Evidence for a serotonin-mediated effect of cocaine causing vasoconstriction and herniated umbilici in chicken embryos

T-Maze Performance after Developmental Exposure to 19F Tagged 5-HTP in Chicks

Chicks were used as a model to investigate behavioral effects of administering a new compound intended for use with magnetic resonance. The compound has multiple 19F atom tags covalently bonded to the indole ring of 5-hydroxytryptophan (PF-5HTP), the immediate precursor to the neurotransmitter serotonin. On incubation Day 17, 5μg of PF-5-HTP, an equivalent amount of 5-HTP, or just 200 μL of the weak phosphate buffered saline (PBS) vehicle was injected into the airsac of each egg. Three days after hatching, chicks were isolated at the top of a simple T-Maze which, when traversed correctly, enabled them to return to their brood mates. A second trial in the T-Maze was conducted about three hours later. The brief period of isolation at the start of a trial causes social distress in chicks who are reinforced by returning to the brood. The task was selected as being sensitive to functioning of the serotonin pathways whose development might be altered by administering the compound during brain development. Repeated-measures analysis of variance yielded a statistically significant main effect for trial within groups, but no significant difference between injection groups. Administering a low dose of the fluorine tagged compound during development did not impair performance on this T-maze task.

A descriptive study to provide evidence of the teratogenic and cellular effects of sibutramine and ephedrine on cardiac- and liver-tissue of chick embryos

Exposure to drugs during pregnancy is a major concern, as some teratogenic compounds can influence normal foetal development. Although the use of drugs during pregnancy should generally be avoided, exposure of the developing foetus to teratogens may occur unknowingly since these compounds may be hidden in products that are being marketed as "all natural." The aim of the current study was to investigate the possible teratogenic and cellular effects of sibutramine-a serotonin-norepinephrine reuptake inhibitor used in the treatment of obesity-on the heart and liver tissue of chick embryos. Ephedrine was used as a positive control. The chick embryo model was chosen because it has been used in studying developmental and experimental biology and teratology with great success. The embryos were exposed to three different concentrations of sibutramine and ephedrine respectively. The results obtained revealed that both compounds exhibited embryotoxicity when compared to the control groups. Liver and heart tissue of the exposed embryos was severely affected by these compounds in a dose-related manner. Morphology similar to that of muscle dystrophy was observed in the heart, where the muscle tissue was infiltrated by adipose and connective tissue. Severe liver steatosis was also noted. A more in-depth investigation into the molecular pathways involved might provide more information on the exact mechanism of toxicity of these products influencing embryonic development.

Teratogens inducing congenital abdominal wall defects in animal models

Congenital abdominal wall defects are common anomalies which include gastroschisis, omphalocele and umbilical cord hernia. Recent reports indicate that gastroschisis is increasing in prevalence, whereas omphalocele has remained steady, suggesting that environmental factors may play a part in their pathogenesis. The aim of this study is to review animal teratogen studies resulting in abdominal wall defects to investigate their possible causes. Each report was examined not only for the teratogens causing the defects, but also to carefully identify the defect occurring and its correlation with the known clinical anomalies. We found many discrepancies between the nomenclature used by animal teratology investigators and that used by clinicians. We were able to confirm the induction of gastroschisis by 22 teratogens, omphalocele by 9 teratogens and umbilical cord hernia by 8. There is no doubt that environmental factors may be responsible, at least in part, for all three of the clinical abdominal wall defects. Future studies should take care to appreciate the differences between these anomalies and describe them in detail, so that accurate and meaningful conclusions can be obtained.

Inhibition of nitric oxide synthase enhances cocaine's developmental toxicity: vascular and CNS effects

Ischemia and/or reperfusion injury from free radicals may cause cocaine's toxicity, including its effect upon neurobehavioral development. We previously used salicylate to measure hydroxyl free radicals in chick embryos exposed to cocaine. The combination was more toxic than cocaine alone. We postulated that salicylate enhanced the vasoconstriction and toxicity via inhibition of compensatory processes (eg by inhibition of the synthesis of vasodilatory prostanoids and/or nitric oxide). A nontoxic dose of N(G)-nitro-L-arginine methyl ester (L-NAME) was used to inhibit nitric oxide synthase to test this hypothesis. In one experiment, cocaine was injected every 1.5 h (total dose =67.5 mg/kg egg) on day 15 of development, 1 h after injection of L-NAME (200 mg/kg egg) to determine viability and hatchability, which are measures of toxicity. Another experiment measured diameters of blood vessels after L-NAME injection, followed by NaCl or cocaine infusion (0.23 mg/egg/min; total dose=67.5 mg/kg egg) at 15 and 5 min afterwards. Lastly, brains of embryos pretreated with L-NAME before cocaine injections were analyzed for nitric oxide synthase activity. Cocaine decreased viability and hatchability. L-NAME enhanced cocaine's effect upon both parameters. Blood vessel diameters were decreased by cocaine after 15 min of infusion. L-NAME+cocaine caused a decrease in vessel diameter as soon as 5 min into the infusion and was greater with time, compared with other groups. Enzyme activity in brains was decreased only in the L-NAME+cocaine group. Thus, inhibition of nitric oxide synthesis interferes with the embryos' capacity to mount a compensatory vasodilatory response.

