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At least 289 records · Page 16Linked to original sources

PubMed2003

Lidocaine inactivation demonstrates a stronger role for central versus medial extended amygdala in medial forebrain bundle self-stimulation.

Given recent attention to the role of the extended amygdala (EA) in brain reward processes, this study examines the relative contributions of the medial versus central aspects of that forebrain macrostructure to the rewarding effects of medial forebrain bundle (MFB) stimulation. Thirty-one rats were self-stimulated at either the rostral or caudal MFB before and after lidocaine-induced inactivation of an EA target. Relative to non-injection baseline tests, the injection of 0.5 or 1.0 microl of 4% lidocaine into the central EA structures of the lateral bed nucleus of the stria terminalis, the central sublenticular EA, and the interstitial nucleus of the posterior limb of the anterior commissure frequently and substantially disrupted the rewarding effect of MFB stimulation, whereas comparable saline infusions did not. The effects were most pronounced when the central EA was inactivated either bilaterally or ipsilateral to the stimulation site. Contralateral inactivation was less effective but did impair the stimulation's reward effects in several cases. Inactivation of medial EA structures did not have as great or as consistent effects on stimulation reward value except when the lidocaine infusion encroached on the MFB itself. These results support prior demonstrations of the EA's role in brain reward and motivational processes and further show that the central rather than medial aspects of the EA are particularly relevant. The results are discussed in the context of possible anatomical substrates supporting MFB self-stimulation.

Amygdala↗

PubMed1975

Self-stimulation and noradrenaline: evidence that inhibition of synthesis abolishes responding only if the "reserve" pool is dispersed first.

Although noradrenaline (NA) is thought to play a critical role in electrical self-stimulation, suppression of NA synthesis by injection of the dopamine-beta-hydroxylase inhibitor, FLA-63 (Hässle) (25 mg/kg), had little or no effect on response rates. But 3 or 5 days after prior reserpinisation, FLA-63 in the same dosage suppressed or profoundly depressed self-stimulation without eliciting signs of general incapacity. Suppression of self-stimulation could be reversed by intraventricular injection of NA, indicating that the depressant effect depended specifically on NA depletion. These findings support the view that NA may play a necessary role in self-stimulation and indicate that the NA available for this purpose included intraneuronal NA in a reserpine-sensitive reserve pool.

Animals↗

PubMedDate not supplied

[The effect of antiparkinson preparations on the self-stimulation reaction of rabbits in a helium-oxygen environment under increased pressure].

The authors studied hypothalamic self-stimulation of 30 rabbits in hyperbaric heliox after intraperitoneal injections of L-DOPA, melanostatin, and cyclodol. The frequency of self-stimulation was decreased with 40 atm of heliox. After L-DOPA administration, a reduction of self-stimulation was twice less than that in heliox without pharmaceuticals.

Animals↗

PubMed1986

Effects of ibotenic acid lesion in the basal forebrain on electrical self-stimulation in the middle part of the lateral hypothalamus.

The aim of the present study was to analyse the involvement of neurons located in some basal forebrain areas in electrical self-stimulation elicited from the middle part of the lateral hypothalamus. The anterior hypothalamic region was unilaterally lesioned by local injection of ibotenic acid. Ten to 20 days later 4 electrodes were implanted bilaterally, two at the lesion level and two in the middle lateral hypothalamus. A small but significant self-stimulation deficit was observed in the lesioned area, while self-stimulation on the contralateral side was normal. At the middle lateral hypothalamic level, no deficit was observed when stimulation was applied either ipsilaterally or contralaterally to the anterior lesioned side. In most cases the lesion destroyed the dorsolateral part of the lateral preoptic area, the ventral pallidum-substantia innominata complex and the lateral part of the bed nucleus of the stria terminalis. Given the fact that these regions are known to project massively to the middle lateral hypothalamic area, our data suggest that descending influences originating in the damaged regions are not involved in self-stimulation elicited from the middle hypothalamus.

