Lesions of the Edinger-Westphal nucleus in C57BL/6J mice disrupt ethanol-induced hypothermia and ethanol consumption

The Edinger-Westphal nucleus (EW) is a brain region that has recently been implicated as an important novel neural target for ethanol. Thus, the EW is the only brain region consistently showing elevated c-Fos expression following both voluntary and involuntary ethanol administration. Ethanol-induced c-Fos expression in the EW has been shown to occur in urocortin I-positive neurons. Moreover, previous reports using several genetic models have demonstrated that differences in the EW urocortin I system are correlated with ethanol-mediated behaviours such as ethanol-induced hypothermia and ethanol consumption. The aim of this study was to confirm these relationships using a more direct strategy. Thus, ethanol responses were measured following electrolytic lesions of the EW in male C57BL/6J mice. Both EW-lesioned and sham-operated animals were tested for several ethanol sensitivity measures and ethanol consumption in a two-bottle choice test. The results show that lesions of the EW significantly disrupted ethanol-induced hypothermia, while having no effect on pupillary dilation, locomotor activity or ethanol-induced sedation. In addition, EW-lesioned animals showed significantly lower ethanol preference and total ethanol dose consumed in the two-bottle choice test. EW-lesioned animals also consumed less sucrose than sham-operated animals, but did not have altered preferences for sucrose or quinine in a two-bottle choice test. These data support previously observed genetic correlations between EW urocortin I expression and both ethanol-induced hypothermia and ethanol consumption. Taken together, the findings suggest that the EW may function as a sensor for ethanol, which can influence ethanol consumption and preference.

Lesions of the Edinger-Westphal nucleus alter food and water consumption

The Edinger-Westphal nucleus (EW) produces several neuropeptides, including urocortin 1 and cocaine-amphetamine-regulated transcript, which regulate feeding, energy balance, and anxiety. Additionally, the EW projects to feeding and anxiety-regulatory brain areas. The authors tested the effect of lesions of the EW on the consumption of food, water and flavored solutions, metabolic indices, and exploratory behavior on the elevated plus maze in male C57BL/6J mice. EW lesion significantly reduced basal and deprivation-induced food and fluid consumption compared with sham and placement controls, but it did not alter behavior on the elevated plus maze. EW lesion had no effect on indices of basal metabolic activity, including plasma glucose level and body temperature. These effects suggest that the peptidergic neurons of the EW regulate food consumption.

Kernohan's notch phenomenon in chronic subdural hematoma: MRI findings

We report two cases of Kernohan's notch phenomenon secondary to chronic subdural hematoma detected by MRI. In the first case, the patient was drowsy with an oculomotor palsy and a hemiparesis ipsilateral to the chronic subdural hematoma. MRI in the post-operative period showed no abnormal signal or deformity of the crus cerebri. The neurological signs immediately resolved after trephination. In the second case, the patient was admitted with progressive decrease in their level of consciousness and ipsilateral hemiparesis with the chronic subdural hematoma. MRI on admission revealed an abnormal signal in the contralateral crus cerebri against the chronic subdural hematoma. After surgery, the mental state gradually recovered to normal with some degree of residual hemiparesis. In patients with chronic subdural hematoma, a compressive deformity of the crus cerebri, without abnormal signal on MRI, may predict a better neurological recovery in patients with Kernohan's notch phenomenon.

A test of the opponent-process theory of motivation using lesions that selectively block morphine reward

The opponent-process theory of motivation postulates that motivational stimuli activate a rewarding process that is followed by an opposed aversive process in a homeostatic control mechanism. Thus, an acute injection of morphine in nondependent animals should evoke an acute rewarding response, followed by a later aversive response. Indeed, the tegmental pedunculopontine nucleus (TPP) mediates the rewarding effects of opiates in previously morphine-naive animals, but not other unconditioned effects of opiates, or learning ability. The aversive opponent process for acute morphine reward was revealed using a place-conditioning paradigm. The conditioned place aversion induced by 16-h spontaneous morphine withdrawal from an acute morphine injection in nondependent rats was abolished by TPP lesions performed prior to drug experience. However, TPP-lesioned rats did show conditioned aversions for an environment paired with the acute administration of the opioid antagonist naloxone, which blocks endogenous opioids. The results show that blocking the rewarding effects of morphine with TPP lesions also blocked the opponent aversive effects of acute morphine withdrawal in nondependent animals. Thus, this spontaneous withdrawal aversion (the opponent process) is induced by the acute rewarding effects of morphine and not by other unconditioned effects of morphine, the pharmacological effects of morphine or endogenous opioids being displaced from opiate receptors.

