P2-16-01: A Multi-Centre Prospective Cohort Study Evaluating Health Related Quality of Life after Types of Immediate Latissimus Dorsi (LD) Breast Reconstruction

Introduction: Evidence for the clinical effectiveness of breast reconstruction based on Patient Reported Outcome Measures (PROMS) is lacking. Methodology evaluating PROMS after types of breast reconstruction has been poor with respect to study design, statistics, missing data and absence of prospective documentation of pre-defined complication data in a systematic review of all studies since 19781. Furthermore, there is no reliable data on the effects of associated radiotherapy (RT) in this context. As a prelude to a proposed randomised trial in breast reconstruction, our aim was to conduct a ‘robust’ cohort study evaluating the effects of either implant-assisted LD (LDI) or tissue only (ALD) LD flap reconstruction in relation to key determinants including clinico-pathological parameters, complications and treatment schedules over a 36 month period.

Methods: An MREC approved prospective longitudinal cohort study involving 6 centres commenced in early 2007. Serial PROMS using the EORTC QLQ-C30, BR-23, FACT-B, BIS and HADS, were completed pre-operatively and at 3, 6, 12, 24 and 36 months after surgery. Data up to 12 months were included in this analysis as data were sparse beyond this point; follow-up is ongoing. Demographic and clinical data were compared between the surgical groups. Generalised estimating equations were used to investigate demographic and clinical predictors of HRQL over time.

Results: A total of 189 patients (107-ALD, 82-LDI) were recruited, with a mean age of 50 years (range 22–70). Baseline questionnaires were completed by 149 (79%) women, with 167 (88%) available at 12 months. Patients in the ALD group had a higher BMI (mean 27.3 versus 25.2 in LDI, p=0.001) and a greater likelihood of post-mastectomy RT (52% versus 30% in LDI, p=0.004).

Only role functioning (p=0.001) and pain (p=0.003) were significantly adversely affected in the ALD v LDI group, with no statistically significant effects from PMRT on HRQL, although chemotherapy impaired global QoL (p<0.001) and social functioning (p=0.001), and increased fatigue (p=0.007). Early complications (< 3 months) significantly impaired HRQL in general, as did poor baseline scores (p<0.01 for various subscales). Significant improvements over time were noted for global QoL, role and social functioning, fatigue, pain and breast symptoms (p<0.001 for all).

Conclusion: There is increasing evidence of clinical equipoise between types of LD breast reconstruction and despite acknowledged cosmetic disadvantages the overall effects of PMRT on HRQL are minimal. The identification of important variables that may affect HRQL is crucial in all studies evaluating the effects of surgery on PROMS. Their integration into study results is essential for correct interpretation of clinically based assessments. This remains a challenging aspect in cohort studies, and emphasises the need for pragmatism in design of trials in the field.

1. Winters ZE, Benson JR, Pusic AL. Annals of Surgery 2010;252(6):929–42

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-16-01.

Conjugation of gold nanoparticles to polypropylene mesh for enhanced biocompatibility

Polypropylene mesh materials have been utilized in hernia surgery for over 40 years. However, they are prone to degradation due to the body's aggressive foreign body reaction, which may cause pain or complications, forcing mesh removal from the patient. To mitigate these complications, gold nanomaterials were attached to polypropylene mesh in order to improve cellular response. Pristine samples of polypropylene mesh were exposed to hydrogen peroxide/cobalt chloride solutions to induce formation of surface carboxyl functional groups. Gold nanoparticles were covalently linked to the mesh. Scanning electron microscopy confirmed the presence of gold nanoparticles. Differential scanning calorimetry and mechanical testing confirmed that the polypropylene did not undergo any significantly detrimental changes in physicochemical properties. A WST-1 cell culture study showed an increase in cellularity on the gold nanoparticle-polypropylene mesh as compared to pristine mesh. This study showed that biocompatibility of polypropylene mesh may be improved via the conjugation of gold nanoparticles.

