Short-term Sensitivity Research Articles

High sensitivity methane analyzer based on tuned near infrared diode laser

A portable automatized high sensitive gas analyzer was developed for the detection of trace gas concentration measurements in the atmosphere. Methane was chosen as an example gas for demonstration of the possibilities of the device. Main features of the instrument are long path Chernin optical multipass cell (50 cm base and up to 100 m optical path length) and original data processing. A near infrared (IR) tunable diode laser (DL) operating at wavelength 1.65 μm at room temperature allowed the avoidance of coolants. The measurements can be produced in open atmosphere as well as with gas mixture samples at various pressures. Short term sensitivity of methane detection in the open atmosphere was found to be 30 ppb, long term stability—100 ppb, which is enough for methane concentration monitoring in the open atmosphere.

Effect of atrazine on growth, photosynthesis, and between-strain variability in scenedesmus subspicatus (Chlorophyceae)

The magnitude of between-strain differences in the sensitivity of algal species to toxicants is not well known. Yet, informations obtained with a single strain are used for ecotoxicological assessment and for interspecific comparisons. Using 12 strains, we determined whether intraspecific variability occurs in the green alga Scenedesmus subspicatus. We examined growth, photosynthetic activity, and short-term sensitivity thereof to the herbicide atrazine (500 &mgr;g. L-1) as well as how these responses are affected by chronic exposure to low atrazine concentrations (0, 1, 5, and 20 &mgr;g. L-1). Independent of chronic exposure to atrazine, the strains differed in growth rate and photosynthesis rate. Yet the short-term sensitivity to atrazine was affected by the chronic treatments. All but one strain became more tolerant, their short-term sensitivity being inversely related to the applied atrazine concentration and dependent on the duration of exposure. Differences in response to increments in atrazine concentration resulted in differences in rank order of sensitivity of strains. Moreover, between-strain variability was markedly higher in the atrazine treatments than in the controls. These results can be explained by the significant role of genotype versus environment interactions in determining intraspecific differences in adaptive physiological responses of S. subspicatus to chronic exposure to atrazine.http://link.springer-ny. com/link/service/journals/00244/bibs/37n1p36.html

Short- and long-term heterologous sensitization of adenylate cyclase by D4 dopamine receptors.

The D4 dopamine receptor, a member of the D2-like dopamine receptor family, may be important in the etiology and treatment of schizophrenia. The present study was designed to examine the effects of dopamine agonist exposure on adenylate cyclase activity in HEK293 cells stably expressing recombinant-D4 receptors. Two hour pretreatment with dopamine receptor agonists resulted in heterologous sensitization of forskolin-stimulated cyclic AMP accumulation in intact cells expressing the D4.2, D4.4, or D4.7 dopamine receptor variant. The potency and efficacy of dopamine for sensitization of cyclic AMP accumulation was comparable at all D4 receptor variants. D4 dopamine receptor-mediated sensitization was blocked by the D4 antagonist, clozapine, and prevented by overnight pretreatment with pertussis toxin, implying a role for Gi/Go proteins in heterologous sensitization. Further, long-term (18 h) agonist exposure resulted in a greater degree of sensitization of forskolin-stimulated cyclic AMP accumulation in both intact cells and membrane preparations of cells expressing the D4 receptor, compared to 2 h agonist exposure, without altering the density of the receptors. In addition, long-term agonist exposure decreased the abundance of Gialpha without altering the abundance of Gsalpha, whereas short-term agonist treatment had no effect on the immunoreactivity of either G protein. In summary, long-term agonist-induced sensitization of adenylate cyclase by the D4 receptor may involve mechanisms that do not contribute to short-term sensitization.

