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Urethane-anaesthetized Rats (urethane-anaesthetized + rat)
Selected AbstractsCharacterization in vivo of bilaterally branching pontocerebellar mossy fibre to Golgi cell inputs in the rat cerebellumEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2009Tahl Holtzman Abstract Golgi cells regulate the flow of information from mossy fibres to the cerebellar cortex, through a mix of feedback and feedforward inhibitory actions on granule cells. The aim of the current study was to examine mossy fibre input to Golgi cells, in order to assess their impact on switching Golgi cells into feedforward behaviour. In urethane-anaesthetized rats, extracellular recordings were made from Golgi cells in Crus II (n = 18). Spikes were evoked in all Golgi cells by microstimulation within the contralateral hemispheral cortex, via branches of mossy fibres that terminate in both cerebellar hemispheres. The latencies of these responses were very short, consistent with a monosynaptic mossy fibre contact [average onset latency 2.3 ± 0.1 ms (SEM)]. The same stimuli had no measurable effect on spike responses of nearby Purkinje cells (n = 12). Systematic mapping in the contralateral cerebellar hemisphere (Crus Ib, IIa, IIb and the paramedian lobule) usually revealed one low-intensity stimulus ,hotspot' (12,35 ,A) from which short-latency spikes could be evoked in an individual Golgi cell. Microinjections of red and green retrograde tracers (latex beads, ,50,150 nL injection volume) made at the recording site and the stimulation hotspot resulted in double-labelled neurons within the pontine nuclei. Overall, this suggests that subsets of pontine neurons supply mossy fibres that branch to both hemispheres, some of which directly target Golgi cells. Such an arrangement may provide a common feedforward inhibitory link to temporally couple activity on both sides of the cerebellum during behaviour. [source] Cardiovascular effects of noradrenaline microinjected into the dorsal periaqueductal gray area of unanaesthetized ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2005Gislaine Garcia Pelosi Abstract The periaqueductal grey area (PAG) is a mesencephalic region that is involved in the modulation of cardiovascular changes associated with behavioural responses. Among the neurotransmitters present in the PAG, noradrenaline (NA) is also known to be involved in central nervous system cardiovascular regulation. In the present study we report the cardiovascular effects of the microinjection of NA into the dorsal portion of the PAG (dPAG) of unanaesthetized rats and the peripheral mechanism involved in their mediation. Injection of NA in the dPAG of unanaesthetized rats evoked a dose-dependent pressor response accompanied by bradycardia. The magnitude of the pressor responses was higher at more rostral sites in the dPAG and decreased when NA was injected into the caudal portion of the dPAG. The responses to NA were markedly reduced in urethane-anaesthetized rats. The pressor response was potentiated by i.v. pretreatment with the ganglion blocker pentolinium and blocked by i.v. pretreatment with the vasopressin antagonist dTyr(CH2)5(Me)AVP. The results suggest that activation of noradrenergic receptors within the dPAG can evoke pressor responses, which are mediated by acute vasopressin release. [source] In Vivo Modulation of Post-Spike Excitability in Vasopressin Cells by ,-Opioid Receptor ActivationJOURNAL OF NEUROENDOCRINOLOGY, Issue 8 2000C. H. Brown Abstract An endogenous ,-opioid agonist reduces the duration of phasic bursts in vasopressin cells. Non-synaptic post-spike depolarizing after-potentials underlie activity during bursts by increasing post-spike excitability and ,-receptor activation reduces depolarizing after-potential amplitude in vitro. To investigate the effects of ,-opioids on post-spike excitability in vivo, we analysed extracellular recordings of the spontaneous activity of identified supraoptic nucleus vasopressin cells in urethane-anaesthetized rats infused with Ringer's solution (n = 17) or the ,-agonist, U50,488H (2.5 µg/h at 0.5 µl/h; n = 23), into the supraoptic nucleus over 5 days. We plotted the mean hazard function for the interspike interval distributions as a measure of the post-spike excitability of these cells. Following each spike, the probability of another spike firing in vasopressin cells recorded from U50,488H infused nuclei was markedly reduced compared to Ringer's treated vasopressin cells. To determine whether U50,488H could reduce post-spike excitability in cells