The effects of cocaine exposure prior to and during pregnancy in rats fed low or adequate protein diets

The GNE-KLH anti-cocaine vaccine protects dams and offspring from cocaine-induced effects during the prenatal and lactating periods

Protecting children from prenatal cocaine exposure is a significant challenge for physicians and childbearing women with cocaine use disorder. Cocaine use is highly prevalent among reproductive-aged women and prenatal cocaine exposure produces obstetric, foetal neurodevelopmental and long-term behavioural impairments. Cocaine crosses the maternal and foetal blood-brain barrier and the placenta by diffusion. The best approach to prevent prenatal cocaine exposure is to stop cocaine use. However, only 25% of cocaine users can discontinue their use during pregnancy. Anti-cocaine vaccination decreases cocaine passage through the blood-brain barrier. This study describes an innovative approach for preventing prenatal cocaine exposure using the GNE-KLH anti-cocaine vaccine, a novel use for the named anti-drug vaccines. Here, we show that anti-cocaine vaccination with GNE-KLH produced and maintained anti-cocaine IgG antibody titres and avidity during pregnancy. These antibodies protected the pregnant rats and their pups against prenatal cocaine damage during pregnancy until weaning. The present work is the first preclinical evidence of the efficacy of an innovative mechanism to prevent prenatal cocaine exposure damage, a worldwide public health care issue. In the future, this mechanism may be useful in pregnant women with cocaine use disorder. Further studies to understand the mechanisms of how anti-cocaine antibodies exert their protective effects in pregnancy are warranted.

Differential Effects of Prenatal Protein Malnutrition and Prenatal Cocaine on Radial Arm Maze Performance in Adult Male Rats

The effects of prenatal cocaine and protein malnutrition were examined on acquisition of the radial arm maze in adult male Sprague-Dawley rats whose mothers were provided with a 6% casein, a 25% casein or a standard chow diet and cocaine (30mg/kg) or saline injections beginning 5 weeks prior to mating and continuing to parturition. Rats were tested using an 8-arm radial maze with 4 baited arms and were required to collect all 4 food pellets within 5 min to complete a trial. Subjects were tested for 1 trial/day until they met criterion for successful acquisition of the task. Criterion was attained when the rat collected 3 out of the 4 food pellets within their first 4 arm entries within a trial (while still completing the trial) with this level of performance being maintained for 3 consecutive trials. The results showed dissociation between the effects of prenatal protein malnutrition and prenatal cocaine. Prenatally protein malnourished adult male rats required a greater number of trials to criterion, made more reference memory (but not working memory) errors, and required a longer time to complete each trial when compared with control males. However, rats with prenatal cocaine exposure showed no significant impairments in the radial arm maze. These results contrast with our previous findings using the Morris maze task in which adult male subjects exhibited impaired acquisition following prenatal cocaine while there were no effects following prenatal protein malnutrition. Thus, the radial arm maze and water maze procedures appear to engage different processes that are differentially sensitive to the prenatal insults.

Prenatal intravenous cocaine and the heart rate-orienting response: a dose-response study

Attentional dysfunction is a persistent behavioral abnormality that is emerging as one of the cardinal features in the investigations of the teratogenic effects of cocaine in humans and rodents. The present study sought to extend this work by using a dose-response design with an alternate strain of rat. Virgin Long-Evans female rats, implanted with an IV access port prior to breeding were administered saline, 0.5, 1.0, or 3.0 mg/kg of cocaine HCl from gestational day (GD) GD8-21 (1x per day-GD8-14, 2x per day-GD15-21). Cocaine had no significant effect on maternal or litter parameters. At 14-15 days of age, 1 male and 1 female from each litter were tested to evaluate the heart rate orienting response (HR-OR). Following 20 min for acclimation, pups were presented an olfactory stimulus for 20s per trial, across four trials, and with an intertrial interval of 2 min. The initial baseline HR was not significantly different across the treatment groups, although cocaine did alter the stability of the QRS complex duration. The magnitude of the HR-OR averaged across trials increased as a linear function of dosage of cocaine. A more complex (quadratic) interaction between cocaine dose and sex of the offspring was also noted. When examined across trials, the controls failed to display any significant within-session variation in the HR-OR; in contrast all of the prenatal cocaine treated groups displayed either sensitization (low and high dose) or habituation of the response (middle dose). Analysis of the peak HR-OR confirmed that the controls were indeed displaying the response on at least one trial of the session, albeit not consistently on any specific trial. The more vigorous HR-OR of the prenatal cocaine groups, relative to vehicle controls, most likely reflects an alteration in development of the neural basis of response; as previously shown, the most vigorous response to the olfactory stimulus is seen early (12 days of age) and progressively decreases across the preweaning period. In sum, prenatal exposure to cocaine, at least when administered by the IV route, provides reproducible alterations in attentional processes, as indexed by the noradrenergically-mediated HR-OR. The documentation of a linear dose-response function suggests that there is likely no threshold for the drug-induced alteration. Moreover, the sex of the animal also appears to play some role in the nature of the expression of the altered HR-OR.