Pontine tegmentum lesions increase anxiety-like behavior in rats: a comparison with anxiety produced by beta-CCE

Electrolytic lesions of the pedunculopontine tegmental nucleus (PPTg) have been previously reported to increase anxiety-like behavior in rats. The aim of the present study was to compare these behavioral changes with those produced by an anxiogenic compound, the partial inverse agonist at benzodiazepine receptors, beta-CCE. Three groups of rats, sham-lesioned treated with vehicle, sham-lesioned treated with 10 mg/kg of beta-CCE, and PPTg-lesioned rats treated with vehicle, were tested in the elevated plus-maze, the social-interaction test, and for spontaneous locomotion. Histology showed that lesions were concentrated on the caudal half of the PPTg. Measures of both the PPTg-lesioned and beta-CCE-treated rats indicated increased anxiety-like behavior in the elevated plus-maze and in the social-interaction test. Spontaneous locomotion, measured in the open- field arena, did not differ between sham controls and PPTg-lesioned rats, but was decreased in rats treated with beta-CCE. Our results confirmed that electrolytic lesions of the caudal PPTg produce increased anxiety-like behavior. This behavior is quantitatively and qualitatively similar to that produced by 10 mg/kg of beta-CCE.

Central tegmental field and sexual behavior in the male rat: Effects of neurotoxic lesions

The medial preoptic area/anterior hypothalamus (MPOA/AH) is a key structure in the control of male sexual behavior. This area has reciprocal connections with mesencephalic and brainstem structures including the central tegmental field (CTF). It has been suggested that the CTF receives somatosensory information generated in the genitals promoting activation of the MPOA/AH. In the present study we evaluated the effects of bilateral neurotoxic lesions of the CTF upon male rat sexual behavior. We also explored the effects of these lesions on sociosexual behaviors, partner preference, sexual incentive motivation and motor execution. Tests were performed before and after bilateral quinolinic acid infusions. The lesion was evaluated by quantifying neuronal nuclei (Neu-N) and by the presence of glial fibrillary acidic protein (GFAP) immunohistochemistries. A significant reduction in the percentage of animals displaying mounts, intromissions, and ejaculations was observed in the bilateral and misplaced lesion groups 1 week after the lesion. In the second week post-lesion, only animals with bilateral damage of the CTF showed a significant reduction in sexual behavior. In the third post-lesion test, the percentage of animals displaying sexual behavior returned to control levels. The frequency of pursuit and self-grooming was reduced, and genital exploration was increased after the lesion. Partner preference and sexual incentive motivation were not affected by the lesion suggesting that the CTF is not involved in the appetitive aspects of sexual behavior. Mount, intromission, and ejaculation latency were increased in animals with damage of the CTF and in animals with lesions outside this region. Motor execution was also affected in both groups, suggesting that alterations in latencies could be associated with damage not specific to the CTF.

Experimental parkinsonism in primates

Early in the 1960s the primate model of Parkinson's disease was first introduced by placing an electrolytic lesion in the midbrain. In the 1980s, a dopaminergic neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was accidentally shown to induce parkinsonism in humans, and subsequently was confirmed to reproduce an almost perfect model of parkinsonism in primates. In the late 1980s chemical manipulations of the basal ganglia were shown to induce parkinson symptoms, especially dyskinesia, and more recently, chemical lesioning of the pedunculopontine tegmental nucleus has also been shown to induce parkinsonism. We still do not have a perfect animal model of parkinsonism, however, these models have offered excellent opportunities to study the basic mechanisms in parkinsonism and the function of the basal ganglia.

