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R N Joosten

Publications and source records attributed to R N Joosten.

7 recordsLinked to original sources
PubMed2001

Place and response learning of rats in a Morris water maze: differential effects of fimbria fornix and medial prefrontal cortex lesions.

The question examined in this study is concerned with a possible functional dissociation between the hippocampal formation and the prefrontal cortex in spatial navigation. Wistar rats with hippocampal damage (inflicted by a bilateral lesion of the fimbria fornix), rats with damage to the medial prefrontal cortex, and control-operated rats were examined for their performance in either one of two different spatial tasks in a Morris water maze, a place learning task (requiring a locale system), or a response learning task (requiring a taxon system). Performance of the classical place learning (allocentric) task was found to be impaired in rats with lesions of the fimbria fornix, but not in rats with damage of the medial prefrontal cortex, while the opposite effect was found in the response learning (egocentric) task. These findings are indicative of a double functional dissociation of these two brain regions with respect to the two different forms of spatial navigation. When the place learning task was modified by relocating the platform, the impairment in animals with fimbria fornix lesions was even more pronounced than before, while the performance of animals with medial prefrontal cortex lesions was similar to that of their controls. When the task was again modified by changing the hidden platform for a clearly visible one (visual cue task), the animals with fimbria fornix lesions had, at least initially, shorter latencies than their controls. By contrast, in the animals with medial prefrontal cortex damage this change led to a slight increase in escape latency.

Animals↗
PubMed2001

Dopamine and noradrenaline efflux in the rat prefrontal cortex after classical aversive conditioning to an auditory cue.

We used bilateral microdialysis in the medial prefrontal cortex (PFC) of awake, freely moving rats to study aversive conditioning to an auditory cue in the controlled environment of the Skinner box. The presentation of the explicit conditioned stimuli (CS), previously associated with foot shocks, caused increased dopamine (DA) and noradrenaline (NA) efflux. This conditioned response was dependent on the immediate pairing of the two stimuli; in the pseudoconditioned group that received an equal number of both stimuli, but in an unpaired fashion, no conditioned increases in efflux were observed.

Acoustic Stimulation↗
PubMed1996

Differential effects of learning and recall of a spatial task on phosphoinositide hydrolysis induced by the metabotropic glutamate receptor agonist 1S,3R-ACPD (1S,3R-1-amino-cyclopentane-1,3-discarboxylic acid) in the hippocampus and the prefrontal cortex of rats.

Phosphoinositide (PI) hydrolysis, stimulated by 1S,3R-1-amino-cyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD), an agonist of metabotropic glutamate receptors (mGluRs), was measured in hippocampal and prefrontal cortical slices obtained from rats which had been trained for 8 days in a Morris water maze and had learned an allocentric spatial task. Brain slices were pre-labeled with myo-3H-inositol and 1S,3R-ACPD (100 microM) stimulation was assessed by measuring the accumulation of [3H]inositol phosphates ([3H]IPs) in the presence of Li+. Measurements conducted 24 h following the last training session revealed no differences in 1S,3R-ACPD-stimulated formation of [3H]IPs, either in the hippocampus or in the prefrontal cortex. However, a diminished response to mGluRs stimulation was detected in the hippocampus of animals re-trained after an 11-day interval. The decrease was not evident in the prefrontal cortex. These data indicate a differential involvement of the hippocampus and the prefrontal cortex in the processing of spatial information and correspond to the functional differences attributed to these areas.

Animals↗
PubMed1996

Spatial learning and memory in calpastatin-deficient rats.

The present experiments were concerned with the examination of the hypothesis that a deficiency in calpastatin, the endogenous inhibitor of calpain, enhances learning and memory performance. In the first experiment we used rats with an altered calpain/calpastatin balance (Milan hypertensive strain, MHS, low calpastatin) to investigate the learning and memory of a spatial task in the Morris water maze in comparison with control rats with a normal calpain/calpastatin balance (Milan normotensive strain, MNS). Since the two strains also differ in blood pressure, a third strain of rats was included to assess the role of hypertension (spontaneously hypertensive rats, SHR). Although the acquisition rate of the spatial task was better in the low-calpastatin MHS rats than in their normal-calpastatin MNS controls, their performance was similar to that of the SHR rats, thus thwarting the conclusion that differences were due to the low level of calpastatin. The availability of another mutant strain, low-calpastatin level and normotensive (MH.NE), allowed a further examination of the hypothesis. In the second experiment rats of the MH.NE strain acquired the spatial task as well as their normotensive controls, but their memory retrieval was clearly less than that of their normal-calpastatin controls. This deficiency was not due to impaired visual function or a slower swimming speed. The conclusion is that an inbalanced calpain/calpastatin ratio, although favoring calpain activity, is disadvantageous for remembering a spatial task. This disadvantage is clearly overruled when this inbalance is accompanied by hypertension.

Animals↗
PubMed1994

Effects of local application of dopaminergic drugs into the dorsal part of the medial prefrontal cortex of rats in a delayed matching to position task: comparison with local cholinergic blockade.

Lesions of the medial prefrontal cortex (mPFC) disrupt performance in a variety of delay tasks, which suggests that the mPFC supports short-term memory processes. The putative involvement of the dopaminergic innervation of the mPFC in these mnemonic processes was investigated by evaluating the effects of local infusions of dopaminergic drugs into the mPFC of rats in an operant delayed-matching-to-position (DMTP) task. Trained animals were provided with bilateral guide cannulae aimed at the dorsal part of the mPFC. Two separate groups of rats were tested after microinfusion of several doses of either the dopamine agonist apomorphine (APO) or the dopamine antagonist cis-flupenthixol (FLU). In addition, all animals were tested after infusion of several doses of the muscarinic antagonist scopolamine (SCO). Animals were tested 0 and 135 min after each infusion. At the 0 min interval, neither APO nor FLU affected accuracy of DMTP performance, while both drugs dose-dependently increased response latencies and decreased nosepoke frequencies. At the 135 min interval, APO had almost no effect, whereas the effects of FLU were very prominent. A number of animals no longer responded after infusion of the highest doses of FLU and those that did showed a delay-independent decrease in response accuracy. In contrast, SCO infusions into the mPFC induced a dose- and delay-dependent deterioration of DMTP performance. Taken together, these results support a direct involvement of the rat mPFC in short-term memory processes, although they implicate cholinergic rather than dopaminergic mechanisms in this function.

Animals↗
PubMed1994

SDN-POA volume, sexual behavior, and partner preference of male rats affected by perinatal treatment with ATD.

The present study investigated 1) the importance of the aromatization process during the perinatal period for the development of the sexually dimorphic nucleus in the preoptic area of the hypothalamus (SDN-POA) of male rats, and 2) the relationship between SDN-POA volume and parameters of masculinization in male rats that were treated perinatally with the aromatase-inhibitor ATD. Males were treated with ATD either prenatally or pre- and neonatally, or with the vehicle. Masculine sexual behavior and partner preference were investigated in adulthood. Thereafter, animals were sacrificed and SDN-POA volume was measured. The SDN-POA volume was reduced in both the prenatally and the pre- and neonatally treated group, with a larger reduction in the latter than in the former group. Combined pre- and neonatal ATD treatment resulted in reduced frequency of mounts, intromissions, and ejaculations, as well as a reduced preference for a female over a male. The SDN-POA size was significantly and positively correlated with frequency of masculine sexual behavior, as well as preference for a female over a male.

Androstatrienes↗