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.

Differential effects of spinal (R)-ketoprofen and (S)-ketoprofen against signs of neuropathic pain and tonic nociception: evidence for a novel mechanism of action of (R)-ketoprofen against tactile allodynia.

The spinal activity of racemic ketoprofen and its enantiomers in models of neuropathic and tonic pain was explored in rats. Tactile allodynia and thermal hyperalgesia were induced by tight ligation of the L(5)/L(6) spinal nerves. Tonic pain was modeled by the formalin-induced flinch response. The spinal injection of (S)-ketoprofen alone or of morphine alone did not produce antiallodynic activity. A 1:1 combination of these drugs produced a robust dose-dependent antiallodynic action, consistent with previous observations where (S)-ketorolac combined with morphine also produced antiallodynia. (R)-ketoprofen given alone spinally produced a dose-dependent antiallodynia, but its activity was not augmented by spinal morphine. Conversely, (S)-ketoprofen, but not (R)-ketoprofen, blocked the second phase of the formalin-induced flinch response; neither enantiomer significantly blocked phase one of the formalin response. Again, (S)-, but not (R)-ketoprofen, interacted synergistically with spinal morphine in suppressing the phase II formalin response. These results are consistent with a spinal COX inhibitory action of (S)-ketoprofen. These results also point to a novel, as yet undefined, mechanism of action of (R)-ketoprofen against signs of neuropathic pain that does not appear to involve COX inhibition. The ability to modulate tactile allodynia is of special interest as this represents an aspect of clinical neuropathic pain that is very difficult to treat adequately.

New 1-(heterocyclylalkyl)-4-(propionanilido)-4-piperidinyl methyl ester and methylene methyl ether analgesics.

A series of new 1-(heterocyclyalkyl)-4-(propionanilido)-4-piperidinyl methyl esters and methylene methyl ethers have been synthesized and pharmacologically evaluated. In the mouse hot-plate test, the majority of compounds exhibited an analgesia (ED50 less than 1 mg/kg) superior to that of morphine. These studies revealed a pharmacological accommodation for many more structurally diverse and far bulkier aromatic ring systems than the corresponding components of the arylethyl groups of the prototypic methyl ester (carfentanil, 2) and methylene methyl ether (sufentanil, 3 and alfentanil, 4) 4-propionanilido analgesics. Compound 9A (methyl 1-[2-(1H-pyrazol-1-yl)-ethyl]-4-[(1-oxopropyl)phenylamino]-4- piperidinecarboxylate), which exhibited appreciable mu-opioid receptor affinity, was a more potent and short-acting analgesic, than alfentanil with less respiratory depression in the rat. On the other hand, the phthalimides 57A and 57B, which exhibited negligible affinity for opioid receptors associated with the mediation of nociceptive transmission (i.e., mu-, kappa-, and delta-subtypes), displayed analgesic efficacy in all antinociception tests. In addition, while 57B, compared to clinical opioids, showed a superior recovery of motor coordination after regaining of righting reflex from full anesthetic doses in the rat rotorod test, 57A showed significantly less depression of cardiovascular function at supraanalgesic doses in the isoflurane-anesthetized rat.

Drug-induced rotation in rats without lesions: behavioral and neurochemical indices of a normal asymmetry in nigro-striatal function.

Normal unoperated rats were tested for rotation (i.e., circling behavior) in a spherical "rotometer" and dose-response relationships were generated using d-amphetamine, apomorphine, L-Dopa, haloperidol, and scopolamine. The rotation induced by amphetamine was significantly antagonized by alpha-methyl-p-tyrosine and haloperidol, but not by diethyldithiocarbamate. The rotation elicited by apomorphine was unaffected by alpha-methyl-p-tyrosine. Rotation was not necessarily in the same direction with high and low doses of amphetamine, or amphetamine and apomorphine administered a week apart from each other. Dopaminergic-cholinergic interactions were evident, since pilocarpine antagonized amphetamine-induced rotation whereas scopolamine did not; scopolamine elicited rotation in the same direction as that induced by amphetamine. Left and right striatal dopamine and tel-diencephalic norepinephrine levels were determined in rats injected with various doses of amphetamine and tested for rotation. There were significant bilateral differences in striatal dopamine which were related to the direction of rotation. Since amphetamine was found to be equally distributed to the two sides of the brain, the difference in striatal dopamine appeared to be the neurochemical substrate for rotation in normal rats. These results suggest that normal rats have asymmetrical levels of striatal dopamine as well as an asymmetrical complement of striatal dopamine receptors.

