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Aim: In mammals, rewarding and aversive states are motivational drivers of behavioral expression. However, it is unclear whether such states affect neuronal functions at the level of individual neurons. In the present study, the neuronal effects of rewarding and aversive states were investigated in using PC12 mutant cells (PC12m3 cells) with low sensitivity to nerve growth factor., Main Methods: The intracranial self-stimulation (ICSS) and immobilization (IMM) methods were used to create rewarding and aversive states, respectively, in rats. Furthermore, experiments involving voluntary running on a wheel and forced running on a rotating rod were used to evaluate the effects of behavioral excitement on neurons. Then, the effects of plasma samples collected from the animals on neurite extension were examined microscopically, and p38 mitogen-activated protein kinase (MAPK) activity was assessed using Western blotting., Key Findings: Plasma samples from the ICSS and IMM rats facilitated neurite outgrowth to different degrees. However, their effects were not influenced by behavioral excitement. Furthermore, the plasma from the ICSS rats also induced upregulated p38 MAPK activity, whereas that from the IMM rats produced the same or slightly lower levels of MAPK activity to the control plasma., Significance: These findings indicate that rewarding and aversive states might cause morphological changes, such as neurite extension. As for the effects of these states on p38 MAPK activity, the former state might directly increase p38 MAPK activity, but the latter state might have no effect or cause a slight reduction in p38 MAPK activity., (Copyright © 2017. Published by Elsevier Inc.)

The use of carbamazepine has been reported to be an effective treatment for severe depression. We have already shown that the antidepressant-like effects of tricyclic antidepressants in the rat forced swim test (FST) are blocked by chronic treatment with adrenocorticotropic hormone (ACTH). In the present study, we examined the effect of the chronic administration of carbamazepine on the FST and the wet-dog shakes induced by (+/-) -1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), a 5-HT(2A) receptor agonist, in ACTH-treated rats. Chronic administration of carbamazepine did not affect the duration of immobility in saline-treated and ACTH-treated rats. The reduction of immobility, induced by chronic administration of imipramine, was blocked by treatment with ACTH. When carbamazepine was administered concurrently with imipramine, we observed a significant decrease in immobility in rats treated with ACTH. Chronic ACTH treatment increased the number of the wet-dog shakes induced by DOI. This effect of ACTH was significantly increased by the coadministration of carbamazepine and imipramine. These results suggest that the use of carbamazepine together with tricyclic antidepressants had the effect of reducing immobility time in the FST in a tricyclic antidepressant-treatment-resistant depressive model induced by chronic ACTH treatment.

Repeated injections of methamphetamine (METH) cause degeneration of striatal dopaminergic nerve terminals. In the present study, we examined the effects of interferon-gamma (IFN-gamma) on METH-induced striatal neurotoxicity in mice. Intraperitoneal injection of IFN-gamma before METH injection significantly prevented METH-induced reduction of striatal dopamine transporter (DAT)-positive signals and hyperthermia. Furthermore, intracerebroventricular injection of IFN-gamma before METH treatment markedly prevented METH-induced reduction of DAT. Interestingly, central IFN-gamma injection had no effect on METH-induced hyperthermia. In addition, IFN-gamma injected centrally after METH treatment, but not systemically, 1h after the final METH injection significantly protected against METH-induced neurotoxicity. Our results suggest that IFN-gamma injected systemically or its related molecule protects against METH-induced neurotoxicity through intracerebral molecular pathways, while it can prevent METH-induced hyperthermia through different molecular events.

There are many studies of the mechanisms of antidepressants; however, most of these studies were conducted on the hippocampus or frontal cortex. In the present study, we hypothesized that the nucleus accumbens and caudate/putamen might be major targets for antidepressant effects. Thus, we focused on G(olf) protein, a stimulant alpha-subunit of G protein that is coupled with the dopamine D1 receptor and specifically expressed in the striatum (nucleus accumbens, caudate/putamen and olfactory tubercle) in the rat brain. We examined the effects of chronic administration of imipramine, fluvoxamine, maprotiline and, as a negative control, cocaine on the level of G(olf) protein in the rat striatum. We also examined the effect of olfactory bulbectomy. Chronic imipramine treatment (10 mg/kg for 2 or 4 weeks) significantly increased the level of G(olf) in the striatum (by 17% or 18%, respectively), although this increase was not apparent after only 1 week of treatment. The time course of these changes corresponded well to that of the clinical efficacy of imipramine. Chronic fluvoxamine and maprotiline treatment (20 mg/kg for 2 weeks) also significantly increased the level of G(olf) (by 9% and 25%, respectively), but cocaine did not alter it significantly. Bulbectomy decreased the G(olf) protein level by 9%. The increases in G(olf) protein after chronic administration of these three different classes of antidepressants and the decrease after bulbectomy suggest that G(olf) protein may play an important role in the antidepressant effect.

