Chemoreception of the Lateral-Line Organ of an Aquatic Amphibian, Xenopus Laevis

Abstract

Summary The lateral-line organ of Xenopus laevis was studied by recording responses from its afferent nerve fiber. The firing rate was registered with the aid of an electronic rate meter. 1. The firing rate was remarkably increased by stimulation with KCl and NH4Cl. 2. Sodium salts (except for Na-glutamate) suppressed both the spontaneous activity and responses to other cations. Na-glutamate did not show the suppressive effect at all. 3. Salts of divalent cations, CaCl2, and MgCl2, increased the firing rate, in contrast to the results obtained with fish, where they suppressed the responses to monovalent cations. 4. The discharge pattern from all the afferent fibers examined was quite uniform, so that the fibers could not be separated by response patterns into different groups. 5. Neither tetrodotoxin nor Mn++ suppressed the responses to solutions of salts, including those of Ca++. 6. Sucrose and quinine produced no remarkable effects, in contrast to the effects produced on the gustatory organs. 7. Dihydrostreptomycin sulfate (SM) suppressed both mechano-and chemoreception. 8. Along with serving as a mechanoreceptor, the lateral-line organ of Xenopus probably functions as an external chemosensory organ in detecting ions in the environment.Based on morphological and physiological studies, the lateral-line organ of aquatic vertebrates has been believed to be a mechanoreceptor (KATSUKI et al.,

Responses of the carp pit organ to chemical and thermal stimuli.

“…Dual function of the pit organ, that is, chemore ception and mechanoreception was confirmed in some aquatic vertebrates2, 5,6,13) In the present study, we recorded clear responses to chemical and thermal stimuli, but response to mechanical stimuli was ambiguous. In some cases, we observed responses to a drop of water or a slight touch with fine nylon thread on the snout regions but these responses disappeared soon after the chemi cal stimulation.…”

Ionic Stimulation of the Olfactory Epithelium in the Bullfrog and the Carp

“…A very similar phenomenon had already been found in the lateral-line organ of the Xenopus laevis. Spontaneous discharges of the lateral-line nerve were inhibited by NaCl of 10 to 100 mm, but spike discharges were elicited by NaCl of higher concentrations (ONODA et al, 1970;ONODA and KATSUKI, 1972). On the other hand, NaCl showed the dual stimulating action in the palatal organ of the carp (KONISHI, 1966).…”

“…On the other hand, it was made clear that tetrodotoxin is effective only on the excitable tissues in which the action potential is generated by a depolarization dependent Na+ permeability increase, but not effective in the tissues in which excitability depends on Ca2 + permeability. In fact in the lateral-line organs, tetrodotoxin showed an inhibitory effect in the above sharks as well as in the mullet, Mugil and in the carp, Cyprinus, but never in the catfish, Ictalurus, and in the Xenopus KATSUKI and HASHIMOTO, 1969;KATSUKI et al, 1970KATSUKI et al, , 1971ONODA et al, 1970;ONODA and KATSUKI, 1972). Since the olfactory epithelium respond to mono-and divalent cations, just as the lateral-line organs of the catfish and the Xenopus do, and since tetrodotoxin was found ineffective even at 10-5 g/ml, it may be concluded that tetrodotoxin does not affect the olfactory epithelium specifically.…”

Shark research : present status and future direction / Bernard J. Zahuranec, editor and workshop convenor.

“…The function of the pit organ is still uncertain. Onada and Katsuki (1972) imply that it has the dual function of mechanoreception and chemoreception.…”