Clinical endoscopic evaluation of the gastroduodenal tolerance to (R)- ketoprofen, (R)- flurbiprofen, racemic ketoprofen, and paracetamol: a randomized, single-blind, placebo-controlled trial.

Ketoprofen, a nonsteroidal anti-inflammatory drug (NSAID) of the 2-arylpropionic acid class, causes gastroduodenal hemorrhages and erosions in 10-15% of patients. The (S)- enantiomer exhibits most of the anti-inflammatory properties, with concomitant gastrointestinal toxicity. The (R)- enantiomer, however, was recently found to have analgesic properties independent of prostaglandin inhibition. Seventy-two healthy male volunteers not receiving NSAIDs, alcohol, or anti-ulcer drugs, were enrolled in a randomized, investigator-blind, placebo-controlled trial to evaluate the gastroduodenal tolerance of (R)- ketoprofen 100 mg b.i.d., (R)- flurbiprofen 100 mg b.i.d., racemic ketoprofen 100 mg b.i.d., and paracetamol 1,000 mg b.i.d. Gastroduodenal endoscopies at baseline and after 2.5 days of dosing were used to detect newly occurring hemorrhages and erosions. Adverse events were also recorded. The incidence of submucosal hemorrhages was 4/16 in the (R)- ketoprofen group, 5/16 in the (R)- flurbiprofen group, 12/16 in the racemic ketoprofen group, 1/16 in the paracetamol group, and 1/8 in the placebo group. The incidence of erosions was 2/16 in the (R)- ketoprofen group, 4/16 in the (R)- flurbiprofen group, 10/16 in the racemic ketoprofen group, 0/16 in the paracetamol group, and 2/8 in the placebo group. The differences in hemorrhages and erosions among treatments were statistically significant (gastric hemorrhages P = 0.0008; duodenal hemorrhages P = 0.00062; gastric erosions P = 0.0004; duodenal erosions P = 0.0062, Kruskal-Wallis test). At 100 mg b.i.d., (R)- ketoprofen caused fewer gastroduodenal hemorrhages and erosions than racemic ketoprofen (P = 0.019, P = 0.0112, P = 0.0097, P = 0.0139 for gastric, duodenal hemorrhages and gastric, duodenal erosions, respectively). The difference between 100 mg b.i.d. (R)- ketoprofen and 100 mg b.i.d. (R)- flurbiprofen was not statistically significant. The dissociation between analgesic and anti-inflammatory properties for (R)- ketoprofen suggests that it may represent a unique analgesic with a favorable safety profile.

Unilateral cerebral drug administration: pharmacokinetics of haloperidol and amphetamine.

Following cannulation of the right common carotid artery of female Sprague-Dawley rats, 3 microCi (10 micrograms) of either [3H]haloperidol or [3H]amphetamine were infused. At various time intervals, drug concentrations were determined in the right and left striata, anterior forebrains, posterior forebrains and cerebella. One minute following unilateral intracarotid infusion of haloperidol, approximately a 90-100-fold right/left (ipsilateral/contralateral) difference in drug concentrations was attained in the striatum and the posterior forebrain, while more than a 75-fold difference was evident in the anterior forebrain. One minute following amphetamine infusion, a difference greater than 40-fold was seen in all forebrain structures. The right-left differences steadily declined with time as a result of the declining drug concentrations of the infused hemisphere. The pharmacokinetic parameters of both the distribution and elimination phases were similar in each forebrain region for both haloperidol and amphetamine. The kinetic parameters did, however, show specific drug differences. Bilateral drug concentrations in the striatum following intraperitoneal administration of amphetamine to unilaterally cannulated rats were nearly identical. Therefore, the cannulation procedure did not significantly alter the blood supply to either hemisphere. This is the first study to quantify drug concentrations and to analyze pharmacokinetic parameters following unilateral cerebral drug administration in conscious animals. This technique should be useful in studying functional and biochemical interhemispheric relationships as well as lateralized behaviors.

