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J F MacDonald

Publications and source records attributed to J F MacDonald.

At least 73 records · Page 4Linked to original sources
PubMed1994

N-methyl-D-aspartate receptor-mediated voltage oscillations in neurons surrounding the central canal in slices of rat spinal cord.

1. The present study used the whole-cell patch-clamp technique to record from visually identified neurons surrounding the central canal in 300-microns transverse slices of lumbosacral spinal cord from 7- to 14-day-old rats. Neurons in this location are implicated in rhythmical activity during locomotion. We assessed whether similarly located neurons could produce voltage oscillations by local perfusion of neuroactive substances known to initiate locomotor activity. 2. The sample population had mean values for cell resistance and membrane time constant of 1,020 M omega and 61.5 ms, respectively. Three general categories of oscillatory behavior were observed; spontaneous low-frequency voltage oscillations in the absence of an applied agonist, N-methyl-D-aspartate (NMDA)-induced rhythmic low-frequency voltage oscillations in the presence of tetrodotoxin (TTX), and NMDA-induced "unpatterned" low-frequency voltage oscillations in TTX. 3. Three of 42 neurons exhibited spontaneous low-frequency voltage oscillations and one continued to oscillate in the presence of TTX. In 34 other neurons, manual adjustments of membrane voltage in 10 mV increments between -60 and -20 mV failed to elicit voltage oscillations (in TTX). 4. Five of 42 neurons produced rhythmic low-frequency voltage oscillations in the presence of TTX during applications of NMDA (20-100 microM). Oscillation frequency ranged from 0.09 to 1.45 Hz. These neurons were located in a similar region, ventrolateral to the central canal. 5. Thirteen of 42 neurons underwent NMDA-evoked "unpatterned" low-frequency voltage oscillations (in TTX) characterized by great variability in depolarized and baseline membrane potential durations. Three neurons produced single depolarizing phases only. Oscillation frequency ranged from 0.03 to 0.47 Hz. These neurons were located predominantly in the dorsal region surrounding the central canal with two others located just ventral to the canal. 6. Low-frequency voltage oscillations demonstrated a dependence on voltage, applied agonist, and agonist concentration. Rhythmic and unpatterned oscillatory events typically arose from membrane voltages ranging from -70 to -55 mV with plateau peaks from -40 to -30 mV. Although NMDA (20-100 microns) evoked voltage oscillations in neurons, kainate (10-50 microns), serotonin (10-200 microns), and noradrenaline (50-100 microns) failed to evoke voltage oscillations in all neurons tested, including those where NMDA induced voltage oscillations.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Propofol modulates activation and desensitization of GABAA receptors in cultured murine hippocampal neurons.

Propofol (2,6 di-isopropylphenol) is an alkyphenol recently introduced for use as a general anesthetic. The modulation of GABAA receptor activation and desensitization by propofol was studied using a rapid perfusion system and whole-cell voltage-clamp recordings from mouse hippocampal neurons. The effects of concentrations of propofol used clinically on single-channel and synaptic currents were also examined. Propofol evoked current responses (EC50 = 61 microM) and shifted the dose-response curve of GABA-activated current to the left without altering the maximum of the GABA response. Preincubation with propofol and GABA led to desensitization of the GABA response (EC50 = 454 microM and 23 microM, respectively). Saturating concentrations of GABA (600 microM) evoked currents that peaked and then declined in a biexponential fashion with fast and slow time constants of tau f = 1.0 sec and tau s = 3.5 sec. Propofol (10 microM) did not change the amplitude of the peak response but decreased the rates of decay approximately 1.5-fold and enhanced the steady-state current proportionately. Recovery from desensitization was also biexponential (tau f = 11 sec, tau s = 69 sec) but not influenced by propofol. Single-channel recordings from outside-out patches demonstrated that both propofol and GABA activated channels with a 30 pS and 21 pS open state. Propofol increased the frequency but not the duration or conductance of GABA-activated events. Miniature inhibitory postsynaptic currents (mlPSCs) were evoked by the application of hypertonic sucrose to the cell soma. Propofol (2 microM) prolonged the decay time of mlPSCs to an extent similar to which it increased the open probability of GABA-activated channels (2.3- vs 3-fold). A sequential model, based on a previous scheme of GABA receptor gating (Weiss and Magelby, 1989), is presented to summarize propofol's actions on GABAA receptor function. We show through simulation that the model reliably reproduced the whole-cell tracings. Our results indicate that propofol's neurodepressive actions will be associated with enhancement of inhibitory synaptic transmission.

