Accumbens-caudate-septal circuit as a system for hippocampal regulation: involvement of a GABAergic neurotransmission.

Hippocampal-based epileptiform activity may reach the basal ganglia via the nucleus accumbens. Previous data suggested that caudate nucleus is able to influence hippocampal epilepsy, probably sending a projection to the septum. In order to test the hypothesis of a retrograde activation of accumbens-caudate pathway in hippocampal regulation, we electrically stimulated both caudate nucleus and nucleus accumbens and studied modifications of hippocampal EEG in the feline focal epilepsy model. We also performed bilateral electrolytic lesion of nucleus accumbens and repeated caudate stimulation. Results showed that nucleus accumbens stimulation was ineffective in modifying hippocampal epilepsy; o…

Dopaminergic control of feline hippocampal epilepsy: A nigrophippocampal pathway

Abstract Substantia nigra is a mesencephalic structure inserted along several circuits which appear to play a key role in epilepsy. In previous researches we postulated that substantia nigra pars compacta (SNpc) may be the site of a precise control of hippocampal epilepsy while substantia nigra pars reticulata (SNpr) may exert a modulation of both neocortical epilepsy and spreading of hyperactivity toward a motor target. In order to better understand mechanisms subserving nigral action in feline hippocampal epilepsy we electrically stimulated SNpc (dopaminergic), before and after sulpiride (dopamine receptor-antagonist) intravenous injection. Furthermore we compared hippocampal epileptiform…

Study of spindle-spike interactions: Features of basal ganglia control

Summary Changes in cortical spindle distribution following penicillin (PCN) injections were studied in feline generalized PCN epilepsy. PCN activation caused no substantial changes in spindle duration, frequency and intraburst frequency, while significant reductions in the amplitude of the negative waves were noted. At the same time combinations of spindle waves and epileptic complexes were recorded with one or more spikes randomly occurring at the beginning, in the middle, or at the end of a spindle envelope. Low frequency stimulation of the caudate nucleus induced a certain degree of enhancement in cortical precruciate spike frequency while high frequency activation of the entopeduncular …

Relations between basal ganglia and hippocampus: Action of substantia nigra and pallidum

Several interrelationships exist between basal ganglia and hippocampus. The ventral striatum appears to be involved in the control of the dopaminergic nigro-striatal pathway. The caudate, in turn, seems to influence the hippocampal theta rhythm and to inhibit hippocampal spikes. In the present work the role played by globus pallidus pars interna and substantia nigra pars compacta on hippocampal bioelectrical activity is studied. Injection of sodium penicillin i.v. produces steady interictal spikes in the hippocampus. Substantia nigra stimulation induces regular theta rhythm and inhibits the spikes. Pallidal stimulation, on the contrary, appears to strongly enhance epileptiform activity, pro…

Effect of acetylcholine and dopamine iontophoretically applied on the sensory responsive caudate unit

A putative integrative function of the striatum was evaluated through the study of the electrical activity of sensory responsive caudate neurones. Both nervous (radial nerve) and auditory stimulations were delivered in order to characterize populations of neurones affected by peripheral stimuli; the units were previously activated by iontophoretic glutamate. On these units the iontophoretic ejection of ACh and DA was tested. Experimental results demonstrated a prevalent excitatory effect of ACh, while DA appeared to exert a drastic decrease on firing rate. A comparison between peripheral stimuli and chemical substances was made. The result of such study showed a most important action of the…

Effects of desipramine and alprazolam in the forced swim test in rats after long-lasting termination of chronic exposure to picrotoxin and pentylenetetrazol.

Abstract Rats were treated for 5 weeks with three subconvulsant doses of picrotoxin (PTX) and pentylenetetrazol (PTZ) per week to induce a persistent reduction of the GABA A receptor function which results in chemical kindling. Fifteen days after termination of this treatment schedule, the effect of desipramine (DMI) and alpraxolam (ALP) on immobility time in the forced swim test (FST) was evaluated. Chronic PTX and PTZ did not alter the immobility time. Acute PTX and PTZ reduced the immobility of rats chronically treated with vehicle but not of those exposed chronically to PTX and PTZ. Chronic PTX did not influence the anti-immobility effect of DMI, but blocked that of ALP. Chronic PTZ mar…

Nigral influence on focal epilepsy.

