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C J Rogers

Publications and source records attributed to C J Rogers.

10 recordsLinked to original sources
PubMed1992

Chronic ethanol treatment reduces inhibition in CA1 of the rat hippocampus.

The effect of chronic ethanol exposure on inhibition in the rat hippocampal slice was investigated using paired-pulse stimulation techniques with stimulation in stratum radiatum or stratum oriens of CA1. Experimental animals were fed ethanol in a liquid diet for 20 weeks and were withdrawn for at least 8 weeks prior to electrophysiological recording. Prior ethanol treatment had no effect on basic input-output relationships for the extracellular population spike. Ethanol treatment significantly reduced the recurrent inhibition produced by antidromic stimulation in a manner dependent upon stimulus intensity. In addition, with orthodromic paired-pulse stimulation of either stratum radiatum or oriens, a trend toward an augmentation of the facilitation of population spike amplitude was observed, suggesting that feedforward inhibition may also be reduced. These results are similar to those found with treatments that reduce inhibition. Therefore, we conclude that chronic ethanol exposure produces an enduring disruption of inhibitory neuronal function in the rat hippocampus.

Animals↗
PubMed1990

Intraburst kinetic properties of the GABAA receptor main conductance state of mouse spinal cord neurones in culture.

1. The intraburst kinetic properties of the main conductance state of gamma-aminobutyric acidA (GABAA) receptor channels in excised outside-out patches obtained from somata of mouse spinal cord neurones in cell culture were investigated using the patch clamp single-channel recording technique. 2. At 2 microM-GABA, the burst duration distribution was fitted by four exponential functions with time constants of 0.5, 2.4, 8.3 and 31.8 ms. 3. At 0.5, 1 and 2 microM-GABA, frequency distribution histograms of the number of apparent openings per burst were best fitted by three geometric functions with similar mean numbers (1.1, 1.9 and 3.6) of openings per burst. The proportion of bursts with a mean of 1.1 openings per burst decreased with increased GABA concentration while the proportion of bursts with means of 1.9 and 3.6 openings per burst increased with GABA concentration. 4. Analyses of GABA receptor channel intraburst kinetics were performed at all three GABA concentrations. The results were similar for all concentrations, but detailed results are presented only for 2 microM-GABA. 5. The open time distribution for all intraburst openings was best fitted by three exponential functions with time constants of 0.6, 2.9 and 8.9 ms. 6. Intraburst open time and total open time distributions for bursts with one to five openings were fitted with two or three exponential functions or gamma distributions, respectively. The number of components, time constants and relative areas were similar for both distributions. 7. The distributions of open times for the nth opening within bursts of k openings were similar for bursts containing two to five openings. The distributions of open times for the nth opening of all bursts varied with position within the burst. The distributions shifted to longer openings as the opening number increased from one to five. 8. The distributions of all closings within all bursts or within bursts with two to five openings and of closings relative to position in all bursts could be fitted by two exponential functions with time constants of about 0.20 and 3.1 ms and relative proportions of 0.55 and 0.45 at all GABA concentrations. 9. The total closed time distributions for bursts containing two to four closings, however, were all best fitted with only a single gamma distribution with a time constant of 1.3 ms.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Pentobarbital and picrotoxin have reciprocal actions on single GABAA receptor channels.

Pentobarbital (PB) and picrotoxin (PIC) bind to allosterically coupled sites on the GABAA receptor complex but have opposite effects on GABA receptor currents. PB, an anesthetic/anticonvulsant, enhances, and PIC, a convulsant, inhibits GABA receptor currents. PB and PIC also had opposite effects on single main conductance channel GABA receptor currents recorded from excised outside-out patches from mouse spinal neurons in culture. PB prolonged bursts of channel openings by increasing mean duration and number of intraburst openings. PIC shortened bursts by reducing mean duration and number of intraburst openings. The results demonstrate the reciprocal regulation of GABA receptor channels by PB and PIC and suggest that their allosterically coupled binding sites are coupled to the chloride channel in an opposite manner.

Action Potentials↗
PubMed1989

Differential regulation of gamma-aminobutyric acid receptor channels by diazepam and phenobarbital.

The anticonvulsant activity of diazepam and phenobarbital may be mediated in part by enhancement of inhibition involving gamma-aminobutyric acid (GABA). While both diazepam and phenobarbital increase GABA receptor chloride current, they may have different mechanisms of action, since they bind to different sites on the GABA receptor-chloride channel complex. We used the patch clamp technique to compare the effects of diazepam and phenobarbital on single GABA receptor currents. Outside-out patches were obtained from mouse spinal cord neurons grown in cell culture for 2 to 4 weeks. GABA (2 microM) evoked single channel currents that occurred as single brief openings or in bursts of multiple openings. Diazepam (20 nM) and phenobarbital (500 microM) both increased the GABA receptor current by increasing mean open time without altering channel opening frequency. However, the temporal grouping of openings into bursts suggested that the enhancement occurred via different mechanisms. Diazepam increased the frequency of bursting GABA receptor currents with minimal effect on the duration of bursts. Phenobarbital increased the duration of bursting GABA receptor currents without altering the frequency of bursts. These results suggest that diazepam binds to a site that may enhance single channel burst frequency by increasing the affinity of GABA binding, while phenobarbital may stabilize the bursting open state of the channel by binding to a different modulatory site at or near the chloride channel.

Animals↗
PubMed1989

Kinetic properties of the GABAA receptor main conductance state of mouse spinal cord neurones in culture.

