Naloxone antagonism of the thermoregulatory effects of phencyclidine.

Phencyclidine elicits hyperthermia at low doses and hypothermia at high doses in rats. Naloxone antagonizes both effects. Phencyclidine's effects on thermo-regulation are probably mediated by an interaction with a mu opiate receptor.

Facilitation of recovery by -methyl-p-tyrosine after lateral hypothalamic damage.

Rats with bilateral lateral hypothalamic lesions die of starvation in approximately 7 days after surgery. Rats that were treated with alpha-methyl-p-tyrosine for 3 days prior to lateral hypothalamic surgery spontaneously eat, drink, and gain weight after surgery. These data suggest that recovery of function after lateral hypothalamic damage involves denervation supersensitivity.

Neurochemical correlate of a spatial preference in rats.

Spatial (left or right) preferences were determined for rats given foot shock in a T-maze. The animals were killed, and left and right striata were assayed separately for dopamine and left and right teldiencephalic regions were assayed for norepinephrine. Dopamine content was significantly higher (by 12 percent) in the striata contralateral to rats' side preferences than in the ipsilateral striata; there was no such difference for teldiencephalic norepinephrine. The small asymmetry in striatal dopamine content is not due to any learning- or stress-related change induced by the testing procedure but is probably inherent in normal rats. Some spatial behavior appears to be the manifestation of a normal and specific difference in the activity of left and right nigrostriatal systems.

Cocaine-induced rotation: sex-dependent differences between left- and right-sided rats.

Cocaine elicited dose-related rotation (circling) in naïve rats. The maximum effect was greater than observed previously with other drugs. Overall, females were more sensitive to cocaine than males. However, right-biased females were more sensitive than left-biased females, whereas left-biased males were more sensitive than right-biased males. The results suggest that sex-dependent differences in brain asymmetry may be an important determinant of cocaine sensitivity.

Lateralization of reward in rats: differences in reinforcing thresholds.

Fourteen rats with bilaterally implanted lateral hypothalamic electrodes were allowed to self-stimulate each side of the brain during daily test sessions. Rotation (circling behavior) during self-stimulation sessions was also recorded. All rats rotated in preferential direction regardless of the side of the brain stimulated, and, in each case, the direction was the same as that subsequently determined in response to d-amphetamine. All rats had asymmetries in self-stimulation thresholds related to the direction of rotation. Thresholds were lower on the side contralateral to the direction of rotation, and entire rate-intensity functions were displaced to the left on that side. The results, discussed in terms of lateralization of affect, suggest a model in which quantitative differences in neuronal firing can be translated into apparent qualitative specialization, with the two sides of the brain appearing to be specialized for high and low mood, respectively.

Animal-human correlates of narcotic dependence: a brief review.

Knowledge of opiate action in laboratory animals can be of great value in developing a rational clinical approach to the treatment of narcotic dependence. Physiological alterations experimentally produced by narcotics have been confirmed in human subjects, and classical laboratory effects of conditioning and operant behavior also have clinical counterparts. Realization of animal-human correlates of narcotic dependence allows a better understanding of the strengths and weaknesses of existing therapeutic modalities.

Sex difference in reward asymmetry and effects of cocaine.

Male and female rats with bilaterally implanted electrodes in the lateral hypothalamus were tested daily for self-stimulation of each side of the brain, and rotation (circling behavior) was recorded concomitantly. All rats rotated in a preferred direction, regardless of the side of the brain stimulated, and all rats had asymmetries in the sensitivity for self-stimulation (thresholds and rate-intensity functions) related to the direction of rotation. However, the direction of the asymmetry of self-stimulation was sex-dependent: the side of the brain contralateral to the preferred direction of rotation was the more sensitive side in female rats, as reported previously, whereas the ipsilateral side was the more sensitive side in male rats. In both sexes, cocaine acted predominantly on the contralateral side: that is, cocaine lowered the thresholds and shifted the rate-intensity functions to the left on both sides of the brain, but the effects were much greater on the side of the brain contralateral to the preferred direction of rotation. When compared to baseline parameters, cocaine enhanced the asymmetry of self-stimulation in female rats, but reduced or reversed the asymmetry of self-stimulation in male rats; similar effects were produced by d-amphetamine. It is suggested that at least two separate systems (both lateralized) mediate self-stimulation of the lateral hypothalamus, that the relative importance of these systems differs between the sexes and that cocaine selectively affects one of these systems.

Prior morphine exposure enhances ibogaine antagonism of morphine-induced dopamine release in rats.

