Single unit activity in frontal cortex and caudate nucleus of young and old rats

doi:10.1016/0197-4580(85)90058-2

Neurobiology of Aging

Volume 6, Issue 3, Autumn 1985, Pages 245-248

https://doi.org/10.1016/0197-4580(85)90058-2 Get rights and content

Abstract

Spontaneous neuronal activity was recorded extracellularly from isolated single units in frontal neocortex and caudate nucleus of young and aged F344 rats anesthetized with urethane. Average firing rates, mean interspike intervals (ISI)±standard deviations, and ISI frequency histograms were computed and analyzed by microprocessor. For frontal cortex cells (N=226), there was a nonsignificant trend toward slower average discharge rates in the old group. However, a significantly longer mean ISI and proportionally more very slow firing cells (<I Hz) were observed in old rats. A laminar analysis of frontal cortex unit activity in young animals showed average discharge rates to be distributed somewhat evenly throughout the cortical mantle with the exception of the zone 1200–1400 μ beneath brain surface. This depth corresponds approximately to layer V where a 50% increase in mean firing rate in young animals was observed. In aged animals, this increased cell firing in layer V was absent, while mean discharge rates in other laminae remained essentially the same in the young and old rat groups. Caudate nucleus cells (n=70) showed a significant shift towards fewer fast discharging cells in old rats, with the average firing rate diminished by one-third. Although more brain regions need to be examined in a similar fashion, the consistency of the present results with those previously reported for the brainstem and cerebellum suggests that slower firing rates and longer ISIs are likely to be wide-spread throughout the brains of aged rats.

