Influence of feed form and source of soybean meal on growth performance, nutrient retention, and digestive organ size of broilers. 2. Battery study

Two experiments were conducted to determine the apparent ileal digestibility (AID) of the amino acids (AA) of 4 commercial soybean meals (SBM) from the United States (USA-1, 48.1% CP and USA-2, 46.2% CP), Brazil (BRA, 47.6% CP), and Argentina (ARG, 46.3% CP) and the effects of the inclusion of these SBM in diets in mash, crumble, or pellet form on growth performance, total tract apparent retention of nutrients, and digestive organ size in broilers reared in cages from 1 to 25 d of age. In experiment 1, the AID of Lys was higher (P < 0.05) for the USA-2 than for the BRA SBM, with the SBM from USA-1 and ARG being intermediate. In experiment 2, 12 diets were arranged as a 3 × 4 factorial with 3 feed forms (mash, crumbles, and pellets) and the 4 sources of SBM used in experiment 1. The feeds were isonutritive and the AID of the AA of the SBM obtained in experiment 1 was used for diet formulation. Broilers fed mash had lower (P < 0.001) ADFI and ADG and poorer (P < 0.001) feed-to-gain ratio than broilers fed crumbles or pellets but source of SBM did not affect growth performance. Nitrogen retention was higher (P < 0.01) in birds fed mash than in birds fed crumbles or pellets at all ages. The total tract apparent retention of nutrients was lower (P < 0.05) for the BRA and ARG SBM diets than for the USA-1 and USA-2 SBM diets. Gizzard empty relative weight (% BW) was higher and gizzard pH lower for broilers fed mash than for broilers fed crumbles or pellets (P < 0.001). The results indicate that crumbling or pelleting of the diets improved growth performance of broilers from 1 to 25 d of age. Diets formulated with analyzed rather than calculated AID of AA of the SBM sources resulted in similar broiler performance.

Epidemiology of cerebrospinal Elaphostrongylus cervi infection in red deer in central Spain

Elaphostrongylus cervi produces a subclinical cerebrospinal disease in many wild and domestic ruminants from Europe, North America and New Zealand and has recently been described in Spain. To determine some aspects of its epidemiology, 121 red deer (Cervus elaphus) from central Spain were sampled during 2000. The prevalence (7%) and mean worm burden (3.8 worms per brain) were similar to the values previously recorded in other European areas. The infection was only detected in young deer during the winter. The estimation of larval production in the faeces was not a reliable method of diagnosing E. cervi infection.

The CYP2D6 humanized mouse: effect of the human CYP2D6 transgene and HNF4alpha on the disposition of debrisoquine in the mouse

CYP2D6 is a highly polymorphic human gene responsible for a large variability in the disposition of more than 100 drugs to which humans may be exposed. Animal models are inadequate for preclinical pharmacological evaluation of CYP2D6 substrates because of marked species differences in CYP2D isoforms. To overcome this issue, a transgenic mouse line expressing the human CYP2D6 gene was generated. The complete wild-type CYP2D6 gene, including its regulatory sequence, was microinjected into a fertilized FVB/N mouse egg, and the resultant offspring were genotyped by both polymerase chain reaction and Southern blotting. CYP2D6-specific protein expression was detected in the liver, intestine, and kidney from only the CYP2D6 humanized mice. Pharmacokinetic analysis revealed that debrisoquine (DEB) clearance was markedly higher (94.1 +/- 22.3 l/h/kg), and its half-life significantly reduced (6.9 +/- 1.6 h), in CYP2D6 humanized mice compared with wild-type animals (15.2 +/- 0.9 l/h/kg and 16.5 +/- 4.5 h, respectively). Mutations in hepatic nuclear factor 4alpha (HNF4alpha), a hepatic transcription factor known to regulate in vitro expression of the CYP2D6 gene, could affect the disposition of CYP2D6 drug substrates. To determine whether the HNF4alpha gene modulates in vivo pharmacokinetics of CYP2D6 substrates, a mouse line carrying both the CYP2D6 gene and the HNF4alpha conditional mutation was generated and phenotyped using DEB. After deletion of HNF4alpha, DEB 4-hydroxylase activity in CYP2D6 humanized mice decreased more than 50%. The data presented in this study show that only CYP2D6 humanized mice but not wild-type mice display significant DEB 4-hydroxylase activity and that HNF4alpha regulates CYP2D6 activity in vivo. The CYP2D6 humanized mice represent an attractive model for future preclinical studies on the pharmacology, toxicology, and physiology of CYP2D6-mediated metabolism.

