Biomedical subjects

G Wolterink

Publications and source records attributed to G Wolterink.

At least 19 recordsLinked to original sources

PubMed1998

Emotional and footshock stimuli induce differential long-lasting behavioural effects in rats; involvement of opioids.

Rats were exposed to either a footshock stimulus (FS) or emotional stimulus (ES, forced perception of another rat receiving footshocks) during a daily 10-min session for 5 consecutive days. The consequences of FS and ES on their behavioural responsiveness were assessed at different post-stress intervals using a small open-field. FS induced a decrease in ambulation, rearing and sniffing and an increased immobility in the small open field. These effects were present in rats tested immediately after the last session and remained present for at least 15 days. In contrast, ES induced a transient decrease in ambulation and rearing immediately after the last session, but in the period from half an hour until at least 15 days after the stimulus experience, an increase in ambulation, rearing and sniffing was observed. Exposure to one footshock per session for 5 consecutive days or to 10 footshocks in a single session also resulted in a long-lasting reduction in ambulation and sniffing and an increase in immobility. The former regime did not influence the behavioural response of ES rats, but the latter resulted in an increase in ambulation, rearing and sniffing in ES rats. Naloxone (1 mg/kg s.c.) pretreatment antagonized the increased behavioural activity of the ES rats whereas the activity of control and FS animals was not affected, suggesting an involvement of endogenous opioid systems in the behavioural responses observed in ES rats. It is suggested that the behavioural responses of the ES and FS animals are regulated by different mechanisms.

Animals↗

PubMed1997

A homeodomain gene Ptx3 has highly restricted brain expression in mesencephalic dopaminergic neurons.

The mesencephalic dopaminergic (mesDA) system regulates behavior and movement control and has been implicated in psychiatric and affective disorders. We have identified a bicoid-related homeobox gene, Ptx3, a member of the Ptx-subfamily, that is uniquely expressed in these neurons. Its expression starting at E11.5 in the developing mouse midbrain correlates with the appearance of mesDA neurons. The number of Ptx3-expressing neurons is reduced in Parkinson patients, and these neurons are absent from 6-hydroxydopamine-lesioned rats, an animal model for this disease. Thus, Ptx3 is a unique transcription factor marking the mesDA neurons at the exclusion of other dopaminergic neurons, and it may be involved in developmental determination of this neuronal lineage.

Amino Acid Sequence↗

PubMed1996

Modifications in glutamatergic transmission after dopamine depletion of the nucleus accumbens. A combined in vivo/in vitro electrophysiological study in the rat.

The interaction between the glutamatergic and dopaminergic input in the nucleus accumbens was examined by studying the effects of dopamine depletion of the nucleus accumbens on the local field potentials, and the L-glutamate elicited responses of the nucleus accumbens in anaesthetized rats in vivo. A characteristic field potential in the nucleus accumbens is evoked by electrical stimulation of the fornix/fimbria fibres, with a monosynaptic positive peak at 10 ms (P10). Rats were unilaterally injected with 6-hydroxydopamine in the nucleus accumbens. The contralateral accumbens was sham lesioned. The rats were divided into short-term and long-term survival groups of one to two weeks and 24 weeks, respectively. In the short-term group, a striking increase (up to three times) of the amplitude of the P10 components, at the site of the lesion, compared with the sham lesioned contralateral accumbens and untreated rats, was found. The long-term group could still display a slight increase although on average this was not significantly different from controls. In the short-term group, at the centre of the lesion, the paired-pulse facilitation ratio was significantly smaller than at the more ventral, less denervated, border of the accumbens. These differences were no longer visible in the long-term group. Single-unit activity of the accumbens, elicited by the iontophoretical application of L-glutamate showed, in controls, a maximal firing frequency ranging from 5 to 40 Hz (mean 25 Hz), whereas in the short-term group more than 50% of the accumbens neurons fired with higher frequencies, reaching up to 90 Hz (mean 55 Hz). In the long-term group the firing frequency varied from 5 to 60 Hz (mean 41 Hz). No changes in threshold ejection glutamate current were found for both lesioned groups. In control rats the L-glutamate elicited responses of six cells tested could be suppressed by dopamine whereas in lesioned rats three of the six cells tested were unresponsive to dopamine. Intracellular recordings of accumbens cells in slices in 6-hydroxydopamine and sham lesioned rats, showed no significant changes in the intrinsic membrane properties, e.g. resting membrane potential, input resistance, spike threshold, action potential amplitude or duration. We conclude that dopamine denervation leads to an increase of excitability of the principal accumbens neurons. This is reflected by the increase of the firing frequency of these cells and of the amplitude of the evoked field potentials. The former is more likely of postsynaptic origin whereas the latter may also have a presynaptic contribution. These effects cannot be attributed to changes in intrinsic membrane properties of the cells.