Animals↗
PubMed1994

Loperamide blocks high-voltage-activated calcium channels and N-methyl-D-aspartate-evoked responses in rat and mouse cultured hippocampal pyramidal neurons.

The effects of the antidiarrheal agent loperamide on high-voltage-activated (HVA) calcium channel activity and excitatory amino acid-evoked responses in two preparations of cultured hippocampal pyramidal neurons were examined. In rat hippocampal neurons loaded with the calcium-sensitive dye fura-2, rises in intracellular free calcium concentration ([Ca2+]i) evoked by transient exposure to 50 mM K(+)-containing medium [high extracellular potassium concentration ([K+]o)] were mediated by Ca2+ flux largely through nifedipine-sensitive Ca2+ channels, with smaller contributions from omega-conotoxin GVIA (omega-CgTx)-sensitive Ca2+ channels and channels insensitive to both nifedipine and omega-CgTx. Loperamide reversibly blocked rises in [Ca2+]i evoked by high [K+]o in a concentration-dependent manner, with an IC50 of 0.9 +/- 0.2 microM. At the highest concentration tested (50 microM), loperamide eliminated rises in [Ca2+]i evoked by high [K+]o, a result otherwise achieved only in Ca(2+)-free medium or by the combined application of nifedipine, omega-CgTx, and funnel web spider venom to Ca(2+)-containing medium. The action of loperamide was neither naloxone sensitive nor mimicked by morphine and was seen at concentrations substantially less than those required to block influx of Ca2+ through the N-methyl-D-aspartate (NMDA) receptor-operated ionophore. Similar results were obtained in cultured mouse hippocampal pyramidal neurons under whole-cell voltage clamp. Voltage-activated Ca2+ channel currents carried by barium ions (IBa) could be discriminated pharmacologically into nifedipine-sensitive (L-type) and nifedipine-resistant, omega-CgTx-sensitive (N-type) components. Loperamide (0.1-50 microM) produced a concentration-dependent reduction of the peak IBa with an IC50 value of 2.5 +/- 0.4 microM and, at the highest concentration tested, could fully block IBa in the absence of any other pharmacological agent. The loperamide-induced block was rapid in onset and offset, was fully reversible, and did not appear to be related to the known calmodulin antagonist actions of loperamide. The current-voltage characteristics of the whole-cell IBa were unaffected by loperamide and the block was not voltage dependent. Loperamide also attenuated NMDA-evoked currents recorded at a membrane potential of -60 mV, with an IC50 of 73 +/- 7 microM. The block of NMDA-evoked currents was not competitive in nature, was not reversed by elevation of the extracellular glycine or spermine concentration, and was not affected by changes in the membrane holding potential. Steady state currents evoked by kainate and DL-alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid were, in contrast, relatively unaffected by 100 microM loperamide.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Haloperidol interacts with the strychnine-insensitive glycine site at the NMDA receptor in cultured mouse hippocampal neurones.

N-Methyl-D-aspartate (NMDA)-evoked responses in voltage-clamped hippocampal neurones in culture were reversibly, but not completely, attenuated on superfusion with micromolar concentrations (0.1-100 microM) of haloperidol with an IC50 (+/- S.E.M.) value of 1.9 +/- 0.2 microM (n = 7). In contrast, kainate- and (RS)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-evoked responses were relatively unaffected on application of 50 microM haloperidol. The NMDA receptor antagonist action of haloperidol was neither competitive in nature nor voltage-dependent but was reduced upon elevation of the extracellular concentration of glycine. Furthermore, in the absence of added glycine haloperidol (at 0.1 microM) frequently potentiated NMDA-evoked responses. Haloperidol thus appears to be a partial agonist for the strychnine-insensitive glycine site associated with the NMDA receptor-channel complex.

Animals↗
PubMed1993

Phosphorylation and modulation of a kainate receptor (GluR6) by cAMP-dependent protein kinase.