Role of gonadal steroids in the corticotropin-releasing hormone and proopiomelanocortin gene expression response to Delta(9)-tetrahydrocannabinol in the hypothalamus of the rat

Chronic exposure to Delta(9)-tetrahydrocannabinol (Delta(9)-THC) increases corticotropin-releasing hormone (CRH) and proopiomelanocortin (POMC) gene expression in the rat hypothalamus. The levels of circulating gonadal steroids concurrently modulate both neuropeptides in male and female rats. However, it remains unknown whether gonadal steroids regulate Delta(9)-THC effects on CRH and POMC gene expression in the hypothalamus of male and female rats. To explore this hypothesis, experiments were conducted on intact, 2-week-gonadectomized, 1-week-gonadectomized, 1-week-dihydrotestosterone (DHT)- or estradiol-replaced male and female rats. One week after hormonal replacement, animals were treated with vehicle or Delta(9)-THC (5 mg/kg/day, i.p. for 7 days). Administration of Delta(9)-THC to intact male rats increased CRH gene expression. Castration abolished Delta(9)-THC effects of CRH gene expression in males but not in females. On the other hand, POMC mRNA levels were reduced as a result of castration, and DHT treatment did not prevent this decrease. Delta(9)-THC treatment similarly increases POMC gene expression of intact, orchidectomized and DHT-replaced males. In females, ovariectomy decreased CRH gene expression. Delta(9)-THC administration increased CRH gene expression to the same extent in castrated and estradiol-replaced rats. On the other hand, POMC gene expression was increased by ovariectomy, and Delta(9)-THC administration did only increase POMC transcript levels in the estradiol-replaced group. These data show that gonadal steroids differentially regulate the effects of Delta(9)-THC on both CRH and POMC gene expression in the hypothalamus of male and female rats, suggesting gender differences in the reaction to cannabinoids.

Extinction of cocaine self-administration produces a differential time-related regulation of proenkephalin gene expression in rat brain

The purpose of this study was to examine the time course effects of extinction of cocaine self-administration behavior on proenkephalin (PENK) gene expression in caudate-putamen nucleus (ST), nucleus accumbens (Acc), olfactory tubercle (Tu), piriform cortex (Pir), ventromedial hypothalamic nucleus (VMN), and central amygdala (Ce) as measured by in situ hybridization histochemistry. Seventy-two littermate male Lewis rats were randomly assigned in triads to one of three conditions: (1) contingent intravenous self-administration of 1 mg/kg/injection of cocaine (CONT); (2) noncontingent injections of either 1 mg/kg/injection of cocaine (NONCONT); or (3) saline yoked (SALINE) to the intake of the self-administering subject. The self-administering rats were trained to self-administer cocaine under a FR5 schedule of reinforcement for a minimum of 3 weeks. After stable baseline levels of drug intake had been reached, saline was substituted for drug. Following this first extinction period, cocaine self-administration was reinstated for an additional period of 2 weeks. Immediately after cessation of the last session of cocaine self-administration (day 0) and 1-, 5-, and 10-day after the second extinction period, animal brains in each triad were removed to be processed for in situ hybridization. PENK mRNA levels were significantly higher in the cocaine groups when compared with SALINE group in the ST, Acc, Pir, and Tu regions on days 0, 1, 5, and 10 of the extinction and lower in the Ce region of CONT group when compared to NONCONT and SALINE groups on days 1, 5, and 10 of the extinction period. In the VMN nucleus, PENK mRNA content in CONT group versus NONCONT and SALINE groups was also lower, but there were statistically significant differences only on day 5. These results suggest that changes in PENK gene expression after contingent cocaine administration might be involved in cocaine withdrawal states.

