Journal of neurophysiology
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1. The main purposes of this study are to characterize the intracellular and extracellular responses of cells in superficial layers of entorhinal cortex (EC) in chronically epileptic animals, determine whether their altered physiology is dependent on being connected to hippocampus, and investigate whether there is evidence of augmented excitation and inhibitory interneuron disconnection. 2. Functional connectivity was maintained between the hippocampal area and the EC in vitro in a combined rat hippocampal-parahippocampal slice preparation by slicing with a vibratome at a 30-deg angle to the base of the brain. ⋯ IPSPs were not seen or markedly reduced at all stimulus intensities. These intracellular responses never resembled control responses. Intracellur responss correlated precisely in morphology and duration with extracellular field potentials. (ABSTRACT TRUNCATED)
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1. The role of descending brain stem modulatory systems in the development of persistent behavioral hyperalgesia and dorsal horn hyperexcitability was studied in rats with unilateral hindpaw inflammation. Inflammation was induced by intraplantar injection of complete Freund's adjuvant (CFA, 0.05 ml of an 1:1 oil/saline emulsion, 25 micrograms Mycobacterium), or lambda carrageenan (1 mg/ 0.1 ml saline). ⋯ Thoracic saline did not produce a significant change in the receptive field size (105 +/- 9%, n = 4). The increases in responses to noxious thermal and mechanical stimuli after thoracic lidocaine block were also significantly greater in inflamed than in noninflamed rats (P < 0.01). There was no significant difference in the increase in responses to electrical stimulation of the sciatic nerve after lidocaine between inflamed and noninflamed rats.(ASTRACT TRUNCATED)
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1. We have studied the characteristics of the abnormal properties of damaged myelinated fibers (conduction velocity > 2.0 m/ s) after peripheral nerve injury in a novel in vitro model of the rat sciatic nerve/dorsal root ganglion/dorsal root (L4-5) preparation removed from control naíve or sham-operated rats and animals that had received sciatic neurectomy 12-24 days before the in vitro study. A total of 122-245 filaments were recorded in each dorsal root. ⋯ We present an in vitro model for the study of abnormal primary sensory activity in peripheral neuropathy. Although our data are consistent with in vivo electrophysiological findings in published reports, the proportion of damaged afferent fibers displaying spontaneous activity was significantly lower under in vitro conditions. This model may serve as a valuable tool for further physiological and pharmacological studies of peripheral neuropathy.
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1. Presbycusis, age-related hearing loss, is an ever increasing problem in our aging society. It involves changes in both the peripheral and central portions of the auditory system. ⋯ The results of this study support the hypothesis that there is an age-related shift to higher intensities in the working range of most CIC units along with a small, selective deficit in inhibitory processing. When considered in conjunction with the mouse aging studies conducted by other researchers and with the results of a similar study of single units in the visual system (lateral geniculate nucleus) of young and aged rhesus monkeys, these results suggest that compensatory mechanisms are highly active in sensory systems as animals age. Despite deficits that lead to reduced input to the IC and neurochemical changes affecting neurotransmitter levels, IC neurons in aged rats are able to respond to most simple auditory stimuli in a fashion quite similar to that observed in young rats.