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Sleep-related increase in activity of mesopontine neurons in old rats
2002, Neurobiology of Aging
Relationships between age-related changes in sleep patterns and neuronal activity have received scant attention. In the present study, reticularis pontis oralis (RPO) and ventral tegmental nucleus of Gudden (VTN) neurons were recorded in unanesthetized restrained young (3 months) and old (23 months) Sprague-Dawley rats during wakefulness (W), slow wave sleep (SWS) and rapid eye movement (REM) sleep. All RPO neurons displayed a tonic activity. Firing rates were similar during W in young and old rats. In contrast, firing rates were higher during SWS in old rats (P < 0.001). In both young and old rats, firing rates increased significantly during REM sleep as compared to W and SWS but this increase was markedly greater in old rats. Neurons recorded from VTN displayed bursting activity at theta frequencies during W and REM sleep. The frequency of VTN bursting neurons was higher during REM sleep as compared to W in both groups of age. This difference was significantly more pronounced in old as compared to young rats (P < 0.001). Sleep-related hyperactivity of pontine neurons is discussed in terms of a possible deficit in inhibitory processes in old rats.
Aged F344 rats exhibit an increased proportion of dopamine agonist-excited striatal neurons
2002, Neurobiology of Aging
Citation Excerpt :
These decrements, which include decreases in DA synthesis [25,33,46], stimulated release [10,11,39], uptake [8,18], and receptor number [13,23,29], may produce alterations in the electrophysiological properties of striatal neurons that could ultimately affect motor function. While previous studies have demonstrated age-related changes in striatal electrophysiology in anesthetized animals and in vitro [2,4,12,24,42,44], there is a paucity of data regarding striatal activity in young versus aged freely-moving rats [40]. Additional studies using freely-moving animals are warranted based on reported differences in striatal electrophysiological activity between anesthetized versus behaving animals (e.g. [9,21,36]).
In order to study age-related differences in striatal electrophysiological activity in freely-moving animals, multi-wire electrode arrays were chronically implanted in the striatum of young (6–8 months) and aged (24–26 months) Fischer 344 rats. After recording baseline activity, d-amphetamine (D-AMPH; 1.0 mg/kg) and apomorphine (APO; 0.5 mg/kg) were administered to the two age groups. For both the D-AMPH and APO series, the percentage of striatal neurons that increased firing rates as a result of the DA agonists was 19% higher in the old animals than in the young animals. In addition, D-AMPH increased the firing rates of D-AMPH-excited neurons to a greater extent in the old animals than in the young animals. While the rate-increasing effects of APO did not differ significantly as a function of age, its effects were slightly greater in the old animals as well. These results suggest that age-related decreases in nigrostriatal DA function may result in alterations in the way in which the striatum integrates corticostriatal and nigrostriatal inputs to influence motor function.
Age-related changes in striatal function of freely-moving F344 rats
2001, Neurobiology of Aging
Multi-wire electrode arrays were used to record extracellular electrophysiological activity in striatal medium spiny-like neurons of freely-moving young (6–8 months) and aged (24–26 months) Fischer 344 rats. While overall basal firing rates did not differ between the two groups, d-amphetamine (5.0 mg/kg) increased firing rates more in the young rats. D-Amphetamine had heterogeneous effects on firing rates, however, exciting 63% of the neurons while inhibiting 37%. Neurons were classified according to their response to d-amphetamine (excited vs. inhibited) to examine age-related differences in firing rates and bursting activity. In the d-amphetamine-excited neurons, pre-drug intraburst firing rates were higher in the old rats. This effect was reversed by d-amphetamine. D-Amphetamine increased the percentage of spikes within bursts to a greater extent in the aged animals and decreased burst durations greater in the young group. In d-amphetamine-inhibited neurons, firing rates were diminished in the old rats more than they were in the young rats. These results demonstrate age-related alterations in striatal electrophysiological activity that may help explain motor deficits seen in senescence.
Age-induced changes in electrophysiological responses of neostriatal neurons recorded in vitro
1992, Neuroscience
The present studies were undertaken to determine whether the major electrophysiological characteristics of neostriatal neurons are altered during aging. The passive and active membrane properties of 130 neostriatal neurons obtained from young (three to five months,N = 65) and aged (24–26 months,N = 65) Fischer 344 rats were compared using an in vitro slice preparation. The results indicated that in a population of aged neostriatal neurons the majority of the electrophysiological changes that occurred resulted in decreases in cellular excitability. These changes included increased threshold to induce action potentials by intracellular current injection and decreased negativity of membrane potentials at which such action potentials were induced. In addition, there were increases in the amplitude of the action potential afterhyperpolarization and increases in the frequency of occurrence of accommodation when trains of action potentials were induced. These two latter effects can limit the frequency of action potential generation. The thresholds to elicit synaptically evoked depolarizing responses and action potentials were increased. The results also indicated that a number of basic electrophysiological parameters were unchanged by the aging process. These included action potential amplitude, rise time and duration, resting membrane potential, input resistance and time constant. Although thresholds for the induction of synaptic and action potentials by extracellular stimulation were increased, the latency, amplitude and duration of the evoked depolarization remained unchanged.
These findings suggest that the ability of neostriatal neurons to integrate spatiotemporal inputs must be severely compromised in this population of aged cells. Furthermore, the present findings, when compared with age-induced electrophysiological alterations in neurons in other brain areas, indicate that age may differentially alter electrophysiological properties of neurons in separate nuclei. Profiles of age-related changes in neurophysiological properties of neurons provide important information that can be related to the contributions of individual neural areas to the behavioral effects of aging.
Intracellular neurophysiological analysis reveals alterations in excitation in striatal neurons in aged rats
1989, Brain Research
Intracellular recordings were used to characterize the physiological changes underlying decreases in excitation observed in striatal neurons during the aging process. Rats were divided into 3 age groups: young (3–5 months), middle-aged (10–12 months) and aged (>24 months). All experiments were performed in urethane-anesthetized rats. Recordings were obtained from 33 neurons in young, 17 in middle-aged and 20 in aged rats. When identified by intracellular injections of Lucifer yellow all recorded neurons were medium-sized spiny cells. Resting membrane potentials were at least −40 mV and action potentials greater than 35 mV. Postsynaptic responses were evoked by stimulation of frontal cortex. In all recorded neurons, regardless of age, excitatory postsynaptic potentials (EPSPs) could be evoked. However, the threshold currents for eliciting both EPSPs and synaptically driven action potentials were significantly higher in neurons obtained from aged rats than those recorded in the other two groups. Other changes in excitation in aged striatal neurons consisted of absence of spontaneously occurring EPSPs, higher current to induce firing by intracellular injections of depolarizing current and an inability of orthodromically induced action potentials to follow paired stimulation pulses to the cortex at short interpulse intervals. These data were interpreted to indicate that a combination of changes in synaptic connectivity and in membrane properties underlie the decreases in excitation. Together with our previous findings obtained from aged cats these results indicate that decreased neuronal excitability is a major effect of aging in the striatum.
Cortical amino acid neurotransmitter release is altered by CCK perfused in frontal region of unrestrained aged rats
1988, Peptides
The purpose of this study was to investigate in the aged animal the functional interaction between cholecystokinin (CCK) and amino acid neurotransmitter activity in the frontal cortex, a structure of importance in age-related disabilities. Guide cannula for repeated push-pull perfusion were implanted bilaterally in the superficial frontal cortex of male Sprague-Dawley rats. Two groups of animals were selected on the basis of their age at the time of stereotaxic surgery: 90 days and two years. Following post-operative recovery, an artificial CSF solution was perfused repeatedly within the cortex of each animal for a 5.0 min interval. The rate of perfusion was 25 μl/min and a 5.0 min period elapsed between the collection of each sample of perfusate. After the initial control perfusions, CCK octapeptide was incorporated in a concentration of 6.0 or 18.0 ng/μl in the CSF and perfused for 5.0 min under identical conditions. Each sample of perfusate was assayed by high performance liquid chromatography with electrochemical detection (HPLC-EC) for its content of glutamate (Glu), aspartate (Asp), glutamine (Gln), glycine (Gly), taurine (Tau) and gamma-amino-butyric acid (GABA) with homoserine used as an internal standard. Although CCK in the lower 6.0 ng/μl concentration failed to alter significantly the profile of amino acids in the frontal cortex, the higher 18.0 ng/μl solution of CCK enhanced the efflux of Glu as well as Asp, but only in the aged rats. Both concentrations of CCK tended also to augment the release of Gln in the older animals but these changes were not statistically significant. Both Gly and Tau were unaffected by CCK in either dose in both the young and old groups. GABA was not detectable in any of the samples of perfusate throughout the experiments. These results suggest that CCK-8 exerts a selective effect on amino acid neurotransmitter activity in the frontal cortex which is clearly age-dependent. In the older animal, this sensitivity of the cortical cells to CCK may reflect a functional attribute of the peptide in the aging process.

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^☆: Supported by NIA contract NO1-AG-0-219 and a grant from Burroughs Wellcome Co.

^☆☆: Presented in preliminary form at the 13th Annual Meeting of the Society for Neuroscience, 1983.

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Brief communicationSingle unit activity in frontal cortex and caudate nucleus of young and old rats☆,☆☆

Abstract

Electroencephalogr Clin Neurophysiol

Mech Ageing Dev

Neurobiol Aging

Neurobiol Aging

Neurobiol Aging

EEG Clin Neurophysiol

Neurobiol Aging

Brain Res

Brain Res Bull

Exp Neurol

Neurobiol Aging

Behav Biol

Memory deficits associated with senescence: a neurophysiological and behavioral study in the rat

J Comp Physiol Psychol

Brief communication
Single unit activity in frontal cortex and caudate nucleus of young and old rats☆,☆☆