Bilateral changes in striatal dopamine metabolism after unilateral intracarotid and intrastriatal administration of apomorphine.

Following cannulation of the common carotid artery of female Sprague-Dawley rats, 3 microCi (10 micrograms) of [3H]apomorphine were infused. At various time intervals, drug concentrations were determined in the right and left striata, anterior forebrains, posterior forebrains and cerebella. One minute following intracarotid infusion of apomorphine, approximately a 65-fold right/left difference in apomorphine concentrations was attained in all forebrain structures, and this difference steadily diminished with time as a result of declining drug levels in the infused hemisphere. The concentrations of dopamine and its metabolites (DOPAC, HVA and 3-MT) were quantified by gas chromatography-mass spectrometry in the right and left striata at 5 and 15 min after unilateral intracarotid infusion of 1 microgram apomorphine. At both time intervals and regardless of the side infused, the metabolites of dopamine increased ipsilateral to the side of infusion. Moreover, 3-MT levels were significantly decreased in the contralateral striatum. After direct intrastriatal injection of either 0.1 or 1.0 microgram apomorphine into the right striatum, the levels of dopamine metabolites were again increased in the ipsilateral striatum. 3-MT levels were also decreased significantly in the left striatum. In contrast to the effects observed after systemic administration of apomorphine, these results demonstrate that dopamine release in the striatum is increased by selectively delivering higher concentrations of apomorphine to the nerve terminals of the nigrostriatal neurons. The effects of unilateral apomorphine on dopamine metabolism in the contralateral striatum are most likely the effect of interhemispheric communication.

Enantioselective behavioral effects of sibutramine metabolites.

The anti-obesity agent, racemic (RS)-sibutramine, has two active metabolites, desmethylsibutramine and didesmethylsibutramine. To the extent that sibutramine itself mediates some of its side effects, desmethylsibutramine and/or didesmethylsibutramine might be safer and just as therapeutically effective. Because both desmethylsibutramine and didesmethylsibutramine are also optically active, the present study assessed the anorexic effects (2.5-10 mg/kg, i.p., for all drugs), in rats, of the R(+)-and S(-)-enantiomers of both metabolites and compared them to the effects of racemic sibutramine. Locomotor activity (2.5-10 mg/kg, i. p., for all drugs), a dopamine dependent behavior, was also measured in view of some uncertainty regarding dopaminergic effects of sibutramine. In view of sibutramine's antidepressant profile in animal models, the same drugs were also tested in the Porsolt swim test (0.1-2.5 mg/kg, i.p., for all drugs). Lastly, the IC(50)s of all drugs to inhibit uptake in vitro of norepinephrine, serotonin and dopamine were determined. Both (R)-enantiomers had significantly greater anorexic effects than those of their respective (S)-enantiomers as well as of sibutramine. All of the agents increased locomotor activity and reduced immobilized time ("behavioral despair") in the swim test; again, the (R)-enantiomers were more potent than the (S)-enantiomers and sibutramine. However, the anorexic and locomotor effects could be dissociated from each other as well as from effects in the swim test. Both (R)-desmethylsibutramine and (R)-didesmethylsibutramine as well as sibutramine decreased food intake at a time (24-42 h post-treatment) when locomotor activity was unaffected. All of the drugs appeared to be more potent in the swim test than in the other tests and all of the drugs were more potent at inhibiting uptake of norepinephrine and dopamine than of serotonin. The results suggest that these enantioselective metabolites of sibutramine could be safe and effective treatments for obesity as well as possibly for depression.

Sedative and anxiolytic effects of zopiclone's enantiomers and metabolite.

