Modulation by protein kinase C of nitric oxide and cyclic GMP poffation in cultured cerebellar granule cells

The possible modulation of nitric oxide (NO) synthase (NOS) activity by protein kinase C (PKC) was investigated in primary cultures of rat cerebellar neurons. Incubation of the cells with L-arginine and nicotinamide-adenine dinucleotide phosphate (NADPH) produced detectable levels of NO, as quantified by photometric assay [0.14 +/- 0.03 nmol/h/dish (2.5 x 10(6) cells)]. The NO producing activity was paralleled by concomitant accumulation of cyclic GMP (cGMP) (0.12 +/- 0.02 pmol/dish). Downregulation of PKC by prolonged treatment with phorbol esters or inhibition of the kinase by treatment with 4taurosporine raised the basal levels of NO and cGMP five fold. When granule cells were incubated in the absence of extracellular Mg2+, N-methyl-D-aspartate and to a lesser extent, glutamate became effective in enhancing NO formation and cGMP accumulation with respect to the control. The NO and cGMP increases induced by the two agonists were almost doubled by treatment of the cells with staurosporine or depletion of PKC. Calphostin C. an inhibitor of the regulatory domain of PKC, was as effective as staurosporine in increasing the formation of NO in both resting and excited cells. These results indicate that downregulation or inhibition of PKC increase NOS activity in cerebellar neurons, and suggest that phosphorylation of NOS by PKC negatively modulates the catalytic activity of the enzyme in these cells.

Differential effects of acute and chronic fluoxetine administration on the spontaneous activity of dopaminergic neurones in the ventral tegmental area

1. Electrophysiological techniques were used to study the effects of fluoxetine and citalopram on the basal activity of dopaminergic neurones in the ventral tegmental area (VTA) and substantia nigra, pars compacta (SNc) of rats. 2. Acute i.v. injection of fluoxetine (20-1280 micrograms kg-1) caused a dose-dependent inhibition of the firing rate of VTA dopaminergic neurones, but did not affect the activity of dopaminergic cells in the SNc. Citalopram (20-1280 micrograms kg-1, i.v.) inhibited the firing rate of dopaminergic neurones in the VTA, but its effect (maximal inhibition: 14 +/- 7%) was less pronounced than that of fluoxetine (maximal inhibition: 34 +/- 7%). 3. Pretreatment with mesulergine (80 micrograms kg-1, i.v.), a 5-hydroxytryptamine2C/2B (5-HT2C/2B) receptor antagonist, blocked the inhibitory effect of fluoxetine on VTA dopaminergic cells. Selective lesions of 5-hydroxytryptaminergic neurones by the neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT), abolished the fluoxetine-induced reduction of VTA dopaminergic activity. 4. In a series of experiments, fluoxetine (10 mg kg-1, i.p.) was administered once daily for 21 consecutive days. Acute i.v. administration of fluoxetine (20-1280 micrograms kg-1, 72 h after the last i.p. injection) did not cause any change in the basal firing rate of VTA dopaminergic neurones in treated rats, whereas it induced the typical inhibitory effect in control animals. A group of rats chronically treated with fluoxetine, received i.v. m-chlorophenylpiperazine (mCPP; 10-320 micrograms kg-1), a 5-HT2C/2B receptor agonist. This drug significantly inhibited VTA dopaminergic function in control rats, but did not modify the basal activity of dopaminergic cells in animals given chronic fluoxetine. 5 It is concluded that fluoxetine inhibits dopaminergic function in the VTA by enhancing the synaptic levels of 5-HT, which possibly acts through the 5-HT2C/2B receptor subtype. Repeated treatment with fluoxetine induces tolerance to its inhibitory effect on dopaminergic activity, possibly as a consequence of down-regulation of 5-HT2C/2B receptors. The effects of fluoxetine on VTA dopaminergic cell activity might be relevant for its therapeutic actions and may explain the origin of the reported cases of akathisia.

