, ethanol, or both drugs in combination on acquisition and extinction of an appetitive runway task. After implantation with an intragastric cannula, subjects were artificially reared (AR) from postnatal days (PND) 4-10. There were five treatment groups, including: cocaine (20 mg/kg/day), ethanol (4 g/kg/ day), cocaine/ethanol (20 mg/kg/day cocaine and 4 g/kg/day ethanol), stock (an AR control), and sham (a suckled control). Subjects were tested on PND 13-14. The runway task consisted of traversing a runway for nonnutritive suckling on an anesthetized dam and a subsequent milk reward, given manually by the experimenter. Pups from all treatment groups acquired and extinguished the runway task; however, pups exposed to cocaine had longer latencies to leave the start box than controls. Pups exposed to cocaine or ethanol, but not cocaine/ethanol, were impaired on the nipple attachment measures compared to sham controls. These results provide further support that the "third trimester" is a sensitive period for developmental drug exposure.

The behavioral teratogenic potential of fenbendazole: a medication for pinworm infestation.

Fenbendazole (FBZ) is a benzimidazole currently used for anthelmintic treatment of pinworm populations in numerous animal species although it is not currently approved for laboratory rodents in the U.S. It has received considerable interest for treating rodent populations due to its low toxicity, wide safety margin and apparent absence of gross teratogenic effects. The purpose of this study was to assess the behavioral teratogenic potential of FBZ. Pregnant rats were administered either FBZ-medicated feed at a therapeutic level or normal rat chow throughout pregnancy and gestation. FBZ had no effect on pregnancy indicators such as maternal weight gain or water consumption, number of pups born or pup birth weights. Offspring were examined in a variety of paradigms including righting reflex, negative geotaxis, running wheel activity, Morris water maze (MWM) performance and digging maze performance. FBZ offspring did show delayed righting reflex, some modest changes in locomotor activity in a running wheel and minor alterations in performance during the probe session of the MWM relative to controls. However, the effects of FBZ on behavior were subtle and many of the behaviors examined were unaffected. These results suggest that FBZ may be an effective and relatively safe anthelmintic treatment for use in breeding colonies.

The behavioral response to novelty is altered in rats neonatally exposed to cocaine.

It has recently been suggested that the effects of in utero cocaine exposure may result in subtle deficits related to a challenging environment, including exposure to novelty or stress. This study used a neonatal drug-exposure model to examine the behavioral response to a novel environment in rodents. Subjects were artificially reared (AR) from postnatal Days 4-10. There were four treatment groups; AR 40 mg/kg/day cocaine, AR 20 mg/kg/day cocaine, AR control group receiving no drug, and a normally reared control. In Experiment 1, subjects were tested for their preference of maternal home-cage or clean wood-chip odors in a T-maze on postnatal Day 15. Subjects from all treatment groups preferred the maternal odor. In Experiment 2, subjects were habituated to four familiar odors and tested with a novel odor in an open field (postnatal Days 16-21). Neonatal exposure to 20 mg/kg/day cocaine led to an overall increase in exploratory behavior during testing, whereas 40 mg/kg/day did not, supporting the hypothesis that developmental exposure to cocaine at some doses may alter the offspring's response to a changing environment.

Individual differences in behavioral responses to novelty and amphetamine self-administration in male and female rats.

Previous work has shown that individual differences in locomotor activity in an inescapable novel environment can predict acquisition of amphetamine self-administration. The current study examined whether individual differences in approach to novelty in a free choice test could also predict amphetamine self-administration. Further, the current study examined whether individual differences in either free choice or inescapable novelty tests could predict responding for a nondrug reinforcer (sucrose) in the presence and absence of amphetamine. Male and female rats were first tested for their response to free choice novelty (playground maze and novelty-induced place preference tests) and inescapable novelty. They were then tested for acquisition of sucrose-reinforced responding, amphetamine-induced changes in maintenance of sucrose-reinforced responding, and amphetamine self-administration. Based on the inescapable novelty test, acquisition of sucrose-reinforced responding was more rapid in male high responders (HR) compared to low responders (LR). This effect in males did not generalize to females. None of the novelty tests predicted the ability of amphetamine to decrease sucrose-maintained responding. However, using the inescapable novelty test, both male and female HRs self-administered more amphetamine than LRs within the dose range tested (0.03-0.16 mg/kg/infusion). Neither the playground maze nor the novelty-induced place preference test predicted amphetamine self-administration. These results indicate that responses to free choice novelty and inescapable novelty predict different components of amphetamine-induced behavior.

The apeE gene of Salmonella enterica serovar Typhimurium is induced by phosphate limitation and regulated by phoBR.

Mutations in apeR, a regulatory locus of the outer membrane esterase apeE from Salmonella enterica serovar Typhimurium, were shown to be alleles of the pstSCAB-phoU high-affinity phosphate transport operon. Expression of apeE was induced by phosphate limitation, and this induction required the phoBR phosphate regulatory system.

Acquisition of a fixed ratio schedule in adult male rats neonatally exposed to ethanol and/or cocaine.

Acquisition of an operant learning task for sucrose reinforcement was examined in rats after neonatal exposure to ethanol and/or cocaine. Subjects were raised using an artificial rearing procedure from postnatal days 4 to 11 and were intragastrically fed a milk diet containing either ethanol (6 g/kg/day), cocaine (60 mg/kg/day), the combination (6 g/kg/day + 60 mg/kg/day), or an isocaloric control diet. There was also a suckled sham control. Adult male offspring (postnatal day 65 to postnatal day 68) were shaped to lever press for sucrose reinforcement and then began daily 15-min sessions of fixed ratio (FR) training. The number of days to acquire an FR 20 was measured. Neonatal exposure to the ethanol/cocaine combination significantly increased the number of days to reach the FR 20. There was also a trend for fewer of these subjects to reach the FR 20, although this difference was not statistically significant. These results suggest that subjects neonatally exposed to the ethanol/cocaine combination have difficulty learning an operant task. This impairment was unique to the ethanol/cocaine combination group and suggests that polydrug exposure during development may have a more adverse outcome than exposure to ethanol or cocaine alone.