F8 and F9 mutations in US haemophilia patients: correlation with history of inhibitor and race/ethnicity

Both genetic and treatment-related risk factors contribute to the development of inhibitors in haemophilia. An inhibitor surveillance system piloted at 12 US sites has the goal of assessing risk factors through prospective data collection. This report examines the relationship of genotype and race/ethnicity to history of inhibitor in a large cohort of US haemophilia patients. Mutation analysis was performed on 676 haemophilia A (HA) and 153 haemophilia B (HB) patients by sequencing, Multiplex Ligation-dependent Probe Amplification, and PCR for inversions in F8 introns 22 (inv22) and 1 (inv1). Two HB patients with deletions had history of inhibitor. In severe HA, frequency of history of inhibitor was: large deletion 57.1%, splice site 35.7%, inv22 26.8%, nonsense 24.5%, frameshift 12.9%, inv1 11.1% and missense 9.5%. In HA, 19.6% of 321 White non-Hispanics (Whites), 37.1% of 35 Black non-Hispanics (Blacks) and 46.9% of 32 Hispanics had history of inhibitor (P = 0.0003). Mutation types and novel mutation rates were similar across ethnicities. When F8 haplotypes were constructed, Whites and Hispanics showed only H1 and H2. Within H1, history of inhibitor was 12.4% in Whites, 40.0% in Blacks (P = 0.009) and 32.4% in Hispanics (P = 0.002). Inhibitor frequency is confirmed to vary by mutation type and race in a large US population. White patients with history of inhibitor did not exhibit rare F8 haplotypes. F8 gene analysis did not reveal a cause for the higher inhibitor frequencies in Black and Hispanic patients.

A Multi Centre Prospective Longitudinal Study Establishing Level II Evidence of Health Related Quality of Life after Types of Immediate Latissimus Dorsi (LD) Breast Reconstruction

Introduction: NICE recommends that the majority of women undergoing mastectomy should be offered immediate breast reconstruction with its potential benefits to improve health related quality of life (HRQL). A systematic review shows poor and conflicting evidence with a lack of 'hard' data to best inform both clinicians and their patients. Our aim was to evaluate the effects of implant-assisted LD (LDI) versus autologous LD (ALD) breast reconstruction on HRQL over 36 months. Recently, with the exception of the USA Breast-Q module there is a lack of a validated Breast reconstruction questionnaire.Methods: An MREC approved prospective longitudinal cohort study involving 6 centres commenced in early 2007. Serial patient reported outcome measures using the EORTC C30 (global QoL, physical functioning, fatigue, pain), BR-23 (breast and arm symptoms), 10 item Body Image Scale (BIS) and HADS, were completed pre-operatively and at 3, 6, 12, 24 and 36 months after surgery. Overall cosmetic satisfaction of the breast reconstruction was measured by a study-specific question on a 5 point Likert scale. Generalised estimating equations were used to assess change over time and differences between treatment groups.The Spearman's rank correlation coefficient was used to assess associations between patient reported cosmetic satisfaction with BIS and breast symptoms.Results: 118 patients (65 – ALD, 53 – LDI) were recruited to the study with a mean age of 50 years (range 22-70). Compliance with questionnaires at all time points was between 85-90%. There were no significant differences in HRQL domains between LDI and ALD, except a tendency for worse pain with ALD (p=0.06). Significant improvements over time were seen for overall HRQL (p<0.001), fatigue (p<0.001), breast symptoms (p=0.04), arm symptoms (p=0.001), as well as anxiety (p=0.017) and depression (p<0.001). Preliminary data shows that overall cosmetic satisfaction was significantly correlated with better body image and fewer breast symptoms. The study is ongoing in terms of 24 and 36 months follow-up and the evaluation of RT.Conclusion: There is an important need for cumulative clinical evidence in this field on which to base patient informed consent and clinical recommendations. Further analyses will assess whether there is an independent effect of RT on HRQL. A validated EORTC breast reconstruction module is in development.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3106.

Counting abortions so that abortion counts: Indicators for monitoring the availability and use of abortion care services

SUMMARY

Maternal mortality reduction has been a focus of major international initiatives for the past two decades. Widespread provision of emergency obstetric care (EmOC) has been shown to be an important strategy for addressing many of the complications that might otherwise lead to maternal death. However, unsafe abortion is one of the major causes of pregnancy-related deaths, and will be only partially addressed by EmOC. This manuscript presents a comprehensive approach to measuring whether abortion-related needs are met.

