The adaptation of the frog tongue to bitter solutions: Enhancing effect on gustatory neural response to salt stimuli

• 1.1. The initial phasic component of frog gustatory neural responses to various 0.1 M salt solutions was greatly augmented in amplitude after the tongue was adapted for 10 sec to 1 mM quinine-HC1 (Q-HCl), quinine-H₂SO₄ (Q-H₂SO₄) and picric acid.
• 2.2. Out of 103 examined gustatory units responding to both 0.5 M NaCl and 1 mM Q-HCl or to 0.5 M NaCl alone, 67% exhibited an enhancement of response to the NaCl after the Q-HCl adaptation but the remaining 33% showed a suppression or no alteration of NaCl response after the Q-HCl.
• 3.3. Intracellular taste cell responses to salt stimuli after 1 mM Q-HCl adaptation showed an initial phasic depolarization which was not observed under control Ringer adaptation. This de polarization might be concerned with the enhancement of initial phasic neural responses to salts following the Q-HCl adaptation.

     

OFF-RESPONSE OF GUSTATORY NERVE FOLLOWING TERMINATION OF QUININE STIMULI APPLIED TO THE FROG TONGUE

After a Ringer-adapted frog tongue was stimulated with 0.001M quinine-HCl(Q-HCl) in deionized water, the Ringer rinse ofthe tongue elicited a large gustatory nerve response. Sincethe Ringer-adapted tongue did not respond to Ringer solution,this nerve response after Q-HC1 is termed an off-response. Itwas revealed that the off-response of gustatory nerve to theRinger rinse resulted from the enhancing effect of Q-HCl adaptationupon the response to 111.2 mM NaCl component of Ringer whichwas ineffective for Ringer-adapted tongue. Weaker enhancementof the response to NaCl of Ringer was also produced by adaptingthe tongue to water. Therefore, the enhancing effect of Q-HClin deionized water is the summed effect of Q-HCl solute andwater solvent. Microelectrode study revealed that during theadaptation to Q-HCl the membrance potential of some NaCl-sensitivetaste cells was more hyperpolarized than that of Ringer-adaptedstate. The larger membrane potential maintained under Q-HCladaptation was markedly depolarized by the NaCl component ofthe Ringer. This sufficient depolarization response of the tastecells might be associated with generation of the off-responsein the gustatory nerve.     

A study of excitatory efferent fibres in the intestinal nerve of the fowl (Gallus domesticus)

• 1.1. The intestinal nerve of the fowl was studied in vitro.
• 2.2. A significantly larger amplitude spike discharge was recorded in side branches of the nerve which innervate the gut when the aboral end of the main nerve trunk was stimulated than when the oral end was stimulated.
• 3.3. Postganglionic autonomic neurones innervating the smooth muscle of the ileum are not located in the intestinal nerve. Evidence is presented, however, supporting the idea that such neurones innervating the rectum are located in the rectal position of the nerve.
• 4.4. The increase in intraluminal pressure and circular muscle tension in the ileum was greater following aboral nerve stimulation than following oral nerve stimulation.
• 5.5. It is suggested that excitatory efferent nerve fibres ascend the intestinal nerve to innervate the ileum.

     

Mechanism of desensitization in taste responses: Prolongation of frog taste nerve responses to bitter substances by adapting the tongue to CaCl2 solution

• 1.1. The taste nerve responses to bitter substances declined rapidly to the spontaneous level during stimulation, but were remarkably prolonged when the tongue was stimulated after adapting to CaCl₂ solution.
• 2.2. The prolongation of the responses (inhibition of desensitization) to bitter substances was not inhibited by the Ca-channel blockers, suggesting that the inhibition of the desensitization occurs not inside taste cells but at membrane level.

