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1.
Child Abuse Negl ; 154: 106867, 2024 Jun 08.
Article in English | MEDLINE | ID: mdl-38852432

ABSTRACT

BACKGROUND: Children and young people (CYP) who are in contact with social care are at higher risk of developing mental health difficulties compared to the general population. This has been attributed to their experience of significant childhood adversity. With an increased likelihood of experiencing poorer health outcomes which can persist into adulthood, it is crucial that key factors for their positive mental health development are identified. OBJECTIVE: To identify factors associated with the poor mental health of CYP in contact with social care from the perspective of practitioners working in children's social care and mental health. PARTICIPANTS AND SETTING: Social care and mental health practitioners; three Local Authorities across the North-East of England. METHODS: Four focus groups were conducted with 23 practitioners between April and May 2022. A semi-structured topic guide exploring the nature and associated factors of mental health was used to focus discussion. Data were thematically analysed and informed by the four levels of the socio-ecological model. RESULTS: Individual level risk factors were associated with the CYP's emotional health and included what practitioners described as the 'sense of shame'. Interpersonal level risk factors were most recurrent and included parental factors within the home environment. Community level risk factors consisted of characteristics of settings and institutions that increased the risk of the CYP developing mental health and wellbeing difficulties. Societal level risk factors included broader societal factors such as poverty. Practitioners maintained that certain protective factors possessed or developed by CYP including secure attachments, prevent the development of mental health difficulties. CONCLUSIONS: Our current study provides strong evidence for the interlinkage between multiple levels of risk and their interacting impact on the CYP's mental health and emotional wellbeing. It is imperative that this, and the need to strengthen protective factors, whilst reducing risks are carefully considered for the development of effective support interventions for CYP in contact with social care.

2.
J Prev (2022) ; 2024 Jun 17.
Article in English | MEDLINE | ID: mdl-38884876

ABSTRACT

Mental health problems are the leading cause of childhood disability worldwide, resulting in poor outcomes for children and young people that persist into adulthood. It is essential that those young people most at risk of developing mental health problems receive effective preventative interventions. Whilst there have been a number of systematic reviews which have examined the effectiveness of secondary prevention interventions for specific groups of children and young people, or to address identified mental health concerns, no review has engaged with the breadth of this literature. We conducted a systematic review of systematic reviews to map this complex field of secondary preventative interventions and identify effective interventions to prevent mental health problems in children and adolescents aged 3-17 years. The review protocol was registered on PROSPERO. We searched five electronic databases from inception to February 2023. The certainty of the evidence was appraised using the AMSTAR 2. We included 49 unique systematic reviews each including between 2 and 249 (mean 34) unique studies; the majority of which were reviews which included only or mostly randomised controlled trials (70%). The reviews examined selective interventions (defined as interventions which are delivered to sub-group populations of young people at increased risk of mental health problems) (n = 22), indicated interventions (defined as interventions which target young people who are found to have pre-clinical symptoms) (n = 15) or a synthesis of both (n = 12). The certainty of the evidence in the reviews was rated as high, (n = 12) moderate (n = 5), low (n = 9) and critically low (n = 23). We found evidence to support both selective and indicated interventions in a range of populations and settings, with most of this evidence available for children and young people in their mid-years (6-10 years) and early adolescence (11-13 years). There was a large body of evidence suggesting that resilience enhancing, cognitive behaviour therapy-based and psychoeducational interventions for children who experience adversity, or those with subclinical externalising problems may offer promise. Early selective interventions for a subpopulation of children and young people who have experienced adversity which combines risk reduction and resilience enhancing approaches directed at children and their families may be effective at reducing mental health problems.