PROPOSED METHODS

We propose a set of indicators for monitoring the implementation of safe abortion care (SAC) interventions. We build on the model developed for monitoring the availability and use of Emergency Obstetric (EmOC) services. We describe the critical elements ("signal functions") of SAC - including treatment of abortion complications, legal, induced abortion and postabortion contraception - and define the indicators necessary to assess the availability, utilization and quality of abortion-related services.

SAMPLE EVIDENCE

Data from 5 countries suggest there are sufficient service delivery points to provide decentralized abortion care, but that the full range of necessary abortion care services may not be provided at all these sites. Studies from several countries also show that many women receiving services for the treatment of abortion complications accept contraceptive methods when offered prior to discharge. This is an important strategy for reducing unwanted pregnancy, repeat unsafe abortion and risk for abortion-related mortality. Both findings suggest there are considerable opportunities within the present facilities to improve the delivery of abortion care services.

CONCLUSION

This article recommends that the proposed model undergo field-testing on its own or in conjunction with the EmOC indicators, and encourages increased support for this important but often neglected aspect of pregnancy-related health.

Sex-specific influences of vasopressin on human social communication

Arginine vasopressin (AVP) and related peptides affect social behaviors in numerous species, but AVP influences on human social functions have not yet been established. Here, we describe how intranasal AVP administration differentially affects social communication in men and women, and we propose a mechanism through which it may exert those influences. In men, AVP stimulates agonistic facial motor patterns in response to the faces of unfamiliar men and decreases perceptions of the friendliness of those faces. In contrast, in women, AVP stimulates affiliative facial motor patterns in response to the faces of unfamiliar women and increases perceptions of the friendliness of those faces. AVP also affected autonomic responsiveness to threatening faces and increased anxiety, which may underlie both communication patterns by promoting different social strategies in stressful contexts in men and women.

How research can affect policy and programme advocacy: example from a three-country study on abortion complications in sub-Saharan Africa

OBJECTIVE

To provide a basis for continued policy dialogue and reform to address the problem of death due to abortion complications among the ECSA Health Community countries. The anticipated short-term outcome of this study was increased awareness among African health officials about the problem of incomplete abortion in SSA, especially CRHCS/ECSA countries.

DESIGN

The study undertaken in 1993/1994, involved primary data collection of abortion-related morbidity and mortality statistics, the cost of treating patients with abortion complications and provider and abortion patient perspectives. Data were collected via one on one interviews and reviews of logbook data. A computerized literature review on abortion in the region covering the years 1980-1994 complemented the primary data collection.

STUDY SETTING

Primary data collection was conducted in three countries (Zambia, Uganda and Malawi) at selected districts and tertiary care hospitals.

SUBJECTS

Nurses and physicians providing care to women with complications of abortion in participating hospitals were interviewed as well as hospital administrators. Women receiving care in the selected hospitals during the data collection period also were interviewed.

MAIN OUTCOME MEASURES

This analysis focused on cross-country comparisons of nurse and doctor attitudes and knowledge about abortion and family planning-related issues.

INTERVENTIONS

At a 1994 CHRCS conference, Health Ministers from 12 Commonwealth countries reviewed and endorsed the results of this study. In a 1995 ECSA Director Joint Consultative Committee meeting, participants discussed the study findings and developed regional action plans which were subsequently endorsed by the Health Ministers' at their 1995 annual conference.

RESULTS

Abortion complication patients in the three countries were on average 24-26 years old with two children. Patients experienced long hospital stays while receiving care for complications. The average monthly number of post-abortion patients was substantially higher in urban facilities as compared to mixed/rural ones. Opinions regarding factors that led to the abortion, access to abortion services and the legal provisions surrounding abortion were inconsistent between doctors and nurses. Patients were aware that complications of abortion were a major cause of maternal mortality. Overall, provider opinion about access to family planning (FP) information among abortion complication patients was also inconsistent between doctors and nurses but there was agreement on factors influencing use of FP. Opinions regarding access to FP services both before and after the abortion varied from easy to very difficult to obtain.

CONCLUSIONS

These data represent the situation as it was in the region some years ago and the paper describes important implications of the findings for policy and programme development. This research provided some impetus for stakeholders in these countries to put safe abortion and management of abortion complications on their health agenda. Ensuring that research results will be shared with appropriate decision-makers is key to maximizing the extent to which research findings may affect policy and programme advocacy.