that displayed spontaneous phasic activity, we infused U50,488H (50 µg/h at 1 µl/h, i.c.v.), for 1,12 h while recording vasopressin cell activity. Nine of 10 vasopressin cells were silenced by i.c.v. U50,488H 15 ± 5 min into the infusion. Six cells exhibited spontaneous phasic activity before U50,488H infusion and recordings from three of these phasic cells were maintained until activity recovered; during U50,488H infusion, the activity of these three cells was irregular. Generation of the mean hazard function before and during U50,488H infusion revealed a reduction in post-spike excitability during U50,488H infusion. Thus, ,-receptor activation reduces post-spike excitability in vivo; this may reflect inhibition of depolarizing after-potentials and may thus underlie the reduction in burst duration of vasopressin cells caused by an endogenous ,-agonist in vivo. [source] Ganglionic transmission in a vasomotor pathway studied in vivoTHE JOURNAL OF PHYSIOLOGY, Issue 9 2010Bradford Bratton Intracellular recordings were made in vivo from 40 spontaneously active cells in the third lumbar sympathetic ganglion of urethane-anaesthetized rats. In 38/40 cells ongoing action potentials showed strong cardiac rhythmicity (93.4 ± 1.9% modulation) indicating high barosensitivity and probable muscle vasoconstrictor (MVC) function. Subthreshold excitatory postsynaptic potentials (EPSPs) showed the same pattern. The 38 barosensitive neurons fired action potentials at 2.9 ± 0.3 Hz. All action potentials were triggered by EPSPs, most of which were unitary events. Calculations indicated that <5% of action potentials were triggered by summation of otherwise subthreshold EPSPs. ,Dominant' synaptic inputs with a high safety factor were identified, confirming previous work. These were active in 24/38 cells and accounted for 32% of all action potentials; other (,secondary') inputs drove the remainder. Inputs (21 dominant, 19 secondary) attributed to single preganglionic neurons fired at 1.38 ± 0.16 Hz. An average of two to three preganglionic neurons were estimated to drive each ganglion cell's action potentials. When cells were held hyperpolarized to block spiking, a range of spontaneous EPSP amplitudes was revealed. Threshold equivalent was defined as the membrane potential value that was exceeded by spontaneous EPSPs at the same frequency as the cell's original firing rate. In 10/12 cells examined, a continuum of EPSP amplitudes overlapped threshold equivalent. Small changes in cell excitability could therefore raise or lower the percentage of preganglionic inputs triggering action potentials. The results indicate that vasoconstrictor ganglion cells in vivo mostly behave not as 1:1 relays, but as continuously variable gates. [source] Select spinal lesions reveal multiple ascending pathways in the rat conveying input from the male genitaliaTHE JOURNAL OF PHYSIOLOGY, Issue 7 2010C. H. Hubscher The specific white matter location of all the spinal pathways conveying penile input to the rostral medulla is not known. Our previous studies using rats demonstrated the loss of low but not high threshold penile inputs to medullary reticular formation (MRF) neurons after acute and chronic dorsal column (DC) lesions of the T8 spinal cord and loss of all penile inputs after lesioning the dorsal three-fifths of the cord. In the present study, select T8 lesions were made and terminal electrophysiological recordings were performed 45,60 days later in a limited portion of the nucleus reticularis gigantocellularis (Gi) and Gi pars alpha. Lesions included subtotal dorsal hemisections that spared only the lateral half of the dorsal portion of the lateral funiculus on one side, dorsal and over-dorsal hemisections, and subtotal transections that spared predominantly just the ventromedial white matter. Electrophysiological data for 448 single unit recordings obtained from 32 urethane-anaesthetized rats, when analysed in groups based upon histological lesion reconstructions, revealed (1) ascending bilateral projections in the dorsal, dorsolateral and ventrolateral white matter of the spinal cord conveying information from the male external genitalia to MRF, and (2) ascending bilateral projections in the ventrolateral white matter conveying information from the pelvic visceral organs (bladder, descending colon, urethra) to MRF. Multiple spinal pathways from the penis to the MRF may correspond to different functions, including those processing affective/pleasure/motivational, nociception, and mating-specific (such as for erection and ejaculation) inputs. [source] | ||||||||||