3.
Psychol Med ; 47(14): 2548-2555, 2017 Oct.
Article in English | MEDLINE | ID: mdl-28464965

ABSTRACT

BACKGROUND: The potential for drugs of abuse to induce acute psychotic symptoms is well recognised. However, the likelihood of transition from initial substance-induced psychotic disorder (SIPD) to chronic psychosis is much less well understood. This study investigated the rate of SIPD transition to schizophrenia (F20), the time to conversion and other possible related factors. METHODS: Using data from the Scottish Morbidity Record, we examined all patients (n = 3486) since their first admission to psychiatric hospital with a diagnosis of SIPD [International Classification of Diseases, Tenth Revision (ICD-10) codes F10-F19, with third digit five] from January 1997 to July 2012. Patients were followed until first episode of schizophrenia (ICD-10 code F20, with any third digit) or July 2012. Any change in diagnosis was noted in the follow-up period, which ranged from 1 day to 15.5 years across the groups. RESULTS: The 15.5-year cumulative hazard rate was 17.3% (s.e. = 0.007) for a diagnosis of schizophrenia. Cannabis, stimulant, opiate and multiple drug-induced psychotic disorder were all associated with similar hazard rates. The mean time to transition to a diagnosis of schizophrenia was around 13 years, although over 50% did so within 2 years and over 80% of cases presented within 5 years of SIPD diagnosis. Risk factors included male gender, younger age and longer first admission. CONCLUSIONS: SIPD episodes requiring hospital admission for more than 2 weeks are more likely to be associated with later diagnosis of schizophrenia. Follow-up periods of more than 2 years are needed to detect the majority of those individuals who will ultimately develop schizophrenia.


Subject(s)
Disease Progression , Hospitals, Psychiatric/statistics & numerical data , Psychoses, Substance-Induced/epidemiology , Schizophrenia/epidemiology , Adolescent , Adult , Female , Humans , Length of Stay/statistics & numerical data , Longitudinal Studies , Male , Middle Aged , Patient Admission/statistics & numerical data , Psychoses, Substance-Induced/etiology , Psychoses, Substance-Induced/therapy , Scotland/epidemiology , Time Factors , Young Adult
4.
Nephron Clin Pract ; 124(3-4): 141-50, 2013.
Article in English | MEDLINE | ID: mdl-24335564

ABSTRACT

Chronic kidney disease (CKD) is a growing public health problem. Cardiovascular disease is common in CKD, but standard risk assessment tools perform poorly in this population. Equally, despite CKD being associated with an increased risk for death and dialysis, standard biochemical measurements have limited prognostic value. Novel serum biomarkers may aid risk assessment; however, studies have shown varying clinical utility in relation to progression of CKD, incident cardiovascular disease and death. This inconsistency may relate to limitations in our understanding of the biological actions and interactions of these biomarkers. This review discusses a range of biomarkers in relation to these clinical endpoints in CKD-mineral bone disorder. We consider where biomarkers may enhance risk stratification and improve clinical management, but also highlight where they fall short of achieving this objective.


Subject(s)
Bone Density/physiology , Bone Diseases/metabolism , Bone Diseases/therapy , Patient Care/standards , Renal Insufficiency, Chronic/metabolism , Renal Insufficiency, Chronic/therapy , Biomarkers/metabolism , Bone Diseases/diagnosis , Disease Progression , Humans , Renal Insufficiency, Chronic/diagnosis
5.
J Neurochem ; 102(1): 112-20, 2007 Jul.
Article in English | MEDLINE | ID: mdl-17419804

ABSTRACT

Urotensin II is a neuropeptide first isolated from fish and later found in mammals: where it has potent cardiovascular, endocrine and behavioral effects. In rat brain the urotensin II receptor (UII-R) is predominately expressed in the cholinergic neurons of the pedunculopontine (PPTg) and laterodorsal tegmental nuclei. Typically, the function of the PPTg has been examined using excitotoxins, destroying both cholinergic and non-cholinergic neurons, which confounds interpretation. We took advantage of UII-R's unique expression profile, by combining UII with diphtheria toxin, to engineer a toxin specific for cholinergic neurons of the PPTg. In vitro, two different toxin constructs were shown to selectively activate UII-R (average EC50 approximately 30 nmol/L; calcium mobility assay) and to be 10,000-fold more toxic to UII-R expressing CHO cells, than wildtype cells (average LD50 approximately 2 nmol/L; cell viability). In vivo, pressure injection into the PPTg of rats, resulted in specific loss of choline transporter and NADPH diaphorase positive neurons known to express the UII-R. The lesions developed over time, resulting in the loss of over 80% of cholinergic neurons at 21 days, with little damage to surrounding neurons. This is the first highly selective molecular tool for the depletion of mesopontine cholinergic neurons. The toxin will help to functionally dissect the pedunculopontine and laterodorsal tegmental nuclei, and advance the understanding of the functions of these structures.