Clavel Chapelon F. Paoletti C. Benhamou S. A randomised 2 × 2 factorial design to evaluate different smoking cessation methods: Revue d'Épidemiologie et de Santé Publique 1992; 40: 187–190

This study examined whether category boundaries between Black and White faces relate to individual attitudes about race. Fifty-seven (20 Black, 37 White) participants completed measures of explicit racism, implicit racism, collective self-esteem (CSE), and racial centrality. Category boundaries between Black and White faces were measured in three separate conditions: following adaptation to (1) a neutral gray background, a sequence of (2) Black or (3) White faces. Two additional conditions measured category boundaries for facial distortion to investigate whether attitudes relate to mechanisms of racial identity alone, or to more global mechanisms of face perception. Using a two-alternative forced-choice staircase procedure, participants indicated whether a test image appeared to be Black or White (or contracted or expanded). Following neutral adaptation, participants with higher CSE showed category boundaries shifted toward faces with a higher percentage of Black features. In addition, the strength of short-term sensitivity shifts following adaptation to Black and White faces was related to explicit and implicit attitudes about race. Sensitivity shifts were weaker when participants scored higher on explicit racism, but were stronger when participants scored higher on implicit but lower on explicit racism. The results of this study indicate that attitudes about race account for some individual differences in natural category boundaries between races as well as the strength of identity aftereffects following face adaptation.

Clinical evaluation of two desensitizing agents for use under Class 5 silver amalgam restorations

Statement of problem. Postoperative sensitivity is sometimes reported to be a clinical problem after placement of silver amalgam restorations. Purpose. This study compared postoperative sensitivity of Class 5 caries restored with amalgam restorations and Copalite or DentinBloc cavity liners. Material and methods. At least 1 pair of amalgam restorations were placed in each of 16 patients and tested for sensitivity at 5 time periods. Results. Sensitivity was significantly less with DentinBloc cavity liner ( P<.05) at 24 hours, and 2 and 4 weeks. There was a directional but nonsignificant effect ( P>.05) in favor of DentinBloc cavity liner at 1 and 16 weeks. Conclusion. DentinBloc cavity liner was more effective than Copalite cavity liner in reducing short-term postoperative sensitivity for amalgam restorations. (J Prosthet Dent 1998;80:269-73.)

DOES DIZOCILPINE (MK-801) INHIBIT THE DEVELOPMENT OF MORPHINE-INDUCED BEHAVIOURAL SENSITIZATION IN RATS?

Intermittent morphine pretreatment (10 mg/kg/day for 14 days) induced long-lasting (one month post-treatment) sensitization to the locomotor effects of morphine and amphetamine in rats. Co-administration of the non-competitive NMDA-receptor antagonist dizocilpine (MK-801) (0.1 mg/kg) with morphine did not prevent the development of long-term behavioural sensitization. However, this dose of MK-801 did cause long-term sensitization to its own locomotor effects. Co-administration of 0.25 mg/kg MK-801 with morphine caused death in 60% of the animals. In the animals that survived MK-801 plus morphine pretreatment, neither short-term (3 days) nor long-term morphine-induced sensitization was observed. MK-801 alone (0.25 mg/kg/day for 14 days) induced short-term cross-sensitization to morphine. Thus, the development of long-term morphine-induced locomotor sensitization could only be prevented by a dose of MK-801 that yields a lethal combination with morphine. In addition, MK-801 induced sensitization to its own locomotor effects and cross-sensitization to morphine. These findings seriously question whether MK-801 can be used to study the development of morphine-induced behavioural sensitization. © 1997 Elsevier Science Inc.

