CONTROL OF THE POTENTIAL RHYTHM OF THE ISOLATED FROG BRAIN

Abstract

The influence of various agents on the 6 per sec. rhythm of the olfactory bulb of the isolated frog brain was studied. Wave size and irregularity at first improve after isolation and the beat continues 3-4 hrs. Brief stimulation of the olfactory nerve increases potentials by 25% for 10 mins. following. Increased temp. improves regularity, increases amplitude, and speeds up frequencies. Avg. Q10 is 2.3. Doubled osmotic pressure, radically reduced Na-ion, moderately increased Ca- or Mg-ions, or lowered pH produce slow waves; while increased K, Na, or pH and reduced Ca produce fast ones. Na and K are antagonistic to Ca, K in small concs. being more effective than Na. Effects are generally progressive with conc. Changes in frequency are usually discontinuous, and when extreme are irreversible. Anions are generally without marked effects. Although originating in a small homogeneous neurone population, potential patterns may vary greatly in frequency, wave shape, and regularity depending on the factors studied. These and other related facts are discussed in relation to the problems of frequency and amplitude of single neurone rhythms and of the mechanism coordinating them to give the recorded potential. Significant parallels appear between rhythmic nerve potentials and those of cerebral neurones.