Steven A. Signs

The role of dopamine and serotonin receptors in the mediation of the ethanol interoceptive cue

The drug discrimination paradigm was used to evaluate the contribution of dopamine or serotonin receptors in the mediation of the stimulus properties of ethanol. Briefly, rats were trained to discriminate between ethanol (600 mg/kg, IP) and water vehicle. Dose-response relationships were observed for ethanol and rats were tested with various dopamine and serotonin receptor agonists and antagonists. The specific dopamine receptor agonists SKF 38393 (DA1) and LY 171555 (DA2) failed to produce appreciable ethanol-like stimulus effects. Furthermore, the dopamine receptor antagonists SCH 23390 (DA1) and haloperidol (DA2) did not affect ethanol-appropriate responding when administered in combination with the training dose of ethanol. A number of specific serotonergic receptor ligands were also tested. Quipazine, 5-MeODMT, buspirone, 8-OH-DPAT elicited intermediate ethanol-like stimulus properties in rats. The serotonin receptor blockers pizotifen, pirenperone and (-)propranolol were ineffective in blocking the interoceptive cue produced by 600 mg/kg ethanol. However, TFMPP produced strong ethanol-like discriminative properties and completely substituted for the training dose of ethanol. These results indicate that the stimulus properties of TFMPP are similar to those of a low dose of ethanol.

Nicotine-induced potentiation of ethanol discrimination

Rats were trained in a 2-lever, food-motivated operant task to discriminate intraperitoneal administration of ethanol (600 mg/kg) from vehicle. Dose-response curves for the ethanol cue were analyzed before and after pre-treatment of rats with intraperitoneal doses of 0.4 mg/kg or 0.2 mg/kg nicotine. Results demonstrate that nicotine potentiates ethanol-appropriate responding in test sessions. The results are discussed in light of the recognized correlation between smoking and alcohol intake.

Concurrent Use of Cocaine and Alcohol by Patients Treated in the Emergency Department

STUDY OBJECTIVE To compare the demographics, presenting signs and symptoms, morbidity, and mortality of emergency department patients with drug screen results positive for benzoylecgonine ester (BE; a cocaine metabolite) and those positive for BE and alcohol. METHODS We carried out a retrospective cohort study, in a university-affiliated community hospital, of 190 patients positive for BE alone and 125 patients positive for BE and alcohol. RESULTS Patients positive for BE and alcohol were more often male and single. They were more likely to have been intubated, admitted to an ICU, and involved in violent trauma and to have demonstrated altered mental status than patients who tested positive for BE alone. These patients had higher mean heart rate and blood pressure values than patients positive for BE alone, and the two patients with myocardial infarction were positive for BE and alcohol. The incidence of rhabdomyolysis and the mean blood urea nitrogen value were lower in the patients positive for BE and alcohol. The two deaths in our study were patients in the BE-and-alcohol group, but these were due to trauma and not to the toxic effects of cocaine or alcohol. CONCLUSION Cocaine use was associated with a low incidence of morbidity and mortality, but patients who combined it with alcohol had decreased mental status and required a higher intensity of care.

Stability of the stimulus properties of drugs over time

Three separate groups of rats were trained to discriminate the stimulus effects of either 600 mg/kg ethanol (n = 5), 0.8 mg/kg d-amphetamine (n = 8) or 1.0 mg/kg 1-(3-trifluoromethylphenyl)piperazine (TFMPP; n = 10). Once criterion performance was attained, each group was tested with various doses of the drug used in their training, thus allowing for calculations of dose-response curves and ED50 values. A second dose-response relationship was established at a later time, averaging over a year later, and this result was compared to the initial curve. In none of the three groups was there substantial change in the sensitivity of the rats to different doses of the drug used in training as indicated by similar ED50 values. These results suggest that the drug discrimination procedure is stable over a period of continuous training and testing.

