[Normotest in the early neonatal period]

The aim of this study is the behavior of Normotest (NT) values in newborns in the first 4 days of life. The study has been carried out between January, 1982, and December, 1984, at the Department of Child Health and Neonatal Medicine - School of Medicine - University of Genoa. The number of infants tested was 1320. 694 were males and 626 females, 529 preterm (G.A. less than 37 weeks) and 791 full term babies. Infants have been tested from one to five times in the first four days of life, with the first evaluation within 12 hours of life. 1215 newborns (92%) presented NT values greater than 20%, 105 babies (8%) had NT below 20% in at least one evaluation, and received Vitamin K1 (0.5 mg/kg i.m.) as prophylaxis, being thereafter excluded from this study. Among the neonate with NT greater than 20%, 426 babies have been considered, who had, at least, three evaluations in the first four days of life. 288 (68%) of the 426 newborns, had not important disease, while 138 (32%) were sick neonates; of these babies 88 (64%) had respiratory distress syndrome and 50 (36%) had an infectious condition. The mean of NT values of the 426 newborns decreased from the first (33.84%) to the 2nd day (32.72%), with a following increment in 3rd (35.29%) and 4th day of life (39.01%). Newborns with gestational age (G.A.) less than 34 weeks showed significantly lower values than newborns with G.A. between 34-37 weeks and those with G.A. greater than 37 weeks. No newborn with NT values greater than 20% either received vitamin K or showed symptoms of haemorrhagic disease in early or later neonatal period.

The oxytocin antagonist d(CH2)5Tyr(Me)-Orn8-vasotocin inhibits male copulatory behaviour in rats

The effect of an intracerebroventricular (i.c.v.) injection of the oxytocin antagonist, d(CH2)5Tyr(Me)-Orn8-vasotocin, on the copulatory behaviour of vigorous male rats in the presence of females in estrus was studied. The peptide (2.5, 25 and 50 ng, 15 min before mating tests) decreased the number of mounts and intromissions, and abolished ejaculation almost completely at all doses tested. The peptide failed to significantly influence motor activity at the doses used. The results support the hypothesis that central oxytocin plays a physiological role in the expression of copulatory behaviour.

Hypophysectomy prevents ACTH-induced yawning and penile erection in rats

The intracerebroventricular administration of ACTH1-24 (3-5 micrograms/rat) produced a behavioural syndrome characterized by recurrent episodes of penile erection and yawning in rats. Hypophysectomy prevented ACTH1-24-induced yawning and penile erection. These results suggest that pituitary has a "trophic" action not only on peripheral target organs but also on structures in brain controlling specific behavioural responses.

Yawning is elicited by D2 dopamine agonists but is blocked by the D1 antagonist, SCH 23390

The subtype of dopamine (DA) receptors mediating the yawning response to DA agonists was determined in rats. Yawning was elicited both by the mixed D1-D2 agonist apomorphine and by the specific D2 agonist LY 171555, but not by the selective D1 agonist SKF 38393. Both apomorphine- and LY 171555-induced yawning were antagonized not only by the selective D2 antagonist sulpiride but, unexpectedly, also by the selective D1 antagonist SCH 23390. The results suggest that DA receptors mediating the yawning response are of the D2 type, and that these receptors are connected with D1 receptors in such a way that the blockade of the latter results in the functional inactivation of the former.

Dopamine receptors mediating yawning: are they autoreceptors?

Yawning was induced in rats by the (+) enantiomer of 3PPP, while (-)-3PPP was inactive. Yawning was present 24, but not 1, 6 and 12 h after reserpine treatment. The (+)-3PPP-induced yawning was antagonized by haloperidol and sulpiride but not by domperidone. Reserpine-induced yawning was antagonized by sulpiride and by alpha-methyltyrosine suggesting that this behavior may be induced by endogenously released dopamine. Reserpine-pretreatment potentiated (+)-3PPP-induced yawning. The results argue against the view that yawning is the behavioural correlate of autoreceptor-mediated inhibition of DA transmission, and suggest that this behaviour is due to the stimulation of a special population of central postsynaptic DA receptors.