Subject(s)
Diphtheria Toxin/chemistry , Diphtheria Toxin/toxicity , Neurons/drug effects , Neurotoxicity Syndromes/pathology , Neurotoxins/chemistry , Neurotoxins/toxicity , Parasympathetic Nervous System/drug effects , Pons/pathology , Tegmentum Mesencephali/pathology , Urotensins/chemistry , Urotensins/toxicity , Animals , CHO Cells , Cell Survival/drug effects , Cricetinae , Cricetulus , Diphtheria Toxin/isolation & purification , Electrophoresis, Polyacrylamide Gel , Escherichia coli/genetics , Male , NADPH Dehydrogenase/metabolism , NADPH Dehydrogenase/physiology , Neurons/pathology , Parasympathetic Nervous System/pathology , Plasmids/genetics , Rats
6.
Clin Oncol (R Coll Radiol) ; 18(8): 594-9, 2006 Oct.
Article in English | MEDLINE | ID: mdl-17051949

ABSTRACT

AIMS: A retrospective audit was carried out to determine the rate of local recurrence (recurrent tumour within the lesser pelvis or the perineal wound) in 88 rectal cancer patients treated with 20 Gy/four fractions of adjuvant preoperative radiotherapy and curative surgery. MATERIALS AND METHODS: All patients were followed-up by clinical examination with rigid sigmoidoscopy at 6 monthly intervals if the rectum was intact, and computed tomography of the pelvis at 1, 2 and 5 years after surgery. In total, 171 patients with rectal cancer were identified under the care of one surgeon over a period of 11 years from May 1992 to April 2003. We excluded patients with rectal cancer from preoperative adjuvant radiotherapy if they had evidence at presentation of distant metastases, if they had fixed rectal tumours, were treated by local excision and had previous radiotherapy to the pelvis. On this basis, only 88 were considered for preoperative radiotherapy and curative resection with a median follow-up of 5.16 years. RESULTS: The 5-year survival by stage was Dukes A 96%, Dukes B 65% and Dukes C 36%. Overall, four patients (of 88) developed a recurrence within the lesser pelvis or the perineal wound, giving a local recurrence of 4.2% at 3 years (from a Kaplan-Meier graph). CONCLUSIONS: This single-centre audit suggests that a lower dose of radiotherapy to a smaller volume provides an acceptable local recurrence rate that compares very favourably with the well-publicised Swedish and Dutch trials of 25 Gy/five fractions. It was not the intention of this audit to suggest that this dose should be widely adopted. However, given the long-term gastrointestinal morbidity and risk of second malignancies, we advise caution when formulating even more intensive radiotherapy and chemoradiotherapy regimens for rectal cancer.


Subject(s)
Adenocarcinoma/radiotherapy , Neoplasm Recurrence, Local/epidemiology , Rectal Neoplasms/radiotherapy , Adenocarcinoma/mortality , Adenocarcinoma/surgery , Aged , Female , Follow-Up Studies , Humans , Kaplan-Meier Estimate , Male , Middle Aged , Preoperative Care , Radiotherapy Dosage , Radiotherapy, Adjuvant , Rectal Neoplasms/mortality , Rectal Neoplasms/surgery , Retrospective Studies
7.
Neuroscience ; 125(2): 349-58, 2004.
Article in English | MEDLINE | ID: mdl-15062978

ABSTRACT

The pedunculopontine tegmental nucleus (PPTg) has long been suggested to have a role in reward-related behaviour, and there is particular interest in its possible role in drug reward systems. Previous work found increased i.v. self-administration (IVSA) of d-amphetamine following PPTg lesions when training had included both operant pre-training and priming injections. The present study examined the effect of excitotoxin lesions of the PPTg on d-amphetamine IVSA under three training conditions. Naive: no previous experience of d-amphetamine or operant responding. Pre-trained: given operant training with food before lesion surgery took place. Primed: given single non-contingent d-amphetamine infusion (0.1 mg/0.l ml) at the start of each session. Rats in all conditions were given either ibotenate or phosphate buffer control lesions of the PPTg before d-amphetamine (0.1 mg/0.1 ml infusion) IVSA training took place. Rats received eight sessions of training under a fixed ratio (FR2) schedule of d-amphetamine IVSA, followed by four sessions under a progressive ratio (PR5) schedule. In the naive condition, PPTg-lesioned rats were attenuated in their responding under FR2, and took significantly fewer infusions under PR5 than the control group. Under FR2 in the pre-trained condition, there was no difference between PPTg excitotoxin and control lesioned rats; however, PPTg-lesioned rats took significantly fewer infusions under the PR5 schedule. In the primed condition, there were no differences between PPTg-lesioned and control rats under either FR2 or PR5 schedules. These data demonstrate that operant training prior to PPTg lesion surgery corrects some, but not all, of the deficits seen in the naive condition. PPTg-lesioned rats in both naive and pre-trained conditions showed reduced responding for d-amphetamine under a PR5 schedule. These deficits are overcome by priming with d-amphetamine. We suggest that alterations in striatal dopamine activity following PPTg lesions underlie these effects.


