Haloperidol catalepsy consolidation in the rat as a model of neuromodulatory integration

Conditioned catalepsy vs. Increase in locomotor activity induced by haloperidol

Previous research has revealed a high degree of complexity of the conditioned response that appears after associating a context with the effects of the dopaminergic antagonist haloperidol. Specifically, when a drug-free test is performed in the presence of the context, conditioned catalepsy is observed. However, if the test is extended over time, the opposite effect occurs, namely, a conditioned increase in locomotor activity. In this paper, we present the results of an experiment with rats that received repeated administration of haloperidol or saline before or after exposure to the context. Next, a drug-free test was performed to evaluate catalepsy and spontaneous locomotor activity. The results revealed, on the one hand, the expected conditioned response of catalepsy for those animals that received the drug prior to context exposure during conditioning. However, for the same group, an analysis of locomotor activity for an extended period of ten minutes after registering catalepsy revealed an increase in general activity and more faster movements compared to the control groups. These results are interpreted considering the possible temporal dynamics of the conditioned response that could induce changes in dopaminergic transmission responsible for the observed changes in locomotor activity.

Long-term deep sedation using Zoletil and haloperidol for the treatment of streptococcal pneumonia in an orangutan (Pongo pygmaeus)

A 13-year-old Bornean orangutan diagnosed with life threatening Streptococcus pyogenes broncho-pneumonia was kept in a state of deep sedation for 20 days via continuous intra-venous (IV) infusion of zolazepam -tiletamine and IV haloperidol to allow consistent IV administration of ceftazidime and gatifloxacine. The use of long-term deep sedation allowed carrying out a particularly demanding treatment not generally associated with zoological patients. The treatment was ultimately successful.

Evidence that haloperidol impairs learning and motivation scores in a probabilistic task by reducing the reward expectation

Activation of midbrain dopamine neurons in response to positive prediction errors and reward predictive cues is proposed to "energize" reward seeking behaviors and approach responses to places where the reward is expected. In the present study, we tested the effect of the D2-dopamine receptor antagonist haloperidol on response latencies to enter two arms of a Y-maze with different reward probabilities. Adult male Wistar rats were trained to explore the Y-maze with sucrose pellets placed 30% of times at the end of one arm and 70% of times at the opposite arm. Therefore, the reward expectation was different among arms, and was updated in the trials when the reward was omitted. After training, rats received 0.05, 0.10, 0.15 mg/kg haloperidol, or saline 30 min before the test session. In the last, but not in the first trials, haloperidol caused a dose-dependent increase in arm choice latency and response latency. Saline, but not haloperidol, treated rats presented significantly longer response latencies for the 30% compared to the 70% reward probability arm. Haloperidol also caused a dose-dependent decrease in the number of entries in the 70% reward probability arm, increased the number of non-responses, and caused a dose-dependent increase in the number of re-entries in the 30% reward probability arm after non-rewarded trials. Control experiments suggested that haloperidol did not cause motor impairment or satiation, but rather impaired learning and motivation scores by reducing the reward expectation.

Neurochemical and behavioral features in genetic absence epilepsy and in acutely induced absence seizures

The absence epilepsy typical electroencephalographic pattern of sharp spikes and slow waves (SWDs) is considered to be due to an interaction of an initiation site in the cortex and a resonant circuit in the thalamus. The hyperpolarization-activated cyclic nucleotide-gated cationic I h pacemaker channels (HCN) play an important role in the enhanced cortical excitability. The role of thalamic HCN in SWD occurrence is less clear. Absence epilepsy in the WAG/Rij strain is accompanied by deficiency of the activity of dopaminergic system, which weakens the formation of an emotional positive state, causes depression-like symptoms, and counteracts learning and memory processes. It also enhances GABAA receptor activity in the striatum, globus pallidus, and reticular thalamic nucleus, causing a rise of SWD activity in the cortico-thalamo-cortical networks. One of the reasons for the occurrence of absences is that several genes coding of GABAA receptors are mutated. The question arises: what the role of DA receptors is. Two mechanisms that cause an infringement of the function of DA receptors in this genetic absence epilepsy model are proposed.

Differential effect of testosterone and repetitive induction on cataleptic and dorsal immobility in mice

In nature, many species under conditions of stress (e.g., predator attack, pups carried by the mother, mating) show immobility states called "immobility responses" (IRs), which are characterized by the complete absence of movement and a relative unresponsiveness. These IR states can be induced by several kinds of sensorial stimuli. Many brain neurotransmitters from diverse cerebral areas participate in the expression of IRs. Other factors are also involved in IRs, such as learning and hormones, but at present, there is not enough experimental support about these factors. Our purpose was to investigate whether the IRs are subject to sexual hormone modulation and to examine the possible relation to learning processes. We tested the effects of acute testosterone decanoate (30 mg/kg, s.c.) and repetitive induction of two IRs; cataleptic immobility (CAT) and dorsal immobility (DI). These were tested in mice of both sexes which were either gonadectomized or sham-treated. CAT and DI were measured before and then 1 and 5 h after testosterone injection. The results show a differential effect of the repetitive induction on CAT and DI. CAT was augmented with repetition, and DI was decreased. Sex differences of the effects of the acute testosterone treatment were observed. Sham and castrated male mice showed CAT potentiation; in contrast, DI was reduced albeit only in sham male mice. Sham and ovariectomized female mice were not affected by testosterone. These results support the hypothesis that there are multiple immobility systems that can be differentially modulated by brain regions associated with processes of learning.