Estrogens antagonize apomorphine-induced yawning in rats

The administration of a small dose of apomorphine (50 micrograms/kg s.c.) induced repeated episodes of yawning in male rats. Short-term (3 days) treatment with 17 beta-estradiol antagonized apomorphine-induced yawning in male rats. Moreover, apomorphine induced yawning much less effectively in female than in male rats. These results suggest that both endogenous or exogenously administered estrogens induce subsensitivity of the DA receptors mediating yawning in rats.

Pattern electroretinogram in multiple sclerosis

The pattern electroretinogram obtained in patients affected by multiple sclerosis were compared with those in a normal population. The pattern electroretinogram amplitude in multiple sclerosis optic neuritis frequently appeared normal, but pattern electroretinogram amplitude abnormalities were found in patients suffering from recurrent multiple sclerosis optic neuritis. Pattern electroretinogram examination appears a useful method in the differential diagnosis between axonal and demyelinating optic nerve impairment.

[The origin of the electroretinogram induced by structured stimuli in man]

The Authors studied the checkerboard pattern electroretinogram (PERG) behaviour in normal subjects and in patients suffering from traumatic lesion of optic nerve, demyelinating optic neuritis, axonal optic neuritis, retinal vascular disorders and retinitis pigmentosa in order to verify the PERG origin. According to our data the PERG appears to originate from ganglion cells since the signal diminished or disappeared in axonal lesion of optic nerve, as a result of retrograde ganglion cell degeneration. Furthermore, the demyelinating lesions of optic nerve were not able to modify the PERG wave. In patients suffering from retinal receptor disturbances the flash electroretinogram (FERG), which is probably an expression of receptor activity, was greatly impaired, whereas PERGs were either normal or less impaired than FERGs. These data demonstrate the different origin of PERG and FERG.

[The effect of fatigue on the biopotential of muscle fiber cells]

Muscular fatigue is a biological situation which is very difficult to quantify. The Authors studied through a computer analysis the power spectrum of electromyogram, recorded from abductor digiti minimi muscle during maximal and minimal contraction effort before and after fatigue and after muscle prolonged relaxation in 8 normal subjects. No significant spectrum differences were found between maximal and minimal effort in each trial, and between the spectra obtained before fatigue and after muscle prolonged relaxation. On the contrary significant differences were found between the spectra obtained after fatigue and the other conditions. The power spectrum analysis appears, also, to be a reliable neurophysiological parameter for the study of biological aspects of muscular fatigue.

[The effect of thoracic pressoreceptors on heart rate in man]

Sinus arrhythmia (SA) is a physiological event related to the respiratory activity. The aim of this study was to find a relation between SA and different deep breathings. A transductor monitored the chest respiratory movements and a cardiotachometer calculated and plotted the instantaneous heart rate, synchronously during different breathing efforts. In 10 normal subjects a good linear correlation was found between the breathing depth and SA quantifying the relation between the chest receptor activity and SA also with limited chest expansion.

[The conduction of optic nerve fibers using different visual patterns]

The Authors have studied the behaviour of checkerboard pattern visual evoked potential (VEP) latencies by using different spatial frequency stimuli and different stimulating visual fields in order to demonstrate whether spatial frequency might constitute a parameter capable of exciting different retinal regions like different stimulus fields. According to the recent literature low spatial frequency stimuli generate VEP with latencies which are significantly shorter than high spatial frequency stimuli, making this method more reliable for the differentiation of macular and peripheral retinal fields.

Muscle-nerve ephaptic excitation in some repetitive after-discharges

We describe high frequency muscular repetitive after-discharges (MRDs), induced by maximal or near maximal electrical nerve stimulation, in 5 patients suffering from different peripheral neuropathies. No MRDs were observed at rest or during voluntary contraction. In all the MRDs the interval between the onset of the M wave and the onset of the MRD did not change in relation to the nerve stimulation point; double supramaximal stimulation with adequate delay, delivered at the same nerve site, could suppress the MRDs. From the electrophysiological features the authors suggest an interpretative model: the muscular electric field of the M wave could reexcite ephaptically an intramuscular axon, with defective repolarizing capacity, producing a muscle-nerve reverberating loop.