A survey of breast cancer patients' views on entry into several clinical studies

During the course of their treatment and follow-up, women with breast cancer are likely to be asked to join a number of different clinical studies. Some local research ethics committees have expressed concerns about entry of individual patients into multiple research studies. A survey was undertaken to improve understanding of patients' own perceptions of participation in several clinical studies. A total of 96 patients who had previously undergone surgery for breast cancer from January to June 2000 were sent a questionnaire 6-12 months after completion of primary treatment. Eighty four per cent of questionnaires were returned of which 62% were from patients who had been approached to enter at least one clinical study. Sixty-four per cent of patients believed that there should not be a limit on the number of clinical studies offered to patients. Furthermore, three quarters of all patients would have considered entering more than one study if adequate explanation and written information were provided. Most patients felt that their participation in a clinical study was worthwhile and no patients surveyed regretted their decision to take part in a study. Almost two-thirds of patients who returned questionnaires believed there should not be a maximum number of studies offered to them. This survey suggests that the majority of patients are prepared to participate in more than one clinical study when adequate information and explanation are provided.

Clinical Sarcocystis neurona encephalomyelitis in a domestic cat following routine surgery

Sarcocystis neurona is an important cause of equine protozoal myeloencephalitis (EPM) in horses in the Americas. An EPM-like neurological disease also has been reported from other mammals but it is difficult to induce this disease in the laboratory. A 4-month-old male domestic cat developed neurological signs 3 days following castration. The cat was euthanized 12 days later because of paralysis. Encephalomyelitis was the only lesion and was associated with numerous Sarcocystis schizonts and merozoites in the brain and spinal cord. The protozoa reacted positively with S. neurona-specific polyclonal rabbit antibody. Two unidentified sarcocysts were present in the cerebellum. It may be possible that stress of surgery triggered relapse of S. neurona infection in this cat.

Comparison of peripheral and central venous pressures in critically Ill patients

We conducted a prospective study to determine the relationship between central (CVP) and peripheral (PVP) venous pressures in critically ill patients. CVP and PVP were measured on five different occasions in 20 critically ill patients in the intensive care unit. Results showed that the mean difference between PVP and CVP was 4.4 mmHg (95% CI = 3.7 to 5.0). However, PVP might be 1.9 mmHg below (95% CI = 0.7 to 3.1) or 10.6 mmHg above (95% CI = 9.4 to 11.8) the CVP. The mean difference between changes in PVP and corresponding changes in CVP was 0.3 mmHg (95% CI = -0.1 to 0.7). The actual change in PVP could be 3.0 mmHg below (95% CI = 2.3 to 3.7) or 3.6 mmHg above (95% CI = 2.9 to 4.3) the change in CVP. Overall, the direction of change in PVP (rise or drop) predicted a same direction of change in CVP with an accuracy of 78%. Changes in PVP > or = 2 mmHg predicted a change in same direction of CVP with an accuracy of 90%. The direction of changes in CVP > or = 2 mmHg were predicted by the direction of change in PVP with an accuracy of 91%. We conclude that PVP measurement does not give an accurate estimate of the absolute value of CVP in individual patients. However, as changes in PVP parallel, in direction, changes in CVP, serial measurements of PVP may have a value in determining volume status and guiding fluid therapy in critically ill patients.

Hyperbaric oxygen therapy of iatrogenic cerebral arterial gas embolism

We describe our experience using HBO2 therapy for iatrogenic cerebral arterial gas embolism (CAGE) in this retrospective review of nineteen patients treated for iatrogenic CAGE, from 1987 to 1999. Immediately after treatment, five patients completely resolved all signs and symptoms, eleven had improvement, one had no change, and two were not assessable. Within two months post treatment, three additional patients completely resolved and six had further improvement. Patients with a venous source all experienced pulmonary signs or symptoms, with eight of nine chest x-rays demonstrating pulmonary edema. Patients with an arterial source had no pulmonary symptoms; all chest x-rays were clear. Imaging studies prior to HBO2 therapy demonstrated gas in six of 23 exams; five of the remaining 17 exams showed secondary changes consistent with gas embolism. Iatrogenic CAGE patients improved with HBO2 therapy, and improvement for some continued for several months. Patients with CAGE from a venous source have pulmonary signs or symptoms. Diagnosis of CAGE should be made on clinical suspicion without reliance on imaging studies.