Locomotor responses and neuron excitability in conditions of haloperidol blockade of dopamine in invertebrates and vertebrates

Levels of movement activity were used to identify two groups of rats: those with high- and low-activity levels. Blockade of dopamine receptors with haloperidol led to suppression of locomotor activity in both groups of rats; in common snails, haloperidol decreased the rate of locomotion. The excitability of spinal centers in rats decreased 5 min after single i.v. injections, with gradual recovery seen by 30 min. Chronic administration of haloperidol suppressed post-tetanic potentiation of the H response in the gastrocnemius muscle of spinal rats. Prolonged use of haloperidol induced significant hyperpolarization of the membrane potential of command neurons in common snails and increased the action potential generation threshold. Selective pharmacological exclusion of the brain dopamine system was found to lead to decreases in the excitability of defined neurons in snails and the spinal motor centers in rats, also producing impairments in locomotor responses in these animals.

Anticataleptic activity of cathinone and MDMA (Ecstasy) upon acute and subchronic administration in rat

It was recently demonstrated that acute administration of 3,4-methylenedioxymethamphet-amine (MDMA, "Ecstasy") is capable of counteracting haloperidol-induced catalepsy in rats. The present study was done with another psychostimulant, S-(-)-cathinone. In these experiments, 32 male Sprague-Dawley rats, 225 +/- 25 g, were used. They were divided into three groups. All groups received 0.5 mg/kg haloperidol in normal saline (s.c.) as a first injection. Then 30 min later each group received either isotonic phosphate-buffered saline, 1 mg/kg S-(-)-cathinone, or 2.5 mg/kg (RS)-MDMA (s.c.) as a second injection. The results of descent latency on both the horizontal bar and vertical grid showed that S-(-)-cathinone or (RS)-MDMA upon acute administration induces a strong anticataleptic activity (P < 0.0001) compared to rats treated with haloperidol plus vehicle. The effect of both drugs was later masked upon subchronic administration (days 2-7, 26-29). This is probably due to sensitization of cataleptic behavior. However, when the same groups of rats were tested on day 8 in a different task, i.e., open-field, they showed a significant difference (P < 0.05). The detailed mechanism of the observed strong anticataleptic activity of S-(-)-cathinone (which is considered a potent dopamine releaser) requires further investigation.

Changes in urinary monoamine excretion in hyperkinetic children

The pathogenetic mechanisms of hyperkinetic syndrome are not clear and need further investigation. The aim of the study was to find certain features of monoamine metabolism that are characteristic of children with hyperkinetic syndrome (HKS) with special regard to different degrees of severity (i.e. mild HKS and severe HKS ). The levels of L-dopa, dopamine, noradrenaline, adrenaline, homovanillic, vanillylmandelic and 5-hydroxyindoleacetic acids were measured in daily urine of children (7-11 years old) with mild and severe HKS using fluorimetric and chromatographic methods. Severe HKS was characterized by a significant increase of L-dopa (by 186%), dopamine (by 201%) and adrenaline (by 160%) excretion but an unchanged excretion of noradrenaline compared with those with mild HKS. The study revealed principle differences in monoamine metabolism between the mild and severe forms of HKS which may be of importance in deciding different pharmacotherapeutic approaches to use in patients with HKS of differing severity.

The differential effect of haloperidol and repetitive induction on four immobility responses in mouse and guinea pig

The modification by haloperidol and repetitive induction on four immobility responses -- tonic immobility, cataleptic immobility, immobility by clamping the neck and dorsal immobility -- were compared in mice and guinea pigs. Without drug, three out of four responses (cataleptic, neck clamp and dorsal immobility) were induced in mice; guinea pigs displayed all four responses. Haloperidol (5 mg/kg i.p.) potentiated the three responses shown by mice, but did not potentiate the four responses in guinea pigs. In both undrugged and haloperidol-treated mice, only the cataleptic immobility response was potentiated by repetition. In guinea pigs, none of the four immobility responses was affected due to repetition, haloperidol or a combination of both. These data are discussed, considering that, although these immobility responses could be mediated by the same neurotransmitters (e.g. dopamine), they are possibly expressed in a differential manner as a function of the kind of stimulus used to trigger the response, characteristics of the species and, in some immobility responses such as cataleptic immobility, as a function of their interaction with habituation or another learning-like process.