Bovine luteal cells elicit major histocompatibility complex class II-dependent T-cell proliferation

Major histocompatibility complex (MHC) class II molecules are expressed in the bovine corpus luteum (CL) in a manner correlating with luteolysis. Whether bovine luteal cells can stimulate T-cell proliferation in a class II-restricted manner was investigated. Staphylococcal enterotoxin B (SEB) enhances T-cell proliferation by a mechanism requiring MHC class II molecules and was used to examine stimulation of T-cell proliferation by luteal cells. Luteal cells from midcycle or regressing CL (induced by prostaglandin F2 alpha) were cocultured with autologous T cells in the presence of no treatment, SEB (1 microgram/ml), or SEB + anti-MHC class II antibody (3 micrograms/ml); and proliferation was assessed by incorporation of tritiated thymidine. T cells proliferated in the presence of cells from regressing CL more than when in the presence of midcycle cells (118,309 +/- 20,567 vs. 75,261 +/- 12,494 cpm; p < 0.05). Anti-MHC attenuated this response of cells from regressing CL (81,108 cpm +/- 13,249; p < 0.05). Without SEB, T cells proliferated when cultured with cells from regressing, but not midcycle, CL (4637 +/- 816 vs. 2117 +/- 589 cpm; p < 0.03). These results suggest that luteal cells can function as antigen-presenting cells in vitro and that prostaglandin F2 alpha may enhance their ability to present antigen.

RGDS tetrapeptide and hippocampal in vitro kindling in rats: evidence for integrin-mediated physiological stability

We have examined a potential role for integrins in an animal model of epileptogenesis termed in vitro kindling. Integrins mediate cell-cell and cell-matrix interactions, and also participate in the transduction of information from the extracellular environment to the intracellular milieu. As many extracellular matrix (ECM) molecules contain the conserved amino acid sequence arg-gly-asp-ser (RGDS) at the integrin recognition site, integrin-ECM binding can be disrupted using RGDS peptides. Hippocampal slices were washed in either RGDS, gly-gly-gly-gly (GGGG), vehicle or artificial cerebral spinal fluid (ACSF) for 1 h prior to in vitro kindling. Baseline electrophysiological responses were unaltered by RGDS peptide. The RGDS-treated slices displayed a significant decrease in the rate of spontaneous bursts, whereas the period of spontaneous bursting increased dramatically. Our results indicate that the competitive peptide, RGDS, changed hippocampal slice excitability over time, indicating that interference with ECM-integrin binding may alter neuronal signaling through an RGDS binding site.

The effects of nursing care guided by self-regulation theory on coping with radiation therapy

PURPOSE/OBJECTIVES

To test the hypotheses that preparatory informational interventions based on self-regulation theory delivered to radiation therapy (RT) recipients by staff nurses would reduce disruption in patients' usual life activities and have a positive effect on the moods of patients who tended to have pessimistic expectations about outcomes.

DESIGN

A quasi-experimental design with repeated measures.

SETTING

University-affiliated RT department.

SAMPLE

226 patients receiving RT for breast or prostate cancer.

METHODS

The control-group patients received the nursing care that was the standard of practice before the experimental interventions were introduced. The experimental-group patients received theory-based interventions four different times from staff nurses. Patient data were collected by interview four different times.

MAIN RESEARCH VARIABLES

Type of nursing interventions generated, optimistic or pessimistic expectations about outcomes (Life Orientation Test), amount of disruption in usual life activities (Sickness Impact Profile), and moods (Bi-Polar Profile of Mood States).

FINDINGS

The patients who received the self-regulation theory-based nursing interventions experienced less disruption in their usual life activities during and following RT. Among the patients who tended to be pessimistic, those who received the theory-based interventions had a more positive mood than those who did not receive the interventions.

IMPLICATIONS FOR NURSING PRACTICE

Staff nurses should use self-regulation theory-based interventions to help patients cope with RT.