Animals↗

PubMed2000

Lack of glucocorticoids attenuates the self-stimulation-induced increase in the in vivo synthesis rate of dopamine but not serotonin in the rat nucleus accumbens.

Our previous study demonstrated that intracranial self-stimulation of the medial forebrain bundle can increase the in vivo synthesis turnover rate of dopamine (DA) and serotonin (5-HT) in the nucleus accumbens of adrenal-intact rats. The present study examined using microdialysis whether such increases in DA and 5-HT syntheses are influenced by adrenal hormones, which are also activated following intracranial self-stimulation. A decarboxylase inhibitor, NSD-1015, was perfused through reversed microdialysis which enabled the simultaneous measurement of 3,4-dihydroxyphenylalanine (DOPA) and 5-hydroxytryptophan (5-HTP) as an index of the in vivo turnover rate of DA and 5-HT syntheses. Adrenalectomy (ADX) attenuated significantly the self-stimulation-induced increase in dialysate levels of DOPA but not 5-HTP. Corticosterone (Cort) replacement reversed the attenuation in DOPA levels in adrenalectomized rats. The finding indicates that activation of DA synthesis in vivo in the nucleus accumbens during intracranial self-stimulation is dependent on, whereas that of 5-HT synthesis is independent of glucocorticoid modulation.

5-Hydroxytryptophan↗

PubMedDate not supplied

[Effect of monoamines microinjected into the amygdaloid nucleus on the lateral hypothalamic self-stimulation response].

The effect of serotonin and noradrenaline injections in the amygdalar nuclei on the reaction of self-stimulation of the lateral hypothalamus was studied in rats. The increase of exogenous serotonin level in the amygdala phasically intensified the self-stimulation and activated emotionally negative forms of behaviour. The increase of noradrenaline content phasically lowered the frequency of self-stimulation and evoked emotionally positive forms of behaviour which did not depend on the lateral hypothalamus stimulation. It is supposed that the amygdala takes part in the mechanism of sensory reinforcement connected with learning and being in definite relations with the centres of positive reinforcement of the lateral hypothalamus, while amygdalar monoamines form the neurochemical basis for the control of the reinforcing properties of external stimuli.

Amygdala↗

PubMed1998

Involvement of the ventral tegmental area opiate receptors in self-stimulation elicited from the ventral pallidum.

Enkephalinergic and dopaminergic mechanisms have been implicated in the electrical self-stimulation (SS) behavior. The present set of experiments investigated the role of opioid receptors within DA-innervated brain regions (nucleus accumbens and ventral tegmental area) in the ventral pallidum self-stimulation (VP-SS). Forty-one rats used in this study were implanted with a monopolar moveable stimulating electrode in the VP. A rate-frequency curve-shift method was applied to determine the reward (threshold) and motor functions (asymptotic rate) of self stimulation elicited from the VP. One group received systemic treatment of graded doses (vehicle; 1.25; 2.50 mg/kg) of morphine injected IP, 60 min before behavioural testing. The results showed a tendency for increased threshold of VP-SS and of the asymptotic rate of responding. Three additional groups were implanted with guide cannulae in the nucleus accumbens (NAC), the ventral tegmental area (VTA) or dorsally to the VTA and received microinjections of morphine (vehicle: 1.25; 2.50; 5.0; 10.0 microg/0.5 microl per side). Central injections of morphine higher than 1.25 microg/side into the VTA were associated with a significant reduction in VP-SS thresholds, indicating a potentiative effect on reward. Microinjections of morphine either into the NAC or into the dorsal tegmentum did not produce significant alterations on thresholds or responding of VP-SS. In order to investigate the extent to which the VTA-NAC dopamine projection was involved in the SS behavior elicited from the ventral pallidum, we tested SS in animals that suffered NAC 6-hydroxydopamine (6-OHDA) lesions. Rats suffering NAC dopamine depletion along with their corresponding controls showed similar levels of thresholds and responding to the ones exhibited prior to the lesion, revealing that NAC dopamine is not necessary to maintain VP-SS. The results suggest that stimulation of opioid receptor in the VTA increases the rewarding efficacy of VP-SS. This effect might be due to the modulation of VTA-DA neurons projecting to the VP rather than to the NAC.