Adrenergic Agents↗

PubMed1995

Prolyl-leucyl-glycinamide, thyrotropin-releasing hormone and beta-endorphin-(10-16), like antidepressants, antagonize melatonin-induced behavioural changes in rats.

beta-Endorphin-(10-16), as well as a variety of antidepressants, has been reported to block the behavioural changes induced by injecting melatonin into the nucleus accumbens. In the present study the influence of subcutaneously administered prolyl-leucyl-glycinamide (PLG) and thyrotropin-releasing hormone (TRH) on the behavioural changes induced by melatonin administration in the nucleus accumbens were investigated and compared with that of beta-endorphin-(10-16). PLG and TRH were found to be as effective as beta-endorphin-(10-16) in counteracting the melatonin-induced behavioural changes. The data suggest that these peptides may serve as a starting point for the development of a new class of antidepressants.

Animals↗

PubMed1995

Behavioral studies on the putative gamma-type endorphin receptor using different antibodies.

To investigate the significance of endogenous, neuroleptic-like gamma-type endorphins and their putative receptors, polyclonal and monoclonal antibodies against gamma-type endorphins, which may bio-inactivate the ligands for the receptors, and monoclonal anti-idiotype antibodies, which presumably bind to the receptors, were injected into the nucleus accumbens of the rat brain. The desenkephalin-gamma-endorphin-induced antagonism of the hypomotility response elicited by challenge with apomorphine injected into the nucleus accumbens was used as test system. Both the anti-desenkephalin-gamma-endorphin antibodies and anti-idiotype antibodies blocked the action of exogenous desenkephalin-gamma-endorphin. Thus, the anti-idiotype antibodies may serve as receptor antagonists. Chronic treatment (injection into the nucleus accumbens) with the anti-idiotype antibodies induced sustained hypermotility, decreased habituation and impaired passive avoidance behavior. In such treated animals local treatment with apomorphine did not elicit hypomotility. It is suggested that gamma-type endorphins influence the setpoint for feedback regulation in dopaminergic neurons equipped with gamma-type endorphin receptor systems.

Animals↗

PubMed1995

Regulation of masculine sexual behavior: involvement of brain opioids and dopamine.

In recent years much has become known about the substrates in the brain involved in the regulation of masculine sexual behavior and the involvement of specific neurochemicals in these brain areas. In the present paper the experimental data concerning the involvement of a number of brain areas in sexual behavior are reviewed, in relation to an incentive motivational theory of sexual behavior. The review is restricted to the involvement of opioids and dopamine, of which the role in sexual motivation and behavior is best documented. Opioids in the medial preoptic area (mPOA) impair sexual performance, although the endogenous opioids systems may be quiescent in normal, sexually active rats. Dopamine in the mPOA has a facilitative role in the masculine sexual performance. The corticomedial amygdala is involved in processing of sensory information, especially olfactory stimuli, which are subsequently directed towards the mPOA. Local beta-endorphin infusion interferes with this processing. Endogenous opioids in the ventral tegmental area activate the mesoaccumbens dopamine system and stimulate the sexual motivation. Increased dopamine transmission in the nucleus accumbens correlates with increased sexual motivation and vice versa. The basolateral amygdala plays an essential role in the association of environmental stimuli with reward and therefore in the expression of conditioned sexual motivation. Finally, the reviewed data are integrated and a comprehensive view on the relations between various neural substrates is composed.