The present study examines the effect of prior morphine exposure on ibogaine antagonism of morphine-induced dopamine release. Female Sprague-Dawley rats were pretreated once a day for 2 days with morphine (20 mg/kg, i.p.) or saline and given a low dose of ibogaine (10 mg/kg, i.p.) or saline 5 hr after the last morphine or saline injection. Nineteen hours later, rats (awake and freely moving) were challenged with morphine (5 mg/kg, i.p.), and dopamine and its metabolites were monitored in the striatum and nucleus accumbens using in vivo microdialysis. Neither saline pretreatment, morphine pretreatment, nor ibogaine alone altered morphine-induced increases in extracellular dopamine and dopamine metabolites in either structure. However, when morphine pretreatment was combined with ibogaine, the morphine-induced elevation of dopamine, but not of metabolites, was completely blocked. These data suggest that prior morphine exposure enhances an opioid antagonist action of ibogaine on dopaminergic systems and that prior drug exposure may be a clinically significant determinant of ibogaine efficacy and/or potency in the treatment of opioid addiction.

Acetylcholine metabolism in the rat hippocampus and striatum following one-trial passive training.

The steady state levels of acetylcholine and choline and the synthesis of acetylcholine in the hippocampus and striatum of rat brain have been determined after one-trial passive avoidance training. Steady state levels of acetylcholine and choline were not altered, but the rate of acetylcholine synthesis was significantly elevated in the striatum but not significantly elevated in the hippocampus at one hour after training.

Effects of ibogaine on acute signs of morphine withdrawal in rats: independence from tremor.

Because of the claim that ibogaine suppresses the symptoms of "narcotic withdrawal" in humans, the effect of ibogaine on naltrexone-precipitated withdrawal signs in morphine-dependent rats was assessed. Morphine was administered subcutaneously through implanted silicone reservoirs for 5 days. Ibogaine (20, 40 or 80 mg/kg, i.p.) or saline was administered 30 min prior to challenge with naltrexone (1 mg/kg, i.p.) and withdrawal signs were counted for the following 2 hr. Ibogaine (40 and 80 mg/kg) significantly reduced the occurrence of four signs (wet-dog shakes, grooming, teeth chattering and diarrhea) during naltrexone-precipitated withdrawal; three other signs (weight loss, burying and flinching) were unaffected. Ibogaine induces head and body tremors lasting for 2-3 hr and the tremors might have interfered with the expression of opioid withdrawal. To examine this issue, another experiment was conducted in which ibogaine (40 mg/kg) or saline was administered 4 hr prior to challenge with naltrexone. Although there was a complete absence of tremors, ibogaine still significantly reduced the occurrence of the same four signs of withdrawal.

No evidence for histamine-mediated morphine analgesia.

A role for brain histamine in the acute action of morphine was studied in mice. In contrast to earlier reports, whole brain histamine levels were not changed 30 min after morphine (1-56 mg/kg). Levels of the brain histamine metabolite, tele-methylhistamine were also unchanged. Morphine (1.8-10 mg/kg) caused a dose-dependent antinociceptive response that was unaffected by histamine H1-antagonists (i.p.), H2-antagonists (i.p. or i.vent.), or metoprine (i.p.), an inhibitor of histamine metabolism. alpha-Fluoromethylhistidine, the inhibitor of brain histamine synthesis, unexpectedly potentiated the response to low doses of morphine. These results find no evidence for a role of brain histamine in opiate analgesia.

14 beta-[(p-nitrocinnamoyl)amino]morphinones, 14 beta-[(p-nitrocinnamoyl)amino]-7,8-dihydromorphinones, and their codeinone analogues: synthesis and receptor activity.