Animals↗

PubMed1994

Streptozotocin-induced diabetes produces a naltrexone-reversible lowering of self-stimulation threshold.

Stimulation frequency thresholds for lateral hypothalamic self-stimulation were monitored for 3 weeks following the induction of diabetes with streptozotocin (STZ). In each of the 3 weeks following STZ treatment, thresholds of diabetic rats were significantly lower than their pre-STZ baseline while thresholds of control animals did not change. Naltrexone (5.0 mg/kg, s.c.) increased thresholds of diabetic rats while having no effect on thresholds of control rats. These results suggest that STZ-induced diabetes is associated with an opioid-mediated lowering of self-stimulation threshold. The possible relationship between this finding and similar findings obtained in food-restricted animals is discussed.

Animals↗

PubMedDate not supplied

Hypothalamic self-stimulation in cats exposed to a hyperbaric environment.

We measured changes in the frequency of hypothalamic self-stimulation in cats during their stays in a normal-oxygen nitrogen-oxygen environment under a pressure of 6 kg/cm2. A 200-300% increase in the frequency of self-stimulation was observed during the initial exposure. A depression of the reaction with a subsequent normalization by the third day took place after decompression. The second exposure led to an adaptation of the organisms to the effect of the elevated partial pressure of nitrogen. It is suggested that the changes in the self-stimulation reaction are connected with the "narcotic" effect of nitrogen under elevated pressures.

Air Pressure↗

PubMedDate not supplied

Self-stimulation and local injections of 6-hydroxydopamine into the rat brain: enhanced behavioral depressive effects of alpha-methylparatyrosine.

The effects of intracerebral injections of 6-OHDA on self-stimulation were examined. Small amounts of 6-OHDA were injected either in the area ventralis tegmenti (AVT) or laterally in the pedonculus cerebellaris superior (PCS), then all rats were implanted in the AVT. In spite of marked depletion of brain catecholamines, self-stimulation learning was not altered by PCS 6-OHDA injections, whereas, AVT 6-OHDA injections produced a small perturbance. The administration of low doses of AMPT which had no observable effect in control rats, produced a severe depression of self-stimulation rates in 6-OHDA pretreated rats. The depressive effect of AMPT is always more important in rats injected with 6-OHDA in the AVT than those injected at the level of PCS. The respective role of noradrenergic and dopaminergic neurons in AVT self-stimulation are discussed.

Animals↗

PubMed1984

Effects of chronic haloperidol and chlordiazepoxide treatment on lateral hypothalamic self-stimulation behavior in rats.

The effects of chronic administration of haloperidol and chlordiazepoxide for 14 days on self-stimulation behavior were investigated in rats with electrodes chronically implanted in the lateral hypothalamus. Haloperidol produced a prominent decrease in self-stimulation behavior during chronic treatment, followed by a significant increase in the lever-pressing rate during a 2 week withdrawal period, with a return to the control level about 5 weeks after drug withdrawal. Chlordiazepoxide produced a significant increase in self-stimulation behavior during chronic treatment. However, the lever-pressing rate was not significantly different from the control level during a 3 week observation period following drug withdrawal. These results indicate an increase in the sensitivity of central dopaminergic receptors following chronic haloperidol treatment, but not following chronic chlordiazepoxide treatment.

Animals↗

PubMed2006

Muscimol inactivation of the septo-preoptic complex affects medial forebrain bundle self-stimulation only when directed at the complex's ventrolateral components.