Subject(s)
Central Nervous System Stimulants/administration & dosage , Dextroamphetamine/administration & dosage , Pedunculopontine Tegmental Nucleus/drug effects , Analysis of Variance , Animals , Behavior, Animal , Conditioning, Operant/drug effects , Drug Administration Schedule , Excitatory Amino Acid Agonists , Food , Ibotenic Acid , Male , NADP , Pedunculopontine Tegmental Nucleus/injuries , Pedunculopontine Tegmental Nucleus/physiology , Rats , Reinforcement Schedule , Reinforcement, Psychology , Self Administration/methods
8.
J Biomech ; 37(3): 339-48, 2004 Mar.
Article in English | MEDLINE | ID: mdl-14757453

ABSTRACT

The placement of a rigid stent within an elastic vessel produces wave reflection sites at the entrance to and exit from the stent. The net haemodynamic effects of these reflections depend critically on the degree of stiffness of the stent and on its length and position within the diseased vessel, variables that have been found to affect the clinical performance of a stent. Here these effects are examined analytically, using a segmented tube model. The results indicate that the presence of the stent within the larger diseased vessel has the effect of producing higher pressure at the vessel entrance than that at exit. This pressure difference, when superimposed on the underlying pressure distribution within the vessel, has the net effect of actually aiding rather than impeding the flow, but the extent of this depends on the length and position of the stent. A short stent placed near the entrance of the diseased vessel may be favoured clinically for producing the least perturbation in the underlying haemodynamics and thus reducing the chance of restenosis, while a long stent placed near the exit may be favoured for producing a positive pressure difference and thus aiding the flow.


Subject(s)
Blood Vessel Prosthesis , Blood Vessels/physiopathology , Equipment Failure Analysis/methods , Hemorheology/methods , Models, Cardiovascular , Stents , Vascular Surgical Procedures , Blood Flow Velocity , Blood Pressure , Computer Simulation , Elasticity , Stress, Mechanical , Vascular Capacitance , Vascular Resistance
9.
Neuroscience ; 118(2): 311-5, 2003.
Article in English | MEDLINE | ID: mdl-12699767

ABSTRACT

The pedunculopontine tegmental nucleus (PPTg) interacts with anatomical systems thought to be involved in mediating sensitisation of the locomotor response to repeated d-amphetamine. The PPTg has direct and indirect connections with the nucleus accumbens and prefrontal cortex, and also influences midbrain dopamine activity through direct projections to substantia nigra and ventral tegmental area. In this experiment, the development of behavioural sensitisation to the locomotor stimulant effects of repeated d-amphetamine was examined in rats bearing excitotoxic lesions of the PPTg, and sham-lesioned controls. Rats were given repeated d-amphetamine (1.5 mg/kg i.p.) treatment in an on-off procedure, with saline and d-amphetamine given on alternate days, such that rats received a total of seven d-amphetamine and seven saline treatments. Locomotor responses were measured in photocell cages. On the first day of d-amphetamine treatment, there was no difference between excitotoxin and sham-lesioned rats. Development of sensitisation to the locomotor stimulant effects of d-amphetamine was delayed in PPTg-lesioned rats, relative to the sham-lesioned control rats. However, there was no difference between lesion and control groups in the locomotion seen on saline-treatment days. These data suggest that the PPTg is involved in the development of behavioural sensitisation to the locomotor stimulant effects of repeated d-amphetamine, and indicate that traditional striatal circuitry models of the mechanisms underlying sensitisation should be extended to include the PPTg.