Ligand-gated ion channels gated by glutamate constitute the major excitatory neurotransmitter system in the mammalian brain. The functional modulation of GluR6, a kainate-activated glutamate receptor, by adenosine 3',5'-monophosphate-dependent protein kinase A (PKA) was examined with receptors expressed in human embryonic kidney cells. Kainate-evoked currents underwent a rapid desensitization that was blocked by lectins. Kainate currents were potentiated by intracellular perfusion of PKA, and this potentiation was blocked by co-application of an inhibitory peptide. Site-directed mutagenesis was used to identify the site or sites of phosphorylation on GluR6. Although mutagenesis of two serine residues, Ser684 and Ser666, was required for complete abolition of the PKA-induced potentiation, Ser684 may be the preferred site of phosphorylation in native GluR6 receptor complexes. These results indicate that glutamate receptor function can be directly modulated by protein phosphorylation and suggest that a dynamic regulation of excitatory receptors could be associated with some forms of learning and memory in the mammalian brain.

Amino Acid Sequence↗
PubMed1993

A comparison of two alternatively spliced forms of a metabotropic glutamate receptor coupled to phosphoinositide turnover.

A comparison of the pharmacological and physiological properties of the metabotropic glutamate 1 alpha and 1 beta receptors (mGluR1 alpha and mGluR1 beta) expressed in baby hamster kidney (BHK 570) cells was performed. The mGluR1 beta receptor is an alternatively spliced form of mGluR1 alpha with a modified carboxy terminus. Immunoblots of membranes from the two cell lines probed with receptor-specific antipeptide antibodies showed that mGluR1 alpha migrated with an M(r) = 154,000, whereas mGluR1 beta migrated with an M(r) = 96,000. Immunofluorescence imaging of receptors expressed in BHK 570 cells revealed that the mGluR1 alpha receptor was localized to patches along the plasmalemma and on intracellular membranes surrounding the nucleus, whereas mGluR1 beta was distributed diffusely throughout the cell. Agonist activation of the mGluR1 alpha and the mGluR1 beta receptors stimulated phosphoinositide hydrolysis. At both receptors, glutamate, quisqualate, and ibotenate were full agonists, whereas trans-(+)-1-aminocyclopentane-1,3-dicarboxylate appeared to act as a partial agonist. The stimulation of phosphoinositide hydrolysis by mGluR1 alpha showed pertussis toxin-sensitive and insensitive components, whereas the mGluR1 beta response displayed only the toxin-insensitive component. The mGluR1 alpha and mGluR1 beta receptors also increased intracellular calcium levels by inducing release from intracellular stores. These results indicate that the different carboxy terminal sequences of the two receptors directly influences G protein coupling and subcellular deposition of the receptor polypeptides and suggest that the two receptors may subserve different roles in the nervous system.

Animals↗
PubMed1993

Selective reduction of N-methyl-D-aspartate-evoked responses by 1,3-di(2-tolyl)guanidine in mouse and rat cultured hippocampal pyramidal neurones.

1. The effects of 1,3-di(2-tolyl)guanidine (DTG) were examined on the responses of cultured hippocampal neurones to the excitatory amino acid analogues N-methyl-D-aspartate (NMDA), kainate, quisqualate and (RS)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA). 2. In rat hippocampal neurones loaded with the Ca(2+)-sensitive dye Fura-2, DTG (10-100 microM) produced a concentration-dependent depression of the NMDA-evoked rises in intracellular free calcium ([Ca2+]i), an effect that was not modified by changes in the extracellular glycine concentration. DTG (at 50 and 100 microM) also attenuated, although to a lesser extent, the rises in [Ca2+]i evoked by naturally-derived quisqualate. In contrast, 50 and 100 microM DTG did not depress responses evoked by kainate, AMPA and synthetic, glutamate-free (+)-quisqualate although on occasions DTG enhanced kainate- and AMPA-evoked rises in [Ca2+]i. 3. DTG attenuated NMDA-evoked currents recorded from mouse hippocampal neurones under whole-cell voltage-clamp with an IC50 (mean +/- s.e. mean) of 37 +/- 5 microM at a holding potential of -60 mV. The DTG block of NMDA-evoked responses was not competitive in nature and was not dependent on the extracellular glycine or spermine concentration. The block did, however, exhibit both voltage-, and use-, dependency. The steady-state current evoked by naturally-derived quisqualate was also attenuated by DTG whereas those evoked by kainate and AMPA were not. 4. We conclude that DTG, applied at micromolar concentrations, is a selective NMDA antagonist in cultured hippocampal neurones, the block exhibiting both Mg(2+)- and phencyclidine-like characteristics. Given the nanomolar affinity of DTG for sigma binding sites it is unlikely that the antagonism observed here is mediated by sigma-receptors, but the data emphasize the potential danger of ascribing the functional consequences of DTG administration solely to sigma receptor-mediated events.