Elements of the septo-preoptic basal forebrain complex, particularly the lateral and medial septum, the diagonal band of Broca, and the magnocellular preoptic area, have been linked to medial forebrain bundle (MFB) self-stimulation. This study examines the roles of these areas in MFB self-stimulation by temporarily inactivating them with 25 and 50ng doses of the GABA(A) receptor agonist muscimol. Changes in performance capacity and stimulation reward effectiveness were evaluated with the rate-frequency curve shift paradigm. When infused into the lateral and medial septum and the vertical limb of the diagonal band of Broca, both doses of muscimol were as ineffective as saline in altering either the rats' maximum rate of response for stimulation or the frequency required to maintain half-maximal response rate (required frequency). However, when infused into the horizontal limb of the diagonal band of Broca or the magnocellular preoptic area, muscimol substantially decreased maximal response rate and modestly increased required frequency. Changes in maximum rate were dose-dependent, but changes in required frequency were not. Muscimol infusions contralateral to the stimulated hemisphere were as effective as ipsilateral infusions; bilateral infusions tended to so suppress responding that resulting rate-frequency curves were often invalid. These results suggest a role in MFB self-stimulation for only the ventrolateral components of the septo-preoptic complex, and support past observations of considerable bilaterality in the neural systems that support self-stimulation.

Animals↗

PubMed1989

Inverse relationship between intensity of vaginal self-stimulation-produced analgesia and level of chronic intake of a dietary source of capsaicin.

Women who chronically ingest a diet rich in capsaicin, the pungent ingredient in hot chili peppers, showed a significantly lower magnitude of analgesia in response to vaginal self-stimulation than women with relatively low or medium levels of ingestion. Vaginal self-stimulation-produced analgesia was quantified by measuring (on the hand) pain detection thresholds, pain tolerance thresholds and tactile thresholds. Whereas vaginal self-stimulation produced a 32.6-43.8% increase in pain detection and pain tolerance thresholds in the low chili diet group, it produced only a 2.3-7.3% increase in these measures in the high chili diet group. The medium chili diet group showed an intermediate effect on the pain thresholds. Tactile thresholds were not increased by the vaginal self-stimulation. Baseline (no stimulation) pain thresholds did not differ significantly among the three groups. These findings are consistent with earlier studies in laboratory rats, in which capsaicin administered neonatally abolished vaginal stimulation-produced analgesia, but did not affect baseline pain thresholds to mechanostimulation.

Adult↗

PubMed1984

Self-stimulation in 7- and 10-day-old rats.

Recently, it has been shown that the infant rat exhibits learned behaviors characteristic of the adult. With a modified self-stimulation paradigm, this study explored whether 7- and 10-day-old rat pups could learn a discriminated operant to obtain direct electrical stimulation in neural sites that support self-stimulation in adults. By nudging one of two response manipulanda, at two ages (7 and 10 days) and temperatures (22 and 35 degrees C), pups self-stimulated with electrodes implanted in a variety of forebrain sites, including the prefrontal cortex, bed nucleus of the stria terminalis, medial nucleus of the amygdala, and the medial forebrain bundle. The only temperature-sensitive site might be the nucleus accumbens which was positive only at the higher temperature in 10-day-olds. These results indicate that several forebrain sites demonstrate rewarding properties of stimulation in the preweanling rat pup.

Aging↗

PubMed1985

Suppression of self-stimulation of the medial prefrontal cortex after local micro-injection of kainic acid in the rat.

The question of whether neurons versus fibers of passage in the medial prefrontal cortex (MPC) are essential in maintaining self-stimulation of this same area of the brain was examined. Rats were prepared with electrode-guide cannulae implanted stereotaxically to rest within MPC. A micro-injection of (KA), 10 nmol/1.0 microliter, into the right MPC produced a clear degeneration of neuronal cell bodies characterized by picnocytosis and glial invasion of the tissue surrounding the tip of the electrode. These histopathological changes were correlated with a permanent abolition of self-stimulation of the right MPC. In contrast, self-stimulation of the contralateral side of the MPC, micro-injected with 0.9% NaCl vehicle as a control, was unaffected. These results suggest that neurons of the MPC are part of the neural substrate underlying self-stimulation behavior in this cortical area of the rat.