We evaluated racemic zopiclone, its (S)- and (R)-enantiomers and a metabolite, (S)-desmethylzopiclone, for their actions on locomotor activity, rotarod performance, the elevated plus maze and the Vogel conflict test of anxiety, and electroconvulsive shock-induced seizures duration. Zopiclone and its (R)- and (S)-enantiomers reduced locomotor activity, and zopiclone and its (S)-enantiomer disrupted rotarod performance at 10 mg/kg. (S)-desmethylzopiclone did not alter these measures at doses of less than 200 mg/kg. (S)-desmethylzopiclone altered plus maze performance at the lowest dose of all the zopiclone derivatives tested, caused a dose-related effect on the Vogel conflict test and caused a dose-related reduction of electroconvulsive shock-induced seizure durations. The data indicate that (S)-desmethylzopiclone can bring about an anxiolytic effect without a substantial degree of central nervous system depression, and suggest that the agent may be particularly useful clinically in the treatment of anxiety.

Intersex difference in striatal amphetamine concentration is independent of age.

Amphetamine sulfate (1.0 mg/kg) was administered intraperitoneally to two groups of male and female rats, 5 and 15 weeks of age. After 30 minutes, striata were removed and analyzed for amphetamine concentrations using gas-liquid chromatography. Females were found to have significantly higher levels of amphetamine regardless of age. These results indicate that mechanisms other than drug disposition are responsible for the previously reported behavioral sex differences that occur after administration of amphetamine.

An in vivo alpha-2 assay reversal of opioid-induced muscular rigidity and neuroleptic-induced ptosis.

A method is described to detect selective alpha-2 adrenergic agonists in vivo. Palpebral ptosis is induced in rats by the neuroleptic agent haloperidol (Hal), or by tetrabenazine (TBZ) methanesulfonate. Twenty minutes later, test compounds are injected, and ptosis is scored. In a separate test, muscular rigidity is induced by the opioid, fentanyl, and subsequently, test compounds are assessed for their ability to reverse muscular rigidity. Results indicate that only alpha-2 agonists reliably reverse neuroleptic-induced and TBZ-induced ptosis, as well as opioid-induced rigidity. An alpha-1 antagonist reversed only rigidity, whereas, alpha-2 antagonists and beta-agonists were generally ineffective in all tests. Therefore, the ability to reverse neuroleptic and TBZ-induced ptosis along with the ability to reverse opioid-induced muscular rigidity is a characteristic unique to alpha-2 agonists.

Single versus multiple infusions of fentanyl analogues in a rat EEG model.

Administration of anesthetic agents to rats produces a loss of righting (LOR) which is predictive of clinical anesthesia. Following bolus i.v. administration of fentanyl, sufentanil, alfentanil, and remifentanil, the ED100 doses for LOR were 0.035, 0.003, 0.05, and 0.020 mg/kg, respectively. For the EEG infusion studies, rats were implanted with jugular catheters and 5 cortical electrodes on the surface of the dura mater. Each agent was infused at a rate of 0.02 ml/min such that each animal received the ED100 dose every 60 seconds until LOR was observed and the infusion was stopped. Following a single infusion to LOR, the difference in time from the return of righting (ROR) to baseline EEG for fentanyl, sufentanil, alfentanil, and remifentanil was 30.9, 35.3, 14.9, and 1.3 minutes, respectively. Following a three hour washout period, multiple infusions (three successive infusions to LOR) were administered. Following ROR (after the third LOR) the return to baseline EEG for fentanyl, sufentanil, alfentanil, and remifentanil was 56.1, 58.5, 13.6, and 2.9 minutes, respectively. There were no statistically significant differences between the single and multiple infusions for the return to baseline EEG for alfentanil and remifentanil, but there were significant increases in time to return to baseline following multiple infusions of fentanyl and sufentanil. These results show that there was no cumulation of alfentanil and remifentanil with respect to EEG effects but cumulation was observed for fentanyl and sufentanil.

