Effects of sensory restriction upon responses to cortical stimulation in rats.

Assigned 43 Long-Evans hooded rats to 7 groups receiving normal, visually restricted, or auditory restricted rearing experience. Ss were then implanted with bipolar pairs of electrodes in the auditory and visual projection areas. Electrical stimulation of the cortex was used as a discriminative stimulus for a lever-pressing response. The ease of using electrical stimulation of visual or auditory cortex as a discriminative stimulus was related to Ss' paranatal sensory experience. Deleterious effects were limited to the restricted cortical projection area, and there were suggestions of facilitated performance in response to stimulation of the nonrestricted cortical areas. These effects were absent when restriction was induced in adulthood. (28 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Laser irradiation abates neuronal responses to nociceptive stimulation of rat-paw skin

The effects of diode laser irradiation on peripheral nerves was examined by monitoring neuronal discharges elicited by application of various stimuli to the hind-paw skin of rats. Neuronal discharges elicited by brush, pinch, cold, and/or heat stimulation, as well as chemical stimulation by injection of turpentine (0.1 ml, SC) were recorded from L5 dorsal roots in urethane-anesthetized rats. Diode laser irradiation (830 nm, 40 mW, 3 min, continuous wave) of the saphenous nerve exposed from the muscle of the lower leg significantly inhibited neuronal discharges elicited by pinch (68.4 +/- 6.5%), cold (45.4 +/- 9.2%), and heat stimulation (49.2 +/- 11.3%). Neuronal discharges induced by brush stimulation (104.3 +/- 4.7%) were not affected by laser irradiation. Injection of turpentine, a chemical irritant, into the hind-paw skin (0.1 ml, SC) elicited neuronal discharges in the ipsilateral dorsal root, and these discharges were significantly inhibited or abolished by laser irradiation. In 6- to 7-week-old rats treated neonatally with capsaicin (10 mg/kg, SC), injection of turpentine into the hind-paw skin did not elicit neuronal discharges and laser irradiation did not affect the background discharges. These data suggest that laser irradiation may selectively inhibit nociceptive neuronal activities.     

Novel approaches to the symptomatic treatment of parkinsonian syndromes: alternatives and adjuncts to dopamine-replacement

A total of 74 non-pregnant women with a previous episode of thrombosis were investigated for activated protein C (APC) resistance in the aPTT-based and factor IXa-X-based assays and for the presence of mutations in all APC-cleavage sites in the heavy chains of factor V and factor VIII. DNA fragments were amplified with the polymerase chain reaction (PCR) and those encoding for the Arg-306 and Arg-506 (factor V) and for Arg-740 (factor VIII) cleavage sites were subjected to restriction enzyme analysis. DNA fragments of 29 selected patients corresponding to the Arg-306 and Arg-679 cleavage sites in factor V, and to the Arg-336 and Arg-562 cleavage sites in factor VIII were sequenced. APC resistance was found in 40 cases, using the aPTT-based assay and in 35, using the factor IXa-X-based assay (23 patients were APC resistant in both assays), whereas 22 individuals had a normal response to APC. Forty-three patients carried Arg-506 to Gln mutation in factor V. No other polymorphism or mutation was found in the genes for factors V or VIII in the vicinity of the APC cleavage sites. It was concluded that the difference in response to APC in the two assays may not be explained by the presence of mutations in the APC cleavage sites of factor V and factor VIII in this group of patients. The data do not exclude the presence of mutations elsewhere in the factor V or factor VIII genes.     

Brain pH responses to acetazolamide and hypercapnia in cats

The involvement of increased brain tissue CO2 tension in acetazolamide-induced brain acidosis was investigated by comparing the brain pH response to acetazolamide with that to hypercapnia. CO2 and pH sensors were placed bilaterally into cerebral white matter to 15 mm depth in cats. Group 1 cats (n = 9) breathed spontaneously, and in situ brain tissue PCO2, and pH (PbCO2 and pHb) were measured after intravenous acetazolamide administration (20 mg/kg). Group 2 cats (n = 9) were paralyzed and ventilated mechanically, and the changes of pHb were investigated by adjusting the ventilation to maintain the same Pbco2 values as in the acetazolamide-treated group. PbCO2 changes were not significantly different between the two groups. However, pHb responses were quite different: the fall in pHb was progressive in Group 1 but transient in Group 2. Brain acidosis after acetazolamide administration is not due to the rise in brain tissue CO2 tension.     