The formation of cocaethylene and clinical presentation of ED patients testing positive for the use of cocaine and ethanol

The purpose of this investigation was to document the clinical presentation of emergency department (ED) patients who tested positive for concurrent cocaine (COC) and ethanol (EtOH) use and the incidence of cocaethylene (CE) formation in this study population. Four study groups were evaluated: (1) drug-free, (2) EtOH-only, (3) COC-only, and (4) COC plus EtOH. CE was detected in plasma or urine specimens in 88% of the COC/EtOH-positive patients, and correlated directly with plasma COC and its metabolite benzoylecognine. Blood pressure and body temperature did not vary across study groups. COC/EtOH-positive patients displayed a significantly higher mean respiratory rate while the EtOH-only study group had an elevated mean heart rate. No significant differences were detected with respect to cardiac and neurological complaints between study groups. Trauma complaints in the drug-positive groups were more frequent than the incidence reported in the drug-free population. COC/EtOH-positive patients had the greatest percentage of trauma complaints (34.6%). Nearly half of the patients who tested positive for CE cited trauma as the primary reason for reporting to the ED. We conclude that ED patients who have concurrently used COC and EtOH are more closely associated with presentations related to traumatic injury than to those related to toxicologic complications.

Expression of alpha-cardiac myosin heavy chain in normal and denervated rat muscle spindles.

Whether any fibers in rat hindlimb muscles express alpha-cardiac myosin heavy chain (MHC) is uncertain. Expression of alpha-cardiac MHC mRNA and the polypeptide for which it codes were examined in control and denervated rat muscle spindles using in situ hybridization (ISH) and immunocytochemistry (ICC). Both nuclear bag2 and bag1 intrafusal fibers in the extensor digitorum longus (EDL) muscles expressed alpha-cardiac MHC and its precursor mRNA. Furthermore, denervation of the hindlimb down-regulated alpha-cardiac MHC mRNA expression in rat nuclear bag intrafusal fibers, even though they continued to display a strong affinity for anti-alpha-cardiac MHC monoclonal antibody. These data show that (1) intrafusal fibers express the alpha-cardiac MHC gene; (2) innervation regulates alpha-cardiac MHC gene expression at a pre-translational level; and (3) ISH is more sensitive than ICC to changes in alpha-cardiac MHC gene expression in adult rat muscle spindles.

Induction of ethanol dependence increases signal peptidase mRNA levels in rat brain.

Differential Northern blot hybridization was used as a screening tool to identify mRNAs that respond quantitatively to the induction of ethanol dependence. Adult male rats were treated with repeated, high doses of ethanol for 4 consecutive days. This regimen resulted in the development of tolerance and dependence upon ethanol. RNA isolated from the ethanol-dependent rat brains was used to construct a cDNA library. One cDNA was identified that hybridized to a mRNA which increased in rat brain during the ethanol treatment. Sequence analysis of the cDNA indicated that it recognized a mRNA in rat brain which was very similar to that which encodes the 18 kDa subunit of canine signal peptidase. The rat signal peptidase mRNA was observed to increase in brain nearly 2-fold within 48 h after the initiation of ethanol treatment. Ethanol did not significantly alter β-actin mRNA levels during the treatment period. These results support the existence of an ethanol-responsive signal peptidase mRNA in rat brain.

Serotonergic involvement in the regulation of prolactin and vasoactive intestinal peptide mRNA expression in the rat anterior pituitary