IFN-gamma-deficient mice develop experimental autoimmune uveitis in the context of a deviant effector response

Experimental autoimmune uveitis (EAU) is a T cell-mediated disease that targets the neural retina and serves as a model of human uveitis. Uveitogenic effector T cells have a Th1-like phenotype (high IFN-gamma, low IL-4), and genetic susceptibility to EAU is associated with an elevated Th1 response. Here we investigate whether the ability to produce IFN-gamma is necessary for the development of EAU by immunizing IFN-gamma-deficient (GKO) mice with the uveitogenic protein interphotoreceptor retinoid binding protein (IRBP) and characterize the associated immunologic responses. GKO mice developed EAU comparable in severity and incidence to that of their wild-type littermates. However, the cytokine profile in their uveitic eyes as well as the cytokines produced by primed lymph node cells in response to IRBP showed a distinct profile: undiminished TNF-alpha and elevated IL-5, IL-6, IL-10, and lymphotoxin (but not IL-4) responses. The inflammatory infiltrate in GKO eyes contained an excess of granulocytes and IL-5- and IL-6-producing cells, but uveitic GKO mice did not up-regulate inducible nitric oxide synthase. GKOs had enhanced lymphocyte proliferation and delayed-type hypersensitivity responses to IRBP. Histology of the delayed-type hypersensitivity lesion in GKO had superimposed elements of an allergic-like response. Anti-IRBP Ab isotypes of GKO mice showed a reduction of IgG2a, but no enhancement of IgG1. Comparison of responses in +/+ and +/- wild-type mice revealed some limited evidence of a gene-dose effect. We conclude that IFN-gamma is not required for priming of pathogenic T cells or for effecting the retinal damage and photoreceptor loss typical of EAU. However, what appears to be a grossly similar disease is caused in the GKO by a deviant type of effector response.

IFN-gamma-deficient mice develop experimental autoimmune uveitis in the context of a deviant effector response

Experimental autoimmune uveitis (EAU) is a T cell-mediated disease that targets the neural retina and serves as a model of human uveitis. Uveitogenic effector T cells have a Th1-like phenotype (high IFN-gamma, low IL-4), and genetic susceptibility to EAU is associated with an elevated Th1 response. Here we investigate whether the ability to produce IFN-gamma is necessary for the development of EAU by immunizing IFN-gamma-deficient (GKO) mice with the uveitogenic protein interphotoreceptor retinoid binding protein (IRBP) and characterize the associated immunologic responses. GKO mice developed EAU comparable in severity and incidence to that of their wild-type littermates. However, the cytokine profile in their uveitic eyes as well as the cytokines produced by primed lymph node cells in response to IRBP showed a distinct profile: undiminished TNF-alpha and elevated IL-5, IL-6, IL-10, and lymphotoxin (but not IL-4) responses. The inflammatory infiltrate in GKO eyes contained an excess of granulocytes and IL-5- and IL-6-producing cells, but uveitic GKO mice did not up-regulate inducible nitric oxide synthase. GKOs had enhanced lymphocyte proliferation and delayed-type hypersensitivity responses to IRBP. Histology of the delayed-type hypersensitivity lesion in GKO had superimposed elements of an allergic-like response. Anti-IRBP Ab isotypes of GKO mice showed a reduction of IgG2a, but no enhancement of IgG1. Comparison of responses in +/+ and +/- wild-type mice revealed some limited evidence of a gene-dose effect. We conclude that IFN-gamma is not required for priming of pathogenic T cells or for effecting the retinal damage and photoreceptor loss typical of EAU. However, what appears to be a grossly similar disease is caused in the GKO by a deviant type of effector response.

Inhibition of LTB4 biosynthesis in situ by CGS 23885, a potent 5-lipoxygenase inhibitor, correlates with its pleural fluid concentrations in an experimentally induced rat pleurisy model

An intrapleural injection of carrageenan in rats induced LTB4 and LTC4/D4/E4 biosynthesis, exudate formation, and cellular influx in the pleural cavity. An injection of calcium ionophore (A23187, 100 nmol) 16-18 h after carrageenan injection augmented leukotriene biosynthesis and exudate formation, but not cellular influx. The carrageenan-induced pleurisy model modifid by A23187 administration was used to study the oral effect of CGS 23885 (N-hydroxy-N-[(6-phenoxy-2H-1-benzopyran-3-yl)-methyl]urea), a potent 5-lipoxygenase (5-LO) inhibitor, on inflammatory parameters. CGS 23885 dose-dependently (1 to 30 mg/kg) inhibited the enhanced LTB4 and LTC4/D4/E4 (1 to 10 mg/kg) biosynthesis, but had no effect on enhanced exudate formation. An inhibitory effect of CGS 23885 of small magnitude on cellular influx due to carrageenan stimulation was seen at 30 mg/kg. The concentrations of CGS 23885 in the pleural fluid were dose-related, and a positive correlation (r2=0.989) between pleural fluid concentration of LTB4 and CGS 23885 was observed. The results confirm that CGS 23885 is a specific, orally active 5-LO inhibitor which can achieve concentrations in the pleural cavity sufficient to inhibit production of LTB4 and LTC4/D4/E4 in an ongoing inflammatory response.