Organization of the CYP1A cluster on human chromosome 15: implications for gene regulation

The sequence and organization of the CYP1A cluster on human chromosome 15 was determined. A human genomic clone from a BAC library, containing both CYP1A1 and CYP1A2 genes, was isolated and sequenced. The results of Southern blot analysis using human genomic DNA were compatible with the structure of the BAC clone. The CYP1A1 and CYP1A2 genes are separated by a 23 kb segment that contains no other open reading frames. The CYP1A1 and CYP1A2 genes are in opposite orientation, revealing that the 5' flanking region is in common between the two genes. Analysis of the sequence obtained revealed the presence of xenobiotic response elements (XREs) previously reported for CYP1A1 and CYP1A2 and several additional consensus sequences for putative XREs. The presence of all the XREs upstream of both genes suggest that some of the regulatory elements known to control CYP1A1 gene expression, could also control CYP1A2 gene expression.

Feedback inhibition of the retinaldehyde dehydrogenase gene ALDH1 by retinoic acid through retinoic acid receptor alpha and CCAAT/enhancer-binding protein beta

Aldehyde dehydrogenase 1 (ALDH1) plays a major role in the biosynthesis of retinoic acid (RA), a hormone required for several essential life processes. Recent evidence, using the aryl hydrocarbon receptor-null mouse, suggests that elevated hepatic RA down-regulates ALDH1 in a unique feedback pathway to control RA biosynthesis. To determine the mechanism of suppression of the ALDH1 gene by RA, transactivation studies were carried out in Hepa-1 mouse hepatoma cells. RA decreased expression of an ALDH1-CAT construct containing -2536 base pairs of DNA upstream of the transcription start site. Retinoic acid receptor alpha (RARalpha) transactivates the ALDH1 gene promoter through a complex with an RA response-like element (RARE) located at -91/-75 bp, which bound to the RARalpha/retinoid X receptor beta heterodimer. CCAAT/enhancer-binding protein (C/EBPbeta) also transactivates the ALDH1 gene promoter through a CCAAT box located 3' and directly adjacent to the RARE, and the ALDH1 gene is down-regulated in C/EBPbeta-null mouse liver. Exposure of Hepa-1 cells to RA results in a decrease in C/EBPbeta mRNA levels; however, there was no difference in mRNA and protein levels between wild-type and AHR-null mouse liver. These data support a model in which the RARalpha and C/EBPbeta activate the ALDH1 gene promoter through the RARE and C/EBP response elements, and in Hepa-1 cells, high levels of RA inhibit this activation by decreasing cellular levels of C/EBPbeta.

Cannabinoids as potential new analgesics

Among other pharmacological properties analgesia is one of the important features of cannabinoids with therapeutical prospects. Cannabinoids have been shown to produce antinociception in experimental animals and humans. Recently a new system of neuromodulation based upon the existence of cannabinoid receptors and their endogenous agonists has emerged. This has been proposed as another of the endogenous pain control systems. Current evidence indicate an interaction between cannabinoid and opioid systems, the latter being of known relevance in nociception. The fact that either exogenous or endogenous opioids enhanced cannabinoid-induced antinociception suggests simultaneous activation of both opioid and cannabinoid receptors by drugs as a new analgesic strategy.

Opioid and cannabinoid receptor-mediated regulation of the increase in adrenocorticotropin hormone and corticosterone plasma concentrations induced by central administration of delta(9)-tetrahydrocannabinol in rats

The purpose of this study was to investigate the cannabinoid and opioid mediated regulation on the effects of central Delta(9)-tetrahydrocannabinol (Delta(9)-THC) administration on hypothalamus-pituitary-adrenal (HPA) axis activity in the male rat. Intracerebroventricular (i.c.v.) administration of delta(9)-THC (25, 50, 100 microg/rat) markedly increased plasma adrenocorticotropin hormone (ACTH) and corticosterone concentrations. Time course effect studies revealed that both hormones secretion peaked at 60 min after Delta(9)-THC i.c.v. administration (50 microg/rat), decreased gradually and returned to baseline levels by 480 min. The i.c.v. administration of the specific cannabinoid receptor antagonist SR-141716A (3 microg/rat) significantly attenuated the increase of both hormones secretion induced by Delta(9)-THC (50 microg/rat). Nevertheless, higher doses (12.5 and 50 microg/rat) of this compound increased both ACTH and corticosterone plasma concentrations. Subcutaneous (s.c.) administration with the opiate receptor antagonist naloxone (0.3 mg/kg) was without effect but significantly diminished the increase of both hormones secretion induced by Delta(9)-THC (50 microg/rat). Taken together, these results indicate that opiate and cannabinoid receptors are involved in the activation of the HPA axis induced by Delta(9)-THC. Furthermore, the increase of ACTH and corticosterone secretion after the administration of higher doses of SR-141716A than those required to block such activation, suggests that endogenous cannabinoids are tonically inhibiting the release of both hormones or that this agonist-like activity may be part of an uncharacterized action of this compound not mediated by cannabinoid receptors.