Vasoconstriction caused by cocaine is enhanced by sodium salicylate: is inducible nitric oxide synthase mRNA related?

We have previously found that sodium salicylate (NaSal), injected into chicken eggs at nontoxic doses used for quantifying hydroxyl free radicals in hearts and brains of embryos, caused or exacerbated hemorrhages and dramatically reduced hatchability when combined with cocaine (Coc). It has also been reported that inducible nitric oxide synthase (iNOS) gene expression is altered in brain in response to vascular damage and inflammation. In this study we measured diameters of membrane-bound blood vessels (BV) before and after pretreatment with saline (NaCl) or NaSal (100 mg/kg egg), followed by infusion of either NaCl or Coc HCl (total of 67.5 mg/kg egg) during 15 min. Brains and hearts of the embryos were then analyzed for iNOS messenger RNA (mRNA) concentrations. Coc caused vasoconstriction that was significant 5 min postinfusion (5 min PI) of the entire dose (ie after 67.5 mg/kg egg). Significant vasoconstriction was evident within 5 min in the group injected with NaSal followed by infusion with Coc (ie after 22.5 mg Coc/kg egg). Expression of iNOS mRNA was significantly increased only in the brains of the group exposed to NaSal plus Coc, and the increase was inversely related to BV diameter. These data are discussed in relation to effects of salicylate upon prostanoid synthesis and/or nitric oxide synthesis via iNOS inhibition and their possible relationship to Coc-associated cerebral vascular and/or cardiovascular events in abusing humans.

Effects of poppy seed meal on egg production and hatching results in quail (Coturnix coturnix japonica)

This study was carried out to determine the effects of poppy seed meal (PSM) on the egg production and hatching of quail. Two experiments were undertaken. In the first experiment, 240 quail, reared under the same conditions, were divided into four groups of 60 birds each (which were, in turn, subdivided into four subgroups of 15 each for experimental replicates). The first, second, and third experimental groups were fed ratios containing 5%, 15%, and 25% PSM, respectively, over 12 weeks. The control group received no PSM. Feed and water were supplied ad libitum and artificial light was provided for 16 h a day. During the first experiment, egg production, egg weight, and feed conversion ratio (FCR) were measured. In the second experiment, 240 female and 48 male quail were divided into four groups, as in the preceding experiment, and the birds were housed in cages at a ratio of one male to five females. The diets and their presentation to the quails were the same as in the preceding experiment. The results of the two experiments showed that the addition of PSM to the feed ratios increased egg production, feed consumption, and feed conversion per kg of eggs and per dozen eggs. However, PSM addition at all percentages significantly reduced (P<0.001) hatchability, mainly because of increased infertility and embryonic deaths.

Prenatal opiate withdrawal activates the chick embryo hypothalamic pituitary-adrenal axis and dilates vitelline blood vessels via serotonin(2) receptors

Opiate withdrawal during pregnancy may occur because of voluntary or forced detoxification, or from rapid cycling associated with exposure to short-acting "street" opiates. Thus, animal modeling of prenatal withdrawal and development of potential therapeutic interventions is important. Direct developmental effects of opiates and/or withdrawal can be studied using a chick model. In ovo administration of the long-acting opiate N-desmethyl-l-alpha-noracetylmethadol (NLAAM) induces opiate dependence in the chick embryo. We examined activation of the hypothalamic-pituitary-adrenal (HPA) axis (assessed via serum corticosterone) and hemodynamic changes (assessed as changes in apparent diameter of vitelline (extraembryonic) blood vessels) after chronic NLAAM exposure and naloxone (Nx)-precipitated withdrawal during late stages of embryogenesis. Nx-precipitated withdrawal increased corticosterone 2- to 4.5-fold and diameters of vitelline blood vessels by 15 to 45%. NLAAM exposure itself did not effect these measures. In a second set of experiments, isobutylmethylxanthine (IBMX), a phosphodiesterase inhibitor, was injected into eggs with embryos. IBMX similarly increased corticosterone and vitelline vessel diameter, with a similar time course and response magnitude. Previous studies found that serotonin(2) (5-HT(2)) receptors were involved in other withdrawal manifestations, so we determined whether they were likewise involved. Pretreatment with the 5-HT(2) antagonist ritanserin completely blocked HPA axis activation and vasodilation associated with both Nx-precipitated withdrawal and IBMX administration. This indicates that 5-HT(2) receptors, directly or indirectly, mediate these withdrawal manifestations in the chick embryo.

