[Capillary networks and osmotic uptake in fungiform papillae]. / Rete capillare e richiamo osmotico delle papille fungiformi.

In the research it has been tested the ability of convoluted capillary network of the fungiform papillae to act as countercurrent ionic exchanger and therefore to give rise a water uptake from the external environment. Manometric determinations of the water inflow during immersion of the tongue in solutions of different osmolality have shown a conspicuous water uptake, osmotic in nature and largely supported by the Na+ absorbed from the external solutions. The Na+ inhibits also the receptor electrical response to the stimulating Ca++ solutions. These observations show that the papillae can be considered as osmotic devices and emphasise also that the Na+ is directly involved in the papillary functional activity.

[Effect of metavanadate on papillary water uptake]. / Influenza del metavanadato sul richiamo idrico papillare.

It has been examined the influence of vanadium on the papillary osmotic water-salts uptake in order to differentiate it from water flow of other biological substrates as amphibia epithelia. Between the different vanadium compounds only the metavanadate is active and only after administration in the abdominal vein. The general influence of metavanadate is a facilitating one and concerns: electrical receptor afferent discharge, osmotic water uptake and ciliary motility. At the papillary level therefore vanadium is not at all an inhibitory agent as observed in many biological substrates. This observation rule out any analogy in the processes of water inflow operating respectively at the fungiform papillae and amphibia epithelia.

[Quantitative aspects of ciliary apparatus motility of fungiform papillae]. / Aspetti quantitativi della motilità dell'apparato ciliare delle papille fungiformi.

The present research is intended to evaluate the frequency of the ciliary beat in different formations of the frog's oral cavity. The phenomenon has been quantitatively evaluated on the television images of mucus-ciliary waves by means of a photometric method, in order to obtain an electrical indication of the beat frequency. The results show that frequency of the ciliary beat is not uniform in all formations examinated. Differences in the beat frequency were evidenced in the single coronae ciliatae, further the frequencies of the beat decreases sistematically from the base to the tip of the tongue. The cilia on the lingual edge and on the palat exhibit a similar behaviour. The uniformity of the ciliary behaviour in the whole oral cavity is stressed and the factors contributing to a particular ciliary frequency in the fungiform papillae are discussed.

[Facilitating effects of axotomy of the glossopharyngeal nerve on the motor reflex response of the frog medulla oblongata]. / Effetti facilitanti dell'assotomia del glossofaringeo sulla risposta riflessa motoria del midollo allungato di rana.

In the previous papers we have reported that the innervation of the frog lingual mucosa exercises a presynaptic inhibition at the bulbar region in order to integrate the mechanoreceptive information coming from the tongue. The present investigation was undertaken to establish if also the complementary tactile innervation of fungiform papillae has a similar ability. First of all it has been assayed the evocation of PAD tests by papillary innervation; then the facilitating effects, induced by the glossopharyngeal axotomy, on the afferents mass discharges recorded from hypoglossal nerve have been examined. Electrical stimulation of mechanical neurons at the root of IX produced DRP and DRR both at glossopharyngeal and hypoglossal nerves. After 5 and 10 days from glossopharyngeal axotomy becomes evident a considerable enhancement of efferent responses in many diastaltic arches of bulb. These effects strongly suggest a very evident inhibitory activity at the bulbar projection of papillary innervation. From all these observations it follows that presynaptic inhibition is joint to all the lingual mechanoreceptive afferences.

[Inhibitory effect on crossed bands in the tongue mechanoreceptor innervation]. / Influenza inibitoria dei fasci crociati cell'innervazione meccanocettiva linguale.

The inhibitory influence exercised at the bulbar level by crossed afferent innervation of the lingual mechanoreceptors has been examined in the frog. To reach this aim it has been electrically stimulated the central stump of both glossopharyngeal and hypoglossal unilaterally axotomized nerves and recorded the crossed reflex effects in the controlateral hypoglossal motoneurones. By comparison a similar reflex has been evoked by means of stimulation of intact glossopharyngeal and hypoglossal nerves in the same preparation. As regards the glossopharyngeal crossed afferences it has been observed that the stimulation of axotomized nerves intensifies controlateral reflex response, while stimulated intact afference produces an increased reflex only after controlateral hypoglossal section. This last kind of effect has been observed also in the case of a crossed innervation of the hypoglossal lingual afference. These results show a notable extension of lingual crossed mechanoreceptors innervation and indicate its ability to obtain complex contralateral inhibitory effects. This ability however is more evident as regards the glossopharyngeal nerve. These observations are useful in order to explain the properties of the same inhibitory influences exercised homolaterally by the mechanoreceptors afference.

[Direct observation of the inhibitory action of lingual mechanoreceptor afferents in the frog]. / Osservazione diretta dell'azione inibitoria delle afferenze meccanocettive linguali di rana.