We examined the influence of imipramine, a serotonin (5-HT) and noradrenaline (NA) reuptake inhibitor, desipramine, a NA reuptake inhibitor, bupropion, a dopamine reuptake inhibitor, fluvoxamine, a selective 5-HT reuptake inhibitor, and mazindol, a catecholamine reuptake inhibitor, on a 5-HT2A receptor-mediated behavior, (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI)-induced wet-dog shakes, in naive and adrenocorticotropic hormone (ACTH)-treated rats. Chronic administration of imipramine, desipramine and mazindol suppressed the number of wet-dog shakes in naive rats. Chronic ACTH (100 microg/rat, s.c.) treatment increased the number. Chronic administration of imipramine did not decrease the number of wet-dog shakes in ACTH-treated rats. On the other hand, desipramine and mazindol inhibited the increase in wet-dog shakes in ACTH-treated rats. Fluvoxamine and bupropion did not have any effect on the (+/-)-DOI-induced response in naive and ACTH-treated rats. NA reuptake inhibitors may improve the hyperfunction of 5-HT2A receptors induced by chronic ACTH treatment.

Previous studies suggested that the onset of phenytoin-induced gingival overgrowth depended on serum phenytoin concentration. Cytochrome P450 2C (CYP2C) plays an important role in phenytoin metabolism. Recently, single nucleotide polymorphisms in the coding region of CYP 2C influencing phenytoin metabolism were identified. The purpose of the present study was to see if CYP 2C polymorphisms might relate to the onset and severity of phenytoin-induced gingival overgrowth. Twenty-eight epileptic patients taking phenytoin aged 15 to 75 (mean age: 42.2 years old, 20 males and 8 females) and 56 unrelated healthy subjects aged 30 to 48 (mean age: 36.8 years old, 48 males and 8 females) were examined for CYP 2C polymorphisms. All epileptic subjects were examined for the degree of gingival overgrowth, daily phenytoin dose and serum phenytoin concentration. The results indicated about 7% of the subjects including epileptic and healthy subjects examined were positive for CYP 2C9*3. However, the degree of gingival overgrowth did not directly correlate with CYP 2C polymorphisms. Nevertheless, the subjects with severer gingival overgrowth exhibited significantly higher serum phenytoin concentration, indicating that phenytoin metabolism is an important determinant for the severity of the disease. Additionally, CYP 2C9*3 carriers exhibited significantly higher serum drug concentration to drug dose. Therefore, we concluded although the gene analysis is not directly related to diagnose the disease itself, it can be utilized in estimating serum phenytoin concentration from drug dose, which in turn serves to predict the future development and clinical course of the disease.

The effects of acute and repeated administration of MK-801 on flurothyl (FE)-induced seizure were investigated in mice. In the acute effect of MK-801 (0.01-0.1 mg/kg ip) in naive and FE-kindled mice, there were no changes on the latencies of clonic seizures. However, MK-801 dose-dependently inhibited both latencies and incidence of tonic seizures in mice and suppressed the grade of seizure severity in FE-kindled mice. Repeated administration of MK-801 at doses of 0.01 and 0.1 mg/kg 2 h prior to each exposure to FE for 8 days did not show any effects on the latencies of clonic seizure. However, seizure severity was significantly exacerbated in the 0.1 mg/kg treated group when mice were re-exposed to FE without MK-801 1 week after the last administration. A week after the repeated administration of MK-801 at a dose of 0.1 mg/kg for 8 days without exposure to FE, mice were exposed to FE 2 h after readministration of MK-801 until tonic seizure occurred. The latencies of clonic seizures were almost the same in the acute experiment in naive controls. The latency of tonic seizure was significantly delayed compared to the acute experiment with MK-801 at a dose of 0.1 mg/kg. These findings suggested that MK-801 possessed an anticonvulsant action against FE-induced tonic seizure. However, the efficacy of this acute effect of MK-801 was impaired at 1 week of withdrawal after repeated administrations. This may be related in part to the changes in sensitivity to NMDA receptors.