A simple, inexpensive rotometer for automatically recording the dynamics of circling behavior.

An inexpensive, automated system for recording circling behavior in small animals is described. The apparatus provides information concerning: left and right full (360 degrees) rotations, half (180 degrees) turns, the time it takes for a rotation, the number of consecutive rotations in each direction, reversals (180 degree changes in direction), net rotations which are displayed directly without a source of electrical power, plus other parameters of circling behavior. The system is simple in principle and construction, and is virtually maintenance free. Depending on the options desired, a single rotometer can be built for approximately $350 or less than $70 by anyone able to use basic hand tools.

Bilateral neurochemical changes induced by unilateral cerebral haloperidol administration: evidence for cerebral asymmetry in the rat.

Bilateral alterations in dopamine metabolism were determined in the striatum, olfactory tubercle, and frontal cortex of rats pretested for circling behavior. Dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), norepinephrine, and 5-hydroxyindole-3-acetic acid (5-HIAA) were measured by high-performance liquid chromatography 15 min after right or left intracarotid infusion of haloperidol. Concentrations of DOPAC and HVA were significantly increased in the striatum and frontal cortex ipsilateral to the side of haloperidol infusion, regardless of whether it was right or left. In contrast, the concentrations of these metabolites were unchanged in the olfactory tubercle after a right side infusion, but bilateral increases were evident after a left side infusion. Higher levels of DOPAC and HVA were also apparent in the left striatum and olfactory tubercle after intravenous jugular administration of haloperidol. Dopamine levels were significantly lower in the left striatum and right olfactory tubercle after intravenous haloperidol infusions. 5-HIAA concentrations were higher in the left olfactory tubercle following left side infusions of haloperidol. These data indicate that unilateral cerebral administration of haloperidol induces asymmetric and side-dependent alterations in dopamine and serotonin metabolites. These differences appear to be due to intrinsic variations in the sensitivity to haloperidol, but are not associated with the direction of circling behavior.

Sexual dimorphism in rats with respect to locomotor activity and circling behavior.

Male and female rats were tested for locomotor activity and spontaneous circling (rotation) at 4, 6, 8, 11, 13 and 15 weeks of age. Locomotor activity of females increased with age, and significant intersex differences which became apparent by 8 weeks of age were attributed to the greater persevering tendency of the females. Spontaneous rotation, on the other hand, did not change with age and significant intersex differences were not evident. Moreover, locomotor activity and rotation were not correlated at any age. In contrast to spontaneous rotation, amphetamine induced significantly more rotation in older (18 week) than in younger (5 week) females and males of both ages. Apomorphine, on the other hand, also elicited more rotation in older than in younger females, but not in males. In addition, intersex differences were not evident in younger animals tested with either drug. These data suggested that the greater persevering tendency and lateralization of females compared to males may be related to bilateral functional imbalances in nigrostriatal activity.

Reversal of opioid-induced muscular rigidity in rats: evidence for alpha-2 adrenergic involvement.

Compounds from several different pharmacological classes were tested for their ability to reverse the muscular rigidity induced by an intravenous dose of fentanyl that also caused loss of the righting reflex (LOR). Opioid antagonists reversed the entire syndrome--LOR and rigidity but, generally, rigidity could be reversed nonspecifically by doses of compounds that caused LOR by themselves (e.g., CNS depressants). Muscle relaxants and agonists of histamine, which appeared to be acting peripherally, were also effective. On the other hand, serotonergic drugs and dopamine agonists were not. However, dopaminergic antagonists with adrenolytic activity (i.e., chlorpromazine, haloperidol) reversed rigidity, whereas sulpiride did not. Moreover, rigidity reversed by neuroleptics could be restored by piperoxane, an alpha-2 adrenergic antagonist. In addition, clonidine and other alpha-2 agonists selectively reversed only rigidity following systemic or central administration at doses several orders of magnitude lower than other compounds tested. It is proposed that opioid-induced rigidity is reversed by inhibition of sympathoadrenal outflow which can be accomplished selectively, centrally, by alpha-2 agonists.