In previous researches it has been demonstrated that the frog's tongue mechanoreceptors afferences exercise a presynaptic inhibition on the motor reflex activity evoked by themselves at the bulbar level. Since the indication on this effect were only indirectly obtained this present investigation is now devoted to obtain on the same subject also more direct observations. Therefore it has been examined the behavior of glossopharyngeal-hypoglossal reflex response after conditioning stimulation in different experimental conditions. In intact preparation it has been tested that the crossed inhibition between the mucosal and papillary tongue afferences. This conditioning activation of mucosal afference obtains persistent inhibition of the small reflex response evoked by electrical stimulation of single fungiform papillae. As expected this effect is no evident when the hypoglossal nerve was axotomized. In these preparations however the papillary test response is enhanced and becomes maximal after conditioning stimulation. Also the glossopharyngeal-hypoglossal reflex is depressed after the conditioning stimulation, but the inhibitory influence remains present as much after axotomization of glossopharyngeal nerve. The results show directly the inhibitory influence of frog lingual mechanoreceptors innervation on the bulbar reflex activity and also its correlation with presynaptic properties of the afferences themselves. In fact the facilitating effects observed after axotomy in the reflex response clearly indicate the ability of presynaptic inhibition to control the spread of excitation in the bulbar neuron circuitry. In this context the presynaptic inhibition appears an essential property of lingual mechanoreceptors innervation in the frog.

[Effect of section of the hypoglossal nerve on the glossopharyngeal-hypoglossal reflex in the frog]. / Effetti della sezione dell'ipoglosso sul riflesso glos sofaringeo-ipoglosso di Rana.

This research concerns the modulation by lingual afferences of the reflex activity of frog XII nucleus. Some informations on the processes utilized to obtain this effect has been achieved by comparing the glossopharyngeal-hypoglossal reflex evoked bilaterally after excision of one hypoglossal nerve. The reflex response and electrotonic potential become more intense omolaterally to the section of XII at the IV-V day; However these effects disappear later (XII-XV day). These observations completely disagree with the presence of a large injury normally produced in the nucleus of XII by retrograde motoneuron degeneration. The reflex facilitation has been attributed therefore to the degeneration of the afferent component which is associated in the amphibia to the XII and exerts centrally a PAD effects.

[Importance of the degeneration of afferent components of the hypoglossal nerve on the reflex activity of the nucleus of the hypoglossal nerve in the frog]. / Importanza della degenerazione della componente afferente dell'ipoglosso nel comportamento riflesso del nucleo del XII di Rana.

The section of frog XII cranial nerve facilitates the reflex activity given by its nucleus. Since this positive effects is not dependent upon any motoneurons degeneration, the hypothesis has been put forward that only the afferent component of the XII nerve is able to modulate the reflex activity by means of PAD effect at the solitarius nucleus. This hypothesis has been tested examining the effect both on the glossopharyngeal reflex response and on the DRR following excision respectively of the dorsal root and of the whole hypoglossal nerve. In preparations with a XII dorsal root transected, electrical stimulation of the homolateral glossopharyngeus nerve evoked a much more intense reflex response than at the intact side. The same effect was evident after the section of the whole nerve.

[Activation of afferent pathways and of control frog olfactory bulb and extracellular field potentials]. / Attivazione delle vie afferenti e di controllo del bulbo olfattivo di rana e potenziali di campo extracellulari.

It has been recorded the extracellular field potentials of the frog's olfactory bulb produced by electrical stimulation of the commissura anterior and small branches of the olfactory nerve. The activation of the commissural system obtain a positive, long-lasting field potential generated at the soma of the granular cells. The olfactory nerve stimulation produce also a positive surface wave bath at the end of bulbar reply: this effect can be attributed to the activation of the bulbar component of commissural system at the NOA. The recognizable electrical effects of the commissural system allow to make clear the sources of the extracellular field potentials in the bulbar neuronal circuits.

[Integration of oral mechanoreception of amphibia]. / L'integrazione della sensibilita' meccanocettiva orale degli anfibi.

The study concerns the effects obtained at the medulla by electrical stimulation of mechanoreceptive afferences associated to the hyomandibularis nerve and branches of V and VII cranial nerves of the frog. Each of the afferences examined activates both nuclei of XI and XII in spite of the different medullary input; this action is very similar to that carried out by the mechanoreceptor afferences coming from papillae fungiformes. These result show very well the common ability of all the afferences coming from the mouth to obtain a similar action at the medulla. These properties suggest a convergence of the oral mechanoreceptor information on a mechanism of integration in order to obtain a coordination of the tongue and oesophagus motor reflex.

[Extrapapillary mechanoceptive afferent system of the frog tongue]. / Il sistema afferente meccanocettivo extrapapillare della lingua di Rana.

Tactile stimuli applied to the interpapillary spaces of the frog's tongue surface, activated mechanoreceptor afferences. The neurons of these afferences are associated only to the hypoglossal nerve and are able to make a complex central influence. A first effect is a hypo-hypoglossal reflex concerning the muscles of the tongue and of its floor. A second effect is a antidromic discharge of impulses travelling in the dorsal root of hypoglossal nerve and thus representing a DRR. Possibly this effect is related to the PAD phenomena of central terminals of the mechanoreceptors extrapapillary afferences.