We investigated the characteristics of the flurothyl-induced seizures and the effects of antiepileptic drugs on the flurothyl-induced seizure model in a previously untested Mongolian gerbil species. Mongolian gerbils demonstrated tonic extension immediately after or within 1 min after the appearance of clonic convulsion. Very high amplitude spike waves appeared in these regions concurrent with the appearance of clonic convulsion. When the tonic extension appeared immediately after the clonic convulsion, the high amplitude spike waves continued during tonic convulsion. When the tonic extension occurred, high amplitude spike waves appeared in these three regions within a very short time, and afterward Mongolian gerbils died. Administration of valproic acid-Na (200 mg/kg), ethosuximide (100 and 200 mg/kg), clonazepam (2 mg/kg) and diazepam (0.5, 1 and 2 mg/kg) significantly prolonged the latency of clonic convulsion. Zonisamide-Na, phenytoin and carbamazepine, however, had no such effect. In Mongolian gerbils, tonic extension was demonstrated immediately after the appearance of clonic convulsion, yet, this effect was inhibited by all these drugs in a dose-dependent manner. Diazepam completely blocked the appearance of any behavioral changes in animals. These findings suggest that diazepam has a significant effect on flurothyl-induced seizures. Flurothyl-induced convulsions are associated with GABA receptors; hence, benzodiazepine (BDP) suppression may result from the strong relation between BDP and GABAnergic neurons.

We examined the influence of imipramine and lithium on wet-dog shakes induced by the (+/-)-DOI, 5-HT2A receptor agonist in adrenocorticotropic hormone (ACTH)-treated rats. The administration of imipramine for 14 days decreased the (+/-)-DOI-induced wet-dog shakes response; chronic administration of lithium for 14 days, however, had no effect. Chronic ACTH (100 microg/rat sc) treatment increased the wet-dog shake response induced by (+/-)-DOI. This effect of ACTH for 14 days, increasing the (+/-)-DOI-induced wet-dog shakes, was not inhibited by a 14-day administration of imipramine. Chronic coadministration of imipramine and lithium, lasting 14 days, decreased the wet-dog shakes response induced by (+/-)-DOI in rats treated with ACTH for 14 days. These findings indicate that lithium inhibits the hyperfunction of the 5-HT2A receptor in rats treated with ACTH when coadministered with imipramine.

We examined the effects of adrenocorticotropic hormone (ACTH) on the immobilization of rats in the forced swim test with the administration of imipramine, desipramine, or lithium. A single administration of either imipramine (10-30 mg/kg, i.p.) or desipramine (30 mg/kg, i.p.) significantly decreased the duration of immobility in normal rats in a dose-dependent manner. Lithium (10-100 mg/kg, p.o.), however, had no affect on the performance of rats in the forced swim test. ACTH (100 microg/day), administered subcutaneously to rats for 1, 3, 7, and 14 days, had no apparent effect on the duration of immobility in this test. The immobility-decreasing effect induced by a single administration of either imipramine (10-30 mg/kg, i.p.) or desipramine (30 mg/kg, i.p.) was blocked by chronic administration of ACTH for 3-14 days. The reduction of immobility, induced by chronic administration of imipramine (10 mg/kg, i.p.) for 15 days, was blocked by treatment with ACTH for 14 days. When lithium (100 mg/kg, p.o.) was administered for 15 days concurrently with imipramine (10 mg/kg, i.p.), we observed a significant decrease in immobility in rats treated with ACTH for 14 days. We suggest that chronic treatment of rats with ACTH may prove to be an effective model of tricyclic antidepressants-treatment-resistant depression.

The influence of oral adsorbent AST-120 (Kremezin) on the anticonvulsive effect and pharmacokinetics of zonisamide was investigated. Oral administration of zonisamide (50 mg/kg) blocked the appearance of the tonic extension induced by maximal electroshock seizure. This effect of zonisamide was inhibited by the oral coadministration of AST-120 (5 g/kg). In pharmacokinetics study, the serum zonisamide concentration after coadministration of zonisamide and AST-120 was significantly lower than that of single administration of zonisamide. However, the anticonvulsive effect of zonisamide was not affected by the administration of AST-120 1.5 h after zonisamide administration. In this condition, the serum zonisamide concentration was not changed. In the in vitro study, AST-120 completely adsorbed zonisamide. These findings suggest that when AST-120 is administered concurrently with zonisamide, a significant inhibition of the anticonvulsive effect of zonisamide occurs, and the decrease in serum zonisamide concentration by the adsorption effect of AST-120 is related to this phenomenon.