Orthotic variants

When patients present with problems for which existing devices are not adequate, research is stimulated. However, new methods and devices must improve on the older versions and should not result in variation that is less effective than the original versions. Variants less effective than the originals will be discussed with illustrative examples. Orthoses, prostheses, and pressure-reduction techniques for the diabetic foot will be considered.

Evidence of reciprocity of bcl-2 and p53 expression in human colorectal adenomas and carcinomas

Evidence of accumulating for the failure of apoptosis as an important factor in the evolution of colorectal cancer and its poor response to adjuvant therapy. The proto-oncogene bcl-2 suppresses apoptosis. Its expression could provide an important survival advantage permitting the development of colorectal cancer. The expression of bcl-2 and p53 was determined by immunohistochemistry in 47 samples of histologically normal colonic mucosa, 19 adenomas and 53 adenocarcinomas. Expression of bcl-2 in colonic crypts > 5 cm from the tumours was confined to crypt bases but was more extensive and intense in normal crypts < 5 mm from cancers. A higher proportion of adenomas (63.2%) than carcinomas (36.5%) expressed bcl-2 (P < 0.05). A lower proportion of adenomas (31.6%) than carcinomas (62.3%) expressed p53 (P < 0.02). A total of 26.3% of adenomas and 22% of carcinomas expressed both bcl-2 and p53. To determine whether these samples contained cells which expressed both proteins, a dual staining technique for bcl-2 and p53 was used. Only 1/19 adenomas and 2/53 carcinomas contained cells immunopositive for both bcl-2 and p53. Moreover there was evidence of reciprocity of expression of bcl-2 and p53 in these three double staining neoplasms. We suggest that bcl-2 provides a survival advantage in the proliferative compartment of normal crypts and colorectal neoplasms. However, its expression is lost during the evolution from adenoma to carcinoma, whereas p53 expression is increased, an event generally coincident with the expression of stabilised p53, which we presume to represent the mutant form.

Integrins: possible functions in the adult CNS

Integrins comprise a large family of heterodimeric proteins that mediate cell-cell and cell-extracellular-matrix adhesive connections. There is an extensive literature on their importance in neural development and cancer, but evidence for the existence of integrins in the adult CNS has emerged only recently. With growing immunohistochemical and molecular biological evidence for the presence of integrins in the adult CNS, a variety of functions from microglial migration to synaptic rearrangements can be considered for these adhesive proteins.

1994 Oncology Nursing Society Research Priorities Survey

PURPOSE/OBJECTIVES

To determine oncology nursing research priorities as well as the type of research needed to address these priorities.

DESIGN

Cross-sectional survey design.

SETTING

Mail-out survey with return, postage-paid envelope provided.

SAMPLE

A random sample of 10% of Oncology Nursing Society (ONS) members who identified patient care as their primary functional area, the ONS leadership group (e.g., Board of Directors, all committee chairs), all doctorally prepared ONS members, and all members of the ONS Advanced Nursing Research Special interest Group (N = 2,178).

METHODS

The questionnaire was based on prior ONS Research Surveys and updated to reflect issues or topics that currently are relevant to oncology nurses.

MAIN RESEARCH VARIABLES

Priority ranking of 93 research topics organized into seven major categories.

FINDINGS

Seven hundred eighty-nine surveys were returned, for a 36% return rate. The top 10 priorities according to the priority index were pain; prevention; quality of life; risk reduction/screening; ethical issues; neutropenia/immunosuppression; patient education; stress, coping, and adaptation; detection; and cost containment.

CONCLUSIONS

The top 10 research issues can be used to develop priorities for the direction of research in oncology nursing.

IMPLICATIONS FOR NURSING PRACTICE

The findings provide a basis for identifying trends in nursing practice. The fact that prevention, risk reduction, and detection appear in the top 10 suggests that nurses are moving toward a definition of practice that is not limited to managing symptoms of disease. These findings also provide guidance for forming health policy in cancer care.

