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At least 595 records · Page 33Linked to original sources
PubMed1978

Self-stimulation in the rat: quantitative characteristics of the reward pathway.

Quantitative characteristics of the neural pathway that carries the reinforcing signal in electrical self-stimulation of the brain were established by finding which combinations of stimulation parameters give the same performance in a runway. The reward for each run was a train of evenly spaced monophasic cathodal pulses from a monopolar electrode. With train duration and pulse frequency held constant, the required current was a hyperbolic function of pulse duration, with chronaxie c approximately 1.5 msec. With pulse duration held constant, the required strength of the train (the charge delivered per second) was a hyperbolic function of train duration, with chronaxie C approximately 500 msec. To a first approximation, the values of c and C were independent of the choice either of train duration and pulse frequency or of pulse duration, respectively. Hence, the current intensity required by any choice of train duration, pulse frequency, and pulse duration dependent on only two basic parameters, c and C, and one quantity, Qi, the required impulse charge. These may reflect, respectively, current integration by directly excited neurons; temporal integration of neural activity by synaptic processes in a neural network; and the peak of the impulse response of the network, assuming that the network has linear dynamics and that the reward depends on the peak of the output of the network.

Animals↗
PubMed1977

The effect of amphetamine and L-dopa on tetrabenazine-induced suppression of intracranial self-stimulation in the rat.

The administration of d-amphetamine sulphate resulted in a restoration of intracranial self-stimulation (ICSS) suppressed by tetrabenazine (TBZ). A dose-dependent increase in the rate of ICSS was seen after L-dopa in animals pretreated with TBZ. d-Amhetamine is believed to act by facilitating the nerve-impulse induced release of central catecholamines (CA) whereas the blockage of the granular uptake-storage mechanism by TBZ will prevent the storage of CA formed from the administrated L-dopa and thereby interfere with their release by nerve-impulses. Thus, in the latter case, an activation of central CA receptors in all probability will be due to a dose-dependent diffusion of CA from nerve terminals. It is suggested that the failure to completely antagonize the TBZ-induced suppression of behaviour by L-dopa is due to the fact that a direct activation, independent of the nerve-impulse flow, of central CA receptors easily results in an overstimulation and a reduced specificity in behaviour.

Amphetamine↗
PubMed1986

Further evidence against adaptation of prolonged electrical self-stimulation reward.

Using a Y-maze preference test paradigm, we examined the temporal characteristics of the neural network subserving self-stimulation reward. The first part of the experiment demonstrated that when prolonged electrical brain stimulation is initially delivered with a low pulse frequency (100 Hz), rats prefer an increase over either a decrease or no change in the pulse frequency of subsequent stimulation. However, the second part showed that when prolonged brain stimulation is initially delivered with a high pulse frequency (250 Hz), an increase is not preferred. The data are inconsistent with an adaptation model of summation. These results are explained in terms of an improved model of summation involving two integrators and fatigue.

Adaptation, Physiological↗
PubMed1977

Dose- and time-dependent effects of narcotic analgesics on intracranial self-stimulation in the rat.

Rats were trained to bar-press in order to obtain electrical stimulation of the medial forebrain bundle through chronically implanted electrodes. Dose-response and time-effect curves were determined for morphine (1.0-30 mg/kg), levorphanol (0.1 to 3.0 mg/kg), methadone (0.1-3.0 mg/kg), meperidine (1.0-30 mg/kg), oxymorphone (0.03-1.0 mg/kg), and d-amphetamine (0.1-3.0 mg/kg). Dose-response and time-effect curves were also determined for morphine (1.0-30 mg/kg) in rats that had received multiple injections of morphine over a period of 3 days. All of the narcotic analgesics produced dose-related decreases in responding; the durations of these decreases were also dose-related. The relative potencies of the five narcotic analgesics with respect to the rate-decreasing effects for selt-stimulation responding were: oxymorphone greater than levorphanol greater than methadone greater than morphine greater than meperidine. In morphine-tolerant rats the rate-decreasing effects of morphine on responding for selt-stimulation were attenuated. These findings suggest that narcotic analgesics from diverse chemical families have a similar, predominantly depressant, effect on self-stimulation behavior and that the relative potencies of a series of narcotics for this effect are similar to those demonstrated for other properties of these drugs.

Analgesics, Opioid↗
PubMed1988

Chronic l-dopa fails to lessen rebound enhancement of self-stimulation after chronic haloperidol.