Identification of endocannabinoids and cannabinoid CB(1) receptor mRNA in the pituitary gland

Most data on effects of natural and synthetic cannabinoids on anterior pituitary hormone secretion point out to a primary impact on the hypothalamus. There is also some evidence, however, of possible direct actions of these compounds on the anterior pituitary, although the presence of cannabinoid receptors in the pituitary has not been documented as yet. In the present study, we evaluated the presence of cannabinoid CB(1) receptor-mRNA transcripts in the pituitary gland by in situ hybridization. We observed CB(1) receptor-mRNA transcripts in the anterior pituitary and to a lesser extent in the intermediate lobe whereas they were absent in the neural lobe. We then examined whether CB(1) receptor-mRNA levels in both pituitary lobes responded to chronic activation by a specific agonist, as did receptors located in adjacent hypothalamic nuclei and in other brain regions. Daily administration of CP-55,940 for 18 days produced a small, but statistically significant paradoxical increase in CB(1) receptor-mRNA levels in the anterior pituitary, with no changes in the intermediate lobe, in contrast to reduced CB(1) receptor-mRNA levels observed in the ventromedial hypothalamic nucleus (VMN), and to decreased CB(1) receptor binding in the VMN and the arcuate nucleus. The time-course of up-regulation of CB(1) receptor-mRNA transcripts in the anterior lobe was biphasic; daily administration of Delta(9)-tetrahydrocannabinol produced an early and marked decrease in CB(1) receptor-mRNA levels after 1 and 3 days, followed by normalization after 7 days and by a small increase after 14 days. We also checked whether endogenous cannabinoid ligands are present in the anterior pituitary and the hypothalamus. Although anandamide itself was detected only in trace amounts, concentrations of its precursor N-arachidonoyl-phosphatidyl-ethanolamine and of 2-arachidonoyl-glycerol were found in both tissues, suggesting that endocannabinoids may be synthetized in the anterior pituitary. In summary, CB(1) receptors and corresponding ligands seem to be expressed in cells of the anterior and intermediate lobes of the pituitary, but the response of CB(1) receptor-mRNA transcripts in the anterior lobe to chronic agonist activation is different than the desensitization observed in hypothalamic nuclei.

Pathological alterations caused by Anoplocephala perfoliata infection in the ileocaecal junction of equids

The pathological alterations caused by Anoplocephala perfoliata in the ileocaecal junction of 28 equids slaughtered in an abattoir in Madrid (Central Spain) are described. The lesions were scored in grades based on the intensity of the damage and were related to the tapeworm number observed. The first grade (grade I) of alterations consisted of a slight enteritis associated with focal erosions observed in 43% of parasitized animals with low parasitic burden (1-26 tapeworms). The second grade (grade II) was a focal pseudomembranous enteritis, present in the ileocaecal junctions of 36% infected animals with moderate to high burden (23-188 tapeworms), and the third grade (grade III) was a regional necrotizing enteritis, present in the animals (21%) with the highest burden (72-248 tapeworms). The possible role of the lesions caused by this parasite in the aetiology of colic is discussed.

Pharmacological and biochemical interactions between opioids and cannabinoids

Opioids and cannabinoids are among the most widely consumed drugs of abuse in humans. A number of studies have shown that both types of drugs share several pharmacological properties, including hypothermia, sedation, hypotension, inhibition of both intestinal motility and locomotor activity and, in particular, antinociception. Moreover, phenomena of cross-tolerance or mutual potentiation of some of these pharmacological effects have been reported. In recent years, these phenomena have supported the possible existence of functional links in the mechanisms of action of both types of drugs. The present review addresses the recent advances in the study of pharmacological interactions between opioids and cannabinoids, focusing on two aspects: antinociception and drug addiction. The potential biochemical mechanisms involved in these pharmacological interactions are also discussed together with possible therapeutic implications of opioid-cannabinoid interactions.