Patients' use of prevention behaviors in managing side effects related to chemotherapy

PURPOSE/OBJECTIVES

To describe the use of prevention and early detection behaviors related to the side effects of chemotherapy.

DESIGN

Cross-sectional, descriptive, and secondary analysis.

SETTING

A large university hospital and university-affiliated community hospital.

SAMPLE

46 adult patients with cancer starting a cycle of IV chemotherapy who were predominantly white, married, and female.

METHODS

Self-report utilizing a 17-item, self-administered prevention and early detection questionnaire called the Prevention Behaviors Questionnaire (PBQ); questionnaires were completed two days and five days after treatment.

MAIN RESEARCH VARIABLE

Prevention and early detection behaviors.

FINDINGS

Patients reported using an average of 8.8 prevention behaviors two days after chemotherapy and 9.2 behaviors five days after chemotherapy. "Tried to think more positively" was the most frequently used behavior. Internal consistency and test-retest correlation coefficients on the questionnaire were calculated to be 0.81 and 0.78, respectively.

CONCLUSIONS

The PBQ had adequate internal consistency and test-retest reliability. Patients reported using many prevention and detection behaviors, although very little is known about the efficacy of these behaviors in reducing or preventing the side effects of chemotherapy.

IMPLICATIONS FOR CLINICAL PRACTICE

This exploratory study does not have direct implications for practice but identifies an area for future research that may affect what nurses teach patients and how they assist patients to cope with treatment.

Dermorphin-induced hyperexcitability in hippocampal CA3 and CA1 in vitro

Dermorphin, a specific mu 1-opioid receptor agonist, has been studied for its effects on the physiology of the rat hippocampal slice. Population responses in CA3 to threshold levels of stimulation from both the Schaffer collaterals and mossy fibers were markedly enhanced in the presence of 50-100 nM dermorphin, while CA1 responses to threshold Schaffer collateral stimulation were less effected. Responses at higher stimulus levels than threshold were negligibly responsive to dermorphin, although at 500 nM dermorphin all responses became epileptiform and in some slices spontaneous bursting erupted. [L-Ala2]Dermorphin, a biologically inactive dermorphin analogue, did not increase response amplitudes nor evoke epilepsy in the slice. 5 microM naloxone blocked the effect of dermorphin on Schaffer collateral and mossy fiber-evoked responses, though less effectively in the latter case. These data provide in vitro evidence to support in vivo observations that excessive mu-opioid receptor activation can be proconvulsant in the hippocampus, but that normally the receptors may function as facilitatory modulators of responses in the threshold range.

Hippocampal in vitro kindling is not blocked by nitric oxide synthase inhibitors

Effects of nitric oxide synthase (NOS) inhibitors on the induction of an in vitro model of kindling were investigated in the rat hippocampal slice. It has been reported that NMDA receptor activation stimulates NOS and guanosine 3',5'-cyclic monophosphate (cGMP) production and that the interruption of this pathway interferes with LTP in the CA1 hippocampal field. Because the induction of LTP and kindling both involve NMDA receptor activation, we tested the effects of NOS inhibitors on the genesis and initial rate of interictal-like spontaneous bursts in CA1 and CA3 of the rat hippocampal slice. Experimental groups were exposed to 100 microM methyl-L-arginine (active NOS inhibitor), nitro-L-arginine (active NOS inhibitor), or methyl-D-arginine (inactive isomer of the NOS inhibitor) for 1 h prior to in vitro kindling. These results indicate that rather than preventing the induction of kindling in this model of epileptogenesis, NOS inhibition may facilitate the initiation of interictal-like spontaneous bursts in the rat hippocampal slice.

A comparison of patient-reported side effects among three chemotherapy regimens for breast cancer

Patient's perceptions of side effects and the influence of treatment on daily activities are important considerations in choosing a chemotherapy regimen. However, there are no studies comparing patients' experiences with three commonly used chemotherapy regimens for breast cancer. The authors compared the patient-reported side effects and disruption in usual activities for cyclophosphamide and fluorouracil combined with methotrexate (CMF), doxorubicin (CAF), or mitoxantrone (CNF) in 86 women receiving treatment for breast cancer. The incidence and severity of side effects and disruption in usual activities were recorded by patients in a self-care diary (SCD) 2 and 5 days after the first and second drug cycles. Patients reported a mean of 3.2 to 4.9 side effects at each point in time. Fatigue, nausea, anorexia, taste changes, and headache were the most frequently reported side effects and did not differ in incidence among the three drug regimens. When repeated measures analysis of covariance was conducted using mean substitution for missing data and controlling for stage of disease, women receiving CAF reported more severe nausea than women receiving CMF or CNF (P < 0.05). Fatigue was significant for time; however, a distinct clinical pattern of fatigue was not apparent. Patients reported moderate levels of disruption in activities of daily living, with those receiving CAF having greater disruption. There was no difference among treatment groups in reports of overall disruption in activities. These data on patient reported experiences with side effects of chemotherapy can be used to prepare patients for specific side effects of treatment and facilitate symptom management.