Animals↗

PubMed1995

The behavioral effects of habituation and challenge with apomorphine after 6-OHDA lesioning of the nucleus accumbens in rats.

In rats the function of the dopamine system in the nucleus accumbens was tested after 6-OHDA lesioning of this brain area and after ORG 2766 induced facilitation of recovery in 6-OHDA lesioned animals. A low dose of systemically administered apomorphine (50 micrograms/kg) decreased motility when sham operated rats were placed in a novel environment. A similar decrease was found in saline treated rats tested for the second time 1 day later. In thus habituated animals, the low dose of apomorphine did not induce hypomotility. Thus habituation and hypomotility after a low dose of apomorphine may be due to a similar mechanism, viz. diminished dopamine release. A higher dose of apomorphine (125 micrograms/kg) increased motility, but only when the rats were habituated to the test environment. Animals with a bilateral 6-OHDA lesion of the nucleus accumbens showed hypomotility when tested for the first time 1 week after the lesion. The low and the higher dose of apomorphine elicited hypermotility in both nonhabituated and habituated lesioned rats. Their activity was higher than in sham operated animals, suggesting supersensitivity of postsynaptically located dopamine receptor systems in lesioned rats. Treatment with the ACTH(4-9) analog ORG 2766 during the first week after induction of the lesion counteracted the hypomotility of the lesioned rats. Furthermore ORG 2766 enhanced the supersensitivity as revealed by challenge with the low dose of apomorphine.

Adrenocorticotropic Hormone↗

PubMed1994

Lack of evidence for an involvement of nucleus accumbens dopamine D1 receptors in the initiation of heroin self-administration in the rat.

The involvement of dopamine D1 receptor systems in the reinforcing properties of opiate reward was studied by examining the effect of the dopamine D1 antagonist SCH23390 on the initiation of heroin self-administration in rats. The D1 antagonist was administered daily systemically or locally in the nucleus accumbens (NAC), after which the animals were allowed to self-administer heroin (IV) in a 3-h session for 5 consecutive days. Systemic treatment with SCH23390 (0.17 and 0.5 mg.kg-1) significantly decreased heroin intake during initiation of heroin self-administration, while a dose of 0.06 mg.kg-1 was not effective. Local administration of SCH23390 (0.5 and 2.5 micrograms/site) in the NAC did not affect heroin intake. Both systemic and intra-accumbal administration of SCH23390 dose dependently decreased motor behavior measured in a small open field. The attenuation of heroin intake during initiation of heroin self-administration by blockade of dopamine D1 receptor systems may be due to a decrease in the reinforcing effects of heroin or more likely to a reduction in non-reinforcement-related behavior. The dopamine D1 receptors present in the NAC are probably not involved in opiate reward.

Animals↗

PubMed1994

Subchronic treatment with the neuroleptic-like peptide desenkephalin-gamma-endorphin may decrease dopaminergic neurotransmission in the nucleus accumbens of rats.

In rats, subchronic administration of desenkephalin-gamma-endorphin (DE gamma E) into the nucleus accumbens or subcutaneously for 10 days resulted in hypoactivity. Intra-accumbens administration caused a significant reduction in the nucleus accumbens tissue levels of the dopamine (DA) metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). Systemic administration of DE gamma E decreased DOPAC and 5-hydroxyindoleacetic acid (5-HIAA) levels in nucleus accumbens tissue. Subchronic subcutaneous DE gamma E treatment reduced the basal release of [3H]DA from rat nucleus accumbens slices in vitro and the basal release of endogenous DA and DOPAC in vivo as assessed with on-line dialysis in the nucleus accumbens of freely moving rats. The DA agonist N,N-dipropyl-7-hydroxy-2-aminotetralin (DP-7-ATN) was equally effective in inhibiting [3H]DA release elicited by electrical stimulation from slices of subchronically DE gamma E and placebo treated rats. Administration of a small dose of apomorphine caused similar reductions of the in vivo release of DA and DOPAC in both placebo and DE gamma E treated rats. These results indicate that subchronic DE gamma E treatment may decrease dopaminergic neurotransmission in the nucleus accumbens. This effect is probably not due to alterations in the sensitivity of presynaptically located DA autoreceptors mediating DA release in vitro and in vivo.