Chronic treatment with CP-55,940 regulates corticotropin releasing factor and proopiomelanocortin gene expression in the hypothalamus and pituitary gland of the rat

The purpose of the present study was to explore the molecular mechanisms by which the cannabinoid system may interact with the hypothalamic-pituitary adrenal axis and the proopiomelanocortin opioid system. To this aim and by using in situ hybridization histochemistry, the effects of chronic (18 days) administration with the synthetic cannabinoid receptor agonist [(-)-cis-3-[2-hydroxy-4-(1,1,-dimethylheptyl)-phenyl]-trans-4(-3-h ydroxypropyl)cyclohexanol)], CP-55,940 (1 mg/kg/day; i.p.) on corticotropin releasing factor and proopiomelanocortin gene expression were examined in the paraventricular and arcuate nuclei of the hypothalamus and anterior and intermediate lobes of the pituitary gland in the rat. Chronic administration with CP-55,940 increased corticotropin releasing factor mRNA levels (41%) in the paraventricular nucleus and proopiomelanocortin mRNA levels in the arcuate nucleus (25%) and anterior lobe of the pituitary (30%), but decreased (28%) of proopiomelanocortin transcript amounts in the intermediate lobe of the pituitary. These results revealed that chronic cannabinoid administration enhances corticotropin releasing factor and proopiomelanocortin gene expression in the hypothalamus and anterior pituitary, a process that may be considered as part of a molecular integrative response to the stress associated to cannabinoid drug abuse.

Time-dependent differences of repeated administration with Delta9-tetrahydrocannabinol in proenkephalin and cannabinoid receptor gene expression and G-protein activation by mu-opioid and CB1-cannabinoid receptors in the caudate-putamen

The purpose of the present study was to examine the time-related effects of repeated administration of Delta9-tetrahydrocannabinol during 1, 3, 7 and 14 days on cannabinoid and mu-opioid receptor agonist-stimulated [35S]GTPgammaS binding, and CB1 cannabinoid receptor and proenkephalin gene expression in the caudate-putamen. Repeated administration with Delta9-tetrahydrocannabinol produced a time-related reduction in cannabinoid receptor synthesis and activation of signal transduction mechanisms in the caudate-putamen. Indeed, WIN-55,212-2-stimulated [35S]GTPgammaS binding decreased 24% on day 1 and then progressively decreased finding a 42% decrease on day 14. Similarly, CB1 cannabinoid receptor mRNA levels decreased (22%) on day 3, reaching 50% reduction on day 7. In contrast, a pronounced increase is detected in DAMGO-stimulated [35S]GTPgammaS binding and proenkephalin mRNA levels in the caudate-putamen. The highest degree of increase was reached on day 7 of the treatment (35% of proenkephalin mRNA levels and 62% of DAMGO-stimulated [35S]GTPgammaS binding) and then values slightly decreased on day 14. Taken together, the results of the present study indicate that, in the caudate-putamen, repeated administration with Delta9-tetrahydrocannabinol produces a time-related increase in proenkephalin gene expression and mu-opioid receptor activation of G-proteins, and a time-related decrease in CB1 cannabinoid receptor gene expression and reduction in CB1 cannabinoid receptor activation of G-proteins. These results also suggest a possible interaction between the cannabinoid and opioid systems in the caudate-putamen which may be potentially relevant in the understanding of the alterations of motor behavior that occur after prolonged exposure to cannabinoids.

A single nucleotide change in the MNR1 (VCX1/HUM1) gene determines resistance to manganese in Saccharomyces cerevisiae

Several spontaneous Mn2+-resistant mutants were isolated from Saccharomyces cerevisiae strain W303-1b. All displayed an identical semidominant resistance phenotype. The gene responsible for this phenotype from one of these mutants, as well as that from the wild-type, was cloned and sequenced, which allowed the identification of a single nucleotide change in the former. Further sequencing work with the remaining mutants, as well as with others on the MNAR1 gene (Bianchi et al., 1981), indicated that all displayed the same mutation (mnr1 allele). In addition, MNR1 was shown to correspond to VCX1 and HUM1, which determine a vacuolar membrane protein. The nucleotide sequence has been deposited at EMBL, with Accession No. AJ001272.