Chronic treatment with haloperidol (approximately 4.8 mg/rat/day PO for 18 days) severely impaired variable-interval hypothalamic self-stimulation. Cessation of treatment was followed by a strong rebound increase in response rates at submaximal currents, to well above pretreatment rates. The rebound increase in responding was not prevented (and at submaximal currents was actually enhanced) by treatment with l-dopa plus benserazide (respectively 240 and 60 mg/kg/day PO) for 6 days after withdrawal of haloperidol. This result is at variance with previously reported findings.

Animals↗
PubMed1982

Self-stimulation and circling reveal functional differences between medial and lateral substantia nigra.

Functional differences between medial and lateral substantia nigra (SN) sites mediating intracranial self-stimulation (ICSS) and circling behaviours were explored. It was found that, for medial SN stimulation sites, D- and L-amphetamine (1 mg/kg) had equipotent, slightly facilitatory effects on ICSS rates while for lateral SN stimulation sites, D-amphetamine increased and L-amphetamine decreased ICSS rates. It is suggested that these effects may be due to medial and lateral dopamine cells having different sensitivities to amphetamine isomers. Imposed continuous stimulation of the ICSS sites induced contralateral circling from the medial SN placements and ipsilateral circling from the lateral SN placements. In rats receiving lesions through the ICSS electrode, D-amphetamine (2 mg/kg) induced ipsilateral circling following medial SN damage and contralateral circling after lateral SN damage. These results suggest that lateral and medial SN mechanisms of ICSS and circling differ, and that the lateral SN may be antagonistic to medial SN mechanisms involved in circling behaviour.

Amphetamine↗
PubMed1980

Acute effects of neuroleptics on brain self-stimulation thresholds in rats.

The acute effects of 5 neuroleptic drugs were tested in rats implanted with stimulating electrodes in the medial forebrain bundle and trained in a brain self-stimulation threshold procedure. Haloperidol (0.01-0.10 mg/kg) and loxapine (0.03-0.56 mg/kg) produced increases in reinforcement thresholds accompanied by reductions in response rates. Chlorpromazine (0.10-3.0 mg/kg) did not significantly alter reinforcement thresholds, but did produce dose-dependent reductions in response rates. Pimozide (0.1-1.75 mg/kg) was similar to chlorpromazine and significantly increased the reinforcement threshold only at the highest dose, although a graded decrease in response rates occurred over a wide dose-range. Clozapine (0.1-1.75 mg/kg) increased reinforcement thresholds without producing any significant changes in response rates, but when 3.0 mg/kg was administered, a marked disruption of behavior occurred. The results suggested that a distinction can be made between the effects of neuroleptics on motor behavior and on central reinforcement thresholds, and this may help in the interpretation of the relation between the chemical and clinical potency of antipsychotic drugs.

Animals↗
PubMed1988

Basal forebrain knife cuts and medial forebrain bundle self-stimulation.

Current autoradiographic and electrophysiological data suggest that fibers coursing from the diagonal band/medial septum and lateral preoptic area through the medial forebrain bundle (MFB) to the midbrain may carry the reward signals generated by lateral hypothalamic stimulation. To test this hypothesis, 40 rats were given a unilateral lateral hypothalamic stimulating electrode and an ipsilateral guide cannula for knife cut transection. In baseline self-stimulation testing, both the animal's capacity to respond for the stimulation and the reward efficacy of the stimulation were measured. A coronal plane knife cut transection was given following stabilization of baseline behavior, and any changes in response capacity and stimulation reward efficacy were observed for up to two weeks, beginning 24 h after transection. Cuts to the diagonal band/medial septal region or the outflow therefrom did not permanently or significantly alter stimulation reward effectiveness. Cuts in the lateral preoptic area or in the MFB just anterior to the stimulating electrode decreased stimulation reward effects only if considerable concomitant rostrocaudal tissue damage was apparent around the knife cut. Even in these cases, reward degradation was rarely permanent. These results suggest that the majority of reward-relevant fibers probably do not arise in forebrain nuclei rostral to the stimulating electrode. A possible role of neurons endemic to the lateral hypothalamus in stimulation reward effects is discussed.

Animals↗
PubMed1984

The effects of the beta-carboline FG 7142, on intracranial self-stimulation in the rat.

The effects of FG 7142 were examined, alone and in combination with chlordiazepoxide, on self-stimulation of the mid-lateral hypothalamus. Rewarding stimuli were delivered according to a 10-sec variable-interval schedule of reinforcement. FG 7142 (1-20 mg/kg) produced a dose-related depression in responding, and chlordiazepoxide (5 mg/kg) enhanced it. When these two drugs were given together, response rates did not differ significantly from control rates.