Serotonin-dopamine interaction in the rat ventral tegmental area: an electrophysiological study in vivo

Electrophysiological techniques were used to study the effects of various serotonin (5-HT) agonists and antagonists on the activity of dopamine (DA) neurons in the ventral tegmental area (VTA) of rats. Systemic administration of the selective 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (1.25-80 micrograms/kg i.v.) increased the firing rate of the majority (75%) of DA cells studied and stimulated their bursting activity. A subpopulation (25%) of DA neurons was inhibited by 8-OH-DPAT. Selective lesions of 5-HT neurons by the neurotoxin 5-7-dihydroxytryptamine abolished completely the excitatory effect of 8-OH-DPAT on both firing rate and bursting activity of DA neurons. Microiontophoretic application of 8-OH-DPAT into the VTA did not cause any change in the firing rate of DA neurons. Treatment with the selective 5-HT1B agonist CGS 12066B (7-trifluoromethyl-4-(4-methyl-1-piperazinyl)-pyrolo[1,2-a] quinoxaline 1:2 maleate salt) (1.25-160 micrograms/kg i.v.) did not cause any change in basal firing rate of VTA DA cells. Systemic administration of trifluoromethylphenylpiperazine (TFMPP) (1.25-160 micrograms/kg i.v.) and m-chlorophenylpiperazine (mCPP) (1.25-320 micrograms/kg i.v.), two mixed 5-HT1B/5-HT1C receptor agonists, significantly reduced the firing rate of all VTA DA neurons studied. The effect of mCPP (maximal inhibition, 40%) was more pronounced compared to that of TFMPP (maximal inhibition, 25%). Microiontophoretic application of mCPP into the VTA caused a marked inhibition of the basal activity of DA neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinetics of bromocriptine release from microspheres: comparative analysis between different in vitro models

This paper describes how the use of different in vitro experimental systems can influence the determination of (a) the drug release profile from microparticles and (b) the interpretation of the release mechanism(s). We employed, as model dosage form, the Parlodel LA, a recently marketed microsphere system especially designed for bromocriptine-controlled delivery. The release kinetics of bromocriptine from microspheres were determined by using two different experimental approaches: a dialysis method and a flow-through cell method. From the comparison of the obtained data it clearly appears that different in vitro experimental models lead to distinct results in terms of drug availability. On the contrary both series of data can be convincingly fitted with the same mathematical equation, giving almost identical results in terms of postulated release mechanism. Taken together these results indicate that different experimental approaches should always be employed to determine drug release kinetics from microparticles in order to obtain more reliable information on the therapeutic dose (bioavailable drug, for in vivo experiments) and on the uniformity of different batches of microspheres.

Activation of glutamate receptors stimulates the formation of nitrite in synaptosomes from rat cerebellum

Synaptosomes from rat cerebellum were used to investigate the involvement of different glutamate receptor subtypes in the control of the synthesis of nitric oxide (NO), measured as its breakdown product nitrite (NO2-). Synaptosomes incubated in the presence of NADPH and L-arginine produced measurable levels of NO2-, which were reduced by addition of N omega-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthase. The selective ionotropic glutamate receptor agonist N-methyl-D-aspartate (NMDA) induced a pronounced increase in NO2- formation, which was prevented by N omega-nitro-L-arginine methyl ester and by the specific NMDA receptor antagonist DL-2-amino-5-phosphonovaleric acid (AP-5). The NMDA-induced increase in NO2- formation was blocked by chelation of extracellular Ca2+ with EGTA. Both L-glutamate and the selective agonist for the metabotropic glutamate receptors (+/-)-1-aminocyclopentane-trans-1,3-dicarboxylic acid raised NO2- production, which returned to control levels after addition of N omega-nitro-L-arginine methyl ester. The selective glutamate ionotropic receptor agonist (R,S)-alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid did not cause any change in NO2- formation. The stimulatory effect of L-glutamate was blocked by the metabotropic glutamate receptor antagonist DL-2-amino-4-phosphonobutyric acid but was unaffected by the selective NMDA receptor blocker AP-5. Removal of extracellular Ca2+ by EGTA did not affect the action of L-glutamate; whereas W-7, an inhibitor of calmodulin, and dantrolene, a compound that blocks the mobilization of Ca2+ from intracellular stores, abolished the effect of L-glutamate on NO2- formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Production and in vitro evaluation of gelatin microspheres containing an antitumour tetra-amidine