The role of the dorsolateral tegmentum in the control of male sexual behavior: A reevaluation

The medial preoptic area/anterior hypothalamus (MPOA/AH) plays a key role in the control of male sexual behavior. Independently of the type, MPOA/AH lesions permanently eliminate male sexual behavior in the rat. The MPOA/AH projects among other structures to the dorsolateral tegmentum (DLT). Bilateral electrolytic lesions of the DLT or the unilateral electrolytic destruction of the MPOA/HA combined with a contralateral electrolytic lesion of the DLT eliminate male sexual behavior. In the present experiment, we evaluated if neurotoxic lesions of the DLT produce the same behavioral deficits as those observed after electrolytic lesions. This would allow us to evaluate if neurons of the DLT or the fibers passing through this area are important in the control of male sexual behavior. To this aim, sexually experience male rats were tested for socio-sexual behavior, partner preference and motor execution in order to determine if the possible behavioral changes could be attributed to alterations in sexual motivation or motor execution. One week after the bilateral DLT lesions the animals were evaluated in the same behavioral tests. The lesions were identified by glial fibrillary acidic protein (GFAP) and neuronal nuclear protein (Neu-N) immunohistochemistry. No significant consistent effects upon sexual behavior were observed in any of the groups, including the group with clear bilateral damage of the DLT. A reduction in the percentage of males displaying ejaculation in the first post-lesion test was observed for all groups injected with quinolinic acid. No effects upon partner preference or motor coordination were observed after the lesion in any of the groups. The lack of effect of DLT neurotoxic lesions upon mating suggests that neurons of this structure are not involved in the control of male sexual behavior.

Diazepam modifies the effect of pedunculopontine lesions on morphine but not on amphetamine conditioned place preference

We have previously shown that T-maze learning impairments caused by lesions to the pedunculopontine tegmental nucleus (PPTg) can be reversed by the anxiolytic diazepam. We now report that diazepam also reverses the effect of PPTg lesions on conditioned place preference (CPP) to morphine but not to amphetamine. Rats with bilateral sham or N-methyl-D-aspartate lesions (0.1 or 0.05 M) to the PPTg were trained in a unbiased CPP paradigm with 2 mg/kg morphine or 2 mg/kg D-amphetamine associated with one compartment of the apparatus and vehicle injections in the alternative compartment. After three drug/saline-compartment pairings, the preference of the animals was assessed by allowing them to explore the entire apparatus for 20 min. In contrast to sham-lesioned subjects, the rats with PPTg lesions did not show a preference for the compartment paired with morphine or amphetamine. In two experiments the expression of a morphine CPP was restored by injecting the lesioned animals with 1 mg/kg of diazepam 30 min before the test session. Diazepam pre-treatment did not restore the expression of amphetamine CPP.

Lesions of the dorsal noradrenergic bundle augment the renin response to blood loss but do not alter hypothalamic Fos expression

The goal of this study was to determine if the dorsal noradrenergic bundle (DNAB) plays an essential role in mediating increased plasma renin activity (PRA) and hypothalamic activation, as indicated by increased Fos expression, in response to a small volume blood loss in unanesthetized animals. Male Sprague-Dawley rats were prepared with bilateral 6-hydroxydopamine or sham lesions of the dorsal noradrenergic bundle. In both groups of animals, blood pressure decreased by only 10-15 mmHg following hemorrhage (10 ml/kg over 15 min). Plasma renin activity increased similarly in both groups after 5 ml/kg blood loss, but showed a significantly greater increase after 10 ml/kg blood loss in animals with 6-hydroxydopamine lesions than in those with sham lesions (increase of 13.8 +/- 2.0 ng/ml/h versus 8.4 +/- 1.2 ng/ml/h; P < 0.025). There were numerous Fos-immunoreactive cell nuclei in the supraoptic nucleus (SON) and parvicellular paraventricular hypothalamic nucleus (PVN) of hemorrhaged animals. The number of Fos-positive neurons did not differ between groups, indicating that the dorsal noradrenergic bundle does not convey the primary drive for supraoptic and paraventricular nucleus activation during blood loss. However, one or more of the forebrain regions innervated by the dorsal noradrenergic bundle may attenuate the sympathetic outflow that initiates renin release in response to hemorrhage.