Differential basal proenkephalin gene expression in dorsal striatum and nucleus accumbens, and vulnerability to morphine self-administration in Fischer 344 and Lewis rats

We have previously shown that the acquisition rate of intravenous morphine self-administration under a fixed ratio one (FR1) schedule of reinforcement was greater in Lewis (LEW) than Fischer 344 (F344) rats. The purpose of the present experiment was to examine the relative motivational properties of morphine (1 mg/kg) or food under progressive ratio (PR) schedules of reinforcement in LEW and F344 rats. In addition, by using in situ hybridization histochemistry we have measured in both strains of rats the basal level of proenkephalin (PENK) gene expression in dorsal striatum and nucleus accumbens (NAcc). The results show that LEW rats responded to significantly higher breaking points (BPs) than F344 rats for intravenous morphine self-administration. In contrast, no differences were found in BPs for food pellets. Basal PENK mRNA levels were significantly higher in the dorsal striatum and nucleus accumbens of F344 than in LEW rats. Taken together, these results reveal a strain difference in the reinforcing efficacy of morphine and in the basal PENK gene expression in brain regions involved in the reinforcing actions of opiates. These data also suggest that the strain differences in opiate self-administration behavior found in this and other studies may be related, at least in part, to differences in basal opioid activity between LEW and F344 rats.

Repeated administration of delta9-tetrahydrocannabinol produces a differential time related responsiveness on proenkephalin, proopiomelanocortin and corticotropin releasing factor gene expression in the hypothalamus and pituitary gland of the rat

The purpose of the present study was to explore the time related effects of repeated administration of delta9-tetrahydrocannabinol on opioid and corticotropin releasing factor gene expression in the hypothalamus and pituitary gland of the rat. By using in situ hybridization histochemistry, the effects of delta9-tetrahydrocannabinol (THC, 5 mg/kg per day; i.p.) were examined after 1, 3, 7 and 14 days of repeated administration on; (1) proenkephalin gene expression in the paraventricular (PVN) and ventromedial nuclei (VMN) of the hypothalamus, (2) proopiomelanocortin gene expression in the arcuate nucleus (ARC) of the hypothalamus and anterior (AL) and intermediate lobe (IL) of the pituitary gland, and (3) corticotropin releasing factor gene expression in the PVN. The results revealed that, in most of the hypothalamic and pituitary regions examined, repeated cannabinoid administration upregulates opioid and corticotropin releasing factor gene expression. However, the onset, the degree of magnitude of gene expression reached and the time related effects produced by repeated administration with delta9-tetrahydrocannabinol are dependent upon the brain and pituitary regions examined. Taken together, the results of the present study suggest that cannabinoids produce a time related differential responsiveness in opioid and corticotropin releasing factor gene expression, in areas of the hypothalamus and pituitary that may be related, at least in part, to a molecular integrative response to behavioral, endocrine and neurochemical alterations that occur in cannabinoid drug abuse.

Time-course of the cannabinoid receptor down-regulation in the adult rat brain caused by repeated exposure to delta9-tetrahydrocannabinol