The preparation and characterization of gelatin microspheres (GMs) containing the antitumour aromatic tetra-amidine TAPP-Br and its release characteristics from microspheres are described. Spherical gelatin microspheres, showing a high percentage of drug encapsulation (over 95 per cent) and an average diameter of 16 microns were obtained by a coacervation method. In addition, the effects of various reaction parameters on the production and chemical hardening of GMs have been investigated. In order to compare the TAPP-Br release profiles from GMs prepared with different procedures, in vitro studies were carried out. The biological effect of TAPP-Br released from gelatin microspheres was determined on 'in vitro' cultured tumour cell lines, showing that, after encapsulation, TAPP-Br still retains antiproliferative activity comparable with that exhibited by the free drug. Taken together, the results obtained suggest that gelatin-based microspheres offer excellent potential as carriers for the controlled release of polyamidines in anticancer chemotherapy.

Rapid and simple method for the determination of nitrite in synaptosomal superfusates by liquid chromatography with electrochemical detection

A rapid and simple technique using reversed-phase high-performance liquid chromatography with electrochemical detection (HPLC-ED) was developed for the determination of nitrite. Standard solutions of sodium nitrite produced a linear current response over the concentration range 1.5-30 microM. The chromatographic peaks of sodium nitrite were superimposable with peaks obtained after injection into the chromatograph of supernatants from rat cerebellar synaptosomes. The concentrations of nitrite in synaptosomes measured with HPLC-ED were similar to those found with a widely used colorimetric procedure. Therefore, this new method may represent a useful means of measuring nitrite in biological samples.

Tertatolol, a new beta-blocker, is a serotonin (5-hydroxytryptamine1A) receptor antagonist in rat brain

The interaction of tertatolol (d,l-hydroxy-2'-t-butylamino-3'propyloxy-8-thiochromane HCl) with 5-hydroxytryptamine (serotonin; 5-HT) receptors in several brain areas were investigated. Both ligand binding techniques and an electrophysiological approach were used. First, the affinity of tertatolol for different 5-HT receptor subtypes was measured, as assayed by a competition binding experiment using specific ligands in several brain areas. It was found that (-)-tertatolol binds to 5-HT1 receptor subtypes in rat brain, particularly the 5-HT1A subtype in the hippocampus (Ki = 5.9 nM). (-)-Tertatolol showed much lower affinity for 5-HT1B (Ki = 118.4 nM), 5-HT1C (Ki = 699.6 nM) and 5-HT2 (Ki = 678.6 nM) receptors. The binding of tertatolol to hippocampal 5-HT1A receptors was stereospecific in that the affinity of (+)-tertatolol to these receptors (Ki = 311.6 nM) was about 20 times lower as compared to that of (-)-tertatolol. There was no significant binding of tertatolol to 5-HT1D, 5-HT3, alpha-1 adrenergic receptors or to the serotonin uptake site. Electrophysiological techniques were used to study the effects of (-)-tertatolol on the activity of 5-HT-containing neurons in the rat dorsal raphe nucleus. Acute i.v. injection of (-)-tertatolol caused a slight increase in the basal firing rate of the majority of 5-HT neurons studied. Pretreatment with (-)-tertatolol (1 mg/kg i.v.) significantly reduced the inhibitory effect of 8-hydroxy-2-(di-n-proylamino) tetralin (0.25-64 micrograms/kg i.v.) on the firing rate of dorsal raphe nucleus 5-HT neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

[Use of enoximone in the postoperative course of heart surgery]

The aim of this study was to evaluate the efficacy and safety of enoximone, an imidazolonic compound inhibiting cardiac phosphodiesterase III, during the postoperative period. The drug was administered prior to the usual stages of weaning the patient off extracorporeal circulation, to a group of 20 subjects who presented an ejection fraction of less than 35% following hemodynamic studies. Patients were randomly subdivided into 4 groups each of which received a different dose of enoximone according to the following protocol: Group A, 1 mg/kg bolus and slow infusion at 10 gamma/kg/min; Group B, 0.5 mg/kg bolus and slow infusion at 15 gamma/kg/min; Group C, 0.5 mg/kg bolus and slow infusion at 10 gamma/kg/min; Group D, slow infusion at 10 gamma/kg/min. The best results in hemodynamic terms and with regard to the positive inotropic and vasodilatory action of the drug in question were obtained in Group C. Increased cardiac output was observed in all patients within 120 minutes of enoximone administration and reduced systemic vascular resistance after approximately 6 hours of infusion. Special attention should be drawn to the use of the drug in patients who do not respond to conventional therapy due to its mechanism of action which is not dependent on beta receptors, thus enabling good results to be achieved even when these are down regulated. Special care must be taken however in administrating enoximone to platelet-deficient patients since the reduction of platelet levels is one of its collateral effect. Other collateral effects observed were: supraventricular arrhythmias and ventricular tachyarrhythmias.