Subject(s)
Amphetamine/pharmacology , Central Nervous System Stimulants/pharmacology , Locomotion/drug effects , Tegmentum Mesencephali/drug effects , Animals , Behavior, Animal/drug effects , Brain Mapping , Male , Neurotoxins/adverse effects , Rats , Tegmentum Mesencephali/physiology
10.
Neuroscience ; 112(2): 417-25, 2002.
Article in English | MEDLINE | ID: mdl-12044459

ABSTRACT

The pedunculopontine tegmental nucleus has connections with sites in both dorsal and ventral striatum, and a number of studies have suggested that it has a role in reward-related behaviour. The present experiment aimed to investigate the perception of reward in pedunculopontine tegmental nucleus-lesioned rats responding for food under a progressive ratio schedule, which measures willingness to work for a given reward. Rats were trained on a progressive ratio-5 schedule for food reward, then given ibotenic acid or sham lesions of the pedunculopontine tegmental nucleus. Their performance under this schedule was examined again following recovery from surgery. Compared with sham-lesioned rats, those with lesions of the pedunculopontine tegmental nucleus showed significantly reduced breaking points and significantly longer post-reinforcement pauses. However, there was no difference between the groups in their latency to collect food pellets once earned, suggesting that pedunculopontine tegmental nucleus excitotoxin and sham-lesioned rats were equally motivated by the presence of food. Excitotoxin-lesioned rats made significantly more responses on the control lever and more entries to the food hopper as progressive ratio increment increased, but did not differ from controls when the schedule requirement was low. These results are interpreted as indicating no global loss of motivation, since lesioned rats performed normally at low schedule requirements, and were as fast as controls to collect pellets. But as the schedule requirement increased, excitotoxin-lesioned rats showed reductions in responding on the active lever (that is, a reduction in breaking point) and an increase in inappropriate responses towards the food hopper and the control lever.We consider these data to indicate that the behavioural deficits in pedunculopontine-lesioned rats arise not from a sensory or hedonic change, but from alteration in the control of motor output.


Subject(s)
Mesencephalon/physiology , Pons/physiology , Reinforcement, Psychology , Tegmentum Mesencephali/physiology , Animals , Appetitive Behavior/drug effects , Appetitive Behavior/physiology , Behavior, Animal/drug effects , Behavior, Animal/physiology , Conditioning, Operant , Ibotenic Acid/administration & dosage , Male , Mesencephalon/drug effects , Neurons/drug effects , Neurons/physiology , Pons/drug effects , Rats , Rats, Inbred Strains , Reaction Time/drug effects , Reaction Time/physiology , Reward , Tegmentum Mesencephali/drug effects
11.
J Biomech ; 34(11): 1455-62, 2001 Nov.
Article in English | MEDLINE | ID: mdl-11672720

ABSTRACT

The question of whether the mechanical stiffness of a coronary bypass or that of a diseased coronary artery can have a significant effect on the hemodynamics in these vessels is addressed analytically, with emphasis on the effects of wave reflections. The analysis is based on a model of the vessels involved, and the results show the essential hemodynamic effects in each vessel. It is found that in the absence of a bypass graft, wave reflections resulting from a narrowing and stiffening of a diseased coronary artery have the effect of actually aiding the flow in the diseased vessel. In the presence of a bypass graft, however, the effects of wave reflections are reversed and become adverse to flow in both the bypass graft and the diseased coronary artery. A stiffer bypass moderates these effects and is therefore preferable to a more elastic bypass. The adverse effects also depend critically on the relative diameter of the bypass. Here the results indicate that a bypass of smaller diameter than that of the native coronary artery can moderate and even reverse the adverse effects of wave reflections resulting from the presence of the bypass.


Subject(s)
Blood Vessel Prosthesis/standards , Models, Cardiovascular , Anastomosis, Surgical/standards , Animals , Biomechanical Phenomena , Coronary Artery Bypass , Elasticity , Hemodynamics , Hemorheology , Humans , Vascular Patency/physiology
12.
Psychopharmacology (Berl) ; 153(4): 455-63, 2001 Feb.
Article in English | MEDLINE | ID: mdl-11243493

ABSTRACT

RATIONALE: It has been suggested that the nucleus accumbens (NAcc) may be involved in heroin reward, and the core and shell regions respond differently following administration of a number of drugs of abuse. OBJECTIVE: The possible role of the NAcc core and shell subregions in the acquisition of heroin self-administration behaviour was investigated. METHODS: Rats were given selective excitotoxic lesions of either the nucleus accumbens core or shell before the acquisition of responding for i.v. heroin (0.04 mg/infusion) under a continuous reinforcement schedule in daily 3 h sessions. After sham-lesioned rats reached a stable baseline, a between-sessions heroin dose-response function was established. RESULTS: Rats with lesions of the NAcc shell did not differ significantly from sham controls in either the acquisition of heroin self-administration or in their heroin dose-response function. The NAcc core lesion group showed reduced levels of responding during the acquisition of heroin self-administration and a reduction in responding during the heroin dose-response function, although this behaviour was sensitive to changes in the dose of heroin. CONCLUSIONS: The NAcc shell does not appear to be critical for heroin self-administration, whereas the NAcc core, although apparently not essential in mediating the rewarding effect of i.v. heroin, may mediate processes that are of special importance during the acquisition of instrumental behaviour.