Astrocytic messenger RNA responses to striatal deafferentation in male rat

This investigation describes the schedule and regional distribution of astrocytic responses in striatum following deafferentation by unilateral frontal cortex ablation. In the ipsilateral deafferented striatum, glial fibrillary acidic protein and clusterin (sulfated glycoprotein-2) messengerRNA showed peak elevations by 10 days postlesioning (Northern blots). Vimentin messengerRNA responded faster, with a transient elevation by three days postlesioning. The messengerRNA for glial fibrillary acidic protein, clusterin and vimentin returned toward control levels by 27 days postlesioning. However, the neuronal marker growth-associated protein messengerRNA, was decreased at all postlesion times. By in situ hybridization, the increased glial fibrillary acidic protein messengerRNA and clusterin messengerRNA signals were localized mainly to the dorsal half of the ipsilateral deafferented striatum and followed the same schedule as found by Northern blots. Glial fibrillary acidic protein messengerRNA was widely diffused in the dorsal striatum and was excluded from fascicles of the internal capsule; a similar distribution was found for glial fibrillary acidic protein-immunopositive astrocytes. While clusterin messengerRNA signal showed a distinct clustering, its immunoreactivity appeared as deposits in the deafferented striatal neuropil; Western blots confirmed the immunocytochemical results. By in situ hybridization, vimentin messengerRNA was mostly localized to the cortical wound cavity dorsal to the deafferented striatum and overlapped the distribution of vimentin-immunopositive cells. These findings suggest a coordination of striatal astrocytic messengerRNA responses with the degeneration of corticostriatal afferents. We also compared these same parameters with those from published reports on the hippocampus after deafferenting lesions. Certain astrocyte molecular responses to deafferentation are detected about five days earlier in the hippocampus than in the striatum. This different schedule in response to decortication may pertain to differences in synaptic remodeling in the hippocampus vs striatum.     

Local uncoupling of the cerebrovascular and metabolic responses to somatosensory stimulation after neuronal nitric oxide synthase inhibition

In order to investigate the remyelinating potential of mature oligodendrocytes in vivo, we have developed a model of demyelination in the adult rat spinal cord in which some oligodendrocytes survive demyelination. A single intraspinal injection of complement proteins plus antibodies to galactocerebroside (the major myelin sphingolipid) resulted in demyelination followed by oligodendrocyte remyelination. Remyelination was absent when the spinal cord was exposed to 40 Grays of x-irradiation prior to demyelination, a procedure that kills dividing cells. Quantitative Rip immunohistochemical analysis revealed a similar density of surviving oligodendrocytes in x-irradiated and nonirradiated lesions 3 days after demyelination. Rip and bromodeoxyuridine double immunohistochemical analysis of demyelinated lesions indicated that Rip+ oligodendrocytes did not divide as an acute response to demyelination. Oligodendrocytes were also identified by Rip immunostaining and electron microscopy at late time points (3 weeks) within x-irradiated areas of demyelination. These oligodendrocytes extended processes that engaged axons, and on occasion formed myelin membranes, but did not lay down new myelin sheaths. These studies demonstrate that (a) oligodendrocytes that survive within a region of demyelination are not induced to divide in the presence of demyelinated axons, and (b) fully-differentiated oligodendrocytes are therefore postmitotic and do not contribute to remyelination in the adult CNS.     

Neural respiratory responses to cortically induced seizures in cats

Seizure activity can lead to profound respiratory stimulation in spontaneously breathing animals with intact respiratory feedback mechanisms (Paydarfar et al., Am. J. Physiol. 260, R934, 1991). The present study was designed to test the hypothesis that peripheral respiratory feedback mechanisms are not important for the genesis of seizure-induced hyperpnea. Studies were performed in 16 anesthetized, vagotomized, glomectomized cats whose end-tidal PCO2 (PETCO2) was kept constant. Integrated phrenic nerve activity was used to represent respiration. Seizures were induced by injection of penicillin into the parietal cortex and electrocorticographic (ECoG) and biceps femoris nerve activities, arterial pressure, airway PCO2 and brain temperature were recorded continuously. Progressive seizure activity was associated with progressive increases of respiratory frequency and peak phrenic activity, despite constancy of PETCO2 and brain temperature. Patterns of entrainment were identified among ECoG spikes, biceps femoris nerve and phrenic nerve activities. Phrenic nerve activity became highly irregular during generalized ictal seizures and ceased to respond to changes of PETCO2. Acute intercollicular decerebration in all experiments resulted in normalization of respiratory rhythm even while ictal ECoG activity continued. We conclude that stimulation of breathing during seizures occurs in the absence of respiratory feedback mechanisms. The findings suggest that an important cause of the respiratory response is a feedforward mechanism, whereby activation of subcortical structures above medulla and pons results in stimulation of breathing.     