The substantia nigra (SN) has been proposed as a structure involved in epileptiform phenomena. Previous investigations demonstrated that SN is able to elicit hippocampal rhythmic slow activity (RSA) as well as to inhibit hippocampal interictal spikes induced by parenteral administration of penicillin. The present series of experiments was carried out in order to characterize the action of SN on a focal model of hippocampal epilepsy. Experiments were performed on encephale isole cats in which steady epileptiform activity was induced by locally applied penicillin. Electrical stimulation of SN pars reticulata (pr) caused a statistically significant decrease of hippocampal spike frequency and a…

Evidence of a contralateral motor influence on reciprocal inhibition in man

The role of contralateral movement on both H reflex and reciprocal inhibition was studied. In normal men H reflex was induced by median nerve stimulation. Reciprocal inhibition was achieved through stimulation of the antagonist radial nerve. On this basis the effects of contralateral arm movement were analized. Furthermore the putative influence of exteroceptive origin was also verified by means of digit stimulation. Results showed that contralateral arm movement did not affect H reflex amplitude; on the contrary, it was able to enhance reciprocal inhibition induced by extensors on flexors. Study of cutaneous afferents demonstrated that contralateral digit stimulation failed to elicit modif…

Interrelations between globus pallidus and hippocampal epilepsy in the cat (1)

AbstractElectrically induced afterdischarge (ADs) were evoked in the cats' dorsal hippocampus. The action of the conditioning prestimulation of the pallidus nucleus on AD duration was studied. A significant facilitatory influence was observed when pallidal conditioning stimulation immediately preceded hippocampal test stimulation. The time course of the phenomenon showed a decrease of the conditioning action when the interval between the two stimulations increased: complete disappearance of the effect occurred after about 800 ms. Results are discussed as far as functional relationships between basal ganglia and rhinencephalic system are concerned.

Negative occurrence between hippocampal rhythmic slow activity and epileptiform spikes: Influence of the striatum

AbstractThe effects of caudate and septal stimulation on hippocampal activity were studied. Sodium penicillin was intravenously injected in order to induce a steady rate of in-terictal epileptic activity. Penicillin injection caused significant reduction of the rate of occurrence and duration of hippocampal rhythmic slow activity (RSA). Spontaneous RSA as well as RSA-eliciting caudate and septal stimulation induced a marked inhibition on frequency of epileptiform complexes. Lesions of the medial septal nucleus made it impossible to record RSA or to observe any sort of influence on hippocampal epileptiform activity by caudate stimulation. This result suggests that the septum is important for…

A feature of caudate control of focal hippocampal epilepsy: evidence for an anterograde pathway

Previous experimental evidences showed that the caudate nucleus has a modulatory effect on hippocampal epilepsy. The caudate's regulating action might reach the hippocampus either via the septal region or, retrogradely, via the accumbens nucleus. In order to obtain new data about the pathway involved in caudate hippocampal influence the spreading of abnormal activity towards the nucleus accumbens was studied. Furthermore the effects of caudate stimulation in animals with electrolytic lesions of the nucleus accumbens were analyzed. It was observed that abnormal penicillin-induced activity spreaded from the hippocampus to the nucleus accumbens in about 30 minutes. In animals with and without …

Studies of network organization and dynamics of e-beam crosslinked PVPs: From macro to nano

Abstract In this work the influence of poly(N-vinyl pyrrolidone) (PVP) concentration in water on the organization and dynamics of the corresponding macro-/nanogel networks has been systematically investigated. Irradiation has been performed at the same irradiation dose (within the sterilization dose range) and dose rate. In the selected irradiation conditions, the transition between macroscopic gelation and micro-/nanogels formation is observed just below the critical overlap concentration (∼1 wt%), whereas the net prevalence of intra-molecular over inter-molecular crosslinking occurs at a lower polymer concentration (below 0.25 wt%). Dynamic–mechanical spectroscopy has been applied as a cl…

Cortical stimulation and reflex excitability of spinal cord neurones in man.

The H reflex technique was used to evaluate the influence exerted by cortical conditioning on the excitability of the alpha-motoneurone pool and on IA interneuronal activity (reciprocal inhibition). In ten subjects at absolute rest electrical and magnetic stimulation of the motor cortex was transcranially applied during flexor carpi radialis H reflex eliciting and in conditions of reciprocal inhibition induced by radial nerve stimulation. The time courses showed that at intensities below motor threshold, electrical brain conditioning induced an increase in the amplitude of the test reflex when the cortical shock was given 4 ms after the test H reflex. On the contrary, reciprocal inhibition …

Effects of Substantia Nigra Stimulation on Electrical and Mechanical Activities of the Duodeno-Jejunal Loop, in the Cat

The effect of substantia nigra stimulation on duodeno-jejunal intraluminal pressure and electrical activity was analysed in the cat. An inhibitory influence was noted to occur on both the intestinal pressure and the electrical response activity (ERA): the effect seemed to be in correlation with the stimulus parameters employed. After bilateral vagotomy, the inhibition remained substantially unchanged. The possibility of the existence of a sympathetic pathway mediating the effect is emphasized.