Embryonic "binge" cocaine exposure alters neural-immune and neural-endocrine interactions in young chickens: involvement of serotonin(2) receptors

As part of our characterization of the developmental consequences of prenatal cocaine exposure, cocaine was injected into eggs containing viable chicken embryos on embryonic day (E) 18 and the fever response to the endotoxin lipopolysaccharide (LPS) and a delayed-type hypersensitivity response to phytohemagglutinin (PHA) were assessed postnatally. E18 cocaine exposure did not affect basal body temperature. LPS induced a fever in the chicks at 4 h post-injection on post-hatch day (D) 4 and 2 h post-injection on D24. E18 cocaine exposure suppressed the peak LPS-induced fever by 50% at both ages. E18 cocaine exposure also suppressed the hypersensitivity reaction to an intradermal injection of PHA on D17, while having no effect on the response to a saline injection. To determine the importance of serotonin(2) (5-HT(2)) receptors in the developmental toxicity of cocaine, varying doses of the 5-HT(2) antagonist ritanserin were injected on E17 followed by cocaine on E18. Ritanserin, like cocaine, did not alter basal temperature, but it dose-relatedly attenuated or blocked cocaine's effect on LPS-induced fever on both D4 and D24. Ritanserin pretreatment was also able to block the blunted isolation stress response seen in D16 chicks following E18 cocaine exposure. Thus, late prenatal cocaine exposure significantly alters adaptive fever and hypersensitivity responses, and embryonic 5-HT(2) receptors played a mediating role in the fever effect.

Embryonic cocaine exposure and corticosterone: serotonin(2) receptor mediation

Cocaine activates the mature hypothalamic-pituitary-adrenal (HPA) axis, increasing corticosterone concentrations in animals and humans and serotonin(2) receptors (5-HT(2)) are involved in this effect. Although prenatal cocaine exposure is associated with altered responsiveness of the HPA axis to "stress" and serotonergic compounds postnatally, it is unknown whether cocaine directly activates the embryonic HPA axis or if 5-HT(2) receptors are involved. Domestic chicken eggs with viable embryos were exposed to either the 5-HT(2) receptor agonist dimethoxyiodophenylaminopropane (DOI: 0.4, 0.8, or 1.2 mg/kg egg) or saline on embryonic day 18 (E18). In a second study, the 5-HT(2) antagonist ritanserin (0.3 mg/kg egg, a dose found effective against other effects of DOI or cocaine) or vehicle was administered on E17, prior to treatment on E18 with either saline or cocaine (5 injections of 12 mg/kg egg, equivalent to a total dose of 3.5 mg/egg). Radioimmunoassay was used to measure serum corticosterone from blood samples taken approximately 1-2 h after drug injections. DOI significantly raised corticosterone in a dose-related fashion. Cocaine-induced corticosterone elevations were blocked by pretreatment with ritanserin, whereas ritanserin by itself did not affect corticosterone concentrations. These data indicate that 5-HT(2) receptors are involved in cocaine's effect on the HPA axis during late chicken embryogenesis.

Salicylate and cocaine: interactive toxicity during chicken mid-embryogenesis

Increased free radical production, due to ischemia and reperfusion, has been postulated as a cause of cocaine's (COC) developmental toxicity. Salicylate reacts with hydroxyl free radicals (*OH) to form stable, quantifiable reaction products, which can be measured with high-pressure liquid chromatography (HPLC). To determine if chicken embryos' brains and hearts were exposed to increased *OH concentrations after injection of COC, an injection of a nontoxic dose of sodium salicylate (NaSAL, 100 mg/kg egg, or 5 mg/egg), followed by 5 injections of COC (13.5 mg/kg or 0.675 mg/egg, every 1.5 h), was administered to eggs containing embryos on the 12th day of embryogenesis (E12). In addition to finding increased *OH concentrations in E12 embryonic hearts and brains, we observed that the developmental toxicity of COC, manifest as vascular disruption (hemorrhage) and lethality, was enhanced by NaSAL injection. These results confirm and extend results of similar experiments performed upon older embryos (E18), and indicate that increased &z.rad;OH concentration in embryonic tissues after COC exposure and toxic interactions of COC and NaSAL can also occur at an earlier stage of development. The results are discussed in light of possible exposure of human fetuses to both COC and salicylates, since COC-abusing pregnant women can be misdiagnosed with pre-eclampsia and aspirin is used to treat this syndrome.