Animals↗

PubMed1993

Cholecystokinin-dopamine interactions within the nucleus accumbens in the control over behaviour by conditioned reinforcement.

Cholecystokinin (CCK) is colocalised with dopamine in the postero-medial nucleus accumbens (NAS). We have utilised an acquisition of a new response procedure to investigate the interaction between CCK and dopamine in the control over behaviour by conditioned reinforcers. A conditioned reinforcer (CR) may be defined as an initially neutral stimulus which gains control over behaviour through selective association with a primary reinforcer. Here, rats learned to associate a light/noise compound stimulus with the imminent availability of 10% sucrose reinforcement. Later, in the absence of sucrose, responding on one of two novel levers (the CR lever) was acquired and maintained by contingent presentation of the CR alone, while responding on the second lever had no programmed consequences. In Expt. 1, infusion of 10 micrograms D-amphetamine within the postero-medial NAS enhanced responding selectively on the CR lever. Infusion of sulphated CCK octapeptide (CCK: 1 or 10 ng) alone within the same area had no effect on response rate. However, infusion of CCK immediately prior to D-amphetamine caused a dose-dependent potentiation of the impact of D-amphetamine upon rates of response on the CR lever. In Expt. 2, infusion of D-amphetamine (10 micrograms) within the postero-medial NAS again enhanced responding selectively upon the CR lever. Intra-accumbens infusion of CCK (10 ng), or s.c. administration of the CCKA receptor antagonist devazepide had no effect upon response rates. However, CCK again potentiated the D-amphetamine-induced increase in rates of response, and this potentiation was blocked by pretreatment with devazepide. These results are discussed in terms of the co-modulation by CCK and dopamine of the processing of reward-related stimuli within the NAS.

Afferent Pathways↗

PubMed1993

Relative roles of ventral striatal D1 and D2 dopamine receptors in responding with conditioned reinforcement.

Several experiments investigated the involvement of D1 and D2 dopamine receptors in the ventral striatum in the control over behaviour by a conditioned reinforcer using an acquisition of new response procedure. Intra-accumbens infusion of either the D1 receptor antagonist, SCH 23390, or the D2 receptor antagonist, raclopride, completely blocked the potentiative effects of intra-accumbens d-amphetamine on responding with conditioned reinforcement and reduced responding to control levels. SCH 23390 was more potent than raclopride. At higher doses in the absence of d-amphetamine, both antagonists also blocked the preference for responding on the lever producing the conditioned reinforcer. Intra-accumbens infusions of either the D1 receptor agonist, SKF 38393, or the D2/3 receptor agonist, LY 171555 (quinpirole), selectively potentiated responding on the lever producing the conditioned reinforcer. Various combined infusions of the D1 and D2 agonists in specific low doses had additive, but not synergistic, effects on responding with conditioned reinforcement. None of the drugs affected the drinking of water in deprived subjects when infused intra-accumbens. These results suggest that both D1 and D2 receptors in the nucleus accumbens are involved in mediating the effects of dopamine in potentiating the control over behaviour by conditioned reinforcers.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed1991

Structural modifications of the ACTH-(4-9) analog ORG 2766 yields peptides with high biological activity.