Anatomical localization of beta 1 integrin-like immunoreactivity in rat brain

beta 1 Integrin-like immunoreactivity was localized in rat brain using a polyclonal antibody raised in rabbit against rat liver beta 1 integrin. One-dimensional immunoblotting of whole rat brain membranes indicated that this antiserum recognized a single molecular species at 116,000 M(r), indicative of rat beta 1 integrins. Specific staining of beta 1 integrin-like immunoreactivity was found in the vascular structures of the brain, including microvessels, the ventricular ependymal cells, and pia mater. The pineal gland stained densely, and diffuse staining was present throughout the gray matter of the brain. This diffuse staining had a patterned appearance in certain structures, such as the apical dendritic field of CA1 in hippocampus, and occasional labeling of astrocytes, verified by labeling with GFAP on adjacent sections, was noted.

Protein synthesis inhibition blocks maintenance but not induction of epileptogenesis in hippocampal slice

We have been examining the role of protein synthesis in the development and maintenance of spontaneous bursting in the rat hippocampal slice. We used stimulus train induced bursting (STIB) as an in vitro model for epileptogenesis, to study the effects of 3 different protein synthesis inhibitors (cycloheximide, anisomycin, puromycin) on the development of bursting. We report here that none of these inhibitors blocked the induction of bursting, suggesting that protein synthesis is not essential for the development of electrically induced bursting. However, when established spontaneous bursting was examined in the presence of cycloheximide, the duration of the bursting phase was markedly reduced, suggesting that the maintenance of spontaneous bursting in the early hours requires ongoing protein synthesis.

Progesterone regulation of luteinizing hormone receptors on cultured bovine luteal cells

During development of the corpus luteum (CL), the numbers of luteinizing hormone (LH) receptors increase. Cultured bovine luteal cells from developing and mature CL were used to examine the influence of progesterone (P4) on this receptor. CL were obtained from dairy cows during the early or middle phase of the estrous cycle. In early CL, the number of receptors per cell was increased by exogenous progesterone treatment but there was no effect on receptor numbers in cells from midcycle CL. Binding affinities did not change with respect to age or treatment. Forskolin elevated endogenous progesterone and also enlarged the receptor population. The action did not appear to be an unmasking of cryptic receptors since the effect was not seen in luteal particulates. Elevation of LH receptor numbers by progesterone in immature CL may be a form of intraluteal regulation contributing to the functional maturation of these steroidogenic cells.

The art of the consultation note

Inherent in the consultation process is the ability to communicate effectively, yet little emphasis is placed on written communication through consultation notes. The art of writing a consultation note is learned primarily through trial and error or by master/apprentice relationships with senior practitioners. This paper reviews the types of consultations in which advanced practitioners are involved and presents a format for preparing a comprehensive consultation note.

Naloxone blocks antiepileptogenic properties of an in vitro electroconvulsive shock model

Electroconvulsive shock-induced seizures elevate seizure thresholds in humans and interfere with kindling in animals; opioids may mediate the anticonvulsant mechanism. In a potential model of acute electroconvulsive shock in hippocampal slices, a high-intensity tetanus via the mossy fibers substantially delayed subsequent in vitro kindling through the Schaffer collaterals. Naloxone blocked this effect, implicating the opioid system in the antiepileptogenic properties of this model.