The effects of immobilization stress on anticonvulsant actions and pharmacokinetics of zonisamide were investigated in mice. Oral administrations of zonisamide (10, 20, and 50 mg/kg) dose-dependently reduced incidence of tonic extension (TE) induced by maximal electroshock seizure (MES). Immobilization stress for 2 h immediately after the administration of zonisamide further enhanced the anticonvulsive actions of it. On the other hand, the serum zonisamide concentrations in stressed group were lower during the first 30 min after the administration compared with that in nonstressed control group. Thereafter, there were no significant differences in the serum concentrations between two groups. The brain zonisamide concentration and the concentration ratio of brain/serum at 2 h after administration of zonisamide (50 mg/kg) were significantly higher in stressed group, rather than that in the nonstressed control group without changing the serum concentration. These results suggest that immobilization stress enhances anticonvulsant actions of zonisamide, and that increases of brain zonisamide concentration by immobilization stress may be related with this phenomenon.

Plasma phenobarbital (PB) concentrations in rat offspring were determined using a 9 microl capillary by high-performance liquid chromatography (HPLC). Capillary plasma which was put into a Bond Elut cartridge column by using 1 ml of 0.01 M KH2PO4 was applied to the column with 50 microl of 2 microg/ml of acetanilide (internal standard, I.S.). After washing the column, PB and I.S. were eluted with methanol and injected into the HPLC system. There were excellent linear correlation between the amount of PB and length of the capillary at three different concentrations. Calibration for PB was linear in the range of 0-50 microg/ml. The coefficients of variation were 3.4-5.0% and 5.9-7.5% in the within-day and between-day assays, respectively. The extraction recovery rates were 87.5-105.4%. By this method, it was possible to measure plasma PB concentrations in rat offspring without killing. These results suggested that this method is very useful to determine the plasma PB concentration derived from mother's milk in newborn rats.

Male Slc:Wistar, Std:Wistar, and Slc:F344/N rats had good acquisition of the conditioned avoidance response (CAR), while that of the male Slc:Wistar/ST, Jcl:Wistar, and Crj:Wistar rats was bad. Reserpine-induced impairment (RII) in CAR was observed 2-72 h after administration of dopaminergic (DAergic) agents in male Slc:Wistar rats. Amitriptyline (5-80 mg/kg, P.O.), imipramine, desipramine, cis-dosulepine, and trans-dosulepine at dose of 40 mg/kg, P.O. showed no antagonism against RII in CAR 20-23 h after reserpine injection (1 mg/kg, S.C.). However, the atypical antidepressive agents sibutramine (5-10 mg/kg, P.O.), bupropion (40 mg/kg, P.O.), and nomifensine (10-40 mg/kg, P.O.) exhibited antagonism against RII in CAR. The calcium channel antagonists flunarizine, nimodipine, and KP-840 at dose of 10 and 100 mg/kg, P.O., the cerebral improving agent indeloxazine (20-80 mg/kg, P.O.), the anticholinergic agent atropine (5-40 mg/kg, P.O.), 5-hydroxy-L-tryptophan (5-HTP) (40 mg/kg, I.P.), a precursor of 5-hydroxytryptamine (5-HT), and (+/-)-threo-dihydroxyphenylserine [(+/-)-threo-DOPS] (20-200 mg/kg P.O.), a norepinephrine (NE) precursor, showed no antagonism against RII in CAR. The DAergic agents methamphetamine (5 mg/kg, P.O.) and amantadine (50-250 mg/kg, P.O.), L-DOPA (200 mg/kg, P.O.), and the DAergic D1/D2 receptor agonist apomorphine (0.1-1 mg/kg, S.C.) showed marked antagonism against RII in CAR. Although the DAergic D1-receptor agonist KF-38393 (0.3-30 mg/kg, I.P.) and the DAergic D2-receptor agonist quinpirole (0.3-10 mg/kg, I.P.) induced only a weak recovery of RII in CAR when they were administered alone, in contrast to a potent synergistic recovery of RII in CAR, which was observed when SKF-38393 (1 mg/kg, I.P.) and quinpirole (1 mg/kg, I.P.) were administered together. These results suggest that the DAergic nervous system rather than the adrenergic or 5-HT nervous system is involved in RII in CAR, and that both the DAergic D1- and D2-mediated nervous systems play important roles in this process.

A simple and rapid method for the quantitation of concentrations of lamotrigine, a novel antiepileptic, in human serum was developed with high-performance liquid chromatography, using a solid-phase extraction technique. The mobile phase was composed of acetonitrile-10 mM phosphate buffer (pH 3.5) containing 5 mM sodium octanesulphonate (27:73, v/v), and components were detected at 265 nm. Retention times of acetanilide as an internal standard and lamotrigine were 3.4 and 10.3 min, respectively. The coefficients of variation were 3.1-4.5% and 4.4-9.8% for the within-day and between-day precision estimates, respectively. The extraction recovery of lamotrigine added to blank serum was 86-107%. The quantitation limit of lamotrigine was ca. 0.2 microgram/ml in 100 microliters of serum. These results suggest that the method employed in this study is useful for the routine monitoring of serum concentrations of lamotrigine in epileptic patients.