Late embryonic ritanserin exposure fails to alter normal responses to immune system stimulation in young chicks

Prior studies in our laboratory have demonstrated that prenatal treatment with the serotonin2 (5-HT2) antagonist ritanserin is effective in blocking some of the lethal, dysmorphic, cardiovascular, and behavioral consequences of excessive direct or indirect stimulation of 5-HT2 receptors in the developing chicken. The efficacious dose range for ritanserin in these studies had very little or no effect on the above measures of toxicity when administered alone. In the present study, we extend our characterization of ritanserin's potential toxicity, or lack thereof, to include the normal behavioral and endocrine responses to immune system stimulation by the endotoxin lipopolysaccharide (LPS). LPS administration induces a syndrome collectively known as sickness behavior, manifest as altered thermoregulatory processes leading to fever, and increased serum concentrations of neuroendocrine hormones, including corticosterone. These survival-promoting responses to LPS were assessed in young chickens that had been treated with doses of ritanserin ranging from 0 to 2.7 mg/kg on embryonic day 17 (E17). When sickness behavior was assessed in 5-7-day-old chicks 1 h post-LPS injection, E17 ritanserin-treated subjects did not differ from controls. At 4-6 h post-LPS, 4-day-old chicks displayed a robust fever, and E17 ritanserin did not affect the magnitude of this response. Similarly, E17 ritanserin treatment failed to affect corticosterone concentrations 2 h post-LPS in 14-day-old chicks. Thus, ritanserin treatment during late embryogenesis, a time when it is effective against direct and indirect acting 5-HT2 agonists, failed to modify the survival promoting and beneficial interactions between the nervous, endocrine, and immune systems that are elicited following immunostimulation.

Open-field and LPS-induced sickness behavior in young chickens: effects of embryonic cocaine and/or ritanserin

Exposure to drugs of abuse during embryogenesis may adversely affect nervous, immune, and endocrine systems development. We compared exposure on embryonic day 18 (E18) by single or multiple cocaine (COC) injections (56.25 mg/kg total dose for both) or saline on hatching and activity measures. In saline-exposed controls, repeated testing, age, and gender affected activity levels. A single or multiple COC injections increased the median latency to explore and multiple COC injections decreased the median number of lines crossed by female chicks in the open field. We also determined if pretreatment with the serotonin2 (5-HT2) receptor antagonist ritanserin could attenuate COC's effects on open-field behavior as well as behaviors sensitive to immune system stimulation (lipopolysaccharide (LPS)-induced sickness behavior). Eggs containing embryos were pretreated on E17 with 0.4 mg ritanserin/kg or its vehicle followed by multiple COC injections or saline on E18. E18 COC treatment decreased the median number of lines crossed and distress vocalizations in females. Ritanserin pretreatment mitigated the COC induced effects. E18 COC exposure also suppressed LPS-induced sickness behaviors in both males and females, increasing food consumption and the time spent awake and active, as well as decreasing the time spent sleeping. Ritanserin alone had no effect on the food consumed or time spent active, nor did this dose affect COC-induced alterations in sickness behavior. Ritanserin alone decreased time spent sleeping and also failed to affect the COC-induced suppression. Thus, embryonic COC exposure can suppress open field and LPS-induced sickness behavior in the young chick, and ritanserin pretreatment can block the former, but not the latter effects at the dose chosen for these experiments.

Relationships between midembryonic 5-HT2 agonist and/or antagonist exposure and detour learning by chickens

The importance of serotonin (5-HT) as both a transmitter and a regulatory signal during development of many species is well established. The availability of 5-HT receptor subtype agonists and antagonists will enable pharmacological dissection of the importance of one or more of the 5-HT receptors for their involvement in the mediation of developmental insults by drugs that are less selective but include actions upon serotonergic function. Such insults include exposure to cocaine or opiate withdrawal, both of which are blocked or attenuated by 5-HT2 antagonists. The 5-HT2 receptor agonist dimethoxyiodophenylaminopropane (DOI), like cocaine, causes vasoconstriction during embryogenesis, herniated umbilici in hatchlings, and altered detour learning by young chickens after injection into eggs at late stages of embryogenesis. The 5-HT2 antagonist ritanserin (RIT) blocks or significantly attenuates these effects. This study describes an effect of DOI on posthatch detour learning when injected earlier during embryogenesis (i.e., on embryonic day 12, E12) which is opposite its effect when injected later (i.e., on E15). Both effects are blocked by an inactive dose of RIT (0.3 mg/kg egg) and by a higher dose of RIT (0.9 mg/kg egg), which itself retards posthatch detour learning following E12 injection. Thus, excessive stimulation or blockade of 5-HT2 receptors around midembryogenesis can cause a similar behavioral teratogenic outcome. The data are discussed in relation to the likelihood that potential use of 5-HT2 antagonists for treating pregnant women and their fetuses who are not at risk is nil.