Growth of Helicobacter pylori in media containing cyclodextrins

We show that solid and liquid media, supplemented only with cyclodextrins and free of blood and its derivatives, support the growth of Helicobacter pylori. These media can be used for primary isolation of the bacteria from biopsy samples, routine laboratory growth, and large-scale industrial fermentation.

DNA binding activity and inhibition of DNA-protein interactions. Differential effects of tetra-p-amidino-phenoxyneopentane and its 2'-bromo derivative

In the present study are reported the differential DNA binding activity of the anti-tumor polyamidine tetra-p-amidinophenoxyneopentane (TAPP-H) and its 2'-halo derivative (TAPP-Br), and their effects on the binding of the recombinant Epstein-Barr virus (EBV) nuclear antigen to a synthetic oligonucleotide mimicking the target DNA sequence present in the EBV genome. In addition, the proliferation kinetics and cell cycle analysis of human leukemia K562 cells treated with TAPP-H and TAPP-Br are reported. The possible in vivo relationship between DNA binding affinity and cytotoxicity is also discussed.

[Adenotonsillectomy: the evaluation of the long-term results after more than 7 years from the intervention]

A study was carried out on 110 patients with various diseases related to chronic inflammation of the tonsils and to hypertrophic adenoids. Sixty-two of these patients underwent adenotonsillectomy, while the others were followed clinically and, where necessary, given medical treatment. At the first observation the patients were between the ages of 2 and 12 (mean age 6.1 years). At the start of the present study the patients ages ranged from 10 to 22 (mean age 17 years). Clinical follow-up was carried out on the patients 2 and 7 years after the first observation and/or adenotonsillectomy. The patients were divided into homogeneous groups according to the severity of symptoms. The A.A. evaluated changes of the following clinical parameters: annual frequency of inflammatory pharyngotonsillar episodes, nasal respiratory obstruction, sore throat, otologic pathology. Evaluations were carried out statistically in each group. After more than 7 years from surgery, the significant reduction of various diseases related to chronic inflammation of the tonsils and to hypertrophic adenoids, in accordance with the findings after 2 years from surgery, underline the effectiveness of adenotonsillectomy in correctly selected candidates.

Physiological significance of long-term potentiation

Long-term potentiation (LTP) is a form of synaptic plasticity that follows repetitive, high frequency stimulation of excitatory presynaptic fibers. It produces a long-lasting enhancement of synaptic strength that is usually revealed as an increased size of excitatory postsynaptic potentials. It is most prominent in the hippocampus, although it may be evoked in other brain regions. Use-dependent modifications in synaptic function are probably the basis of learning and memory, thus the study of LTP may represent a useful model for investigating the physiological mechanisms underlying the process of information storage.

Chronic treatment with DAU 6215, a new 5-HT3 receptor antagonist, causes a selective decrease in the number of spontaneously active dopaminergic neurons in the rat ventral tegmental area

Electrophysiological techniques were used to study the effects of the new compound, DAU 6215 ((3-alpha-tropanyl) 1H-benzimidazolone-3-carboxamide chloride), a selective 5-HT3 receptor antagonist, on the activity of dopamine (DA)-containing neurons in the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA). Acute i.v. injections of DAU 6215 did not cause any change in the basal firing rate of DA neurons in the SNc or in the VTA. Pretreatment with DAU 6215 did not modify the inhibitory effect of apomorphine on the firing rate of midbrain DA neurons. Acute s.c. administration of DAU 6215 caused a significant increase in the number of spontaneously active DA neurons in the VTA but not in the SNc. This effect was similar to that of acute clozapine, whereas acute haloperidol caused a significant increase of spontaneously active DA neurons in both the SNc and the VTA. Repeated consecutive s.c. administration of DAU 6215 and clozapine for 21 days produced a significant decrease in the number of spontaneously active DA neurons in the VTA but not in the SNc. Chronic haloperidol (21 days) decreased the number of DA cells both in the SNc and VTA. The effect of chronic DAU 6215 on the activity of VTA DA neurons was reversed by apomorphine, suggesting that these neurons were probably under a state of depolarization block. These findings indicate that DAU 6215 may have potential antipsychotic activity, probably associated with a low incidence of extrapyramidal side-effects.

