Nuclear expression of PG-21, SRC-1, and pCREB in regions of the lumbosacral spinal cord involved in pelvic innervation in young adult and aged rats.

In rats, ageing results in dysfunctional patterns of micturition and diminished sexual reflexes that may reflect degenerative changes within spinal circuitry. In both sexes the dorsal lateral nucleus and the spinal nucleus of the bulbospongiosus, which lie in the L5-S1 spinal segments, contain motor neurons that innervate perineal muscles, and the external anal and urethral sphincters. Neurons in the sacral parasympathetic nucleus of these segments provide autonomic control of the bladder, cervix and penis and other lower urinary tract structures. Interneurons in the dorsal gray commissure and dorsal horn have also been implicated in lower urinary tract function. This study investigates the cellular localisation of PG-21 androgen receptors, steroid receptor co-activator one (SRC-1) and the phosphorylated form of c-AMP response element binding protein (pCREB) within these spinal nuclei. These are components of signalling pathways that mediate cellular responses to steroid hormones and neurotrophins. Nuclear expression of PG-21 androgen receptors, SRC-1 and pCREB in young and aged rats was quantified using immunohistochemistry. There was a reduction in the number of spinal neurons expressing these molecules in the aged males while in aged females, SRC-1 and pCREB expression was largely unchanged. This suggests that the observed age-related changes may be linked to declining testosterone levels. Acute testosterone therapy restored expression of PG-21 androgen receptor in aged and orchidectomised male rats, however levels of re-expression varied within different nuclei suggesting a more prolonged period of hormone replacement may be required for full restoration.

Benefits of a professional training year for undergraduates on a neuroscience degree scheme.

The benefits of undergraduate students taking a professional training year (PTY) as part of their neuroscience degree have been analyzed for fifteen cohorts of students between 1994 and 2008. Those students taking the PTY scored 4.4% more in their final year aggregated total than those who did not. In addition, these students were 2.58 times more likely to gain a first class degree and 4.8 times less likely to gain a second class (division two) degree than those who did not take the placement year. Analysis of final year marks, whether or not they had taken the PTY, indicated a significantly better performance by female students. Progression onwards to postgraduate study for a PhD was almost four times higher for PTY students than for those not taking the PTY. No PTY students progressed on to a Masters scheme of postgraduate study whereas a small number of three year students did. The benefits of a PTY also extended to students' self-enhancement and maturity as judged by themselves, their peers and by academic staff. This study, the first for the relatively new undergraduate discipline of neuroscience, confirms earlier findings for other academic disciplines.

Age-associated changes in distribution of the P2X2 receptor in the major pelvic ganglion of the male rat.

P2X purinoceptors constitute a group of ligand-gated ion channels one of which, the P2X2 receptor has previously been described in neurons within autonomic ganglia, including the major pelvic ganglion (MPG). Earlier work strongly suggests that age-associated attrition of sympathetic but not parasympathetic MPG neurons occurs but there have been no investigations of age-related changes in P2X2 receptor expression in autonomic ganglia or to determine whether the receptor is localised in one or both of the two MPG neuronal subpopulations. In the current study, immunocytochemistry was employed to label cells expressing the P2X2 receptor in the MPG from young and aged male Wistar rats. By combining P2X2 receptor immunocytochemistry with the immunolocalisation of tyrosine hydroxylase (TH), the numbers of sympathetic (TH+) and parasympathetic (TH-) neurons expressing the P2X2 receptor were determined. In young rats P2X2 receptor expression was found in 93.08+/-3.2% of TH- (parasympathetic) neurons. In aged rats a similar analysis revealed no significant difference in the number of TH- neurons expressing the P2X2 receptor. In contrast a significant increase in the number of TH+ sympathetic neurons expressing P2X2 was observed in the MPG of aged rats (10.70+/-2.26%) in comparison to the young group (2.38+/-0.78%). Age-related changes in the numbers of small intensely fluorescent (SIF) cells which were highly P2X2 positive were also quantified, revealing a small reduction in number with age. This study has demonstrated the preferential localisation of P2X2 receptors to parasympathetic MPG neurons and suggests that purinergic transmission in the pelvic organs maybe largely unaffected by ageing.

Biogenic amine and neuropeptide inputs to identified pelvic floor motoneurons that also express SRC-1.

In the rat, the neurochemical phenotypes of neurons that are presynaptic to motoneurons innervating the levator ani are poorly defined. In this study, motoneurons within the spinal nucleus of the bulbospongiosus (SNB) were revealed, using retrograde labelling, following injection of cholera toxin B subunit into the levator ani muscle. Different classes of neuron making substantial inputs onto these labelled neurons were revealed by using immunocytochemistry for dopamine beta hydroxylase, serotonin and substance P. Appositions (sites of presumptive synapses) between immunoreactive terminals and both the somata and dendrites of labelled SNB motoneurons were commonly seen suggesting that substance P, noradrenaline and serotonin are likely to exert a significant influence on the activity of perineal motoneurons and thus on sexual reflexes. Additionally, steroid receptor coactivator-1 was found to be present in the nuclei of 96% of SNB neurons retrogradely labelled from the levator ani. This suggests that practically all of the neurons that innervate the levator ani are likely to be modulated by circulating steroid hormones.

Changes in the substance P-containing innervation of the lumbosacral spinal cord in male Wistar rats as a consequence of ageing.