     

Responses of dorsal tricorn-type sensilla on Ligia exotica

• 1.1. In order to investigate the function of the dorsal tricorn-type sensilla on Ligia exotica, the morphology and distribution of the setae and neural responses to certain stimulus modalities were studied.
• 2.2. These foraminate sensilla are found to occur over the body surface, except for several appendages and the ventral carapace (sternite); the dorsal carapace (tergite) is covered by only this type of sensilla.
• 3.3. The tricorn-type sensilla located on the dorsal carapace responded to mechanical, gustatory and olfactory stimulation.
• 4.4. The function of the tricorn-type sensilla on the dorsal carapace was discussed.

     

The neural control of release of hyperlipaemic hormone from the corpus cardiacum of Locusta migratoria

• 1.1. The neural control of the release of hyperlipaemic hormone has been studied in isolated corpora cardiaca of Locusta migratoria using electrical stimulation of the nervi corporis cardiaci I and II, and assaying the bathing medium for hyperlipaemic activity.
• 2.2. Stimulation of nervus corpus cardiacum II (NCC II) results in the release of hormone which is dependent upon the arrival of compound action potentials within the glandular lobe of the corpus cardiacum.
• 3.3. Sodium deficient Ringer and Ringer containing 10⁻⁶ M tetrodotoxin abolish the compound action potential and with it the release of hormone.
• 4.4. The mechanism of release is dependent upon the presence of extracellular calcium-ions.
• 5.5. Stimulation of nervus corpus cardiacum I (NCC I) alone does not result in the release of hyperlipaemic hormone, but the presence of action potentials in NCC I potentiates the hyperlipaemic effect obtained by NCC II stimulation.

     

Aldosterone increases the amiloride-sensitivity of the rat gustatory neural response to NaCl

• 1.1. The percentage inhibition of the chorda tympani neural response to NaCI by topical application of amiloride to the tongue was significantly larger in rats pretreated with aldosterone than in control animals.
• 2.2. Adrenalectomized rats pretreated with aldosterone had significantly larger amiloride-induced inhibitions to a NaCl stimulus than did adrenalectomized control animals.
• 3.3. These data suggest that aldosterone may increase the number of active amiloride-sensitive sodium channels in the apical membrane of taste cells, as is known to occur in sodium transporting tissues of amphibians and mammals. They additionally represent a previously unnoticed hormonal influence over the gustatory system.

     

Dye-coupling among frog (Rana catesbeiana) taste disk cells

• 1.1. Dye-coupling among taste disk cells in the bullfrog fungiform papillae was examined histologically by injecting a fluorescent dye (Lucifer yellow) into the cell, and the effects of the dye-coupling on depolarizing responses induced by taste stimuli were studied electrophysiologically.
• 2.2. With dye injection into a taste cell, dye-coupling was found between taste cells (23%) or between taste cell and supporting cell (28%). With dye injection into a supporting cell, dye-coupling was found between supporting cells (34%) or between supporting cell and taste cell (27%).
• 3.3. Depolarizing responses recorded from either a taste cell or a supporting cell to stimulation with 0.5 M NaCl or 10 mM quinine-HCl were the same in amplitude whether the dye-coupling to another cell was present or not. On the other hand, depolarizing responses recorded from a taste cell for 0.5 mM acetic acid became significantly larger when dye-coupled to a supporting cell.
• 4.4. It is concluded that gustatory transduction for acid stimuli is influenced by supporting cells coupled to taste cells.

     

Tetanus responses under rapid bath solution change: Electrotonic depolarization of transverse tubules may release Ca2+ from sarcoplasmic reticulum of Rana japonica skeletal muscle

• 1.1. Single skeletal muscle fibers were transferred from a normal Ringer solution to Na⁺ ion free solution, and vice versa, and tetanus responses were recorded immediately after the transfer.
• 2.2. Fractional tetanus tension recorded immediately after the displacement from the Na⁺ ion free solution to normal Ringer solution was dependent on fiber diameter.
• 3.3. Diffusion of Na⁺ ions along the transverse tubules was simulated [apparent diffusion constant was 3.11 × 10⁻⁶ (cm²/s)].
• 4.4. Our results suggest that the electrotonic spreading of membrane potential, caused by an action potential in the transverse tubules, could release Ca²⁺ ions from sarcoplasmic reticulum.