The anticonflict activities of buspirone and gepirone were examined in the Vogel's water licking test in rats. Acute treatment with buspirone induced a significant increase in water licking response, but gepirone showed slightly more marked effect than buspirone. The anticonflict activities of these compounds were potentiated by chronic administration. Especially, gepirone exhibited a dramatically remarkable anticonflict effect. These results suggest that gepirone has a great possibility of promising drug for anxiety.

Primidone (PRM) and its active metabolites, phenylethylmalonamide (PEMA) and phenobarbital (PB), in rat plasma were simultaneously determined using a solid-phase extraction technique followed by high-performance liquid chromatography (HPLC). Twenty microliters of plasma was applied to a Bond-Elut C-18 cartridge column with 0.1 microgram of acetanilide (internal standard, IS). After the column was washed, PRM, PEMA, PB, and IS were eluted with methanol and injected into the HPLC system. Calibrations for these substances were linear in the range of 0-20 micrograms/mL. The coefficients of variation were 1.5-7.9% and 3.4-9.1% in the within-day and between-day assays, respectively. The recovery rates were 96.8-101.8%. The pharmacokinetics of these substances were examined after oral administration of PRM (50 mg/kg) to rats. The Tmax values for PRM, PEMA, and PB were 1.4, 5.7, and 6.6 h, respectively, and the Cmax values were 18.2, 8.1, and 9.6 micrograms/mL, respectively. This method is useful for pharmacokinetic studies of PRM and its active metabolites.

To clarify the in vivo first-pass metabolism of omeprazole, the pharmacokinetics were examined after oral, intraduodenal (i.d.), intraportal venous (i.p.v), and intravenous (i.v.) administration at various doses to rats. Extraction ratios in the liver and intestinal tract were determined from the areas under the concentration-time curve (AUC) for i.p.v. and i.v. administration and from those for id and ipv administration, respectively. Assuming that the drug was absorbed from the gastrointestinal tract completely, the hepatic and intestinal extraction ratios were 0.80, 0.63, and 0.59 at doses of 2.5, 5, and 10 mg/kg and 0.70 and 0.73 at doses of 5 and 10 mg/kg, respectively. The bioavailability of orally administered omeprazole was 6.4, 9.6, and 12.6% at the doses of 10, 20, and 40 mg/kg, respectively. There were no differences in the distribution volume of steady state, total clearance, or elimination half-life at any doses. In addition, the AUC value after oral administration (20 mg/kg) in rats acutely intoxicated with CCl4 was 2.4 times larger than that in the control. These findings suggest that omeprazole undergoes a first-pass metabolism in the intestinal mucosa and/or lumen, as well as in the liver, and that the major contribution to the dose-dependent increase in bioavailability is a saturation of the first-pass metabolism in the liver.

A rapid and sensitive method for the assay of zonisamide in serum was developed using a solid-phase extraction technique followed by high-performance liquid chromatography. A 20-microliter volume of human serum was first purified with a Bond-Elut cartridge column. Then, the methanol eluate was injected onto a reversed-phase HPLC column with a UV detector. The mobile phase was acetonitrile-methanol-distilled water (17:20:63, v/v) and the detection wavelength was 246 nm. The detection limit was 0.1 micrograms/ml in serum. The coefficients of variation were 4.2-5.6% and 5.1-9.1% for the within-day and between-day assays, respectively. This method can be used for clinical pharmacokinetic studies of zonisamide in serum even in infant patients with epilepsy.

The effects of various beta-adrenergic receptor antagonists on nicotine-induced tail-tremor were investigated in rats. Atenolol (5 and 10 mg/kg, IP), arotinolol (5 and 10 mg/kg, IP), and carteolol (5 and 10 mg/kg, IP), hydrophilic beta-adrenergic receptor antagonists, did not affect the tail-tremor induced by nicotine given at a dose of 0.5 mg/kg SC. However, propranolol (5-20 mg/kg, IP) and pindolol (5-20 mg/kg, IP), nonselective and lipophilic beta-adrenergic receptor antagonists, did suppress the tail-tremor dose dependently. In contrast, metoprolol (5-20 mg/kg, IP), lipophilic and beta 1-selective adrenergic receptor antagonists, did not show such an effect. These results suggest that nicotine-induced tail-tremors may be mediated through central beta 2-adrenergic receptors as an appearance and developmental mechanism.