Subject(s)
Heroin Dependence/psychology , Neurotoxicity Syndromes/psychology , Nucleus Accumbens/physiology , Substance Abuse, Intravenous/psychology , Animals , Conditioning, Operant , Dose-Response Relationship, Drug , Excitatory Amino Acid Agonists/toxicity , Ibotenic Acid/toxicity , Male , Neurotoxicity Syndromes/pathology , Neurotoxins/toxicity , Nucleus Accumbens/drug effects , Nucleus Accumbens/pathology , Quinolinic Acid/toxicity , Rats , Reinforcement Schedule , Self Administration
13.
Brain Res Bull ; 56(6): 599-605, 2001 Dec.
Article in English | MEDLINE | ID: mdl-11786248

ABSTRACT

A number of studies have suggested that the pedunculopontine tegmental nucleus (PPTg) may play a role in reward-related behaviour. The present study was intended to investigate this further using conditioned place preference. In conditioned place preference paradigms the amount of time spent in a preferred environment is proportional to the value of the reinforcement present, until a maximum is reached. In the present experiments we aimed to determine whether this relationship was affected by lesions of the PPTg by examining the formation of a conditioned place preference to either 4%, 12% or 20% sucrose solutions in food-deprived PPTg lesioned rats. The conditioned place preference apparatus had two compartments different in colour, smell and floor texture. During conditioning, rats were restricted to one compartment or the other, one of which was paired with sucrose. This was carried out during 30 min sessions, alternating conditioned or nonconditioned trials for 14 days. On the test day, rats were given access to both compartments through a connecting chamber, and were scored for side preference over 15 min. Both PPTg and sham lesioned rats showed a conditioned place preference to 12% and 20% sucrose, but no place preference was formed by either group to 4% sucrose. There was no significant difference between the groups in the place preference shown. Consumption of 4% sucrose was not affected by excitotoxic lesions of the PPTg, but PPTg lesioned rats consumed significantly more 12% and 20% sucrose than sham controls. This suggests that perception of reward value, as judged by CPP formation, is unchanged by excitotoxic lesions of the PPTg. The increased consumption of 12% and 20% sucrose shown by rats bearing such lesions is therefore not likely to be a product of altered reward perception.


Subject(s)
Conditioning, Psychological/physiology , Eating/physiology , Neurons/physiology , Neurotoxins/pharmacology , Pons/physiology , Reticular Formation/physiology , Reward , Animals , Behavior, Animal/drug effects , Behavior, Animal/physiology , Conditioning, Psychological/drug effects , Dietary Sucrose/metabolism , Dietary Sucrose/pharmacology , Dose-Response Relationship, Drug , Eating/drug effects , Excitatory Amino Acid Agonists/pharmacology , Food, Formulated , Ibotenic Acid/pharmacology , Male , Motor Activity/drug effects , Motor Activity/physiology , Neural Pathways/cytology , Neural Pathways/drug effects , Neural Pathways/physiology , Neurons/cytology , Neurons/drug effects , Pons/cytology , Pons/drug effects , Rats , Rats, Inbred Strains , Reticular Formation/cytology , Reticular Formation/drug effects
14.
Psychopharmacology (Berl) ; 153(1): 111-9, 2000 Dec.
Article in English | MEDLINE | ID: mdl-11255921