Amino Acids↗
PubMed1992

Ethanol modulation of GABA receptor-activated Cl- currents in neurons of the chick, rat and mouse central nervous system.

Modulation of gamma-aminobutyric acidA (GABAA) receptor function by drugs such as ethanol may depend on the genetic heterogeneity of GABAA receptor subunits, which vary across species and cell types. For this reason, the effects of ethanol on gamma-aminobutyric acid receptor-activated chloride currents (IGABA) were examined using whole-cell voltage-clamp recordings in primary cultures of neurons obtained from different species (chick, mouse and rat) and from different brain regions (cerebral cortex, hippocampus, cerebellum and spinal cord), and in acutely dissociated neurons from rat neocortical slices. Low concentrations (1-50 mM) of ethanol produced an enhancement of IGABA in some cells from each brain region examined. In cells obtained from the rat and chick cerebral cortex, 40-58% of cells exhibited an ethanol-sensitive IGABA. Moreover, a statistically significant variation in the response to ethanol was found in rat cortical neurons obtained from different litters. In mouse hippocampal neurons, potentiation of IGABA was obtained with ethanol concentrations (1-10 mM) well below those needed to inhibit neuronal responses to N-methyl-D-aspartic acid (30-50 mM), suggesting a differential sensitivity of these two receptor mechanisms to ethanol. Potentiation of IGABA by ethanol was reversed by the benzodiazepine receptor partial inverse agonist RO15-4513 (ethyl 8-azido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-a][1,4]benzodiazepine - 3-carboxylate), but was not affected by chelation of intracellular calcium. Furthermore, high concentrations of GABA attenuated the ability of ethanol to enhance IGABA. These results are consistent with the hypothesis that ethanol facilitates coupling between receptor binding and chloride channel activation.

Animals↗
PubMed1992

Activation and desensitization of N-methyl-D-aspartate receptors in nucleated outside-out patches from mouse neurones.

1. Activation and desensitization of N-methyl-D-aspartate (NMDA) receptors were studied in large outside-out patches excised from cultured embryonic neurones dissociated from mouse forebrain. The patches were exposed to rapid changes of NMDA or L-glutamate concentrations in the presence of glycine at concentrations (10-20 microM) saturating the modulatory site of the NMDA receptor. 2. Immediately after formation of the patch the responses to NMDA and L-glutamate showed a slow and small desensitization, even with high concentrations of agonist. During the following hour, the peak response either decreased or remained relatively stable, but in all cases the desensitization increased and accelerated until it stabilized. In this 'stabilized' state, the desensitization produced by high concentrations of NMDA (1 mM) or L-glutamate (300 microM) had an exponential time course, with a time constant of about 30 ms. The ratio of the peak over the steady-state current was in the order of 40 for NMDA and about 30 for L-glutamate. 3. Concentration-response curves were built for the peak and the plateau responses, for NMDA and for L-glutamate. The comparison of these curves indicated that (i) the EC50 of the peak (K(app) was always higher than the EC50 of the plateau (Kss); (ii) the two EC50 values for NMDA (K(app) and Kss) were higher than those for L-glutamate; (iii) the Hill coefficient was close to 1.4 for each of the four curves. 4. The application of NMDA or L-glutamate at a low concentration for 3 s periods reduced the response to a subsequent application of the same agonist at a saturating concentration. The IC50 of this 'predesensitization', termed Kpre, was lower than the EC50 of the steady-state response, Kss. 5. The onset rates of desensitization increased with the concentration of agonist. The EC50 of this relation was close to the value of K(app). 6. The decay of the currents at the end of a 3 s application of agonist was usually well described by the sum of two exponentials both of which were faster for NMDA than for L-glutamate. 7. The recovery from desensitization after a long (3 s) pulse of agonist was approximately exponential, with a time constant of about 0.5 s for NMDA and about 3.5 s for L-glutamate.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Regulation of kainate receptors by cAMP-dependent protein kinase and phosphatases.