In the present study, the behavioral effects of apomorphine, methamphetamine, and haloperidol were examined in nicotine-treated rats. All animals were SC administered nicotine at a dose of 0.5 mg/kg or saline once daily for 14 days. Hyperlocomotion induced by apomorphine (0.2 mg/kg, IP) and methamphetamine (1.0 mg/kg, IP) was greater in nicotine-treated rats than in control rats. Stereotyped behaviors induced by apomorphine (1.0 mg/kg, IP) and methamphetamine (5.0 mg/kg, IP) were also potentiated in nicotine-treated rats. However, the incidence of catalepsy induced by haloperidol (0.25-1.5 mg/kg, IP) was slightly lower in nicotine-treated rats. These results suggest that chronic nicotine treatment may increase the susceptibility of the dopaminergic system to dopaminergic drugs.

Influences of exposure to standard- (containing nicotine and tar) and nicotine-reduced-cigarette smoke on the pharmacokinetics of theophylline (20 mg/kg, per os) and cimetidine (50 mg/kg, per os) were investigated in rats. Animals were exposed to standard- or nicotine-reduced-cigarette smoke for 8 min with a "smoking machine". In control rats, theophylline concentrations in plasma increased rapidly, peaked 2 h later, and then decreased gradually. Concentrations of theophylline in plasma of rats exposed to standard- and nicotine-reduced-cigarette smoke were suppressed in comparison with that of control rats, and the suppressive effect of nicotine-reduced-cigarette smoke was weaker than that of standard-cigarette smoke. The suppression of theophylline concentrations in plasma induced by exposure to cigarette smoke may be due to nicotine and other constituents of the cigarette smoke, even if the effects are slight. For cimetidine, no difference was found between drug concentration in plasma of rats exposed to nicotine-reduced-cigarette smoke and that of control rats; however, the drug concentration in plasma of rats exposed to standard-cigarette smoke was markedly suppressed. These results suggest that the suppression of cimetidine concentrations in plasma may be due solely to nicotine in cigarette smoke.

Influences of acute exposure to cigarette smoke on plasma concentrations of nicorandil administered orally and parenterally were investigated in rats by HPLC. The animals were exposed to tobacco smoke of two kinds of cigarettes using a smoking machine (i.e., the cigarette smoke contained either low or high nicotine and tar). The plasma concentration of nicorandil administered orally at a dose of 10 mg/kg had a lower absorption phase in two cigarette smoke-exposed groups, particularly in the high nicotine and tar-containing cigarette smoke-exposed group, compared with the nonsmoking control group. The AUC and MRT values in a high nicotine and tar-containing cigarette smoke-exposed group were lower and higher, respectively, than in the nonsmoking control group. However, there was no marked difference in nicorandil plasma concentrations between the cigarette smoke-exposed group and the nonsmoking control group when nicorandil was administered ip or iv at a dose of 5 mg/kg. These results suggest that cigarette smoke exposure causes the suppression or delay of absorption of nicorandil from the gastrointestinal tract.

Rats were chronically exposed to cigarette smoke for 20 min twice daily using a smoking machine. On days 1, 4, and 14, locomotor activity and rearing were measured for 15 min in an open-field apparatus. On day 1, exposure to cigarette smoke increased locomotor activity and rearing in the latter half of the observation period. This effect became more pronounced on days 4 and 14. Chronic cigarette smoke exposures for 21 days significantly decreased the norepinephrine levels in the hypothalamus, thalamus, and pons-medulla, but not the levels of dopamine, 5-hydroxytryptamine, or their metabolites. These results suggest that repeated cigarette smoke exposure increasingly stimulates locomotor activity and rearing and affects norepinephrine metabolism, especially in the brainstem.

Tremors appearing only in the tail (tail-tremor) induced by cigarette smoke and subcutaneous nicotine were investigated using a smoking machine and Wistar rats. Daily exposure (twice a day) to smokes of two commercial cigarettes (Mild-Seven Select for the first 7 days and Long-Peace for the next 6 days) caused the tail-tremor to appear even if it was slight. A single subcutaneous nicotine (0.5 mg/kg) administration to rats exposed to the cigarette smokes for 13 days markedly caused the tail-tremor. On the other hand, daily subcutaneous injection of nicotine (0.5 mg/kg/day) also caused the tail-tremor to appear beginning on the 4th day and the incidence of tremor increased to 100% by the 12th day. These results indicate that tail-tremor can be caused not only by daily subcutaneous administration of nicotine but also by daily exposure to cigarette smoke.