A series of 14 beta-[(nitrocinnamoyl)amino]codeinones and morphinones, some of which contain a 5 beta-methyl group, were prepared from 14 beta-aminocodeinones and 14 beta-[N-(cyclopropylmethyl)-amino]norcodeinones. The affinities of the target compounds for the mu, delta, and kappa opioid receptors were determined by radiolabeled binding experiments using bovine brain membranes. An analogous series of 7,8-dihydrocodeinones and morphinones was prepared and assayed in the same systems. The 3-methoxy derivatives 3 and 4 were more selective than the corresponding morphinones for the mu receptor. The 5 beta-methylcodeinones 25 and 27 had lower affinity at all receptors than the corresponding morphinones, but the 5 beta-methylmorphinones had affinities similar to the morphinones 5 and 6. A similar pattern was observed in the 7,8-dihydro series. Two compounds, 5 beta-methyl-14 beta-[(p-nitrocinnamoyl)amino]-7,8-dihydromorphinone, 20 (MET-CAMO), and N-(cyclopropylmethyl)-14 beta-[(p-nitrocinnamoyl)amino]-7,8-dihydronormorphinone, 22 (N-CPM-MET- CAMO), acted as nonequilibrium ligands in antinociception and membrane binding studies. In mice after icv administration, neither ligand showed any agonist activity but 8-24 h after administration both compounds acted as potent mu antagonists. A Scatchard plot of the effect of N-CPM-MET-CAMO on [3H]DAMGO ([3H]D-Ala2, (Me)-Phe4, Gly(ol)5] enkephalin) binding to bovine striatal membranes showed that there was a significant decrease in the Bmax value and a marginal effect on the Kd value suggesting that the number of binding sites was reduced. When taken together, these results support the view that 20 and 22 bind covalently to the mu receptor. On the other hand, when N-acetylcysteine and 22 were allowed to react in a buffered solution, 22 was recovered unchanged. Under these conditions no Michael reaction was observed.

Asymmetric syntheses, opioid receptor affinities, and antinociceptive effects of 8-amino-5,9-methanobenzocyclooctenes, a new class of structural analogues of the morphine alkaloids.

Several 8-amino-5,9-methanobenzocyclooctenes have been prepared by asymmetric organic synthesis techniques. Opioid receptor affinity studies have revealed the virtual absence of enantioselectivity for receptor binding, particularly at the mu-receptor, for the (+)-3a-f and the (-)-3a-f series. It is noteworthy that inversion of configuration at the nitrogen-bearing carbon atom [5S,8S,9S)-8-amino-3-hydroxy-5, 9-methano-9-(methoxymethyl)-5-methylbenzocyclooctene, (+)-3a vs (5S,8S,9R)-8-amino-3-hydroxy-5, 9-methano-9-(methoxymethyl)-5-methylbenzocyclooctene, (dl)-22] resulted in a > 10-fold increase in kappa-receptor affinity. Antinociceptive studies demonstrated that (dl)-22 was a full kappa-agonist while (+)-3a and (-)-3a did not possess kappa-activity. Although both (dl)-22 and (+)-3a/(-)-3a had high affinity for the mu-receptor, these compounds did not act as high-affinity agonists or antagonists at this receptor.

Apomorphine-induced and pilocarpine-induced hypothermia in mice: drug interactions and changes in drug sensitivity after caudate nucleus lesions.

1 Apomorphine and pilocarpine each produced dose-dependent hypothermic effects in mice. However, the dose-response curve for pilocarpine was steeper than that for apomorphine.2 Bilateral lesions of the caudate nucleus produced a permanent decrease in sensitivity to apomorphine but had no effect on sensitivity to pilocarpine.3 Apomorphine and pilocarpine had synergistic effects; i.e. the hypothermic effect was greater following a combination of the drugs than following either drug alone.4 The effect of apomorphine was antagonized by either haloperidol or scopolamine; only scopolamine antagonized the effect of pilocarpine.5 These results suggest that a mechanism involving dopaminergic neurones in the caudate nucleus has a modulatory role in temperature regulation.

Possible modulating influence of frontal cortex on nigro-striatal function.

1. After administration of (+)-amphetamine, rats with unilateral ablations of the frontal cortex rotated either ipsilaterally or contralaterally as a function of time after surgery.2. At early postoperative intervals (1-7 days), rotation was towards the side of the lesion.3. At later times (15-30 days), rotation was towards the intact side.4. Repeated testing with amphetamine appeared to slow the time-course of changes in rotational behaviour.5. These results suggest that a dopaminergic nigro-striatal system is modulated by the frontal cortex and that unilateral removal of the latter produces a denervation supersensitivity of the former.

Pharmacological comparison of the effect of ibogaine and 18-methoxycoronaridine on isolated smooth muscle from the rat and guinea-pig.