These studies examined the contribution of serotonin (5-HT) to the control of prolactin (PRL) and vasoactive intestinal peptide (VIP) messenger RNA expression in rat anterior pituitary. Daily injection of rats with the biosynthetic precursor to serotonin, 5-hydroxytryptophan (5-HTP; 25 mg/kg, q.i.d.), resulted on day 5 in a 50% increase in the expression of PRL mRNA in the pituitary while at the same time reducing the levels of both the 1.0 and 1.7 kb VIP mRNA transcripts. Co-treatment of rats with 5-HTP plus the catecholamine biosynthesis inhibitor, alpha-methyl-tyrosine (alpha-MT; 150 mg/kg, q.d. x 2 days), or the dopamine receptor antagonist haloperidol (1.25 mg/kg, b.i.d. x 5 days), resulted in increases in pituitary PRL message levels that were greater than those observed with either anti-dopaminergic agent alone. In contrast, 5-HTP was unable to reverse the inhibition of PRL mRNA expression caused by treatment with the dopamine receptor agonist bromocriptine (2.5 mg/kg, b.i.d. x 5 days). Neither alpha-MT, haloperidol nor bromocriptine had a significant effect on pituitary VIP mRNA expression. Administration of the direct-acting 5-HT receptor agonist quipazine (5 mg/kg, b.i.d.) for 14 consecutive days caused a significant increase in pituitary PRL mRNA levels on day 1 and reached a plateau of 90% above control levels on days 7 and 14. VIP mRNA levels rose significantly on day 1 of quipazine treatment but thereafter fell to a minimum of 22% (1.0 kb) and 52% (1.7 kb) of control by day 14.(ABSTRACT TRUNCATED AT 250 WORDS)

Para-chlorophenylalanine treatment inhibits the expression of vasoactive intestinal peptide messenger RNA in rat anterior pituitary

Adult male Sprague-Dawley rats were treated with para-chlorophenylalanine (pCPA) or alpha-methyl tyrosine (alpha-MT) to study the effect of serotonin or catecholamine depletion on the expression of vasoactive intestinal peptide (VIP) messenger RNA in the anterior pituitary. Single injections of pCPA (300 mg/kg) for two consecutive days resulted on the third day in a dramatic depletion of serotonin in the medial basal hypothalamus, and a significant reduction in the pituitary content of VIP mRNA (1.0 and 1.7 kb). The effect of pCPA on VIP mRNA appeared to be relatively specific for the anterior pituitary since VIP message levels in the cerebral cortex did not decrease. alpha-MT treatment, (150 mg/kg) for 2 consecutive days, reduced dopamine concentrations in the MBH but had no significant effect on pituitary VIP levels. In a time-course study, hypothalamic serotonin and pituitary VIP mRNA levels were significantly depressed 1-3 days after initiation of pCPA treatment; however, 12 days after pCPA treatment, serotonin concentrations in the hypothalamus approached control values and pituitary VIP mRNA content increased an average of 2-fold over control levels in an apparent rebound effect. pCPA-treated rats injected i.p. twice a day with 5-hydroxytryptophan (5-HTP; 50 mg/kg) experienced a partial reversal in the decline in the 1.7 kb VIP mRNA seen 24 h after the first pCPA injection. However, at 72 h, supplementation with 5-HTP did not prevent the pCPA-induced decrease of pituitary VIP mRNA. These data indicate that serotonergic pathways have a major role in the control of VIP mRNA expression in the rat anterior pituitary.

Interaction of ethanol and tetrahydro-beta-carboline (THBC) in a discriminative task

Rats (n = 10) were trained to discriminate between ethanol (600 mg/kg, IP) and its vehicle, or between THBC (20 mg/kg) and its vehicle in a two-lever food-motivated operant task. Once the discriminative training criterion was attained, rats in each group were administered different doses of both ethanol and THBC. The ED50 of ethanol in the ethanol-trained rats was 298.0 mg/kg and 15 mg/kg THBC produced ethanol-like responding. The ED50 of THBC in the THBC-trained rats was 3.63 mg/kg and 1200 mg/kg ethanol produced THBC-like responding. The cross-generalization between ethanol and THBC is, thus, indicated and relates to previous evidence in which both ethanol- and THBC-trained rats generalize to a common agent, TFMPP, a putatively specific 5HT1B receptor agonist. Taken together, these observations suggest that beta-carbolines may play a role in the discriminative stimulus properties of ethanol.