96
TOSHIAKZ J. H A M
sensory messages reach the neural centers in the form of impulses, recording activity in the primary olfactory neurons has some advantages
from the technical point of view. Recording of the electrical activity of
single olfactory nerve fibers may be difficult because of their extremely
fine dimensions.
Gasser (1956) investigated the properties of the isolated olfactory
nerve of the pike Esox estor in a combined electrophysiological and electron microscopic study, He showed that the action potential evoked by
electrical stimulation of the olfactory nerve consists of only one single
wave of 30 msec duration with a conduction velocity of 0.2 meterslsec.
Such a slow conduction velocity of the olfactory nerve has been reported
in other animal species ( Ottoson, 1963).
3. ELECTRICAL ACTIVITY OF THE OLFACTORY BULB
Spontaneous electrical activities (EEG) have been recorded with
bipolar electrodes from the surface of the olfactory bulb of the goldfish
Carassius uurutus (Oshima and Gorbman, 1966a, 1968; Hara, 196713;
Hara and Gorbman, 1967); EEG's were consistent and characteristic
(frequency, 14-16 Hz; amplitude, 70-100 pV) . Infusion of chemical solutions into the nasal cavity induced specific synchronous wave patterns
of high amplitude (150-200 pV) in the EEG. Maximal duration of the
induced response was %6 sec, despite the continued presence of the
chemical stimulant in the olfactory sac (Hara and Gorbman, 1967).
The response to NaCl increased in magnitude linearly with increasing
concentration within the range tested (1-5 x 1e2 M ) . Qualitatively similar patterns of electrical response were obtained with KCl, LiCl, CaCl,,
NaH,PO,, Na,HPO,, Naz-oxalate, and Nag-citrate. No response was induced by choline-chloride at equivalent molar concentrations. Although
the nature of the induced response following chemical stimulation of the
olfactory sac is still unknown, it seems possible that the responses result
from a relatively nonspecific excitation of the olfactory receptor cells. The
highly synchronous activity induced in the mammalian and amphibian olfactory bulb by odorous stimulation seems to be analogous.
A characteristic potential was also evoked in the olfactory bulb when
single electrical stimuli were given to the olfactory mucosa instead of
chemical stimuli. The potential at the surface of the bulb recorded
through bipolar electrodes, was a biphasic wave with a delay of about
20 msec, a maximum amplitude of about 1.2 mV, and a duration of about
50 msec. The potential consisted of three components with distinctly
different properties. The first component lacked a true refractory period
and summated to a sustained potential with repeated stimulation. The
TOSHIAKZ J. H A M
sensory messages reach the neural centers in the form of impulses, recording activity in the primary olfactory neurons has some advantages
from the technical point of view. Recording of the electrical activity of
single olfactory nerve fibers may be difficult because of their extremely
fine dimensions.
Gasser (1956) investigated the properties of the isolated olfactory
nerve of the pike Esox estor in a combined electrophysiological and electron microscopic study, He showed that the action potential evoked by
electrical stimulation of the olfactory nerve consists of only one single
wave of 30 msec duration with a conduction velocity of 0.2 meterslsec.
Such a slow conduction velocity of the olfactory nerve has been reported
in other animal species ( Ottoson, 1963).
3. ELECTRICAL ACTIVITY OF THE OLFACTORY BULB
Spontaneous electrical activities (EEG) have been recorded with
bipolar electrodes from the surface of the olfactory bulb of the goldfish
Carassius uurutus (Oshima and Gorbman, 1966a, 1968; Hara, 196713;
Hara and Gorbman, 1967); EEG's were consistent and characteristic
(frequency, 14-16 Hz; amplitude, 70-100 pV) . Infusion of chemical solutions into the nasal cavity induced specific synchronous wave patterns
of high amplitude (150-200 pV) in the EEG. Maximal duration of the
induced response was %6 sec, despite the continued presence of the
chemical stimulant in the olfactory sac (Hara and Gorbman, 1967).
The response to NaCl increased in magnitude linearly with increasing
concentration within the range tested (1-5 x 1e2 M ) . Qualitatively similar patterns of electrical response were obtained with KCl, LiCl, CaCl,,
NaH,PO,, Na,HPO,, Naz-oxalate, and Nag-citrate. No response was induced by choline-chloride at equivalent molar concentrations. Although
the nature of the induced response following chemical stimulation of the
olfactory sac is still unknown, it seems possible that the responses result
from a relatively nonspecific excitation of the olfactory receptor cells. The
highly synchronous activity induced in the mammalian and amphibian olfactory bulb by odorous stimulation seems to be analogous.
A characteristic potential was also evoked in the olfactory bulb when
single electrical stimuli were given to the olfactory mucosa instead of
chemical stimuli. The potential at the surface of the bulb recorded
through bipolar electrodes, was a biphasic wave with a delay of about
20 msec, a maximum amplitude of about 1.2 mV, and a duration of about
50 msec. The potential consisted of three components with distinctly
different properties. The first component lacked a true refractory period
and summated to a sustained potential with repeated stimulation. The