Animals↗
PubMed1979

Actions and interactions of cocaine on self-stimulation behavior in rats.

The effect of cocaine, over a dose range of 2--60 mg/kg, i.p., on self-stimulation (SS) behavior was studied in rats with electrodes either in the posterior hypothalamus (PH, monoaminergic) or the area ventralis tegmentum (A10, dopaminergic). The drug increased SS behavior with peak effects at 30 mg/kg in PH rats and 20 mg/kg in A10 rats. Azaperone (an alpha-adrenergic blocker) and haloperidol (an antidopaminergic neuroleptic) given at doses that did not affect baseline SS responses reduced cocaine-induced enhancement of SS in both PH and A10 rats, showing the involvement of both noradrenergic and dopaminergic mechanisms in SS behavior. A scopolamine dose that itself facilitated SS responding enhanced the effect of cocaine on this behavior, thus suggesting an additional involvement of cholinergic mechanisms in cocaine effect.

Animals↗
PubMed1985

Auto-titration technique using intracranial self-stimulation and effects of antianxiety drugs.

In order to study effects of antianxiety drugs on the threshold of intracranial self-stimulation (ICSS), the auto-titration technique was used in the two lever Skinner box. This procedure consisted of conventional ICSS except the brain stimulation current intensity was decreased after every 20 lever press for ICSS, and the animal could press the another reset lever (at any time) to reset the stimulation current intensity to the preseted level. The current intensity at which the animal pressed the reset lever (reset current) was defined as the threshold of ICSS. Since reset currents that the animals showed were very stable during this experiment, the effects of chlordiazepoxide, diazepam and meprobamate were studied. The reset current was significantly lowered by 5.0 mg/kg chlordiazepoxide, p.o., at 1 hr after administration accompanied by the significant increase of ICSS, and the reset current was significantly lowered by 20.0 mg/kg of chlordiazepoxide. On the other hand, diazepam did not lower the reset current, although a significant increase of ICSS was observed at 1.0 mg/kg, p.o. The reset current was lowered by meprobamate at 100 mg/kg, p.o., accompanied by the increase of ICSS, and a significant increase of ICSS was observed at 200 mg/kg but not accompanied by lowered reset current. From these results, increased susceptibility to the brain stimulation current may be involved in the facilitating effects of chlordiazepoxide and meprobamate on ICSS.

Animals↗
PubMed1999

Effects of D1 and D2 dopamine receptor antagonists on cocaine-induced self-stimulation and locomotor activity in rats.

To clarify the involvement of D1 and D2 dopamine systems in intracranial self-stimulation (ICSS) and locomotor activity in rats, we studied the acute effects of cocaine and the interaction between cocaine and dopamine antagonists with respect to these behaviors. Although cocaine (5.0, 10.0, or 20.0 mg/kg) dose-dependently increased locomotor activity, it augmented the rate of ICSS only at 5.0 mg/kg. The failure of high doses of cocaine to augment purpose-oriented behavior such as ICSS may result from its induction of a manic-like state. The D1 dopamine receptor antagonist SCH23390 (0.02, 0.1, or 0.5 mg/kg) or the D2 antagonist nemonapride (0.04, 0.2, or 1.0 mg/kg) significantly decreased cocaine augmentation of ICSS. The higher two doses of either antagonist also produced a significant decrease in cocaine-induced locomotor activity. We therefore suspect that cocaine's augmentative effect on those behaviors, especially ICSS, requires activation of both D1 and D2 dopamine receptors.

Animals↗
PubMed1982

Intracranial self-stimulation: temporal interactions among mesencephalic and diencephalic sites.

The monophasic pulse pair technique has been employed to ascertain whether pairs of intracranial self-stimulation (ICSS) sites interact with each other. The present study investigated the interactive properties of ICSS placements in the substantia nigra (SN) and mid-ventral periaqueductal gray (MV) with those hypothalamic ICSS placements within (MFB) or outside of (non MFB) the medial forebrain bundle. ICSS response rates when pulses of each pulse pair were split between two ICSS sites were significantly higher than the sum of rates when each site was stimulated singly with single-pulse trains. Moreover, all interaction conditions yielded higher rates than pulse pairs delivered to the mesencephalic site at an optimal interval, yet similar rates to pulse pair stimulation delivered to the diencephalic site. The symmetry of the interactions depended upon electrode loci: MV/MFB and SN/non MFB interactions were significantly higher when the mesencephalic site received the first pulse of each pair, effects which accounted for 49 and 58% of the variance respectively. Conversely, MV/non MFB and SN/MFB interactions were significantly higher when the mesencephalic site received the second pulse of each pair, effects which accounted for 5 and 14% of the variance respectively. These behavioral ICSS interactions are discussed in terms of interrelated heterogeneous subsystems subserving ICSS behavior.