[Exclusive radiotherapy of carcinoma of the hypopharynx. Retrospective study of a series of 100 patients]

From January 1980 to December 1987, 100 patients with carcinoma of the hypopharynx, staged according to TNM (UICC-1978) criteria, received exclusive radiation therapy at the Radiotherapy Department of the General Hospital of Varese. The median follow-up is 9 months (range: 1-97). Irradiation was delivered with 60Co or with 10 MV photons and tissue-equivalent bolus. Two opposed parallel lateral fields or rotational technique were used, with progressive shrinking of treated volume in order to spare the spinal cord after 45 Gy. Direct fields of electron beams (6-15 MeV) were employed as boosts on the residual nodes. Median total doses: 64.5 Gy to T and N1-3, 45 Gy to N0. A conventional fractionation (2 Gy once a day, 5 times a week) was used in 37 outpatients, while an accelerated hyperfractionated regimen (1.5 Gy twice a day, 5 times a week, with a six hours' interval between each fraction) was employed in 63 inpatients, in order to shorten hospitalization. The five-year overall survival (Kaplan-Meier) of the 100 treated patients is 10%, while the five-year disease-free survival of the 40 patients in complete clinical remission at the end of radiation therapy is 19.8%. The five-year loco-regional control rate after exclusive radiotherapy is 19.1%. Complete remission at the end of treatment seems to represent the only significant prognostic variable affecting survival: five-year overall survival is 32% for the 40 patients achieving complete remission and only 4.4% for the others (p less than 0.05). On the contrary, tumor extension (T class) seems to affect only the two-year local control rate: 35.2% and 10.9% for T1 + T2 and T3 + T4 respectively (p less than 0.1). The main cause of failure after radiation therapy is represented by the lack of control at the primary site (T) alone or associated with regional adenopathies (N). The analysis of isoeffect parameters, according to CRE model, has not shown any evident dose-response relationship for local control. Late effects were observed in 7% of the patients and were similar to those reported in the literature. The occurrence of both distant metastases, 3% in our experience, and secondary tumors (9%) is lower than those previously reported. The present retrospective study strongly reconfirms the inadequacy of exclusive radiation therapy as the sole treatment modality for carcinoma of the hypopharynx and suggests the need of combination therapy (surgery and radiation) as primary treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Calditol tetraether lipids of the archaebacterium Sulfolobus solfataricus. Biosynthetic studies

Lipids from the archaebacterium Sulfolobus solfataricus are based on 72-membered macrocyclic tetraethers made up from two C40 diol units differently cyclized and either two glycerol moieties or one glycerol moiety and a unique branched-chain nonitol named calditol (glycerodialkylnonitol tetraethers, GDNTs). To elucidate the biosynthesis of calditol and related tetraethers, labelled precursors, [U-14C,1(3)-3H]glycerol, [U-14C,2-3H]glycerol, D-[1-14C,6-3H]glucose, D-[6-14C,1-3H]glucose, D-[1-14C,2-3H]glucose, D-[1-14C,6-3H]fructose and D-[1-14C]galactose, were fed to S. solfataricus. Without regard to stereochemistry or phosphorylation, incorporation experiments provided evidence that the biosynthesis of calditol occurs via an aldolic condensation between dihydroxyacetone and fructose, through a 2-oxo derivative of calditol as an intermediate. The latter is in turn reduced and then alkylated to yield the GDNTs. The biogenetic origins of both glycerol and C40 isoprenoid moieties of GDNTs are also discussed.