Fetal development in rhesus monkeys exposed prenatally to cocaine

Using a timed-breeding protocol, one group of female rhesus monkeys was implanted subcutaneously with osmotic minipumps containing 0.3 mg/kg/h cocaine (N=18) or saline (N=18) from day 24 postconception through gestation. Another group received cocaine (N=12) or saline (N=8) from conception through day 42 of gestation. Mean levels of cocaine in maternal serum were approximately 150 ng/ml during pregnancy. A total of 56 pregnancies were documented in 42 adult monkeys, and 39 pregnancies completed full-term. Maternal food consumption and body weight increased during pregnancy, and there were no significant differences among experimental groups. Although both groups with a history of cocaine exposure had lower survival rates compared to pair-fed controls, of the fetuses that survived, fetal heart rate, fetal biparietal diameter, and mean gestational length were in the normal range for all experimental groups. Similarly, body weight, biparietal diameter, body length, and modified Apgar scores at birth did not differ significantly among experimental groups. The results indicate that surviving fetuses exhibited normal growth.

Effects of prenatal cocaine on behavioral adaptation to chronic stress in adult rats

Prenatal exposure to cocaine in rats has previously been shown to alter the behavioral and hormonal responses to acute stressors, although no work has yet examined stress adaptation in these animals in adulthood, a possibility examined in this experiment. Male and female offspring of Sprague-Dawley rat dams given 40 mg/kg/3 ml subcutaneously daily from gestational days 8-20 (C40), saline injected and pair-fed dams (PF), and non-treated dams (NT) were tested in adulthood (90-120 days). Offspring were given a 5-min open field test 24 h following the last of 1 (Acute), 9 (Chronic) or 0 (control) daily 15-min intermittent footshock sessions. Substantially more behavioral adaptation was evident in NT offspring than in C40 and PF animals. The attenuated stress adaptation seen in C40 offspring extends prior work showing altered stress responsiveness in these animals, although the PF data caution against the conclusion that this lack of stress adaptation necessarily reflects gestational exposure to cocaine per se.

Prenatal intravenous cocaine adversely affects attentional processing in preweanling rats

Perhaps the sole, clinically reported, deficit in infants of women that abused cocaine (COC) during pregnancy that persists through early childhood is that of an attentional disorder. Using the heart rate orienting response (HR-OR), a putative valid and reliable measure of attention, we examined the offspring of rats exposed to COC in utero via the clinically relevant intravenous (IV) route. Sprague-Dawley females, implanted with IV access ports prior to breeding, were administered saline or 3 mg/kg COC HC1, 1X/day on gestational day (GD) 8-14 and 2X/day on GD15-21. No significant effects of prenatal COC were apparent for maternal or litter parameters. Six pups/litter were tested: one of each sex on postnatal day (PD) 12, PD16, and PD21. Following 20 min of adaptation, pups were exposed to a novel odor (20 s amyl acetate) for a set of four acquisition trials; after a 4-h retention interval, the same procedure was again employed. At PD12, both prenatal COC and control pups demonstrated a significant HR-OR on the acquisition trials and both groups showed significant within-session habituation. Across the 4-h retention interval, prenatal COC-exposed pups showed habituation whereas control pups did not. At PD16, the magnitude of the HR-OR was significantly greater in prenatal COC-exposed pups relative to control pups. Within-session habituation also characterized the HR-OR of the COC, but not control, pups. For the retention data, within-subject and regression analyses suggested the COC-exposed pups displayed greater between and within-session habituation, respectively. At PD21, the prenatal COC-treated pups displayed an HR-OR that did not habituate across acquisition trials; the control pups displayed a significant HR-OR only during the initial 5 s of the first two trials. During the retention trials, regression analyses again suggested the COC-exposed pups displayed greater evidence of within-session habituation. Collectively, these data demonstrate that prenatal exposure to COC alters attention throughout the preweanling period of development. Given the putative role of norepinephrine, but not dopamine or serotonin, in central mediation of the HR-OR of preweanling rats, the effects of prenatal IV COC exposure in this task are consistent with a noradrenergically based attentional disorder.

Effects of diet on sensitization to cocaine-induced stereotypy in female rats

The progressive increase in cocaine-induced stereotyped behavior that accompanies repeated cocaine injections (sensitization) was examined in rats consuming different diets. Adult female Sprague-Dawley rats were fed one of three diets: low protein (6% casein), adequate protein (25% casein), or a standard chow diet. Following 1 week of adaptation to the diets, the rats were injected every 3-4 days with either cocaine (30 mg/kg, IP) or saline, and the total amount of stereotypy was measured over a 90-min interval following each of four injections. Cocaine-induced stereotypy peaked at 40-50 min following each injection, after which it declined for all diet groups. With repeated injections, the total amount of stereotypy increased in all diet groups. By the fourth injection, the low protein diet group (6% casein) exhibited a slower onset and a possibly prolonged duration of cocaine-induced stereotypy when compared with the two adequate protein diet groups (25% casein and chow). Interestingly, the rats in the two purified diet groups (6% casein and 25% casein) exhibited significantly more stereotypy across injections than those in the chow diet group. Weight differences did not explain the differences in stereotypy present among the diet groups. This study concludes that diet significantly alters the pattern of cocaine-induced stereotypy in female rats, especially after repeated exposure.