Animals↗
PubMed1984

Electrical self-stimulation of the mesencephalic central gray area: facilitation by lateral hypothalamic stimulation.

Three experiments were performed with BALB/c mice implanted both in the lateral hypothalamus (LH) and the dorsal part of the mesencephalic central gray area (CG). Initially, the effects of a brief electrical stimulation (0.2 sec) of the LH on approach and escape responses produced by continuous stimulation of the dorsal CG, were studied in a shuttle-box. Starting at an intensity of 10 microA, imposed LH stimulation both reduced approach latency and increased escape latency with CG stimulation. In the second and third experiments, the animals were placed in a standard self-stimulation (ICSS) box; depressions of a lever delivered brief electrical stimulations (0.2 sec). During the second experiment, it was observed that the very weak ICSS behavior produced by dorsal CG activation was greatly improved by forced LH stimulation. Finally, in the third experiment, simultaneous ICSS in LH and CG was compared with ICSS in LH alone. When low current intensities were used, simultaneous ICSS in LH and CG was more intense than ICSS in LH alone. These data especially suggest that dorsal CG stimulation has an appetitive component, and consequently that neuronal elements related to the positive reinforcement system are present in the dorsal CG area. Furthermore, the fact that one can obtain interactions between mesencephalic and hypothalamic ICSS is in accordance with the claim that the LH has connections with the CG area.

Animals↗
PubMed2005

Nucleotide binding and self-stimulated GTPase activity of human guanylate-binding protein 1 (hGBP1).

The synthesis of human guanylate-binding protein 1 (hGBP1) is induced by interferon-gamma and its biological function is related to antiviral activity and regulation of proliferation. It interacts with guanine nucleotides, and its catalytic activity on GTP hydrolysis leads to the formation of phosphate ions and both GDP and GMP. Similar to other large GTPases like dynamin, hGBP1 shows higher specific GTP hydrolysis activity with increasing concentration of the protein. This is based on nucleotide-dependent self-association of hGBP1, which leads to self-stimulation of its GTPase activity. In this chapter we describe the characterization of the basic biochemical properties of hGBP1. Essentially, the biological activity of a GTPase is controlled by the type of nucleotide bound. Therefore, nucleotide binding is quantified in terms of affinity and dynamics since both of these aspects are important for the occurrence of hGBP1 bound to the one or the other nucleotide. In addition, we analyze the self-stimulated GTPase activity and show how to extract the hGBP1 homodimer dissociation constant from these data. Finally, with the help of size exclusion chromatography, nucleotide-dependent formation of hGBP1 dimers and tetramers is demonstrated. These biochemical characteristics may help to further understand the biological function of hGBP1.

Chromatography, Gel↗
PubMed1987

Effects of acute nicotine and ethanol on medial prefrontal cortex self-stimulation in rats.

The acute effects of nicotine and ethanol were studied in low and high rates of intracranial self-stimulation (ICSS) of the medial prefrontal cortex (MPFC) in the rat. Nicotine tended to increase low ICSS rates but did not change or even reduced high ICSS rates. Independent of ICSS rate, ethanol tended to decrease ICSS, but only at high doses (1.0 g/kg). It is suggested that the effects of nicotine and ethanol on ICSS may be mediated by their effects on dopamine.

Animals↗
PubMed1985

Lesion of the temporo-ammonic perforant path facilitates self-stimulation of the lateral entorhinal cortex in mice.

The effect of a lesion of the perforant path (PP) on self-stimulation (SS) of the lateral entorhinal cortex (LEC) was tested in mice between 8 and 21 days after surgery. The current intensities tested ranged between 0 and 80 microA (peak to peak 100 Hz sine-wave). The PP lesion led to a two-fold increase in SS rates at intensities above 30 microA without affecting the baseline SS rates (0 microA) and SS threshold (30 microA). The lesion also led to a significant increase in LEC after-discharge (AD) threshold and eliminated behavioral convulsions during SS testing. The suppression of AD by i.p. Na phenobarbital injection (10 mg/kg) led to a similar increase in SS rates in sham-lesioned mice; there was no difference in PP-lesioned animals. These results might be interpreted as evidence in favor of an independence of the neuronal processes mediating entorhinal and hippocampal reward-related behaviors.

Animals↗