Laryngeal-receptor responses to phasic CO2 in anesthetized cats

We compared the effects of CO2 applied continuously and during expiration on laryngeal-receptor activity in paralyzed, artificially ventilated and nonparalyzed, spontaneously breathing cats by using an isolated larynx, artificially ventilated to approximate a normal respiratory cycle. The majority of quiescent negative-pressure and all cold receptors were excited by 5 and 9% CO2 applied both continuously and during expiration. In general, quiescent positive-pressure, tonic negative-pressure, and tonic positive-pressure receptors were inhibited by 5 and 9% CO2 applied continuously and during expiration. There were no significant differences between responses to 5 and 9% CO2 or to continuous and expired CO2 or between paralyzed and nonparalyzed preparations. In conclusion, laryngeal receptors respond to changes in CO2 concentration occurring during a normal respiratory cycle. Because laryngeal-receptor stimulation exerts reflex effects on ventilation and upper airway muscle activity, these results suggest that airway CO2 plays a role in reflex regulation of breathing and upper airway patency.     

Sucrose consumption in mice: major influence of two genetic loci affecting peripheral sensory responses

Individual variability in sucrose consumption is prominent in humans and other species. To investigate the genetic contribution to this complex behavior, we conducted behavioral, electrophysiological, and genetic studies, using male progeny of two inbred mouse strains (C57BL/6ByJ [B6] and 129/J [129]) and their F2 hybrids. Two loci on Chromosome (Chr) 4 were responsible for over 50% of the genetic variability in sucrose intake. These loci apparently modulated intake by altering peripheral neural responses to sucrose. One locus affected the response threshold, whereas the other affected the response magnitude. These findings suggest that the majority of difference in sucrose intake between male B6 and 129 mice is due to polymorphisms of two genes that influence receptor or peripheral nervous system activity.     

Cerebral evoked responses to gastrointestinal stimulation in humans

Recent advances have permitted recording of evoked potentials (EPs) in response to electrical and mechanical stimulation of the gastrointestinal (GI) organs via methods used primarily in clinical neurophysiology. Current research involving stimulation of the esophagus, rectum, and colon, and recording the corresponding responses on the scalp, is being practiced in only a few laboratories. This review examines the engineering aspects of recording EPs, such as characteristics of the stimuli, placement of stimulus electrodes in the GI tract, and enhancement of evoked potential signals. We also discuss the physiological concepts involved in the generation of EPs, and how these compare with somatosensory evoked responses. Current experimental techniques employed by various investigators and results reported from their laboratories are compared. We believe that cerebral EPs to GI stimulation could be useful in studying a number of pathophysiological conditions such as gastroesophageal reflux disease, diffuse esophageal spasm, chronic inflammatory bowel disorders, chronic abdominal pain, and irritable bowel syndrome, among others. We hope that the present review will generate interest in the use of EPs arising out of GI stimulation, aiding in understanding their physiological implications in healthy subjects and in GI disorders.     

Hemodynamic responses to stellate ganglion stimulation in mongrels and greyhounds

A comparison of the effects of left stellate ganglion stimulation (SGS) on central and aortic hemodynamics has been made in chloralose-anesthetized mongrel (M), and greyhound (GH) dogs. Measurements of aortic pressure and flow, and left ventricular pressure were made during stimulation of the decentralized left SG at different frequencies from 0 to 20 Hz. The increases in aortic pressure and flow with SGS were larger in the GH, especially for low frequencies of stimulation. Stroke volume was increased with SGS in the GH at all stimulation rates, whereas in the M it was unchanged. A greater decrease in left ventricular end-diastolic pressure with SGS was found in the GH. These results suggest that differences exist in both the intrinsic and extrinsic control of cardiac output in the greyhound dog compared to the mongrel. These differences may be in part responsible for the elevated arterial blood pressure in the greyhound compared to the mongrel.     

Long-term potentiation of the neuronal activity in the motor cortex induced by simultaneous stimulation of the thalamus and somatosensory cortex in cats

Long-lasting potentiation of the cat motor cortex units induced by tetanic stimulation of the VL + SCx led to an increase of the motor cortex unit discharge rate. The findings suggest that co-activation of cortico-cortical and thalamo-cortical afferents modifies neuronal activity of the motor cortex at the specific site which receives convergent sensory input from the thalamus and the somatosensory cortex.     