In the mammalian central nervous system, receptors for excitatory amino acid neurotransmitters such as the alpha-amino-3-hydroxy-5-methyl-4- isoxazolepropionic acid (AMPA)-kainate receptor mediate a large fraction of excitatory transmission. Currents induced by activation of the AMPA-kainate receptor were potentiated by agents that specifically stimulate adenosine 3',5'-monophosphate (cAMP)-dependent protein kinase A (PKA) activity or were supported by intracellular application of the catalytic subunit of PKA by itself or in combination with cAMP. Furthermore, depression of these currents by a competitive inhibitor of PKA indicates that AMPA-kainate receptors are regulated by endogenous PKA. Endogenous protein phosphatases also regulate these receptors because an inhibitor of cellular phosphates enhanced kainate currents. Modulation of PKA and phosphatases may regulate the function of these receptors and thus contribute to synaptic plasticity in hippocampal neurons.

Animals↗
PubMed1991

Mammalian neurons in dissociated cultures form clusters in the presence of retinal pigment epithelium.

The objective of this study was to investigate the cellular processes involved in the formation of the cytoarchitectonics of the retina. Neurons derived from the retina, spinal cord, cerebral cortex and hippocampus were grown in dissociated monolayer tissue culture using standard techniques. The cultures of retina were unique in that the neurons actively formed into cell clusters. On the other hand, cultures of neurons from the other regions of the CNS grew without forming any obvious histotypical pattern. Cell clusters consisted of an apparent monolayer of neurons above a population of flat cells and clusters were observed in retinal cultures derived from all species studied (mouse, cat and guinea pig). Each cluster was surrounded by whorls of fibroblasts; astrocytes (GFAP-positive cells) were often closely associated with clusters. Formation of clusters appeared to depend strongly upon the presence of cells derived from the retinal pigment epithelium (RPE) because the ability of retinal cells to form clusters was markedly impaired when the RPE was omitted from the cultures. Interestingly, monolayer cultures of neurons from other regions of the CNS could be induced to form clusters, but only when cells of the RPE layer were included at the time of plating. In cultures grown without the RPE layer, clusters did not form when media taken from cultures expressing clusters was used, indicating that the formation of clusters was not caused by a media-bourne factor. On the other hand, clusters did form when neurons without RPE were grown on feeder plates in which clusters had previously been expressed and the neurons subsequently killed by prolonged culturing or by treatment with kainic acid. Hence, physical contact between neurons and cells derived from the RPE appears critical for the formation of clusters. Our results suggest that the cellular processes underlying the formation of clusters may reflect those in the development of the retina in vivo. Thus, cluster formation may be a useful model for investigating the initial stages in the development of retinal cytoarchitecture.

Animals↗
PubMed1991

Actions of ketamine, phencyclidine and MK-801 on NMDA receptor currents in cultured mouse hippocampal neurones.

1. Stable N-methyl-D-aspartic acid (NMDA) receptor-mediated currents in cultured mouse hippocampal neurons were evoked by 20 ms pressure pulse applications of L-aspartate, repeatedly applied at 30 or 40 s intervals, to the cell body region of the neurone. We have characterized the voltage- and use-dependent blockade of the currents by three dissociative anaesthetics: ketamine, phencyclidine (PCP) and MK-801 in mouse hippocampal neurones grown in dissociated tissue culture. 2. We have used a simple model of the blockade, based on the 'guarded receptor hypothesis' to interpret our data. The model assumes that receptors are maximally activated at the peak of the response with an open probability (Po) approaching 1, that there is no desensitization and that the blocking drug only associates with, or dissociates from, receptor channels which have been activated by agonist (e.g. open channels). 3. The model allows us to estimate forward and reverse rate constants for binding of the blockers to open channels from measurements of the steady-state level of blockade and the rate of change of the current amplitude per pulse during onset and offset of blockade. As predicted by the model, the estimated reverse rate was independent of blocker concentration while the forward rate increased with concentration. Changing the level of positively charged ketamine (pKa 7.5) tenfold by changing pH from 6.5 to 8.5 caused a corresponding change in the forward rate while having no effect on the reverse rate. Most of the voltage dependence of the blockade could be accounted for by reduction of the reverse rate by depolarization. 4. Estimated forward rate constants for ketamine, PCP and MK-801 were similar to one another when measured under similar conditions and were 3 x 10(4) - 3 x 10(5) M-1 S-1. Most of the differences in potency of the three blockers could be accounted for by differences in the reverse rate constants which were approximately 0.2, 0.03 and 0.003 s-1 for ketamine, PCP and MK-801, respectively. The estimated rate constants actually are the product of the rate constants and 1/Po. Suggestions that maximum Po is much less than 1 for NMDA channels imply that both forward and reverse rate constants of blockade may in fact be larger than we have calculated. However, their magnitudes, relative to one another, are unaffected by this consideration. 5. The reverse rate constant of blockade increased at positive potentials. This increase was prevented when the neurone was loaded with N-methyl-D-glucamine, an impermeant cation which prevented outward currents.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Kindling-induced epilepsy alters calcium currents in granule cells of rat hippocampal slices.

