摘要:

AbstractThe fast as well as the slow contractions of the adductor muscle in the claw ofProcambarus clarkiiare inhibited byL‐proline. This inhibition is dose dependent and decreases with increasing frequency of stimulation of the “slow” fiber. Contractions caused by perfusing the adductor muscle withL‐glutamate solutions are also inhibited byL‐proline. The inhibiting potency ofL‐proline is small; the effective concentration of this amino acid is 50–100 times that of theL‐glutamate applied. It was postulated that the inhibitory effect ofL‐proline is based on competition for excitatory receptor sites ofL‐glutamate, which causes depolarization and contraction, andL‐proline, which lacks these actions. Theoretical considerations suggested a linear relationship between the stimulatingL‐glutamate and the just‐inhibitingL‐proline concentrations. Experimental ev

ISSN:0022-3034    

DOI:10.1002/neu.480110603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractThe stability of neuronal connections in the isolated buccal ganglia ofHelisoma trivolviswas examined duringin vivoculture for periods up to one month. After 4–8 days the characteristic IPSP input to protractor motoneurons (PMNs) was either abolished or reduced in efficacy. This is apparently due to reduced efficacy of chemical synapses, since the input resistance and resting potential of the motoneurons is unchanged and a fraction of spike‐evoked IPSPs from premotor neurons (cyberchrons) onto PMNs was absent. PMNs lacking IPSP input nevertheless exhibit vigorous cyclical bursts of action potentials driven by electrical EPSPs. The IPSP of PMNs showed partial or full restoration after 14–32 days of culture despite the lack of reinnervation of normal targets. Existing electrical synapses were apparently more stable during culture, but electrical connections between cyberchrons and PMNs were strengthened. Probably because of the reinforcement of these electrical synapses, regenerative cycles of activity in both cyberchrons and PMNs may often be initiated by brief stimulation of a single PMN in cultured ganglia. This is in marked contrast to normal ganglia in which PMNs possess a limited ability to generate such activity. It is concluded that isolation of the buccal ganglia results in a predictable, functional alteration of its neuronal circuitry. Such a perturbation of connectivity indicates that a significant degree of plasticity can be exhibited by adult molluscan ne

ISSN:0022-3034    

DOI:10.1002/neu.480110604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractCells derived from the neonatal rat pineal gland were cocultured with cells derived from neonatal rat superior cervical ganglia (SCG) in an attempt to determine whether a sympathetic target organ with only adrenergic properties could enhance the development of adrenergic transmitter properties in sympathetic neurons in tissue culture. Choline acetyltransferase was measured as an index of cholinergic differentiation, and tyrosine hydroxylase was measured as an index of adrenergic differentiation. As indices of total cell number and cellular volume, DNA and protein, respectively, were also measured. We found that the pineal‐SCG cocultures contained ten times greater choline acetyltransferase activity than sister neuronal cultures cultured without pineal cells, thus indicating that the pineal cells enhanced cholinergic properties in the sympathetic neurons. This cholinergic enhancement was dependent upon the presence of nerve growth factor and couldnotbe obtained with pineal‐conditioned medium. Tyrosine hydroxylase activity, measured on cultures sister to those mentioned above, was low in all cultures and decreased somewhat in SCGs cultured alone. TH activity in the pineal‐SCG cocultures, however, increased slightly. Some tyrosine hydroxylating activity developed in pineals cultured alone, however, and may have been responsible for the small increase in tyrosine hydroxylase activity noted in the pineal‐SCG cocultures. The implications of these results for a determination of the role that target organ plays in the development of the transmitter properties of sympathetic neurons are di

ISSN:0022-3034    

DOI:10.1002/neu.480110605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractThe effects of rat obturator nerve extracts on total and 16S acetylcholinesterase (AChE) activity were studied in endplate regions of denervated anterior gracilis muscles maintained in organ culture for 48 hr. The decrease of total AChE activity in cultured muscles was similar to that observed in denervated musclesin vivo. This decrease in activity was partly prevented by addition of either 100 or 200 μl nerve extract (2.7 mg/ml protein) to the nutrient medium. Nerve extract treatment also decreased the release of AChE activity from the muscle into the bathing medium. Conversely, rat serum (20 μl; 90 mg/ml protein) had no effect on total AChE activity in muscle endplates, nor on release of the enzyme by the muscle. The 16S form of AChE was confined to motor endplate muscle regions and its activity was drastically decreased by denervation in both organ culture andin vivopreparations in a comparable manner. Nerve‐extract supplemented cultures contained a significantly (p ≪ 0.001) larger amount of endplate 16S AChE activity (140–145%) than the corresponding controls (100‐). Our results suggest that some nerve soluble substance, other than serum contaminants or 16S AChE itself, affects the maintenance of 16S AChE at the neuromuscular