Trans-fatty acids and colon cancer

Trans-fatty acids have been hypothesized to be carcinogenic, although there are limited data in humans testing this hypothesis. In this study, we examine the association between trans-fatty acids and colon cancer using data from a case (n = 1,993)-control (n = 2,410) study conducted in Utah, Northern California, and Minnesota. Dietary data were collected using a detailed diet history questionnaire, and nutrient values were generated from the Nutrition Coordinating Center nutrient database. After adjustment for other variables, including age at diagnosis, body size, physical activity, aspirin and/or nonsteroidal anti-inflammatory drug (referred to collectively as NSAIDs) use, energy intake, and dietary fiber and calcium, we found a weak association in women [odds ratio (OR) = 1.5, 95% confidence interval (CI) = 1.1-2.0] but not in men (OR = 1.2, 95% CI = 0.9-1.7); no increased risk was observed for the cis form of the fatty acids. For men and women, slightly stronger associations were observed in those > or = 67 years of age (OR = 1.4, 95% CI = 0.9-2.1 for men; OR = 1.6, 95% CI = 1.0-2.4 for women). Those who did not use NSAIDs were at a 50% greater risk of developing colon cancer when they consumed high levels of trans-fatty acids. Women who were estrogen negative, i.e., postmenopausal not taking hormone replace therapy, had a twofold increase in risk from high levels of trans-fatty acids in the diet, while women who were estrogen positive did not experience an increased risk of colon cancer, regardless of level of trans-fatty acids consumed. We believe that these data have important public health implications. It seems prudent to avoid consuming partially hydrogenated fats, since no increased risk was observed for the cis form of fatty acids, while suggestions of increased risk from trans-fatty acids exist for subsets of the population.

Mutations in the factor V, prothrombin and MTHFR genes are not risk factors for recurrent fetal loss

OBJECTIVE

Recurrent fetal loss, defined as the occurrence of three or more consecutive spontaneous abortions regardless of previous live birth, is a condition that affects about 2% of all reproductive-aged women. The role of gene mutations in recurrent pregnancy loss is not fully understood. The present research examined the relationship between factor V Leiden, factor V HR2, prothrombin G20210A and MTHFR and recurrent fetal loss in a case-control study.

METHODS

Women aged 22-45 with a history of three or more fetal losses, being seen at a perinatal medicine clinic in New Jersey or Georgia, were eligible as cases. Overall, the study consisted of 60 women with three or more fetal losses and 92 women with at least one successful pregnancy.

RESULTS

Factor V HR2 and MTHFR were not related to recurrent fetal loss. The prothrombin G20210A mutation appeared to confer an elevation in risk but the association was based upon small numbers and was not statistically significant (OR 4.8, 95% CI 0.50-47.2). Cases were 90% less likely to have the factor V Leiden mutation than controls (OR 0.10, 95% CI 0.01-0.81).

CONCLUSIONS

Our study did not demonstrate that women who are carriers of the factor V, prothrombin, or MTHFR mutations are at higher risk of recurrent fetal loss than women without these mutations. In regards to factor V Leiden, the prevalence in our cases (1.7%) was not statistically different from the known population prevalence of 5%. However, the high prevalence in our controls (14%) was unusual. Factor V Leiden may protect against bleeding in early pregnancy.

Fluorescent multiplex polymerase chain reaction analysis of four genes associated with inpaired fibrinolysis and myocardial infarction

Multiplex polymerase chain reaction (PCR) allows for the simultaneous amplification of several genes, thereby optimizing the use of reagents and decreasing personnel time. Multiplex PCR was used to amplify four genes in one PCR reaction, demonstrating the advantage of multiplex PCR for our study since it allowed us to amplify four separate genes using only 1 microl DNA, thus maximizing the use of study DNA. As compared with conventional multiplex PCR analysis with ethidium bromide, incorporating fluorescence-labeled primers into multiplex PCR reactions facilitated accurate, simultaneous analysis of many DNA fragments within one base discrimination. We have used this fluorescence methodology to analyze polymorphisms associated with either impaired fibrinolysis or myocardial infarction. These include the angiotensin converting enzyme insertion/deletion (I/D) polymorphism in intron 16 of the DCP1 gene, the Alu I/D polymorphism of the tissue plasminogen activator-25 locus in intron 8, the plasminogen activator inhibitor 4G/5G repeat polymorphism, and the variable number tandem repeat of the endothelial cell nitric oxide synthase gene, all characterized by an insertion, deletion, or repeat. The amplified products were diluted 1 : 60 and analyzed on the ABI PRISM 310 Genetic Analyzer using GeneScan software. With this method, we were able to amplify four genes using 75% less reagents and personnel time, thus demonstrating the benefit of multiplex PCR and fluorescence technology.