ABSTRACT

RATIONALE: Second-order schedules of drug-self-administration provide a method of examining drug-seeking behaviour, which is maintained in part by the presentation of a discrete, drug-associated light CS. Previous results have found that lesions of the basolateral amygdala (BLA) impair the acquisition of i.v. cocaine self-administration under this type of schedule. OBJECTIVES: The present experiments examined the effects of excitotoxic lesions of the BLA on the acquisition of i.v. heroin self-administration under both continuous reinforcement and second-order schedules, in order to investigate possible commonalties in the neural basis of heroin- and cocaine-seeking behaviour. METHODS: Rats received quinolinic acid or sham vehicle lesions of the BLA prior to i.v. self-administration training. Initially, heroin self-administration under a continuous reinforcement schedule was acquired. Each active lever-press resulted in a 0.04 mg i.v. heroin infusion, paired with presentation of a 20-s light conditioned stimulus. Following acquisition of responding under this schedule, the response requirement was gradually increased to a second-order schedule of FI15(FR5:S). RESULTS: There was no effect of lesions of the BLA on the acquisition of heroin self-administration under a continuous reinforcement schedule. The acquisition of heroin-seeking behaviour under a second-order schedule of self-administration was not affected by lesions of the BLA, but lesioned rats showed a significantly higher baseline level of responding. CONCLUSIONS: These results indicate that the rewarding effects of heroin do not depend on the integrity of the BLA. The BLA is also not critically involved in mediating heroin-seeking behaviour under a second-order schedule of reinforcement, and this stands in marked contrast to the effects of BLA lesions on the acquisition of cocaine-seeking behaviour. These findings suggest that discrete heroin cues were not critical in maintaining heroin-seeking behaviour under the second-order schedule used here and that other learning systems are engaged in the control of this behaviour.


Subject(s)
Amygdala/physiology , Heroin Dependence/psychology , Amygdala/pathology , Animals , Behavior, Animal/drug effects , Heroin Dependence/pathology , Male , Quinolinic Acid/toxicity , Rats , Reinforcement Schedule , Reinforcement, Psychology , Self Administration
15.
Psychopharmacology (Berl) ; 153(1): 120-33, 2000 Dec.
Article in English | MEDLINE | ID: mdl-11255922

ABSTRACT

RATIONALE: Second-order schedules of heroin self-administration provide a method of measuring heroin-seeking behaviour independently of the effects of the drug on motor behaviour and of investigating the role of heroin-associated stimuli in such heroin-seeking behaviour. OBJECTIVES: These experiments aimed to establish a second-order schedule of heroin self-administration in rats, similar to that already established in this laboratory for cocaine self-administration and to investigate the role of discrete heroin-associated stimuli in the maintenance of heroin-seeking behaviour under a second-order schedule of reinforcement. METHODS: Heroin i.v. self-administration (0.04 mg/infusion) was initially contingent upon a lever press, and each infusion was paired with presentation of a 20-s light-conditioned stimulus (CS). Following acquisition of heroin self-administration, the response requirement was progressively increased so that, ultimately, responding was maintained under a fixed interval (FI) 15 min [fixed ratio (FR)5:S] second-order schedule. The effects of varying the dose of heroin (0.01 mg and 0.08 mg/infusion) and pre-treatment with the mu-opiate receptor antagonist, naloxone, on responding under a FI15(FR5:S) schedule were investigated. In addition, the role of the heroin-associated CS on responding was assessed by measuring the effects of omitting the CS during heroin-seeking behaviour and during extinction of responding, as well as the effect of CS presentation on the reinstatement of heroin-seeking behaviour following extinction. RESULTS: A second-order schedule of heroin self-administration was established. There were no clear effects on heroin-seeking behaviour of increasing or decreasing the dose of heroin. Although no effect of naloxone pre-treatment was seen on heroin-seeking behaviour during the first, drug-free interval of responding, an extinction-like pattern of responding was seen in that interval during subsequent sessions. Omission of the light CS resulted in a reduction in levels of responding for i.v. heroin, indicating its role in maintaining heroin-seeking behaviour. However, under extinction conditions, response-contingent CS presentations did not affect the rate of extinction, nor did non-contingent presentations of the CS following extinction reinstate heroin-seeking behaviour. CONCLUSIONS: These experiments have established a method of measuring heroin-seeking behaviour in rats by adopting a second-order schedule of i.v. heroin self-administration. The results indicate a relatively weak impact of discrete, heroin-associated cues on heroin-seeking behaviour relative to cocaine-seeking behaviour studied under similar conditions.


Subject(s)
Behavior, Animal/drug effects , Conditioning, Operant/drug effects , Heroin Dependence/psychology , Heroin/administration & dosage , Heroin/pharmacology , Narcotics/administration & dosage , Narcotics/pharmacology , Animals , Cocaine/pharmacology , Dopamine Uptake Inhibitors/pharmacology , Dose-Response Relationship, Drug , Extinction, Psychological/drug effects , Male , Naloxone/pharmacology , Narcotic Antagonists/pharmacology , Rats , Reinforcement Schedule , Self Administration
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