ISSN:0022-3034    

DOI:10.1002/neu.480110606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractAxoplasmic transport was studied by employing a new external detection method, comparing it to the scintillation method.32P‐ATP was used as the precursor, and the pattern obtained was one typical of slow transport. The patterns recorded from nerves with the external detector system were seen to be closely similar to those found in the same nerves with the usual scintillation method, the external detector systems having the advantage of allowing studies to be made of changes in the pattern of transport in the same nerve over a period of day

ISSN:0022-3034    

DOI:10.1002/neu.480110607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

Abstractp‐Chloroamphetamine (PCA), an agent known to cause depletion of levels of brain serotonin in rodents, was administered to rats in three sequential injections (10 mg/kg) to study effects on the hypothalamic median eminence and pituitary gland. One week following the initial sequence of injections of PCA, light and electron micrographs revealed degenerate fibers in the outer zone of the median eminence. Lower drug doses or single 10‐mg/kg doses did not lead to morphologic changes. Neuronal processes located in the pituitary intermediate lobe appeared normal, although there was a significant increase in the numbers of secretory granules contained within intermediate lobe cells of drug‐treated rats, as compared to controls. Fluorometric analysis of levels of catecholamine and indoleamine showed a decrease in serotonin in median eminence and pons‐medulla, but no change in that of the pituitary. Levels of dopamine and norepinephrine remained unchanged after PCA treatment. The data suggest that fibers affected in the median eminence contain serotonin. Processes in the intermediate lobe may be resistant to the serotonin‐lowering effects of PCA observed in brain tissue. In addition, PCA may directly affect granule release from pituitary cells, or may alternatively act on hypothalamic regions which affect the release of intermediate lobe cell

ISSN:0022-3034    

DOI:10.1002/neu.480110608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractThe CNS and PNS interact and form an integrated system which mediates adaptive gill withdrawal reflex behaviors evoked by tactile stimulation of the siphon. The CNS exerts suppressive and facilitatory control over the PNS in the mediation of these behaviors. It was found that inAplysiathe CNS's suppressive control over the PNS was significantly greater than in nonsatiated control animals. In the controls, the evoked gill reflex met a mimimal response amplitude criterion with the CNS and PNS present, while in the satiated group the reflex did not meet this criterion. In the control group, the reflex amplitude and the subsequent habituation were the same following removal of the CNS, while in satiated animals the reflex amplitude was larger and the rate of habituation slower with only the PNS intact. Satiation had no effect on youngAplysiasince CNS control was not yet operable. It is thus of prime importance to take the “state” of the preparation into consideration in the analysis of the neural mechanisms that underlie adaptive gill reflex behaviors.The gill withdrawal reflex and its subsequent habituation evoked by repeated tactile stimulation of the siphon inAplysiahas been studied extensively in an attempt to gain an understanding of the neuronal mechanisms that underlie adaptive behavior (Jacklet and Lukowiak, 1975; Kandel, 1976). It has been found that the central (CNS) and peripheral (PNS) nervous systems inAplysiainteract and form an integrated system which normally mediates both the reflex and its subsequent habituation (Peretz, Jacklet, and Lukowiak, 1976; Lukowiak and Peretz, 1977). Further, it was found that in the integrated system the CNS exerted both suppressive and facilitatory control over the PNS in the mediation of gill reflex behaviors (Lukowiak, 1977a). Removal of only the CNS's suppressive control over the PNS, while leaving intact its facilitatory influence, resulted in a significant reduction in reflex latency, a significant increase in reflex amplitude, and a reflex that is resistant to habituation with repeated stimulation (Lukowiak, 1977a). In addition, it was found that an identifiable neuron, L9, could modulate the ability of the reflex to habituate (Lukowiak, 1979a). With induced tonic low‐level activity in Ls the reflex evoked by repeated siphon stimulation did not habituate even though the synaptic decremental process which occurs in gill motor neurons such as L7 and accompanies gill reflex habituation (Castellucci et al., 1970) continued to occur. The neurons in abdominal ganglion, which by their activity exert control over the PNS and thus the reflex, have not yet been identified but it is known that these same neutrons apparently exert control over the synaptic input received by gill motor neurons such as L7 from the central sensory neurons (Byrne, Castellucci, and Kandel, 1974) as a result of siphon stimulation (Peretz and Lukowiak, 1975; Lukowiak and Peretz, 1980). Thus, the relative balance between the CNS's suppressive and facilitatory control will in large measure determine the overall responsiveness of the reflex and its ability to habituate.It is not, however, clear whether the CNS suppressive and facilitatory control over gill reflex behaviors evoked by siphon stimulation is altered as a result of changes in the animal's other behaviors or changes in its immediate environment. What is already known is that the CNS control is absent in young animals (Lukowiak, 1979b). In a related species,Pleurobranchaea, it has been shown that there is a behavioral hierarchy in that certain unrelated behaviors take precedence over other behaviors (Kovac and Davis, 1977; Davis and Gillette, 1978; Davis, 1979). Thus, it may be that inAplysiachanges in the relative balance between the suppressive and facilitatory CNS control over the PNS occur as result of behavioral or environmental factors. For instance, any factor that would increase CNS suppressive control would result in a smaller gill withdrawal reflex and a faster rate of habituation or a factor that increases the facilitatory control would result in a larger reflex and a tendency not to habituate.One aim of these sets of experiments was to determine how satiation affects CNS control of adaptive gill reflex behaviors and the associated synaptic input to central gill motor neurons evoked by tactile stimulation of the siphon. The other aim was to clarify the inconsistency between results previously reported (Lukowiak, 1977a) and the recent report of Carew et al. (1979). They reported that if a minimal response amplitude criterion was imposed on a preparation, that is, the evoked gill withdrawal reflex amplitude must be at least 35% of the amplitude of the large spontaneous gill respiratory movement (SGM), then the CNS mediated 90–95% of the gill reflex amplitude. Previously, it was reported (Lukowiak, 1977a) that there was no significant difference in the reflex amplitude with and without the CNS present when the reflex was evoked by the “tapper” (see Methods section). Thus, in the present study, an examination was made in preparations that met the minimal response amplitude criterion for whether removal of the CNS had a significant effect on the gill reflex amplitude.It is now reported that in adult animals that have had continuous access to food and are satiated, the CNS suppressive control over the PNS is significantly greater than in animals that have not been exposed to food. The increased suppressive CNS control is observed as a significantly smaller reflex amplitude, a faster rate of habituation, and a decrease in excitatory synaptic input to central gill motor neuron L7. Additionally, it was found that in young Aplysia, continual access to food had no effect on the reflex, its habituation, and the synaptic input to gill motor neuron L7.As concerns the second aim of this article, I found that the gill withdrawal reflex evoked by siphon stimulation with the “tapper” in all control group preparations met the minimal response criterion, and in these preparations there was no significant difference in the reflex amplitude with and without the CNS present. In the experimental group (satiated animals) none of the preparations met the minimal response criteria with the CNS intact; but, following removal of the CNS, the evoked reflex was significantly larger, in fact it met the minimal response criterion.Thus, in the control group (i.e., unsatiated animals) the results obtained do not agree with those obtained by Carew et al. (1979). In the control group preparations there was no difference in reflex amplitude or in habituation of the reflex before and after removal of the abdominal ganglion; this is in agreement with earlier results (Lukowiak, 1977a, 1979b). In experimental group preparations (i.e., satiated animals) it was found that the results agreed quantitatively with the Carew et al. (1979) report. That is, the amplitude of the reflex was larger following removal of the abdominal ganglion. However, this was due to the fact that satiation led to greater CNS suppressive control over the PNS. Thus, when the CNS control was removed, the reflex amplitude increased and the rate of hab