Neonatal and preweanling rats are able to express short-term behavioral sensitization to cocaine

The present study assessed the ability of suckling rats to express short-term behavioral sensitization to cocaine prior to weaning. Rat pups, aged either 3, 5, 10, 12, 17 or 19 days at the beginning of the experiment, were placed in a chamber after daily injection with cocaine (7.5 or 15 mg/kg, i.p.) for either 2 or 4 consecutive days, and were tested for behavioral responsiveness to cocaine in the same chamber 24 h later (at either 7, 14 or 21 days of age). Such a short post-treatment interval was adopted, along with a consistent pairing of the testing context with the drug effect and a sensitive technique of behavioral measurement (video recording), in order to maximize the possibility of detecting any cocaine sensitization. Locomotion was sensitized at all ages, after both regimens in 14-day-old pups, but solely after 2 injections in 21- and 4 injections in 7-day-old pups. Sensitization was also expressed via behaviors specific to each age. Four cocaine injections augmented cocaine-induced uncoordinated movements of head, paws and body (horizontal activity) in 7-day-old pups, and mouth movements in 14-day-old pups. In 21-day-old pups, sensitization was dose- and regimen-dependently expressed via adult-like stereotyped head movements. In neonatal 7-day-old pups, cocaine sensitization was also visible as reductions in immobility (both injection regimens). Contrary to previous studies, these results indicate that, given the use of an appropriate methodology, short-term sensitization to the motoric effects of cocaine can be expressed by suckling rats prior to weaning, even after relatively short regimens of daily injections.

Precision Rotation Measurements with an Atom Interferometer Gyroscope

We report the demonstration of a Sagnac-effect atom interferometer gyroscope which uses stimulated Raman transitions to coherently manipulate atomic wave packets. We have measured the Earth's rotation rate, and demonstrated a short-term sensitivity to rotations of $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}(\mathrm{rad}/\mathrm{s})/\sqrt{\mathrm{Hz}}$.

Developmental Emergence of Long-Term Memory for Sensitization inAplysia

AdultAplysiaexhibit both short-term and long-term memory for sensitization in the gill and siphon withdrawal reflex. Previous developmental studies showed that short-term memory for sensitization emerges late in juvenile development (stage 12; Rankin and Carew, 1988; Wright et al., 1991). In the present study, we examined the development of long-term memory for sensitization. Long-term sensitization of the siphon withdrawal reflex was quantified as an increase in mean response duration observed 20–24 h after receiving a training regime of one or more 90-min sessions of electrical shock to the tail. In the first three experiments we assessed the capacity for long-term sensitization in adults and in juveniles of stages late 12 and early 12. Animals in all three age classes showed long-term sensitization. In a fourth experiment we simultaneously trained and tested both early stage 12 animals and stage 11 animals with identical stimulus parameters that were scaled down to a level appropriate to the smaller stage 11 animals. Under these conditions, the early stage 12 animals demonstrated long-term sensitization, while the stage 11 animals still showed no evidence of long-term sensitization. These results indicate that long-term sensitization first emerges at early stage 12, which is the same developmental stage in which short-term sensitization first emerges. Although these behavioral data do not elucidate underlying mechanisms, the fact that short-term and long-term memory emerge according to the same developmental timetable is consistent with the possibility that these two forms of memory may share at least some common mechanistic features.

Serotonin-induced short- and long-term sensitization in the crab Chasmagnathus

On sudden presentation of a passing shadow (a visual danger stimulus), the crab Chasmagnathus granulatus responds with a running reaction that we term an escape response (ER). A single administration of 5-HT in a dose range between 0.005 and 0.1 μg/g enhances the ER at 30 min, and a dose of 10–15 μg/g has a similar effect for at least 24 h. The classical 5-HT antagonist cyproheptadine (CYP) given within a dose range 0.01–2.0 μg/g has no effect on ER at 30 min, but 0.5 μg/g blocks the 5-HT-induced short-term sensitization. An enhancing effect of CYP on the ER is shown at 24 h with 1.0–2.0 μg/g doses. An explanation of this results in terms of a model similar to that proposed for Aplysia, that is two sensitizing processes linked in parallel and mediated by two different types of 5-HT receptors is discussed. Results indicate that the sensitizing effect of 5-HT is confined to high responders, thus suggesting that crabs of a same population have different degrees of sensitivity to the drug according to their different degrees of reactivity to the visual danger stimulus.