Single electrode voltage-clamp recordings were obtained from dentate gyrus granule cells (GCs) in hippocampal slices of control and commissurally kindled rats. Two types of calcium currents, a transient and a sustained current, were studied in control and kindled neurons. The threshold of the transient calcium current was lowered in kindled GCs. The sustained calcium current was absent in kindled neurons but it could be restored by the intracellular administration of the calcium chelator EGTA. Our findings are consistent with the hypothesis that the loss of an intraneuronal calcium binding protein (Calbindin-D28K; CaBP) reduces the intraneuronal calcium buffering capacity in kindled neurons and results in the enhanced calcium-dependent inactivation of sustained calcium currents.

Animals↗
PubMed1990

The PCP site of the NMDA receptor complex.

Evidence from electropharmacological experimentation favors the hypothesis that the PCP site is intimately associated with the channel domain of the NMDA receptor. But it is too early to state that this site lies deep within the NMDA channel pore. Determining the molecular details of the PCP site will require a complete and detailed kinetic analysis of NMDA single channel behavior. Furthermore, it is likely that hydrophobic receptor site(s) are responsible for some aspects of the blockade by at least some members of the dissociative anaesthetic family.

Anesthetics, Dissociative↗
PubMed1990

Mechanisms of blockade of excitatory amino acid receptor channels.

Ion channels coupled to NMDA, kainate and AMPA receptors are the target of pharmacological regulation by a variety of drugs and ions. While these channels are all nonselectively permeated by Na+ and K+ ions, the NMDA receptor-channel complex contains a number of pharmacological sites distinct from those found on the others. For example, Mg2+ ions rapidly and reversibly block open NMDA channels in a highly voltage-dependent manner. Its extreme voltage dependence suggests that the Mg2+ binding site lies deep within the ion channel pore. By contrast the voltage-dependent block of activated channels by the dissociative anesthetic 'slow channel blockers' has unusual characteristics. In the fourth article in our series on excitatory amino acids, John MacDonald and Linda Nowak analyse the characteristics of these two types of block and describe the hypotheses that have been put forward to explain the mechanisms involved.

Animals↗
PubMed1989

A method for isolating and patch-clamping single mammalian taste receptor cells.

Individual taste receptor cells were isolated from the tongue of the mouse by enzymatic treatment followed by mechanical dissociation. The cells were morphologically identical with taste cells from amphibians. Whole-cell voltage-clamp recordings indicated that the murine taste cells possess a variety of voltage-dependent inward and outward currents. Delayed rectifier currents were blocked by denatonium benzoate, one of the most bitter compounds known. This preparation should permit a detailed electrophysiologcal investigation of taste transduction in mammals at the level of taste receptor cells.

Animals↗
PubMed1989

Whole-cell voltage-clamp recordings in granule cells acutely isolated from hippocampal slices of adult or aged rats.

Whole-cell voltage-clamp recordings were undertaken in granule cells acutely dissociated by a simple enzymatic procedure from the dentate gyri of hippocampal slices obtained from adult or aged rats. This dissociation procedure also allowed the concomitant isolation of other neuron types from diverse hippocampal subfields for the study of ionic currents through voltage- and neurotransmitter-gated channels. For example, in isolated granule cells of the dentate gyrus both transient and sustained Ca2+ currents could be observed in the presence of extracellular tetrodotoxin (TTX) and intracellular Cs+. In addition, ionic currents mediated by activation of excitatory amino acid receptors of the N-methyl-D-aspartate (NMDA) type were present. A technique for the rapid dissociation of neurons from brain slices of adult or aged rats is described in detail.

Aging↗