Quantitative image analysis was used to determine age-related changes in the substance P-containing innervation of autonomic and somatic nuclei in the lumbosacral spinal cord, which are associated with the control of micturition and sexual reflexes. In the upper lumbar segments (L1-L2), significant declines in the distribution density of substance P-containing processes were observed in the dorsal grey commissure, the intermediolateral cell column and the ventral horn. More caudally, at levels corresponding to L5 through S1, significant reductions were seen in the dorsal grey commissure and within the sacral parasympathetic nucleus. In contrast to these observations, the substance P-immunoreactive innervation of the dorsolateral nucleus remained robust in aged animals and was not significantly different from young adults. It is possible that these distinct age-related patterns of change in substance P-containing innervation, are reflected in the urinary/sexual dysfunction's in aged animals.

SRC-1 localisation in lumbosacral spinal cord of male and female Wistar rats.

Nuclear receptor co-activators play an important role in enhancing transcriptional activity of steroid hormone receptors, however there is currently little information concerning their distribution within the spinal cord. In this study, the distribution of steroid receptor co-activator-1 (SRC-1) was examined with immunocytochemistry, in the lumbosacral cord of Wistar rats of both sexes. In all rats, regardless of sex, SRC-1 was predominant in neurons of the superficial laminae of the dorsal horn and within motorneurons of lamina IX. Sexually dimorphic nuclei exhibited robust SRC-1 immunoreactivity in young rats, including orchidectomised animals, but this appeared to decline in aged rats. Dorsal horn labelling appeared similarly reduced suggesting a possible age-related down-regulation of the transcription mediated by steroid receptors in some spinal neurons.

The effects of ageing and of DSP-4 administration on the micturition characteristics of male Wistar rats.

This study sought to determine the effects of ageing on the in vivo micturition characteristics of male Wistar rats and to assess whether they might be replicated in young rats by using the neurotoxin DSP-4 to lesion locus coeruleus-derived noradrenergic pathways projecting to spinal cord nuclei controlling micturition. Significant age-related changes in micturition patterns were observed. There was a loss of a diurnal rhythm in micturition patterns and a large increase in voided volume, maximal between 21 and 24 months, which was paralleled by an increased water intake. DSP-4 lesions neither altered micturition patterns nor water intake in the young adult rat. DSP-4 induced changes in the pattern of tyrosine hydroxylase-like immunoreactivity (TH-LI), most notably almost complete depletion of TH-LI in the dorsolateral nucleus and retention of TH-LI in lumbosacral autonomic preganglionic nuclei, did not mimic the changes in the pattern of TH-LI seen in aged rats.

Age-associated changes in the monoaminergic innervation of rat lumbosacral spinal cord.

The effects of ageing on the innervation patterns of lumbosacral spinal nuclei involved in controlling lower urinary tract functions, including micturition, were studied using immunohistochemistry for serotonin (5-HT) and tyrosine hydroxylase (TH) in male Wistar rats of 3 and 24 months. Quantitative image analysis revealed significant age-associated declines in the innervation of most regions including the intermediolateral cell nucleus, sacral parasympathetic nucleus, dorsal grey commissure and in the ventral horn including the dorsolateral nucleus which in the rat is one of the component nuclei homologous to Onuf's nucleus in man. Notable exceptions to this generalised decline were observed in the 5-HT innervation of the sacral parasympathetic nucleus, which was maintained, and in the region of the dorsolateral motor nucleus where TH-like immunoreactivity did not significantly decline. These results suggest that the changes in micturition characteristics observed in aged rats may in part be a consequence of the alterations in, and decline of, aminergic inputs to both autonomic and somatic spinal nuclei associated with bladder function.

Differential susceptibility to ageing of rat preganglionic neurones projecting to the major pelvic ganglion and of their afferent inputs.

We have analysed age-related changes in the morphology of preganglionic neurones in the lumbosacral spinal cord, labelled following injection of retrograde tracers into the major pelvic ganglion of young adult and aged male rats. We have also examined changes in neurotransmitter-characterised spinal afferent inputs to these neurones, or to the nuclei in which they lie, using light and electron microscope immunohistochemistry. In previous investigations of the major pelvic ganglion, the sympathetic, but not parasympathetic, postganglionic neurones were seen to exhibit age-related changes and the same pattern is seen in the preganglionic neurones. This included an apparent reduction in the numbers of sympathetic preganglionic neurones, and a reduction in the length of their dendrites and the complexity of their branches. Ultrastructural immunohistochemical studies described here reveal significant reductions in the area of synaptic contact made by glutamate-immunoreactive boutons onto the dendrites of sympathetic (but not parasympathetic) preganglionic neurones, while contacts from boutons immunoreactive for glycine or gamma-aminobutyric acid (GABA) were unchanged. There is also a reduction in synaptic contacts received by sympathetic somata from boutons immunoreactive for none of these amino acids. Serotonin-immunoreactive terminals are closely associated with preganglionic autonomic neurones, and these are reduced in number in sympathetic, but not parasympathetic, spinal nuclei of aged rats. However, serial section electron microscopy has so far failed to demonstrate conventional synaptic contacts between serotonergic terminals and the dendrites or somata of the preganglionic autonomic neurones. In young animals, axon terminals immunoreactive for thyrotropin-releasing hormone (TRH) are abundant in all spinal laminae including area X, but in aged animals, such terminals are significantly reduced in number in regions containing preganglionic sympathetic, but not parasympathetic, neurones. These results indicate that the sympathetic preganglionic neuron populations that project to the major pelvic ganglion, and the spinal inputs they receive, show a number of degenerative changes in aged rats which are not seen parasympathetic preganglionic neuronal populations.