The effect of acute and chronic treatment with SCH 23390 on the spontaneous activity of midbrain dopamine neurons

The effect of acute and chronic administration of SCH 23390 on the spontaneous activity of dopamine (DA) neurons in the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) was studied. Two groups of rats were given an acute subcutaneous (s.c.) injection of the specific D-1 DA receptor block SCH 23390 (0.5 or 1.0 mg/kg). In four separate chronic experiments, SCH 23390 was administered repeatedly for 21 days either s.c. (0.5 or 1 mg/kg) or orally (5 or 10 mg/kg). No change in the number of spontaneously active DA neurons was found either after acute or chronic treatment with SCH 23390. On the other hand, chronic (21 days) haloperidol (0.5 mg/kg per os) produced a marked reduction in the number of spontaneously active DA neurons both in the SNc and VTA, a finding previously shown to be due to the development of depolarization block. It is concluded that chronic D-1 DA receptor blockade, may not be involved in the development of depolarization block produced by chronic treatment with antipsychotic drugs.

Dopamine denervation of the nucleus accumbens induces a selective increase in the number of delta-opioid binding sites

Selective lesions of dopamine (DA) neurons of the nucleus accumbens were made in rats by local injections of 6-hydroxydopamine (6-OHDA). Seven days after 6-OHDA, the binding affinities and capacities at mu-, delta- and kappa-opioid binding sites were determined in the nucleus accumbens by selective labelling techniques. 6-OHDA pretreatment caused a significant increase in the number of delta-opioid binding sites (+30%) while the number of mu-, kappa- and total sites was not modified. The affinity at mu-, delta- and kappa-sites was unchanged after 6-OHDA pretreatment.

Effects of peripheral and central administration of calcium channel blockers in the naloxone-precipitated abstinence syndrome in morphine-dependent rats

The effects of two calcium channel blockers (verapamil and flunarizine) were evaluated on the naloxone-precipitated syndrome in morphine-dependent rats. The withdrawal signs in saline-treated rats were mainly diarrhea, body weight loss, jumping and ptosis. On i.p. administration, verapamil and flunarizine prevented diarrhea and body weight loss but not jumping. Verapamil also reduced the incidence of ptosis at the highest dose tested (40 mg/kg). Administered i.c.v., 160 micrograms verapamil reduced the body weight loss and the number of jumps without modifying diarrhea or ptosis. The results show that calcium channel blockers inhibit morphine abstinence syndrome manifestations through both peripheral and central mechanisms.

Further evidence that noradrenaline is not involved in the anti-immobility activity of chronic desipramine in the rat

The effect of 10 mg/kg per day desipramine for 7 days on performance in the forced swimming test was studied in rats given various treatments aimed at reducing central noradrenergic transmission. 6-Hydroxydopamine-induced destruction of noradrenaline-containing neurons originating in the locus coeruleus or ascending in the ventral bundle had no effect on the anti-immobility activity of desipramine. Likewise, no changes in the effect of desipramine were seen with an intraperitoneal injection of DSP-4 (50 mg/kg) which destroyed brain noradrenergic neurons, particularly those of the dorsal bundle ascending to the forebrain. The results argue against a role of noradrenaline in the mechanism by which repeated treatment with desipramine reduces the immobility of rats in the forced swimming test.

Noradrenergic and behavioural effects of naloxone injected in the locus coeruleus of morphine-dependent rats and their control by clonidine

Naloxone HCl (10 micrograms/0.5 ml) was injected in the locus coeruleus (LC) of morphine-dependent rats and the behavioural manifestations of morphine withdrawal and the cortical levels of 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO4) were measured 30 min later. Naloxone precipitated a withdrawal syndrome and raised cortical MHPG-SO4 in animals made dependent by ascending doses of morphine for 11 days. An injection of clonidine intraperitoneally (200 micrograms/kg) or in the LC (5 micrograms/0.5 microliter) blocked most aspects of the withdrawal syndrome except jumping and had no effect on the naloxone-induced rise in cortical MHPG-SO4. The findings confirm the hypothesis that the LC is one of the sites where naloxone and clonidine, respectively, precipitate and reduce the narcotic withdrawal syndrome but argue against a role of noradrenergic neurons originating in the LC and innervating the cortex in the ability of clonidine to suppress some aspects of withdrawal syndrome precipitated by naloxone in morphine-dependent animals.