Ontogeny of behavioral sensitization in the rat: effects of direct and indirect dopamine agonists.

In the present study, the abilities of NPA (a direct DA receptor agonist) and amphetamine (an indirect DA receptor agonist) to induce short- and long-term behavioral sensitization were assessed in 11- and 17-day-old rats (age at initial injection). Rats were injected on 4 consecutive days with amphetamine (1.0, 2.5, or 5.0 mg/kg), NPA (1.0 mg/kg), or saline. A final test day occurred either 2 days (experiment 1) or 8 days (experiment 2) later. On the test day, rats given successive agonist injections received a single injection of the same agonist again; whereas rats given successive saline injections received either amphetamine or NPA for the first time. Five minutes after injection, locomotor activity (line-crosses), stereotyped sniffing, and vertical activity were measured during a 30-min testing session. The results showed that 11- and 17-day-old rats exhibited behavioral sensitization when tested with NPA or amphetamine after a 2-day interval. In contrast, neither NPA nor amphetamine was able to sensitize the behaviors of preweanling rats when measured 8 days after initial drug treatments. Therefore, these results show that both direct and indirect DA agonists are able to induce short-term behavioral sensitization in preweanling rats, but that the mechanisms responsible for mediating long-term behavioral sensitization have not yet matured.

Productivity of Long-Term Grazing Treatments in Response to Seasonal Precipitation

Estimates of forage production for long-term ungrazed, lightly, moderately, and heavily grazed treatments (0, 20, 40, 60% removal of annual forage production) established in 1939 in shortgrass steppe communities were subjected to multiple regression analyses to assess long-term temporal trends resulting from grazing and short-term sensitivities to abiotic factors. Average production based upon all data from 1939-1990 was 75, 71, 68, and 57 g m(-2)yr(-1) for ungrazed, lightly, moderately, and heavily grazed treatments, respectively. Variability in forage production was explained mostly by cool-season precipitation, and magnitude of forage production was more sensitive to annual fluctuations in precipitation than to long-term grazing treatments. Production per unit increase of precipitation was greater for cool-season than warm-season precipitation, but only when cool-season precipitation was above average. This was attributed to differences in evaporative demand of the atmosphere resulting in different utilization-efficiencies of small and large rainfall events in the 2 seasons. Based upon a regression model constructed using data from 1939 through 1962, forage production was not affected by grazing to 20 to 35% removal. For pastures of average relative productivity, grazing at 60% level of consumption for 25 years resulted in a 3% decrease in forage production in wet years and a 12% decrease in dry years. Estimates of productivity after 50 years of heavy compared to light grazing treatment were -5 and -18% for wet and average y precipitation, respectively.

Regulatory subunits of cAMP-dependent protein kinases are degraded after conjugation to ubiquitin: a molecular mechanism underlying long-term synaptic plasticity.

In Aplysia, behavioral sensitization of defensive reflexes and the underlying presynaptic facilitation of sensory-to-motor neuron synapses lasts for several minutes (short term) or days to weeks (long term). Short-term sensitization has been explained by modulation of ion-channel function through cAMP-dependent protein phosphorylation. Long-term facilitation requires additional molecular changes including protein synthesis. A key event is the persistent activation of the cAMP-dependent protein kinase at baseline concentrations of cAMP. This activation is due to selective loss of regulatory (R) subunits of PKA without any change in catalytic (C) subunits. To understand the molecular mechanisms that produce the loss of R subunits in long-term facilitation, we investigated how R subunits are degraded in extracts of Aplysia nervous tissue and in rabbit reticulocyte lysates. Degradation of Aplysia R subunits requires ATP, ubiquitin, and a particulate component that appears to be the proteasome complex. Degradation is blocked by hemin, which causes the accumulation of high molecular weight derivatives of R subunits that are likely to be ubiquitin conjugates of R subunits and intermediates in the degradative pathway. We also show that vertebrate RI and RII subunits can be degraded through the ubiquitin pathway. We suggest that degradation is initiated by cAMP, which causes the holoenzyme to dissociate and, further, that the altered R-to-C ratio in Aplysia sensory neurons is maintained in long-term facilitation by newly synthesized proteins that help target R subunits for accelerated degradation.