     

Modulation of smooth muscle activity by excitatory and inhibitory nerves in the guinea-pig stomach

• 1.1. In smooth muscle of the guinea-pig stomach, intramural nerve stimulation evoked cholinergic excitatory junction potential in the fundus and non-adrenergic non-cholinergic inhibitory junction potential in the antrum, yet cholinergic contractions in both regions.
• 2.2. This dissociation between electrical and mechanical responses was mainly due to different sensitivity of the membrane for depolarization to acetylcholine.

     

Discharge patterns of lagenar and saccular neurones of the goldfish eighth nerve: Displacement sensitivity and directional characteristics

• 1.1. The responses of goldfish lagenar and saccular neurones were analyzed for underwater sound stimulation and head vibration in three orthogonal directions.
• 2.2. Both organs show similar sound pressure and displacement sensitivity below 200 Hz, and respond to a motional stimulus component at 100 Hz.
• 3.3. Calculated directions of best sensitivity in the saggital and horizontal planes correspond with hair cell orientation maps.
• 4.4. Stimulus-response phase-angles correspond only roughly with the patterns to be expected from a simple model for hair cell stimulation.
• 5.5. Variation in the degree of coupling between hair cell cilia and the otolith, and complex three-dimensional relative motion patterns probably occur in both organs.

     

Bioelectric activity from isolated brain of Lacerta atlantica

• 1.1. A method of maintaining the isolated lizard brain in a Ringer solution is described.
• 2.2. Microelectrodes and EEG recordings from different areas of telecenphalon and optical tectum were made.
• 3.3. The prolonged cells survival under the experimental conditions described has been demonstrated for several hours.
• 4.4. The isolated brain of Lacerta makes it easy to reach anatomical pathways which otherwise, in the whole animal, would be more difficult to reach.

     

Serotonin or electrical optic nerve stimulation increases the photosensitivity of the Aplysia eye

• 1.1. Exposure of isolated Aplysia eyes to serotonin (10⁻⁷ M) produces large and long-lasting (hours) increases in the ERG recorded from the surface of the eye.
• 2.2. Dopamine, octopamine, or acetylcholine do not mimic the effect of 5-HT on the ERG.
• 3.3. Brief electrical optic nerve stimulation (2 Hz, 2 min) also increases the ERG and this effect also lasts a long period of time (0.5–2 hr).
• 4.4. Our results suggest that serotonin increases the response of photoreceptor cells to light and that efferent optic nerve activity may modulate photosensitivity through release of serotonin in the eye.

     

Basis for hyperexcitation symptom caused by high doses of chlordimeform in the American cockroach

• 1.1. Exposure of isolated ventral nerve cords of the American cockroach to chlordimeform was followed by spontaneous and stimulus-induced hyperactivity which different from that induced by dieldrin in the distribution of spike amplitudes, the delay between stimulus and response and the stimulus threshold to induce hyperactivity.
• 2.2. Calcium (20 mM) abolished the impulse-evoked hyper-response of the nerve to chlordimeform but not to dieldrin.
• 3.3. Magnesium (40 mM) abolished the impulse-evoked hyper-responce of the nerve to dieldrin but not to chlordimeform.
• 4.4. Treatment of the insects with reserpine prior to dissection had no effect on the subsequent hyper-response of the isolated nerve to chlordimeform.
• 5.5. The observed action of chlordimeform is probably axonal, and is unrelated to its known aminergic effects.