Ibogaine and 18-methoxycoronaridine are naturally occurring alkaloids reported to possess antiaddictive properties in several models of drug dependence. We have examined their effect at mu-opioid receptors regulating neurogenic contractions of several smooth muscle preparations and also against spontaneous contractions of the rat isolated portal vein. Ibogaine (pIC(50) 5.28) and 18-methoxycoronaridine (pIC(50) 5.05) caused a concentration-dependent inhibition of cholinergic contractions of the guinea-pig ileum which was not affected by the opioid receptor antagonist naloxone (1 microM). In the rat isolated vas deferens ibogaine and 18-methoxycoronaridine caused a concentration-dependent enhancement of purinergic contractions. Both agents (30 microM) caused a 3 - 5 fold rightward displacement of DAMGO-induced inhibition of purinergic contractions, but similar effects were observed for ibogaine against alpha(2)-adrenoceptor-mediated inhibition of neurogenic responses. In the guinea-pig isolated bladder both ibogaine (10 microM) and 18-methoxycoronaridine (10 microM) caused a 2 fold increase in the purinergic component of neurogenic contractions without significantly altering cholinergic contractions or responses to exogenous ATP. In contrast, ibogaine (1 - 30 microM), but not 18-methoxycoronaridine, caused a concentration-dependent enhancement of spontaneous contractions of the rat isolated portal vein. In summary, while ibogaine and 18-methoxycoronaridine modulated electrically-evoked contractions in the three preparations examined, we have no evidence for a selective interaction with pre-junctional mu-opioid receptors. The pronounced enhancement of purinergic contractions produced by both agents is a novel finding and worthy of further investigation.

Identification and quantification of the indole alkaloid ibogaine in biological samples by gas chromatography-mass spectrometry.

A sensitive and highly selective analytical chemical method for measuring the indole alkaloid ibogaine in biological samples has been developed. The method utilizes organic extraction, derivatization with trifluoroacetic anhydride, and detection by combined gas chromatography-mass spectrometry. The deuterated analog of ibogaine, O-[Cd3]-ibogaine, was synthesized and used as an internal standard for the method. Standard curves, constructed from variable amounts of ibogaine (50-400 ng) and a fixed amount of internal standard (250 ng) were linear. The method has an approximate detection limit of at least 20 ng/mL of tissue extract (180 ng/g tissue), with a coefficient of variation of 8 to 12.5%. Chemical stability studies with the method found that aqueous ibogaine solutions (1-10 mg/mL) could be stored at 10 degrees for up to 7 months with no more than 10% loss. The method was also used to measure brain ibogaine levels in rats 1 and 19 hr after a single dose of drug (40 mg/kg, i.p.); the results suggest a rapid disappearance of the drug after i.p. dosing. The method will help reveal the pharmacokinetic properties of this putative anti-addictive agent in animals and humans.

Circling behavior exhibited by a transgenic insertional mutant.

We report here of an abnormal circling behavior expressed in the TgX15 transgenic mouse line as a result of insertional mutagenesis. Homozygous transgenic mice expressed the phenotype while heterozygous transgenics were normal. We also found that the dopamine D2 receptor binding sites in the striata of the circling mice were significantly elevated by about 31% compared to normal heterozygous transgenic mice. Other transgenic lines constructed with the same transgene appeared normal suggesting that, in the TgX15 line, a genetic locus significant in mammalian motor behavior has been disrupted.

Ontogeny of hyperactivity and circling behavior in a transgenic insertional mutant mouse.

In a previous study (Ratty et al., 1990), the discovery of a transgenic mutant mouse that displayed abnormal circling behavior was reported. Mice homozygous for the transgene display this phenotype, whereas heterozygotes are phenotypically normal. In this study, circling mutants displayed excessive lateralized circling behavior and locomotor hyperactivity by Postnatal Days (PND) 14 and 16, respectively. These abnormalities persisted unattenuated through adolescence and adulthood. Disturbances in rearing and grooming were also observed in circling mutants. Surface-righting ability in the mutants was normal, and the age of eye opening was only marginally delayed. However, body weights of the mutants were reduced compared with normal mice from PND 15 to adulthood. Possible relationships between the behaviors that are exhibited by circling mutants and previous neurochemical findings are discussed.

Classical conditioning of amphetamine-induced lateralized and nonlateralized activity in rats.

Amphetamine-induced lateralized activity (rotation) and nonlateralized activity (extra quarter turns) was classically conditioned in female rats using the test environment as the conditioned stimulus (CS) and 1.25 mg/kg d-amphetamine as the unconditioned stimulus. Conditioned lateralized activity extinguished more rapidly than nonlateralized activity. Also, d-amphetamine-induced nonlateralized activity was selectively decreased by a schedule of 50% partial reinforcement. These results indicate that the two d-amphetamine responses can be distinguished, that they are differentially affected by learning, and that a schedule of partial reinforcement can selectively attenuate one effect of a drug while leaving the other intact. In addition, haloperidol blocked conditioned lateralized activity; this suggests that the conditioned response may be, like the drug-induced response, mediated by dopamine.