The behavioral effects of two peptides (HOE 427) and ORG 31433) related to the ACTH-(4-9) analog ORG 2766 were investigated in Wistar rats in a number of tests in which Org 2766 is active. Subcutaneous administration of HOE 427 in a dose of 0.5 ng/kg or ORG 31433 in doses of 0.5-5.0 ng/kg facilitated passive avoidance behavior whereas these peptides attenuated the avoidance response in doses of 25 ng/kg and 250 ng/kg respectively. ORG 31433 (0.1 - 1.0 microgram/kg) decreased motor activity of group housed rats tested under low light conditions. Furthermore subcutaneous (1.0- 10.0 ng/kg) or oral (10 microgram/kg) administration of ORG 31433 accelerated functional recovery from 6-hydroxydopamine (6-OHDA)-induced lesions in the nucleus accumbens which cause motor hypoactivity. The experiments show that as compared to ORG 2766 the peptides HOE 427 and ORG 31433 induce qualitatively similar responses but are approximately 10 to 100 times more potent. These data may imply that substitution of the C-terminal COOH group of ORG 2766 yields neuropeptides with increased potency.

Administration, Oral↗

PubMed1991

Neuropeptides related to [Arg8]vasopressin facilitates social recognition in rats.

The decrease of social investigations of adult rats during a second encounter session with the same juvenile was used as an index of social recognition or memory. Social recognition was present when the interexposure interval was 15 or 30 min, but not when this interval lasted 60 or 120 min. Animals treated with desglycinamide[Arg8]vasopressin (DGAVP) (6.0 micrograms.kg-1, SC) or [pGlu4,Cyt6]AVP-(4-8) (AVP-(4-8] (1.0 microgram.kg-1, SC), immediately after the first encounter, recognized the same juveniles still after 120 min, suggesting a facilitatory effect of these peptides on social recognition and that this effect of vasopressin is dissociated from the classical endocrine effects of this hormone. The decrease of social investigating behavior, in both placebo- and DGAVP-treated rats, was completely due to a decrease in anogenital exploration, indicating that the social recognition in rats is presumably based on odor cues from the anogenital part of the body.

Animals↗

PubMed1991

Short duration of retroactive facilitation of social recognition in rats.

Adult rats spent less time investigating the same juvenile during a second dyadic encounter session. This decrease served as an index for social recognition. Social recognition was not influenced by isolating the juveniles for 7 days prior to experimentation. Retroactive facilitation of social recognition was observed when the two rats were confronted for a longer period of time on a given day by multiple testing. However, this facilitation was not observed after a 24-h interexposure interval between encounter sessions, even when different housing conditions during that time were taken into account, and animals were tested during 5 consecutive days. It is suggested that social recognition may be a form of short-term memory.

Aging↗

PubMed1991

The ACTH-(4-9) analogue ORG 2766 facilitates denervation supersensitivity after a unilateral 6-OHDA lesion of the corpus striatum in rats.

UNLABELLED: Direct bilateral 6-OHDA lesioning of the nucleus accumbens causes a temporary reduction in motility, followed by a spontaneous recovery in 3-4 weeks. The ACTH-(4-9) analogue ORG 2766 shortens this period to 1 week. The functional and the peptide-induced facilitation of recovery are accompanied by enhanced motility upon administration of the dopamine agonist apomorphine which may be related to denervation supersensitivity. The present experiments were performed to investigate the interaction between ORG 2766 and denervation supersensitivity in another dopaminergic terminal area i.e. the corpus striatum. After a unilateral 6-OHDA lesion of the right corpus striatum, contralateral rotation was observed upon administration of a high dose of apomorphine 2, 3 and 4 weeks after the lesion, indicating supersensitivity of postsynaptic dopaminergic receptor systems. Contralateral rotation upon administration of this dose of apomorphine was observed in ORG 2766 treated animals, already at 1 week after the lesion. Peptide treatment resulted in an enhanced sensitivity for apomorphine, since contralateral rotation was observed in peptide but not in placebo treated, 6-OHDA lesioned animals after a low dose of apomorphine. IN CONCLUSION: treatment with ORG 2766 facilitates the development of denervation supersensitivity and enhances sensitivity for apomorphine probably through an increased affinity of dopaminergic receptors for dopamine agonists.

Adrenocorticotropic Hormone↗

PubMed1991

Analysis of the influence of vasopressin neuropeptides on social recognition of rats.