ISSN:0022-3034    

DOI:10.1002/neu.480110609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractThis study assessed the role of calcium in the activation of the slow potassium current responsible for spike frequency adaptation in molluscan neurons. Inward calcium currents were eliminated by using Co2+, Cd2+, or OCa2+EGTA in the bathing solution. In each case adaptation was found to persist, as did the slow current believed to be responsible for adaptation. Injection of EGTA into neurons was also found not to block adaptation. This potassium current provides an example of a slow voltage‐dependent potassium process which is independent of calcium influ

ISSN:0022-3034    

DOI:10.1002/neu.480110610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractThe neuropeptide proctolin causes a sustained contraction of the opener muscle of the dactyl of the lobster walking leg. This substance acts directly on the muscle at concentrations as low as 10−10M. The contraction is dependent on extracellular calcium. Neither a significant depolarization nor a detectable change in the input resistance accompanies the response. No presynaptic action of proctolin is indicated; excitatory and inhibitory junctional potential sizes and the frequency of spontaneous miniature excitatory junctional potentials are unaffecte

ISSN:0022-3034    

DOI:10.1002/neu.480110611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY

摘要:

AbstractPicrotoxin, 1 × 10−5Mto 1.6 × 10−3M, had little or no effect on the amplitude of intracellularly recorded excitatory junctional potentials (EJPs) at extracellular calcium concentrations [Ca2+]0ranging from 0.5 to 15 mM. The slope of the log EJP vs. log[Ca2+]0relationship was approximately 1 with or without picrotoxin. The reduction of EJP amplitude resulting from the addition of 5 × 10−5MGABA was largely reversed by 10−5M

ISSN:0022-3034    

DOI:10.1002/neu.480110612

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1980

数据来源: WILEY