     

Secretory oedema in diabetic submandibular glands during parasympathetic nerve stimulation: Relationship to microvascular abnormalities in streptozotocin-treated rats

• 1.1. Submandibular secretion during parasympathetic stimulation (5 Hz) was examined in streptozotocin-diabetic and age-matched control rats.
• 2.2. At 3 weeks, but not 3 and 6 months, flow rate was initially greater than in controls, but it declined rapidly after 30 min.
• 3.3. The reduction in flow rate was associated with oedema of the gLond.
• 4.4. At 3 months, graded stimulation revealed a tendency to oedema at frequencies of 10 Hz and above.
• 5.5. Morphologically, submandibular capillary density was increased in diabetic rats.
• 6.6. Thus, in diabetes the submandibular gland appears less able to withstand continuous parasympathetic stimulation, due in part to an increase in tissue capillary area.

     

Axonal mapping of neurosecretory Helix bursting cells. Functional aspects of peripheral multibranched axons

• 1.1. The peripheral axon distribution from two bursting neurons was investigated using electrophysiological methods. Both of these cells send out a bundle of axon branches which goes via the visceral nerve to the heart and in the uterine nerve.
• 2.2. The relative number of axon branches in the two nerves was determined through double-shock experiments.
• 3.3. The axon bundle takes the visceral nerve and its uterine branch, supplying the effector systems in parallel.
• 4.4. Slight differences in conduction velocity between the axon branches produce an enlargement of the efferent volley.
• 5.5. The number of active axon branches conveying orthodromic or antidromic spikes is controlled by inhibitory potentials converging onto the initial part of the bundle, so that the two bursting cells amount to a pool of 35 to 40 interconnected nerve cells.
• 6.6. The atypical axonal distribution of the two bursting cells might be related to their neurosecretory properties.

     

Effects of oxygen on the cercal receptors of the cockroach Periplaneta americana

• 1.1. The activity of the cercal nerve XI and giant interneurons of the cockroach Periplaneta americana is much more intense in situ than in vitro, despite perfusion of the sixth abdominal ganglion by oxygenated saline.
• 2.2. The background cercal nerve activity increases in vitro upon oxygenation from a negligible level. It persists for about 10 min following cessation of oxygenation. The activity in situ remains unaffected.
• 3.3. Oxygenation also substantially increases the frequency of sensory spikes evoked during mechanical stimulation of cercal receptors in vitro, as well as the frequency of generated EPSPs in the interneurons which integrate the cercal activity. The latter effect is apparently due to the increased frequency of afferent spikes.
• 4.4. The intense activity detected in vitro in oxygenated preparations appears to be closer to that existing in situ.

     

Ciliary/decarboxylase activities as indicators of PTZ,photoperiod and Ca-ionophore effect on Crassostrea virginica (gmelin)

• 1.1. Lateral ciliary activity and DOPA decarboxylase were measured in the ctenidium of Crassostrea virginica (Gmelin).
• 2.2. Activity of the lateral cilia is dependent upon branchial nerve (Paparo, 1985a,b) and on intracellular calcium homostasis (Baker, 1963; Rassmussen, 1970, 1971; Romero and Wittman, 1971; Blanstein et al., 1978).
• 3.3. PTZ induced lamella morphogenesis in eytosomes with subsequent release of calcium into the cytosol. This cilio-inhibition was enhanced in the presence of additional calcium in the perfusate.
• 4.4. Prolonged exposure to light also induces fully converted membranous eytosomes with subsequent production of a gradual lateral cilio-inhibition. Darkness produces the opposite effect, in that secondary membranous conversions of cytosomes are inhibited.
• 5.5. In the presence of A-23187 (a calcium releasing agent), inhibition of lateral activity is produced, independent of cytosomal conversion.
• 6.6. It is postulated that photic electrical and chemical stimulation of neuronal chromoproteins can lead to release of calcium from sequestered cytosomal stores which triggers a neuro-exocytosis of a neuroinhibitory transmitter, dopamine.