The facilitatory effect of vasopressin neuropeptides on social recognition of adult male rats was analyzed. The decrease of social investigation behaviors during a second encounter with the same juvenile rat served as index for social recognition. Treatment with desglycinamide-(Arg8)-vasopressin (6 mg.kg-1, s.c.) extended the time that adults recognize the same juvenile from 30 min to 24 h. Structure-activity studies revealed that the effect of vasopressin neuropeptides on social recognition resides in the 5-8 part of the AVP molecule. The peptide (pGlu4,Cyt6) AVP-(4-8) was more potent than DGAVP in this behavioral paradigm. These effects bear similarities with the memory enhancing effects of vasopressin neuropeptides as found in other test procedures.

Animals↗

PubMed1990

Functional recovery after destruction of dopamine systems in the nucleus accumbens of rats. I. Behavioral and biochemical studies.

Bilateral 6-hydroxydopamine (6-OHDA) lesions in the nucleus accumbens of rats induced motor hypoactivity 7 days after the lesion. Spontaneous functional recovery of this impaired behavior occurred in 3-4 weeks. Behavioral and biochemical studies suggest that the hypoactivity is due to damage of the dopamine systems in the nucleus accumbens. The 6-OHDA lesions induced a decrease in the nucleus accumbens levels of dopamine and its metabolites of about 30% both 7 and 20 days after the lesion. The in vitro uptake of [3H]dopamine in nucleus accumbens tissue of the 6-OHDA-lesioned rats was decreased to the same extent at 7, 14 and 28 days after the lesion. Scatchard analysis of [3H]haloperidol binding studies in nucleus accumbens tissue revealed a shift from one type of binding site in tissue of sham-lesioned rats to two types of binding sites in tissue of 6-OHDA-lesioned rats 29 days after the lesion. This shift was not present in nucleus accumbens tissue 8 days after a 6-OHDA lesion. The spontaneously recovered rats showed an enhanced behavioral response upon administration of the dopamine agonist apomorphine. The present data suggest that the spontaneous functional recovery of impaired motor activity is caused by the development of supersensitivity of the dopamine receptor systems in the nucleus accumbens. This supersensitivity may be the result of increased affinity of one type of binding site or an increased number of functional binding sites.

Animals↗

PubMed1990

Functional recovery after destruction of dopamine systems in the nucleus accumbens of rats. II. Facilitation by the ACTH-(4-9) analog ORG 2766.

Functional recovery from motor hypoactivity of rats with 6-OHDA lesions in the nucleus accumbens is accelerated by intra-accumbal or subcutaneous treatment with the ACTH-(4-9) analog ORG 2766. The spontaneous recovery period of 3 weeks is shortened to 7 days by daily treatment with this peptide during the first 6 days after the lesion. The 6-OHDA lesion induced a decrease of about 30-40% in the levels of dopamine, HVA and DOPAC as well as in the uptake of [3H]dopamine in nucleus accumbens tissue in vitro. Treatment with ORG 2766 during the first 6 days following the lesion did not affect the lesion-induced changes in these biochemical parameters. Binding studies with [3H]haloperidol in nucleus accumbens tissue of placebo or ORG 2766-treated sham-lesioned rats revealed a linear Scatchard plot 7 days after the sham lesion. In tissue of placebo-treated 6-OHDA lesioned animals a similar linear Scatchard plot was found but in tissue of ORG 2766-treated 6-OHDA-lesioned rats the Scatchard plot was curvilinear in shape indicating two types of binding sites. In the 6-OHDA-lesioned rats treated with ORG 2766 the behavioral response upon apomorphine challenge was enhanced suggesting the existence of functional supersensitivity of the DA system. Similar changes in Scatchard plots and apomorphine-induced behavioral changes have been previously reported after spontaneous recovery. The present study indicates that ORG 2766 accelerates the process of functional recovery from impaired motor behavior of rats with 6-OHDA lesions in the nucleus accumbens, which may be due to development of denervation supersensitivity.

Adrenocorticotropic Hormone↗