Animals↗

PubMed1985

Self-stimulation of the lateral hypothalamus and ventrolateral tegmentum: excitability characteristics of the directly stimulated substrates.

Recovery from refractoriness in the neural substrate for self-stimulation of the ventrolateral tegmentum (VLT) was estimated using psychophysical techniques, and compared to recovery in the substrate for self-stimulation of the lateral hypothalamus (LH). A computer-controlled testing setup was developed to minimize experimenter error and testing time. In order to assess the performance of this setup, refractory period estimates obtained in the newly designed, computer-controlled equipment were compared to those obtained in the hand-operated equipment used in previous experiments of this type. No meaningful differences were found. Thus, the more convenient computer-controlled setup was used to collect refractory period estimates from the VLT and LH. A comparison of these values revealed differences in the slopes of the recovery curves, and in the C-T intervals bracketing their rising portions. The VLT curves rose more gradually, and both began to rise and levelled off at longer C-T intervals than the LH curves. One explanation of these results is that the distribution of excitability in the LH substrate is shifted towards higher values than the VLT distribution. The overlapping portions of the recovery curves could reflect the contribution of a common bundle of reward-related fibers.

Animals↗

PubMed1979

Intracranial self-stimulation in relation to the ascending noradrenergic fiber systems of the pontine tegmentum and caudal midbrain: a moveable electrode mapping study.

Chronically implanted moveable electrodes were used to map the pontine tegmentum and caudal midbrain for intracranial self-stimulation in relation to the ascending noradrenergic systems as revealed by fluorescence histochemistry. In no area tested was there a consistent correlation between the quality or the presence of self-stimulation and the degree of noradrenergic fiber density or cellular aggregation. Of particular importance was the failure to obtain self-stimulation from the locus coeruleus, despite repeated testing and extensive attempts at behavioral shaping. Those areas supporting self-stimulation included the dorsal raphe nucleus, the superior cerebellar peduncle and the mesencephalic and motor nuclei of the trigeminal nerve. These data appear to rule out activation of the ascending noradrenergic systems as an explanation of the rewarding effects of stimulation in these areas. A gustatory-visceral fiber system is suggested as an alternative possible substrate.

Adrenergic Fibers↗

PubMed1978

Identification of a subregion within rat neostriatum for the dopaminergic modulation of lateral hypothalamic self-stimulation.

Experiments were conducted to test the hypothesis that the involvement of neostriatal dopaminergic transmission in lateral hypothalamic self-stimulation might be specific to a striatal subregion. Crystalline application of dopamine or D-amphetamine increased self-stimulation rate only when made to ventral anterior striatum (VAS); more dorsal or posterior applications were ineffective. A comparison of dose-response functions for dopamine using solution injections in VAS and posterior striatum (PS) confirmed that only VAS was responsive. Injections or applications of 6-hydroxydopamine suppressed responding only when made into VAS. Haloperidol injections decreased responding only for VAS and not PS injection sites. Applications or injections of scopolamine often increased responding when made into VAS, but this effect was unreliable. Applications or injections of scopolamine to more posterior sites consistently suppressed responding. It was concluded that dopaminergic transmission in VAS, alone among the striatal sites tested, is facilitatory on hypothalamic self-stimulation. The effects of drug applications to nucleus accumbens were generally similar to VAS, and it was suggested that these areas may be functionally similar. An examination of the known afferents to VAS indicated that this area of neostriatum, like n. accumbens, may be influenced by activity in limbic structures. This anatomy may help provide an understanding of how neostriatum, traditionally considered to have a motor function, might be involved in central reward processes.

Animals↗