A simplified method for deuterium/hydrogen isotope ratio measurements on water samples of biological origin.

Equilibration of hydrogen gas with the water in a variety of biological sample materials was carried out in Vacutainers using platinum-on-alumina catalyst physically isolated from the liquid water. The equilibration takes 3 days at room temperature--much slower than with catalysts which float on the water surface--but this reduces the short-term temperature sensitivity of the procedure, and the inexpensive materials used allow convenient disposal of biologically contaminated samples after analysis. The slow equilibration also allows time for complete exchange with water contained in a complex sample matrix such as plant stems or soil without the need for prior isolation of the water sample. The method has particular application in studies of human total body water where repeated studies can be carried out over a short time period without the need to wait for the previous dose to wash out. Water turnover rates from total diurnal energy expenditure studies measured by this method were not significantly different from those obtained by the zinc reduction method.

The Rational Effect of Price Promotions on Sales and Consumption

We explore the rational effect of price variation on sales and consumption in markets where consumers are uncertain about the future price of goods. We first derive an optimal ordering policy which expresses the amount a consumer should purchase and consume in a given period as a function of the observed price of the good, the distribution of future prices, and the nature of his or her inventory. This policy extends previous normative models of inventory control, such as those by Golabi (1985) and Kalymon (1970) to the case where the amount to consume in a given period is an explicit decision variable and prices follow a first-order stochastic process. We then use this model to explore how changes in the long-run frequency and temporal correlations of price promotions should normatively affect the contemporaneous relationship between purchase, consumption and price. Among the predictions which follow from the model are that consumption should rationally increase with the size of existing inventories, the short-term sensitivity of sales to prices should be greater than that of consumption to price, and this discrepancy increases with decreases in the temporal correlation of price deals and the long-term relative frequency of price deals.

Functional uncoupling of inhibitory interneurons plays an important role in short-term sensitization of Aplysia gill and siphon withdrawal reflex

Attempts to explain learning-associated potentiation of synaptic transmission in model systems such as withdrawal reflexes in the mollusk Aplysia or the hippocampus of vertebrates have focused on the mechanisms by which transmitter release is increased in the principal elements of the circuit. Increased transmission in neuronal networks such as the gill and siphon withdrawal reflex (GSWR) of Aplysia may, however, also be caused by a decrease of transmitter release by inhibitory interneurons. The importance and function of cholinergic inhibitory transmission in the GSWR network were investigated. Central application of the nicotinic cholinergic antagonist d-tubocurarine (d-TC) considerably potentiated gill contractions, evoked either by nerve stimulation or by tactile stimulation of the siphon. Compound EPSPs evoked in motoneurons upon siphon nerve stimulation were also significantly prolonged following application of d-TC, but were unaffected by hexamethonium, a blocker of excitatory ACh receptors in Aplysia. Recordings from excitatory interneurons showed that they received excitation followed by powerful inhibitory input upon stimulation of the siphon nerve. Application of d-TC completely blocked this rapid inhibition, thus prolonging the compound EPSPs evoked in the interneurons. These effects were obtained at a concentration of d-TC (100 microM) that almost totally blocked fast inhibitory cholinergic transmission, but was without effect on monosynaptic connections between sensory neurons and motoneurons of the reflex. Facilitation of (1) compound EPSCs in motoneurons and (2) evoked excitatory interneuronal firing was reduced in preparations already disinhibited by pretreatment with d-TC. Facilitation of sensory-motor synapses, however, was not reduced in the presence of d-TC, indicating that facilitatory interneurons are still activated under cholinergic blockade. These data show that transmission through the GSWR neuronal network is gated by a feedback inhibitory mechanism. They also suggest that a reduction of cholinergic inhibition onto excitatory interneurons may be a mechanism through which transmission within the GSWR network is increased during various forms of learning, such as sensitization. These data place new emphasis on the important role of inhibitory interneurons in determining the plastic properties of neuronal networks, in both invertebrates and vertebrates.