The influence of footshock stress on the pharmacokinetics of nicorandil was examined in rats. In the group exposed to a 30-min period of footshock immediately after the oral administration of nicorandil (10 mg/kg), plasma nicorandil levels were markedly lower than those in the control group 30-120 min after administration. Plasma levels after the subcutaneous injection of nicorandil (5 mg/kg) were also slightly but significantly lower in stressed rats than in control rats. When footshock was applied from 60 min after oral administration or 30 min after subcutaneous injection (the time when the plasma nicorandil level was maximum), it also significantly decreased the plasma levels thereafter. Furthermore, footshock applied immediately after intravenous injection of nicorandil (3 mg/kg) significantly decreased the plasma levels 30-60 min after injection. Plasma levels of N-(2-hydroxyethyl) nicotinamide, one of the main metabolites of nicorandil, were slightly increased 30 min after the intravenous injection of nicorandil (10 mg/kg) by footshock. Nicorandil levels in the heart, kidney, and skin were significantly lower in the stressed rats similar to the change in the plasma level, but levels in the muscle, liver, and thymus showed no significant difference. The urinary excretion of nicorandil tended to be higher in the stressed rats. These results suggest that footshock stress affects not only the absorption of nicorandil but also its distribution, metabolism, and excretion.

Rats were chronically implanted with electrodes aimed at the lateral hypothalamus (LH) and the dorsal central gray (DCG) and trained to press a lever that delivered rewarding stimulation of the LH and punishing stimulation of the DCG. In this situation, both diazepam (5-20 mg/kg, PO) and bromazepam (2-10 mg/kg, PO) caused a marked dose-dependent increase of the lever pressing response in the punished period. In addition, the facilitation of lever pressing in unpunished period was also seen in diazepam (5 and 10 mg/kg). These results show that behavioral suppression on lever pressing maintained self-stimulation reward is inducible following DCG stimulation, and that benzodiazepines exhibit an anti-behavioral suppression effect in this situation.

Formation of gastric lesions in response to conditioned emotional stimulus (CES) and effects of benzodiazepines were studied in mice. The CES was introduced in the form of affective communication through a communication box. The "senders" were exposed to electric foot shock and the "responders" were able to receive affective cues such as visual, auditory and olfactory from "senders". The "senders" and "responders" exhibited significantly greater gastric lesions than the controls. Diazepam at doses of 2 X 1 - 2 mg/kg (p.o.) and oxazolam at a dose of 2 X 2 mg/kg (p.o.), reduced the formation of gastric lesions of the "responders" induced non-physically by CES. The present results indicate that "responders" showed bodily changes under CES treatment, particularly in the development of gastric lesions, and that gastric lesions produced by CES were protected by diazepam and oxazolam.

Tail-tremor induced by repeated and daily administration (0.5 mg/kg SC x 6 times/day) of nicotine as well as effects of various drugs on this response were investigated in Wistar strain male rats. Daily administration of nicotine in doses of 0.5 mg/kg SC caused tail-tremors to appear beginning on the 3rd day. Tail-tremor induced by the first injection of each day gradually increased with the daily injections, however, the heightened effect of this first injection at the beginning of each day decreased during the day upon repeated administration of 6 times/day at 2-hr intervals. Basically, tail-tremor appeared about 5 min after SC administration of nicotine and reached a peak approximately 7-9 min after injection, declining to zero afterwards. Different drugs showed various effects on this response. While mecamylamine (0.5 and 1.0 mg/kg IP) abolished nicotine-induced tail-tremor, arecoline (0.5 and 1.0 mg/kg IP), atropine (2.5 and 5.0 mg/kg IP), scopolamine (1.0 and 2.0 mg/kg IP) and hexamethonium (0.5 and 1.0 mg/kg IP) showed no such effects. Furthermore, physostigmine (0.1 mg/kg IP) actually potentiated this action. These results suggest that tail-tremor induced by nicotine may be mediated through central nicotine receptor system.

Based on lateral hypothalamic self-stimulation behavior of the rat in a Skinner box, a "conflict" situation was established by combining foot shock punishment with brain stimulation. Diazepam (10-20 mg/kg, PO) caused a marked increase in the lever pressing response in the punished period without affecting the unpunished response. Bromazepam (10--20 mg/kg PO) also caused an increase in the lever pressing response in the punished period and a decrease of the punished response. These results indicate that a "conflict" situation based on self-stimulation behavior is useful for the evaluation of antianxiety action.