     

Morphological and electrophysiological characteristics of a dorsal unpaired median neuron of the cricket,Acheta domesticus

• 1.1. The dorsal unpaired median neuron (DUMDL) of the metathoracic dorsal longitudinal flight muscle was studied using cobalt and neutral red staining, various pharmacological agents and extracellular recording of electrical activity.
• 2.2. The soma of DUMDL is posterior in the group of dorsal unpaired median neurons of the metathoracic ganglion; DUMDL does not degenerate following histolysis of its muscle.
• 3.3. Slow, regular spontaneous activity of DUMDL is generated in the isolated metathoracic ganglion and is suppressed following stimulation of DUMDL and by discharges of the flight motor neurons. This spontaneous activity is increased by acetylcholine and eserine and blocked by anticholinesterase agents.
• 4.4. The neurite of DUMDL appears to have several impulse initiation zones characterized by a low safety factor.

     

Axonal pathways of giant neurons identified in the right parietal and visceral ganglia in the suboesophageal ganglia of an African giant snail (Achatina fulica Férussac)

• 1.1. The axonal pathways of thirteen giant neurons identified in the right parietal and the visceral ganglia, found in the suboesophageal ganglia of an African giant snail (Achatina fulica Férussac), were investigated by intracellular injections of Lucifer Yellow, with regard to their axonal projections into the following six peripheral nerves: lap n (left anterior palliai nerve), lpp n (left posterior palliai nerve), int n (intestinal nerve), anal n (anal nerve), rpp n (right posterior palliai nerve) and rap n (right anterior palliai nerve).
• 2.2. These projections were confirmed by the recording of the axonal responses from the nerves.
• 3.3. On the dorsal surface of the right parietal ganglion, the following four giant neurons were identified: PON (periodically oscillating neuron), TAN (tonically autoactive neuron), RAPN (right anterior palliai neuron), and d-RPLN (dorsal-right parietal large neuron).
• 4.4. The PON axonal pathways projected into int n; those of TAN into all of the nerves examined; those of RAPN into lap n, lpp n, int n, anal n and rap n.; and those of d-RPLN into pd nn (pedal nerves) through the pedal ganglia, lpp n, anal n, rap n and sometimes lap n.
• 5.5. On the dorsal surface of the visceral ganglion, the following four giant neurons were also identified: VIN (visceral intermittently firing neuron), FAN (frequently autoactive neuron), INN (intestinal nerve neuron) and d-VLN (dorsal-visceral large neuron).
• 6.6. The VIN axonal pathways, which had no branch into the six nerves examined, went to both the right and the left pedal ganglia, sending a branch into the cerebro-pleural connective; those of FAN projected into lap n, anal n and rap n, and sometimes into lpp n and rpp n; those of INN into int n; and those of d-VLN into pd nn, lap n, lpp n, anal n and rap n.
• 7.7. On the ventral surface of the right parietal ganglion, v-RPLN (ventral-right parietal large neuron) was identified. The axonal pathways went to pd nn, lap n, lpp n, anal n and rap n.
• 8.8. On the ventral surface of the visceral ganglion, the four giant neurons, v-VNAN (ventral-visceral noisy autoactive neuron), v-VLN (ventral-visceral large neuron), r-VMN (right-visceral multiple spike neuron) and 1-VMN (left-visceral multiple spike neuron) were identified.
• 9.9. The axonal pathway of v-VNAN projected into rpp n and rap n; those of v-VLN into pd nn, lap n, anal n, rap n and sometimes to lpp n; those of r-VMN into int n and rpp n; and those of 1-VMN also into int n and rpp n.
• 10.10. The present morphologial investigations of the giant neurons confirmed well the identifications of the neurons previously studied. The axon of the neurons examined here, except for VIN, projected into some of the peripheral nerves, while the VIN axon extended into the cerebro-pleural connective.
• 11.11. The five neurons, PON, TAN, v-VNAN, r-VMN and 1-VMN, formed fine axonal arborizations terminating at the neuropile, while the arborizations of the other neurons were not clearly observed.
• 12.12. Although the anatomical structures of the portion examined of the suboesophageal ganglia are asymmetrical, three pairs of symmetrically-situated neurons, d-RPLN and d-VLN, v-RPLN and v-VLN, and r-VMN and 1-VMN, were found, indicating the existence of symmetrical components in the ganglia.