Recent studies have demonstrated that the pharmacological tolerance observed after prolonged exposure to plant or synthetic cannabinoids in adult individuals seems to have a pharmacodynamic rather than pharmacokinetic basis, because down-regulation of cannabinoid receptors was assessed in the brain of cannabinoid-tolerant rats. In the present study, we have examined the time-course of cannabinoid receptor down-regulation by analyzing cannabinoid receptor binding, using autoradiography, and mRNA expression, using in situ hybridization, in several brain structures of male adult rats daily exposed to delta9-tetrahydrocannabinol (delta9-THC) for 1, 3, 7, or 14 days. With only the exception of a few number of areas, most of the brain regions exhibited a progressive decrease in cannabinoid receptor binding. Two facts deserve to be mentioned. First, the pattern of this down-regulation process presented significant regional differences in terms of onset of the decrease and magnitude reached. Second, the loss of cannabinoid receptor binding was usually accompanied by no changes in its mRNA expression. Thus, some structures, such as most of the subfields of the Ammon's horn and the dentate gyrus in the hippocampus, exhibited a rapid (it appeared after the first injection) and marked (it reached approximately 30% of decrease after 14 days) reduction of cannabinoid receptor binding as a consequence of the daily delta9-THC administration. However, no changes occurred in mRNA levels. Decreased binding was also found in most of the basal ganglia, but the onset of this reduction was slow in the lateral caudate-putamen and the substantia nigra (it needed at least three days of daily delta9-THC administration), and, in particular, in the globus pallidus (more than 3 days). The magnitude of the decrease in binding was also more moderate, with maximal reductions always less than 28%. No changes were seen in the entopeduncular nucleus and only a trend in the medial caudate-putamen. However, the decrease in binding in some basal ganglia was, in this case, accompanied by a decrease in mRNA levels in the lateral caudate-putamen, but this appeared after 7 days of daily delta9-THC administration and, hence, after the onset of binding decrease. In the limbic structures, cannabinoid receptor binding decreased in the septum nuclei (it needed at least 3 days of daily delta9-THC administration), tended to diminish in the nucleus accumbens and was unaltered in the basolateral amygdaloid nucleus, with no changes in mRNA levels in these last two regions. Binding also decreased in the superficial and deep layers of the cerebral cortex, but only accompanied by trends in mRNA expression. The decrease in binding was initiated promptly in the deep layer (after the first injection) and it reached more than 30% of reduction after 14 days of daily delta9-THC administration, whereas, in the superficial layer, it needed more than 3 days of daily delta9-THC administration and reached less than 30% of reduction. Finally, no changes in binding and mRNA levels were found in the ventromedial hypothalamic nucleus. In summary, the daily administration of delta9-THC resulted in a progressive decrease in cannabinoid receptor binding in most of the brain areas studied, and it was a fact that always occurred before the changes in mRNA expression in those areas where these existed. The onset of the decrease in binding exhibited regional differences with areas, such as most of the hippocampal structures and the deep layer of the cerebral cortex, where the decrease occurred after the first administration. Other structures, however, needed at least 3 days or more to initiate receptor binding decrease. Two structures, the entopeduncular nucleus and the ventromedial hypothalamic nucleus, were unresponsive to chronic delta9-THC administration, whereas others, the medial caudate-putamen and the basolateral amygdaloid nucleus, only exhibited trends.

Perinatal delta9-tetrahydrocannabinol exposure reduces proenkephalin gene expression in the caudate-putamen of adult female rats

Perinatal delta9-tetrahydrocannabinol (delta9-THC) exposure in rats affects several behavioral responses, such as opiate self-administration behavior or pain sensitivity, that can be directly related to changes in opioidergic neurotransmission. In addition, we have recently reported that the administration of naloxone to animals perinatally exposed to delta9-THC produced withdrawal responses, that resemble those observed in opiate-dependent rats. The purpose of the present study was to examine the basal opioid activity in the brain of adult male and female rats that had been perinatally exposed to delta9-THC. To this aim, proenkephalin mRNA levels were measured, by using in situ hybridization histochemistry, in the caudate-putamen, nucleus accumbens, central amygdala and prefrontal cingulate cortex. The results showed a marked reduction in proenkephalin mRNA levels in the caudate-putamen of delta9-THC-exposed females as compared to oil-exposed females, whereas no changes were observed between delta9-THC- and oil-exposed males. There were no differences in proenkephalin mRNA levels in the nucleus accumbens, central amygdala and prefrontal cingulate cortex between males and females perinatally exposed to delta9-THC and their respective controls, although a certain trend to decrease was observed in delta9-THC-exposed females. In summary, perinatal exposure to delta9-THC exposure decreased proenkephalin gene expression in the caudate-putamen of adult rats, although this effect exhibited a marked sexual dimorphism since it was only seen in females. This result is in agreement with a previous observation from our laboratory that females, but not males, that had been perinatally exposed to delta9-THC, self-administered more morphine in adulthood. This suggests that low levels of proenkephalin mRNA may be used as a predictor of greater vulnerability to opiates.