Effect of ambient temperature on sleep-waking cycle in cats with electrolytic dorsolateral pontine tegmental lesions

The effects of ambient temperature on the sleep-waking cycle were studied in intact cats and those with bilateral electrolytic lesions in the pontine tegmentum. At a room temperature of 23 degrees C, the percentage of time spent in paradoxical sleep was significantly lower in the lesioned cats than in intact animals. The mean duration of paradoxical sleep episodes was also decreased in the lesioned animals. The reduction in slow-wave sleep was not significant. At a slightly warmer ambient temperature of 30 degrees C, both the mean duration of paradoxical sleep episodes and the total duration of paradoxical sleep in the lesioned animals were increased toward normal values. Slow-wave sleep increased slightly but not significantly. At a higher ambient temperature of 35 degrees C, as well as at colder ambient temperatures of 15 and 7 degrees C, the durations of both paradoxical sleep and slow-wave sleep were significantly reduced. Under these thermal loads, the reduction in the duration of sleep was significantly greater in the lesioned cats than in the intact animals. The results suggest that: (i) pontine lesions alter the sleep cycle of cats and ambient temperature influences this alteration; (ii) the effects of thermal loads on the sleep cycle are more severe in the lesioned cats; and (iii) a moderately warm ambient temperature (30 degrees C) improves the sleep of pontine-lesioned cats.

Vertical vestibulo-ocular reflex control after supranuclear midbrain damage

The vertical vestibulo-ocular reflex (VOR) and its visual enhancement and cancellation were measured in patients with focal midbrain lesions that caused paralysis of upward, or upward and downward saccades. VOR gain was reduced in darkness during active vertical head pitch at frequencies from 0.25 to 2 Hz. Visual enhancement of the reflex by fixating a stationary target was subnormal upward and downward. Cancellation of the VOR was defective in both vertical directions during eye-head tracking. The VOR showed abnormal phase lead of the eyes in darkness, indicating that pretectal midbrain damage impairs the integration of eye velocity commands.

Ventral tegmental area injury and frontal lobe disorder

A patient developed acute behavioral changes implicating frontal-executive dysfunction. His clinical signs suggested mesencephalic injury, and a cranial MRI scan showed an abnormality restricted to a small region of the ventral midbrain. We suggest that the patient's behavioral disorder originated from disruption of the ventral tegmental area or it projections, structures that influence frontal brain processes via the mesocortical dopamine tract.

Augmentation of ventral tegmental area stimulation-induced feeding by both stimulation and lesion of the contralateral ventral tegmental area in the rat

Unilateral lesions of the ventral tegmental area (VTA) facilitate behavioral responses (feeding and exploration) induced by electrical stimulation of the VTA in the contralateral hemisphere. It was hypothesized that this facilitation may result from a lesion-induced compensatory increase in dopamine transmission in the intact hemisphere. In the present study we tested on the functional level the hypothesis that the activity of bilateral mesocorticolimbic systems is inversely related. For this purpose we compared the effect of unilateral subthreshold activation with the effect of subsequent unilateral lesion of VTA on feeding response evoked by electrical stimulation of the contralateral VTA. In male Wistar rats implanted with bilateral VTA electrodes stimulation-induced feeding was tested in a latency to feed-stimulation frequency curve-shift paradigm. One electrode was used for induction of feeding reaction and the other electrode was used for concurrent stimulation (with the subthreshold current) and subsequent electrolytic lesioning of the contralateral VTA. It was found that both contralateral stimulation and subsequent lesion performed through the same electrode facilitated a feeding response that manifested as a decrease in the reaction's threshold and a leftward shift of the latency-frequency curve. The paradoxical similarity of the effects of the stimulation and lesion is discussed in terms of functional organization of the mesocorticolimbic system and adaptive changes in dopaminergic transmission.

Effects of lesioning of the medial cervical nucleus on the baseline spike activity of neurons in the central and basolateral nuclei of the amygdala

Studies of the characteristics of baseline spike activity in the central and basolateral nuclei of the amygdala demonstrated significant differences between these nuclei. Lesioning of the medial cervical nucleus, which is one of the sources of ascending serotoninergic projections of the forebrain, led to marked and generally reciprocal changes in the spike activity of the amygdalar nuclei studied. It is suggested that serotoninergic afferentation from the medial cervical nucleus modulates the activity of amygdalar nuclei with different functional assignments.