Cell contact dependent extended release of adenovirus by microparticles in vitro

Adenoviral vectors remain one of the most promising methods of gene delivery but are plagued by several inherent problems including immune inactivation and transient expression. This paper reports a novel microparticle-based delivery system for adenovirus that allows high uptake of virus, stable complex formation and extended release. In addition, this microparticle/adenovirus complex has been demonstrated to only release virus upon cell contact. The significant clinical implications of this delivery system are discussed.

Rapid depletion of peripheral antigen-specific T cells in TCR-transgenic mice after oral administration of myelin basic protein

In myelin basic protein (MBP)-specific TCR-transgenic (Tg) mice, peripheral T cells express the Valpha2.3/Vbeta8.2-Tg TCR, demonstrate vigorous proliferative responses to MBP in vitro, and can exhibit experimental autoimmune encephalomyelitis (EAE) within 5 days of pertussis toxin injection. We explored the effects of oral administration of MBP on the cellular trafficking of the MBP-specific TCR-Tg cells and the ability of oral MBP to protect Tg mice from EAE. Tg mice were fed MBP, OVA or vehicle and sacrificed at various times after feeding. An immediate and dramatic decrease in Valpha2.3/Vbeta8.2(+)-Tg cells was observed in the periphery within 1 h after feeding. By 3 days after feeding, the percentage of Tg cells increased to near control levels, but decreased again by 10 days. When MBP or vehicle-fed Tg mice were challenged for EAE at this point, disease was severe in the vehicle-fed mice and reduced in the MBP-fed mice over the 40-day observation period. In vitro studies revealed a biphasic pattern of MBP proliferative unresponsiveness and an induction of Th1 cytokines. Immunohistochemical staining showed that the number of Tg cells found in the intestinal lamina propria increased dramatically as the number of Tg cells in the periphery decreased. There was no apparent proliferation of Tg cells in the lamina propria, indicating that Tg cells trafficked there from the periphery. Taken together, these results suggest that T cell trafficking into the site of Ag deposition acts to protect the TCR-Tg mouse from EAE.

BDNF reduces miniature inhibitory postsynaptic currents by rapid downregulation of GABA(A) receptor surface expression

Changes in neurotransmitter receptor density at the synapse have been proposed as a mechanism underlying synaptic plasticity. Neurotrophic factors are known to influence synaptic strength rapidly. In the present study, we found that brain-derived neurotrophic factor (BDNF) acts postsynaptically to reduce gamma-aminobutyric acid (GABA)-ergic function. Using primary cultures of rat hippocampal neurons, we investigated the effects of BDNF on GABAergic miniature inhibitory postsynaptic currents (mIPSCs) and on the localization of GABAA receptors. Application of BDNF (100 ng/mL) led within minutes to a marked reduction (33.5%) of mIPSC amplitudes in 50% of neurons, recorded in the whole-cell patch-clamp mode, leaving frequency and decay kinetics unaffected. This effect was blocked by the protein kinase inhibitor K252a, which binds with high affinity to trkB receptors. Immunofluorescence staining with an antibody against trkB revealed that about 70% of cultured hippocampal pyramidal cells express trkB. In dual labelling experiments, use of neurobiotin injections to label the recorded cells revealed that all cells responsive to BDNF were immunopositive for trkB. Treatment of cultures with BDNF reduced the immunoreactivity for the GABAA receptor subunits-alpha2, -beta2,3 and -gamma2 in the majority of neurons. This effect was detectable after 15 min and lasted at least 12 h. Neurotrophin-4 (NT-4), but not neurotrophin-3 (NT-3), also reduced GABAA receptor immunoreactivity, supporting the proposal that this effect is mediated by trkB. Altogether the results suggest that exposure to BDNF induces a rapid reduction in postsynaptic GABAA receptor number that is responsible for the decline in GABAergic mIPSC amplitudes.