Chronic administration of cannabinoids regulates proenkephalin mRNA levels in selected regions of the rat brain

This study was designed to examine the interactions between the cannabinoid and enkephalinergic systems in the rat brain. To this aim, we have examined the effects of subchronic (5 days) administration (10 mg.kg-1.day-1; i.p.) of delta 9 -tetrahydrocannabinol (THC) or R-methanandamide (AM356) and chronic (18 days) administration with the synthetic cannabinoid receptor agonist CP-55,940 (1 mg.kg-1.day-1; i.p) on proenkephalin (PENK) mRNA levels in several brain regions of the rat. Twenty micrometer brain sections from striatum, nucleus accumbens, paraventricular nucleus, ventromedial nucleus, periaqueductal grey matter and mammillary nucleus were hybridized with an oligonucleotide probe complementary to PENK using in situ hybridization technique. Subchronic administration of THC or AM356 increased PENK mRNA levels in the ventromedial nucleus of the hypothalamus, (82%) and (39%), in the periaqueductal grey matter, (97%) and (49%), and mammillary nucleus, (43%) and (9%), respectively. In contrast, both drugs were without effect in the striatum and nucleus accumbens. On the other hand, chronic administration of CP-55,940 increased PENK mRNA levels in the striatum (44%), nucleus accumbens (25%), paraventricular (31%) and ventromedial nuclei of the hypothalamus (41%). These results revealed that chronic cannabinoid administration increases opioid gene expression in the rat central nervous system and suggest an interaction between the cannabinoid and enkephalinergic systems that may be part of a molecular integrative response to behavioral and neurochemical alterations that occur in cannabinoid drug abuse.

Reliability of coprological diagnosis of Anoplocephala perfoliata infection

Three coprological methods were tested to establish the reliability of in vivo diagnosis of Anoplocephala perfoliata. A total of 107 faecal samples were analyzed, and the presence of tapeworms were confirmed postmortem in 24 animals with burdens that ranged from 1 to 248 worms; most of them (71%) with less than 100 parasites. Best results were obtained with a combination of two sedimentation/flotation methods, detecting only half the parasitized animals (54% sensitivity). No relationship could be established between tapeworm burden and egg detection, but results indicate that coprological methods have a lower likelihood of diagnosing cestode infection when horses have less than 100 tapeworms.

delta 9-Tetrahydrocannabinol increases proopiomelanocortin gene expression in the arcuate nucleus of the rat hypothalamus

delta 9-Tetrahydrocannabinol, the main psychoactive component of cannabis, produces a large spectrum of pharmacological effects, many of which have been linked to interaction with the opioid system. The aim of this study was to examine the effects of delta 9-tetrahydrocannabinol on proopiomelanocortin (POMC) gene expression in the arcuate nucleus of the hypothalamus and anterior lobe of the pituitary. We report, for the first time, that a 5-day treatment with delta 9-tetrahydrocannabinol (5 mg/kg per day, i.p.) increased (38%) POMC mRNA levels in the arcuate nucleus of the hypothalamus but was without effect in the anterior lobe of the pituitary. These data indicate that delta 9-tetrahydrocannabinol stimulates opioid gene expression and regulates distinctively POMC in the hypothalamus and the anterior lobe of the pituitary in the rat.

delta-9-Tetrahydrocannabinol increases prodynorphin and proenkephalin gene expression in the spinal cord of the rat

Hypoalgesia induced by cannabinoid drugs has been found to implicate the opioid system. The effect of five days treatment with delta-9-tetrahydrocannabinol (THC) was examined on prodynorphin (PDYN) and proenkephalin (PENK) gene expression in the spinal cord of male rats. PDYN and PENK gene expression was estimated measuring by northern blot analysis mRNA levels in the whole spinal cord, containing perikarya of these neurons. The subchronic treatment with THC (5 mg/kg/day; 5 days; i.p.) produced an increase in PDYN (39%) and PENK (34%) gene expression when compared with the vehicle treated group. These results suggest that the effects of THC in the spinal cord involve an increase in opioid activity, and therefore sustain the hypothesis of an interaction between the cannabinoid and opioid systems in this region.