Arousal response to electrical stimulation of the cerebral cortex in cats.

Questions the belief that the arousal response produced by stimulation at various sites in the cortex is due to direct stimulation of the cortical component of a central arousal system. 3 observations of 9 female and 2 male cats were not consistent with this interpretation. Fractionation of the arousal response, subtotal parts of the reaction being produced by varying the intensity of cortical stimulation, occurred only when the S was in the resting state, and the arousal response habituated during repeated cortical stimulation. These observations on the arousal response to cortical stimulation were duplicated closely by the arousal response to an auditory stimulus. In agreement with a 1967 study by H. Ursin, K. Wester, and R. Ursin, it is suggested that the arousal response to stimulation of the cortex is a reflex to a sensory experience created by cortical stimulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interpersonal attachment cognitions and prediction of symptomatic responses to interpersonal stress.

The authors tested a cognitive-interpersonal hypothesis of depression by examining the role of interpersonal cognitions in the prediction of depression associated with interpersonal stressors. A measure of adult attachment assessed interpersonal cognitions about ability to be close to others and to depend on others and anxiety about rejection and abandonment. Participants were women who had recently graduated from high school; they were followed for 1 year with extensive interview evaluation of life events, depression, and other symptomatology. Generally, cognitions, interpersonal events, and their interactions contributed to the prediction of interview-assessed depressive symptoms, but the effects were not specific to depression and predicted general symptomatology measured by diagnostic interviews as well, and results also varied by attachment subscale. Results were discussed in terms of a developmental psychopathology approach to disorders in young women. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decremental motor responses to repetitive nerve stimulation in ALS

Repetitive nerve stimulation (RNS) of the trapezius muscle at slow rates was performed on 192 patients with amyotrophic lateral sclerosis (ALS). Fifty-six patients (29%) showed classical neuromuscular decrement of 10-43% (mean 16.8%) while 44 patients (23%) had a borderline decrement of 5-9%. The trapezius was significantly more sensitive in revealing the defect than the distal hypothenar muscles. In 30 patients followed serially, the decremental response remained constant or increased with time. However, 25% of patients continued to show no decrement in spite of progression of disease. No statistical correlation was found between decrement and clinical severity, disease staging, or disease progression. The finding that at least 50% of ALS patients show some degree of decrement on RNS of the trapezius muscle suggests that functional alterations of the neuromuscular junction accompany this disease.     

Cardiovascular responses to gastric hypo-osmolar stimulation in anesthetized dogs

We compared the cardiovascular response to the gastric infusion of distilled water (DI) with that to the gastric infusion of 0.9% saline (SI) and gastric ballooning with 37 degrees C water (BA) through a gastric fistula in splenectomized mongrel dogs (n = 7). DI, and SI amounting to 5% of body wt and the same volume of water were infused in approximately 20 s through the tube and responses in mean arterial pressure (MAP), CVP, heart rate (HR), and intra-esophageal pressure (EP) were monitored continuously. After DI, SI, and BA, the measured variables showed significant increases and attained maximal increases at about 2 min after the treatments. After DI, the maximum elevation in MAP was 21.3 +/- 1.9 mmHg and 2 times higher than in SI and BA. The corresponding value in CVP was 5.0 +/- 0.3 mmHg and 2-3 times higher than with SI and BA, and HR increased by 26.1 +/- 3.0 beats/min showing 3 to 6 times larger increases compared with SI and BA. These gastro-cardiovascular reflexes were abolished after subdiaphragmatic truncal vagotomy. These findings suggest that both the mechanical and osmotic stimuli to the stomach induce cardiovascular reflexes and that the vagus is involved in the reflex.     

Parallel metabolic and feeding responses to lateral hypothalamic stimulation

Energy metabolism and food intake effect each other. Many studies demonstrated that the lateral hypothalamus (LH) participates in the control of both feeding behavior and energy metabolism. We assessed the effect of a bipolar near threshold feeding eliciting electrical stimulation of the LH first on the feeding response and then on the background metabolism (metabolism free from the part due to locomotion) and respiratory quotient (RQ), on Wistar male rats, during either the light or the dark phase of the nycthemeron. LH stimulation resulted in a delayed and rather long increase in background metabolism that was more dramatic during the light phase. This metabolic response paralleled the delayed feeding response (more than 10 min) we obtained during behavioral tests. The increase in energy production was sustained by release of energy substrates from the endogenous stores, and this showed a circadian dependence. Mainly carbohydrates (rise in RQ) were used during the light phase stimulation whereas lipids (decrease in RQ) were released in the dark phase.