Development of spatial navigation following prenatal cocaine and malnutrition in rats: lack of additive effects

The effects of prenatal cocaine exposure and protein malnutrition on the development of spatial navigation were assessed in rats. Sprague-Dawley dams were fed a low-protein (6% casein), adequate protein (25% casein), or a laboratory chow diet prior to mating and throughout pregnancy. Within each diet group, rats received either cocaine injections (30 mg/kg i.p. two times per week prior to mating and then 30 mg/kg s.c. daily from day 3 to 18 of pregnancy) or saline injections. All litters were fostered on the day of birth to saline-injected mothers fed either the 25% casein diet or the chow diet. Gestation length was decreased by prenatal cocaine exposure whereas litter size was reduced by prenatal malnutrition. On postnatal days 21, 25, 30, or 70, rats were tested for their ability to locate a submerged platform in a Morris water maze. In well-nourished rats, prenatal cocaine increased the mean distance swum during acquisition over days 21-30, a difference that was abolished in rats with prenatal malnutrition. In the absence of drug exposure (saline groups), prenatal malnutrition was itself associated with longer swim paths. Neither prenatal insult affected the accuracy of the spatial navigation at these ages, as determined by their search pattern when the platform was removed. On postnatal day 25, rats raised on the chow diet exhibited superior performance to that of rats raised on the 25% casein diet, but by day 30 these two well-nourished groups were comparable. At day 70, prenatal cocaine impaired spatial performance on the first session, in well-nourished rats only. Thus, these results provide no support for the hypothesis that prenatal cocaine and protein malnutrition combine to produce a greater effect on behavioral development than either insult alone.

Differential effects of prenatal protein malnutrition and prenatal cocaine on a test of homing behavior in rat pups

The effects of prenatal cocaine exposure and protein malnutrition on orientation to home nest material was assessed in rat pups. Sprague-Dawley dams were fed a diet of low protein content (6% casein), and isocaloric diet of adequate protein content (25% casein, control), or a laboratory chow diet prior to mating and throughout pregnancy. Within each diet group, rats received either cocaine injections (30 mg/kg IP 2 times per week prior to mating and the 30 mg/kg SC daily from day 3 to 18 of pregnancy) or saline injections. All litters were fostered on the day of birth to control mothers fed an adequate diet. On postnatal days 7, 9, and 11, a single pup from each litter (n = 11-15 per treatment) was tested repeatedly in a clean test cage for the rapidity of approach, and level of attraction to their own home (nest) bedding compared with fresh bedding. Prenatal malnutrition and prenatal cocaine exposure each gave rise to independent effects on performance, based upon factor analysis. Prenatal malnutrition, but not prenatal cocaine increased the time taken for rat pups to approach their nest bedding, reduced the time spent on this bedding, decreased the number of entries into the sector containing the home bedding and reduced pup weight. Prenatal cocaine, but not prenatal malnutrition, produced a reduction in activity, but had no effect on pup weight. The lower activity level was most pronounced on postnatal day 7. Surprisingly, interactive effects of prenatal cocaine and prenatal malnutrition were not observed on any behavior examined. Nevertheless, the co-existence of drug addiction and malnutrition in human populations raises the possibility that some of the effects generally attributed to drug exposure may, in fact, be due to malnutrition.

Prenatal cocaine but not prenatal malnutrition affects foster mother-pup interactions in rats

The separate and combined effects of prenatal cocaine exposure and malnutrition on mother-pup interactions in rats were assessed daily from postnatal day 2 to day 21. Sprague-Dawley dams were fed a diet of low protein content (6% casein), an isocaloric diet of adequate protein content (25% casein, control), or a laboratory chow diet prior to mating and throughout pregnancy. Within each diet group, rats received either cocaine injections (30 mg/kg IP two times per week prior to mating and then 30 mg/kg SC daily from days 3 to 18 of pregnancy) or saline injections. Litters were fostered on the day of birth to control mothers (i.e., nondrug-exposed dams fed the control or chow diet). Foster mothers fed the 25% casein diet showed increased contact with cocaine-exposed pups compared with nondrug-exposed pups in the second postnatal week but lower levels as the pups approached weaning. Passive nursing was increased in dams caring for prenatally malnourished, cocaine-exposed pups compared with those caring for similar pups with no drug exposure. Chow-fed mothers did not differ in their behavior towards pups with or without prenatal cocaine treatment. Prenatal cocaine and malnutrition independently compromised birth weight and various reflexive milestones but the attainment of physical milestones was affected only by prenatal cocaine. There were no additive effects of the two prenatal insults on any measure of mother-pup interaction or pup development.