1. The kinetic properties of the main conductance state of gamma-aminobutyric acidA (GABA) receptor channels from somata of mouse spinal cord neurones in cell culture were investigated using patch clamp techniques. 2. Whole-cell GABA receptor currents increased in a concentration-dependent manner from 0.5 to 5 microM. 3. Single-channel currents were recorded with a main conductance state of 27.2 pS and a less frequent conductance state of 15.9 pS. The main conductance state opened singly and in bursts of several openings. 4. Mean open times of GABA receptor main conductance currents were increased and open-time frequency histograms were shifted to longer times as GABA concentration was increased from 0.5 to 5 microM. Three exponential functions were required to fit the histograms at all GABA concentrations, suggesting that the channel opened into at least three open states (O1, O2 and O3). The three functions had the same time constants (1.0 +/- 0.2, 3.7 +/- 0.4 and 11.3 +/- 0.5 ms; mean +/- S.D.) at each concentration. The increase in long open times with concentration was due to a shift in relative frequency of occurrence of openings from the shortest (O1) to the two longest (O2 and O3) open states. 5. Closed-time distributions of closures between main conductance state openings were fitted with multiple exponential functions, suggesting that the channel had several closed states. The two shortest time constants (0.24 +/- 0.03 and 2.0 +/- 0.3 ms) were concentration independent (0.5 to 5 microM). Three longer time constants decreased as concentration increased. 6. Bursts were defined as groups of openings surrounded by closures greater than a critical closed time (tc = 5 ms). Mean burst durations were increased and burst duration frequency histograms were shifted to longer times as GABA concentration was increased from 0.5 to 5 microM. Burst-duration frequency histograms were best fitted with three exponential functions. The time constants were concentration independent and were 1.0 +/- 0.2, 5.5 +/- 0.2 and 29.8 +/- 1.6 ms. The increase in burst duration with concentration was due to a relative shift from short duration bursts to longer duration bursts. 7. The shortest burst time constant was similar to the shortest open time constant suggesting that there was a population of single openings of short duration. The two longest burst time constants were longer than the two longest open time constants, suggesting that the bursts from the two longest burst components were composed of two or more openings.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Barbiturate regulation of kinetic properties of the GABAA receptor channel of mouse spinal neurones in culture.

1. Barbiturate regulation of the kinetic properties of gamma-aminobutyric acidA (GABA) receptor channel chloride currents from somata of mouse spinal cord neurones were investigated using whole-cell and excised outside-out patch-clamp recording techniques. 2. GABA (2 microM), GABA (2 microM) plus phenobarbitone (PhB) (500 microM) and GABA (2 microM) plus pentobarbitone (PB) (50 microM), applied by pressure ejection from blunt perfusion micropipettes, evoked inward chloride currents when neurones or patches were voltage clamped at -75 mV and the chloride equilibrium potential was 0 mV. GABA receptor channel currents were increased by PhB and PB. 3. Single GABA receptor channel currents were recorded with a main conductance state of 27 pS and a less frequent subconductance state of 16.5 pS. The conductances of the two states were unchanged by the barbiturates. 4. The main conductance state kinetics were analysed. GABA alone or with the barbiturates gated the channel open singly and in groups of openings. 5. The barbiturates increased GABA receptor channel mean open time and shifted frequency histograms of channel open times to longer times. 6. Three exponential functions were required to fit the frequency histograms of GABA receptor channel open times, suggesting that the channel has at least three open states (O1, O2, O3). The time constants for the exponential functions (0.9, 2.7 and 7.8 ms, respectively) were unchanged by the barbiturates. The increases in mean open times and the shifts of the open-time frequency histograms by the barbiturates were due to a reduction in relative frequency of occurrence of the two short open states (O1 and O2) and to an increase in the relative frequency of occurrence of the longest open state (O3). 7. Frequency histograms of GABA receptor channel closed times were fitted with five exponential functions, suggesting that the channel has multiple closed states. None of the time constants nor areas of the exponential functions were significantly changed by the barbiturates. 8. For analysis, a burst was defined as openings surrounded by closures greater than a critical closed time, tc, of 5 ms. For GABA (2 microM), frequency histograms of GABA receptor channel bursts were fitted with three exponential functions, suggesting that the channel has three burst states (B1, B2, B3). The B1 burst state was probably a single opening to the O1 open state while the B2 and B3 burst states were probably composed of multiple openings to the O2 and O3 open states.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1976

"Attitudes" toward the elderly: a comparison of measures.

College students were presented five questionnaires traditionally used to assess attitudes toward old people. The intercorrelations among the measures were low, accounting for no more than 24% of the variance between any two measures. The results suggest that the measures are not equivalent; it was argued that the practice of utilizing a single instrument to measure attitudes toward the elderly may contribute to inconsistencies reported in the literature.

Aged↗
PubMed1976

Solution shift performance in the elderly.

Seventy-two elderly adults were presented a concept problem which varied as a function of type of solution shift (reversal or nonreversal) and stimulus materials (compact designs, distributed designs, or distributed foods). Both trials to criterion and postshift error patterns were analyzed. Results indicated that stimulus materials affected postshift performance and that the elderly do respond in a dimensional fashion under some circumstances. Examination of individual protocols revealed that a rigidity notion would not account for the difficulty the elderly experienced when solution was shifted. Several alternative explanations were offered for the failure of many volunteers to solve the postshift problem.

Aged↗