Bag cell extract inhibits tail-siphon withdrawal reflex, suppresses long-term but not short-term sensitization, and attenuates sensory-to- motor neuron synapses in Aplysia

The peptides released from the bag cells (bag cell peptides, BCPs) in Aplysia californica are responsible for eliciting or modulating a repertoire of behaviors preceding and accompanying egg laying. Our interest was in determining to what extent behaviors that can occur simultaneously with egg laying are modulated. To address this issue, we examined the effects of an extract (bag cell extract, BCE) that contained BCPs, as well as egg-laying hormone (ELH), an identified BCP, on both the tail-siphon withdrawal reflex and the ability of that reflex to exhibit sensitization, a simple form of nonassociative learning. In addition, we examined the ability of BCE, as well as the individual BCPs, to modulate a component of the circuitry of the reflex. Behavioral experiments indicated that BCE inhibited the baseline withdrawal reflex and suppressed long-term sensitization of the reflex while leaving short-term sensitization unaffected. These effects were not observed in animals receiving an extract of a control ganglion or in animals receiving ELH, and therefore may be attributed to the actions of one or more BCPs, but presumably not to ELH alone. Electrophysiological experiments revealed that BCE also attenuated the monosynaptic EPSP elicited in tail motor neurons by tail sensory neurons. In subsequent experiments in which the BCPs were individually applied, only one BCP, beta-BCP, significantly attenuated the EPSPs. This effect was independent of narrowing of the presynaptic action potential. Taken together, these results suggest a novel behavioral modification attributed to BCPs, inhibition of the tail-siphon withdrawal reflex, and suggest a possible locus of action and peptide candidate for this effect. In addition, these experiments raise the possibility that BCPs may exert a long-lasting effect (> 24 hr), selectively blocking a simple form of long-term memory.

Laser strainmeters: New developments and earthquake prediction applications

Two novel laser strainmeters furnished with airfilled pressure-tight shielding pipe are considered to be an affordable tool for modern geodynamic observations. The thermal-to-strain coefficient of 1 · 10 −8 K −1 provides sufficient long-term instrument stability, while short-term sensitivity of ΔL/ L = 10 −11–10 −12 in the frequency band up to 1 kHz has been achieved. Experimental prototypes of the laser strainmeters have been tested at various sites and certain phenomena concerning earthquake prediction problems have been revealed.