Use and perceived efficacy of self-care activities in patients receiving chemotherapy

Information about chemotherapy side effects and the efficacy of self-care activities used to deal with these side effects is needed to direct nursing interventions for patients receiving chemotherapy. Using the self-care diary (SCD) developed for this study, a sample of 49 adult patients with cancer recorded their side effects, rated the severity of each side effect, and reported on the use and efficacy of self-care activities two days after treatment. Data were collected again five days after treatment to examine the test-retest reliability of the side effect severity component of the SCD. The most common side effect, experienced by 81% of the subjects, was fatigue. Other side effects reported by more than one-third of the subjects were sleeping difficulty, nausea, decreased appetite, and changes in taste or smell. The most frequently reported side effects received mean severity scores indicative of moderate severity. The most commonly used self-care activities were rated as providing some relief to moderate relief of individual side effects. None of the reported self-care activities received mean efficacy ratings that indicated complete side effect relief.

Effects of diisopropyl phosphorofluoridate (DFP) on CA3 and CA1 responses in rat hippocampus

Diisopropyl phosphorofluoridate (DFP), an insecticide, is a potent anticholinesterase that binds essentially irreversibly to acetylcholinesterase, resulting in severe, acute neurologic pathology, and less severe, but longer-lasting, delayed neuropathy. We report here on the short-term effects of bath-applied DFP on extracellularly recorded responses from CA3 and CA1 of rat hippocampus. Exposure to 10 microM DFP evokes low amplitude, spontaneous bursts in CA3 generally within 10 minutes, and the bursting does not reverse with washing. The CA1 neuronal population usually bursts synchronously with CA3, but the population events are of low amplitude and sometimes not detectable, implying a differential sensitivity to DFP. These effects were partially blocked by the muscarinic antagonist atropine, while the cholinergic antagonist gallamine had little effect. Also, the reversible anticholinesterase physostigmine could, within temporal limits, protect slices from DFP's effects, implicating the cholinergic system as the probable mediator in the first stages of DFP-induced epileptogenesis.

Hippocampal epileptiform activity induced by magnesium-free medium: differences between areas CA1 and CA2-3

Hippocampal slices, from which the entorhinal cortex had been removed, were exposed to artificial cerebrospinal fluid containing no magnesium (0-Mg ACSF) to elicit interictal bursts (IIBs) and electrographic seizures (EGSs). In 0-Mg ACSF, IIBs and EGSs occurred in both area CA1 and area CA3. The IIBs in CA3 led the IIBs in CA1 by several milliseconds. The epileptiform bursts occurring during the EGSs seemed to have the opposite relationship, with bursts in CA1 leading those in CA3 by several milliseconds. When the connections between CA1 and CA2-3 were cut, the IIBs ceased in CA1 and continued in CA3. To further characterize the local differences in epileptiform activity, totally separate minislices of area CA1 and area CA2-3 were prepared. In the CA2-3 minislices, a few EGSs occurred and thereafter only persistent IIBs prevailed. Conversely, in the CA1 minislices, many spontaneous EGSs occurred for long periods of time and no IIBs were seen. Periodic stimulation of the CA1 minislices triggered IIBs that suppressed the recurrent EGSs. In the hippocampal slice exposed to low magnesium, IIBs originate in CA2-3 and are propagated to CA1, where they can have a suppressant effect on EGSs. Furthermore, unlike IIBs, the bursts making up the EGSs seem to start in CA1 and invade CA2-3.

Baclofen induces spontaneous, rhythmic sharp waves in the rat hippocampal slice

In rat hippocampal slices, low concentrations of (+/-) baclofen (0.1 to 1.5 microM) elicited spontaneous, rhythmic sharp waves (SRSWs). These low amplitude (0.1 to 0.3 mV) SRSWs were visible with high amplification in the extracellular recordings from the CA1, CA2, and CA3 regions and were roughly synchronous in all areas. SRSW amplitude increased and frequency decreased as baclofen concentration increased up to 1.5 microM, but SRSWs were suppressed at concentrations of 5 microM and higher. The amplitude of the SRSWs was greater in the strata radiatum and the lacunosum moleculare than in the stratum pyramidale. (-)-Baclofen was much more potent in eliciting SRSWs than (+)-baclofen. Low concentrations of baclofen also caused the extracellular excitatory postsynaptic potential in the stratum radiatum of CA3b evoked by stimulation of the Schaffer collaterals to broaden and develop a secondary peak. Slices pretreated with pertussis toxin required much higher concentrations of baclofen to elicit the SRSWs, indicating that the baclofen may be eliciting the SRSWs through a G protein-sensitive mechanism. Baclofen has both inhibitory and disinhibitory effects on neurons. The appearance of these spontaneous population events suggests that, at low concentrations, the disinhibitory effects may be more powerful than the inhibitory effects.