A study of caudate inhibition on an epileptic focus in the cat hippocampus

The mechanisms whereby the caudate nucleus modifies hippocampal spiking activity have been studied. Epileptiform activity was induced in the cat hippocampus by topical application of sodium penicillin in different concentrations. The frequency of induced spikes appeared to be directly correlated to the two doses of epileptogenic agent. The inhibitory effect of 10 Hz caudate stimulation on spike frequency was present even when stimulation lasted for 180 s. Likewise 25 Hz caudate stimulation brought about an inhibition which was maintained by stimulus trains lasting up to 90 s, while the degree of inhibition was reduced by trains of longer duration (120, 150 and 180 s); similar results were a…

NMDA-GABA interactions in an animal model of behaviour: a gating mechanism from motivation toward psychotic-like symptoms

We studied the effects of desipramine, alprazolam, muscimol and dizocilpine (MK-801) (alone or associated with desipramine) in the forced swimming test in rats after long-lasting termination of chronic exposure to vehicle and pentylenetetrazol. Sensitisation with pentylenetetrazol was ineffective in changing immobility time in the forced swimming test compared to vehicle treatment; pentylenetetrazol enhanced the anti-immobility effect of desipramine, abolished the anti-immobility effect of alprazolam and did not affect the anti-immobility effect of muscimol. MK-801 at the dose that did not modify immobility time in vehicle-treated rats and in pentylenetetrazol-treated animals strongly poten…

Bilateral reciprocal organisation in man: focus on IA interneurone

The H reflex of flexor carpi radialis and radial-induced reciprocal inhibition were recorded in normal subjects during conditioning stimulation of the contralateral median or radial nerves. It was found that stimulation of the contralateral median nerve enhanced the degree of reciprocal inhibition exerted by the radial nerve on the median nerve, while contralateral radial nerve stimulation reduced the reciprocal inhibition exerted by the extensor on the flexor. In two subjects in which a pure extensor H reflex was recorded specular features were observed following contralateral median and radial stimulation. These findings are considered to be the electrophysiological manifestation of contr…

Nocturnal obstructive respiratory events severity is associated with low parental quality

Objective: Despite of the large prevalence of obstructive sleep apnea syndrome (OSAS) in pediatric age, numerous aspects of its impact on day life and on parental quality are still poor studied and considered in the clinical management. The study evaluated the stress levels and copying styles in a large sample of mother of children with OSAS. Method: 374 mothers of children affected by OSAS (mOSAS) were compared with a group of mothers of 421 neurotypical healthy children (mTDC) for stress perceived stress levels and for coping strategies. Subjects were recruited from Italian Regions in Sicily, Campania, Calabria and Umbria. Results: Among both groups mOSAS and mTDC no differences were repo…

Habenular effect on hippocampal excitability is not cholinergically-mediated.

Glutathione-sensitive nanogels for drug release

Nanogels (NGs) synthesized by pulsed electron-beam irradiation of semi-dilute poly (N-vinyl pyrrolidone) (PVP) aqueous solutions, at relatively low energy per pulse and doses within the sterilization dose range, represent a very interesting family of polymeric nanocarriers. Ionizing irradiation-induced crosslinking of PVP allows to control particle size, and surface chemistry of the polymer nanoparticles without making use of catalysts, organic solvents or surfactants, and with beneficial effects onto the purity and hence biocompatibility of the final products obtained. Furthermore, the availability of reactive functional groups, either generated by the radiation or purposely grafted via co…

Electrophysiological and microiontophoretic analysis of the habenulo-hippocampal circuit.

In the cat, the effects of lateral habenula stimulation, at different ranges of frequency, on hippocampal units were studied. Habenular stimulation at low frequency excited, while at high frequency inhibited the greater part of hippocampal units. Moreover, in order to clarify the possible pathway involved in the habenulo-hippocampal circuit, the effects of iontophoretic acetylcholine and serotonin on hippocampal units were compared with those of habenular stimulation. Iontophoretic acetylcholine induced both excitatory and inhibitory responses while serotonin induced only inhibitory responses. Iontophoretic atropine blocked the effects of acetylcholine ejection but did not antagonize stimul…