Nicotine self-administered directly into the VTA by rats is weakly reinforcing but has strong reinforcement enhancing properties.

Rationale: Rats will lever press to deliver nanolitre quantities of nicotine or the muscarinic agonist carbachol directly into the ventral tegmental area (VTA). The purpose of these experiments was to investigate further the characteristics of nicotine self-administration directly into the VTA.

Objectives: This study aimed to confirm previous data relating to intra-VTA self-administration of nicotine and carbachol and then test two hypotheses: (a) that pre-sensitisation of nicotinic receptors is needed for robust intra-VTA self administration and (b) that rats will lever press for intra-VTA nicotine if pre-trained to associate lever pressing with a rewarding outcome.

A functional dissociation of the anterior and posterior pedunculopontine tegmental nucleus: excitotoxic lesions have differential effects on locomotion and the response to nicotine.

Excitotoxic lesions of posterior, but not anterior pedunculopontine tegmental nucleus (PPTg) change nicotine self-administration, consistent with the belief that the anterior PPTg (aPPTg) projects to substantia nigra pars compacta (SNC) and posterior PPTg (pPPTg) to the ventral tegmental area (VTA). The VTA is a likely site both of nicotine's reinforcing effect as well as its actions on locomotion. We hypothesized that pPPTg, but not aPPTg lesions, would alter locomotion in response to repeated nicotine administration by virtue of the fact that pPPTg appears to be more closely related to the VTA than is the aPPTg.

The pedunculopontine tegmental nucleus and the nucleus basalis magnocellularis: do both have a role in sustained attention?

Background: It is well established that nucleus basalis magnocellularis (NbM) lesions impair performance on tests of sustained attention. Previous work from this laboratory has also demonstrated that pedunculopontine tegmental nucleus (PPTg) lesioned rats make more omissions on a test of sustained attention, suggesting that it might also play a role in mediating this function. However, the results of the PPTg study were open to alternative interpretation.

The pedunculopontine tegmental nucleus and responding for sucrose reward.

Pedunculopontine tegmental nucleus (PPTg) lesions in rodents lead to increased sucrose consumption, but the psychological deficit behind this remains uncertain. To understand better the relationship between consumption of, and motivation for, sucrose, the authors trained rats to traverse a runway for 20% or 4% sucrose solution; after 7 days, concentrations were reversed. Control rats consumed more 20% than 4% sucrose solution and promptly altered run times in response to concentration change.

Intravenous self-administration of nicotine is altered by lesions of the posterior, but not anterior, pedunculopontine tegmental nucleus.

The reinforcing properties of nicotine involve actions at nicotinic acetylcholine receptors located on dopamine (DA) neurons in the ventral tegmental area (VTA). The pedunculopontine tegmental nucleus (PPTg) is involved in the regulation of these DA neurons, and those of the substantia nigra pars compacta (SNc). The PPTg can be subdivided into anterior (aPPTg) and posterior (pPPTg) regions on the basis of its innervation of midbrain DA neurons - the pPPTg innervates both VTA and SNc while the aPPTg innervates SNc.

Involvement of the laterodorsal tegmental nucleus in the locomotor response to repeated nicotine administration.

The locomotor altering properties of nicotine depend on activation of nicotinic acetylcholine receptors in the ventral tegmental area (VTA). The laterodorsal tegmental nucleus (LDTg) provides a significant proportion of the cholinergic innervation of the VTA. We tested the hypothesis that the locomotor effects of nicotine depend on the functional integrity of the LDTg.

Excitotoxic lesions of the pedunculopontine tegmental nucleus in rats impair performance on a test of sustained attention.

Recent research has suggested that the pontomesencephalic tegmentum might be an important part of a network underlying sustained attention. The largest structure of the pontomesencephalic tegmentum is the pedunculopontine tegmental nucleus, which has ascending connections to thalamus and with corticostriatal systems. In this experiment we examined the performance of rats following bilateral excitotoxic lesions of the pedunculopontine tegmental nucleus on a test of sustained attention previously used to examine frontal cortical function.

Effects of changing reward on performance of the delayed spatial win-shift radial maze task in pedunculopontine tegmental nucleus lesioned rats.

Because it was designed to assess working memory, the delayed spatial win-shift (DSWS) radial maze task has been used to investigate the involvement of corticostriatal structures in executive processing. Excitotoxic lesions of the pedunculopontine tegmental nucleus (PPTg) produce profound deficits in performance of this task that are not accounted for by motor impairment. Thus, PPTg DSWS deficits are hypothesized to support a role for PPTg in complex cognitive processing.

Impaired delayed spatial win-shift behaviour on the eight arm radial maze following excitotoxic lesions of the medial prefrontal cortex in the rat.

The delayed spatial win-shift (DSWS) radial maze task requires that animals hold spatial information for reward location "on-line" both during task performance and across a delay. Temporary lidocaine inactivation of anterior cingulate (AC) and prelimbic (PL) regions of the rat medial prefrontal cortex (mPFC) has revealed dissociable effects on this task, suggesting different roles within working memory for each of these areas. However, further research has shown that mPFC deficits in the rat may only be transient in nature, particularly on the radial maze.

Determination of acetylcholine and dopamine content in thalamus and striatum after excitotoxic lesions of the pedunculopontine tegmental nucleus in rats.

The pedunculopontine tegmental nucleus (PPTg) contains cholinergic neurons whose principal ascending connections are with thalamic nuclei and structures associated with the striatum. It has been hypothesized that PPTg neurons are more closely associated with the substantia nigra (and therefore striatal motor systems) than with the ventral tegmental area (and therefore limbic striatal functions). In the present experiments we have examined the hypothesis that the PPTg is similarly associated with motor nuclei in the thalamus.