Automated Static Perimetry

PART ONE: BASICS 1. Introductory Concepts Anatomy and Function of the Eye Visual Field Correspondence of the Retina and Visual Field Boundaries of the Visual Field 2. Basis of Quantitative Perimetry Visual Characteristics Within the Visual Field Units of Light Intensity Threshold Sensitivity in Terms of Stimulus Intensity Frequency-of-Seeing Curve and Short-Term Fluctuations Long-term Fluctuation Subjective Stimulus Brightness Background Intensity Contrast Sensitivity and Veiling Glare Refractive Error and Retinal Blur Stimulus Size and Spatial Summation Temporal Summation and Stimulus Deviation Learning Effects Fatigue Effects Kinetic and Static Stimuli Chromatic Perimetry Other Types of Perimetry 3. Topographic Classification of Visual Field Defects Anatomical Basis Prechiasmal defects Postchiasmal Defects Stato-kinetic dissociation (Riddoch Phenomenon) 4. Visual Field Loss in Glaucoma Local and diffuse loss Anatomic basis of nerve fiber bundle pattern Hemifield asymmetry and nasal steps Point of Fixation Generalized Depression Summary and Examples PART TWO: OFFICE PERIMETRY 5. Clinical Static Perimetry Basic Goals Mainstream Perimetric Protocols The Original, Classic Central Static Threshold Test New Thresholding Algorithms Determining Test Reliability Current Thresholding Algorithms: Summary Suprathreshold Tests Structuring the Test Conditions 6. The Single Field Printout Basic Identification Reliability Parameters Questions and test time Raw Test Results Total Deviation (From Normal Values For Age) Pattern Deviation (Localized Loss) Global Indices Plain Language Analysis 7. Interpretation of a Single Field Reliability Is The Field Abnormal? How Advanced Is The Disease? Artifacts 8. Selection of Automated Tests Glaucoma Diagnosis in the Office Population Screening for Glaucoma Following the Patient with Glaucoma Neurologic Conditions Retinal Diseases Blepharoptosis Driving Qualification Visual Impairment and Disability Programs That are Obsolete or Rarely Used 9. Follow-Up Examinations Establishing a Baseline Follow-up Visual Field Examinations An Overview Change Analysis Printout Pointwise Changes Interpretation Conclusion 10. Alternate and Supplemental Techniques Amsler Grid Confrontation Techniques PART THREE: TECHNIQUE 11. Administering the Visual Field Test Patient's Perception of the Test Perimetrist's Task Instructing the Patient About the Test Positioning the Patient at the Perimeter Corrective Lenses Monitoring and Modifying the Test After the Test APPENDICES Appendix A - Abbreviations Appendix B - Characteristics and Comparison of the HFA-2 Humphrey Perimeter to the HFA-1 Model Appendix C - Glossary INDEX

Neural and Molecular Bases of Nonassociative and Associative Learning in Aplysiaa

A model that summarizes some of the neural and molecular mechanisms contributing to short- and long-term sensitization is shown in Figure 14. Sensitizing stimuli lead to the release of a modulatory transmitter such as 5-HT. Both serotonin and sensitizing stimuli lead to an increase in the synthesis of cAMP and the modulation of a number of K+ currents through protein phosphorylation. Closure of these K+ channels leads to membrane depolarization and the enhancement of excitability. An additional consequence of the modulation of the K+ currents is a reduction of current during the repolarization of the action potential, which leads to an increase in its duration. As a result, Ca2+ flows into the cell for a correspondingly longer period of time, and additional transmitter is released from the cell. Modulation of the pool of transmitter available for release (mobilization) also appears to occur as a result of sensitizing stimuli. Recent evidence indicates that the mobilization process can be activated by both cAMP-dependent protein kinase and protein kinase C. Thus, release of transmitter is enhanced not only because of the greater influx of Ca2+ but also because more transmitter is made available for release by mobilization. The enhanced release of transmitter leads to enhanced activation of motor neurons and an enhanced behavioral response. Just as the regulation of membrane currents is used as a read out of the memory for short-term sensitization, it also is used as a read out of the memory for long-term sensitization. But long-term sensitization differs from short-term sensitization in that morphological changes are associated with it, and long-term sensitization requires new protein synthesis. The mechanisms that induce and maintain the long-term changes are not yet fully understood (see the dashed lines in Fig. 14) although they are likely to be due to direct interactions with the translation apparatus and perhaps also to events occurring in the cell nucleus. Nevertheless, it appears that the same intracellular messenger, cAMP, that contributes to the expression of the short-term changes, also triggers cellular processes that lead to the long-term changes. One possible mechanism for the action of cAMP is through its regulation of the synthesis of membrane modulatory proteins or key effector proteins (for example, membrane channels). It is also possible that long-term changes in membrane currents could be due in part to enhanced activity of the cAMP-dependent protein kinase so that there is a persistent phosphorylation of target proteins.(ABSTRACT TRUNCATED AT 400 WORDS)