An analysis by means of 14C-2-deoxyglucose autoradiography of the neural systems unilaterally activated by the reinforcing stimulation used in the two accompanying papers revealed strong and reliable effects in the nucleus of the diagonal band of Broca, in the medial forebrain bundle (MFB) and/or the fornix throughout the diencephalon, and in the part of the anterior ventral tegmentum where the dopaminergic projection to the lateral habenula originates. The terminal fields of the dopaminergic forebrain projections were not affected, but there was bilateral suppression of lateral habenular activity. A second experiment found that the same systems are still activated by (automatically administered) reinforcing stimulation in rats treated with reinforcement blocking doses of pimozide. The only clear effect of pimozide was to reverse the bilateral suppressive effect of the stimulation on lateral habenular activity. Animals treated with pimozide show greatly elevated activity in the lateral habenula, whether or not they receive reinforcing stimulation. The results suggest that pimozide's effect on reinforcement is mediated by the circuitry interconnecting the lateral habenula with the nucleus of the diagonal band of Broca and/or the anterior ventral tegmentum.

When given non-contingent pretrial stimulation (priming stimulation) rats ran an alley for brain-stimulation reward faster than when there was no priming. This is one manifestation of the priming effect of rewarding stimulation. After treatment with the neuroleptic, pimozide, the first few trials fell in the range of normal primed performance when the rats were primed, and in the range of normal unprimed performance when they were not. In either case, an extinction-like decline in performance occurred after the first few trials. Run in a T-maze with water in one arm and a lever producing brain stimulation reward in the other, thirsty rats chose the stimulation reward when primed and the water reward when unprimed. Pimozide in doses that produced extinction of Skinner box responding did not alter this effect of priming on reward preference. These results demonstrate that the priming effect is unaltered by doses of pimozide that block the reinforcing effect of the stimulation.

Methamphetamine induced mortality in physically stressed and non-physically stressed mice was investigated by employing a communication box in which shocked mice communicated their distress to unshocked mice in neighboring boxes. Intraperitoneal administration of methamphetamine 30 mg/kg caused greater mortality in both the shocked "sender" mice and the unshocked "responder" mice than in control when maintained at 27 +/- 1 degree C. Forty-eight hours after injection, the "sender", "responder" and control mice showed mortality of 80, 60 and 10%, respectively. This result indicates that the mortality of methamphetamine may be potentiated not only by physical stress but also by non-physical stress.

Satiated rats could be trained to give stable rates of responding for rewarding stimulation of the lateral hypothalamus delivered on differential reinforcement of low rate (DRL) schedule requiring 2 to 8 sec interresponse intervals for reinforcement (DRL-2 to 8). The performance on a DRL-8 schedule was tested 30 min after the oral administration of benzodiazepines. Diazepam (5 and 10 mg/kg) and meprobamate (200 mg/kg) caused significant increases in response rates during the first 5 min of a session, but not thereafter. Bromazepam (1 and 5 mg/kg) also caused a significant increase in the rates during the first and second 5 min. On the other hand, chlorpromazine (20 mg/kg) caused no effect in the first 5 min but decrease in second and third 5 min. These results indicate that DRL schedules with a brain stimulation reward provided a useful tool for evaluation of antianxiety drugs. The advantage of the brain stimulation reward over food reward is that the possible effects of the drugs on hunger motivation need not be considered.

In the acquisition process of discrimination avoidance conditioning, bilateral olfactory bulbectomized rats showed poor discrimination conditioning since both the avoidance responses to positive conditioned stimuli (CS) and the incorrect responses to negative CS increased. The effects of various psychotropic drugs upon this poor discrimination conditioning were examined. Chlordiazepoxide 5 mg/kg, IP, produced an increase in the avoidance responses with simultaneous decrease in the incorrect responses, thus making the discrimination possible. Chlorpromazine 2 mg/kg, IP, worsened the discrimination by decreasing both the avoidance and incorrect responses as compared with saline-treated rats. Amitriptyline 10 mg/kg, IP, decreased the incorrect responses without affecting the avoidance responses, thus making the discrimination possible. Methamphetamine 0.5 mg/kg, IP, increased both the avoidance and incorrect responses resulting in poor discrimination conditioning. From these results, it was found that the poor discrimination conditioning of O.B. rats was improved by psychotropic drugs like chlordiazepoxide and amitriptyline.

The neuroleptic pimozide produces an extinction-like decline in the runway and Skinner box performance of rats rewarded with electrical stimulation of the medial forebrain bundle (MFB) in the lateral and posterior hypothalamus. The required dose is an order of magnitude less than the dose that incapacitates. The extinction-like decline is seen even when the drug treated rats run and receive brain stimulation in a running wheel prior to runway testing. The decline is also task-specific: after extinguishing in the Skinner box, rats readily perform in the runway, but soon show extinction in this task, too. The characteristics of pimozide's effects on rewarded behavior imply that the drug, whatever other effects it may have, does block the reinforcing effect of the brain stimulation reward.