1. ANATOMY AND PHYSIOLOGY OF THE CENTRAL NERVOUS SYSTEM
59
Bardach et al., 1967; Fujiya and Bardach, 1966; Hidaka and Yokota,
1967; Konishi et al., 1966; Konishi and Zotterman, 1961, 1963; Tateda,
1961, 1961; Teichmann, 1962; Tester, 1963). Recordings of chemoreceptive function have been made from palatine nerves (Cr.N.IX) of ostariophysid fish, nerves from barbels (Cr.N.VII), and nerves (spinal nerve 3 )
from the modified fin rays of the hake Urophysis chum and sea robin
Prionotus carolinus (Bardach and Case, 1965). The palatine nerve fibers
in Japanese and Swedish carp, Cvprinus carpio, were found to respond
to salt (sodium chloride solution), acid, sugars, and to a broad gustatory
spectrum. Broad spectrum gustatory fibers which comprise the large
majority of axons in the palatine nerve responded differently in the
Swedish carp and the Japanese carp when the same solution stimulated
these chemoreceptors. For instance, an extract of earthworm resulted
in a massive response from nerve fibers in the Japanese carp and only a
moderate response in the Swedish carp (Konishi and Zotterman, 1963).
It is interesting that there was no response of the taste receptors to
water, unless animals were previously adapted to isotonic salt solutions
( Konishi and Zotterman, 1963). In addition, there were chemoreceptors
which were specific for sodium chloride and responded to changes in
the ionic environment ( Hidaka and Yokota, 1967).
Using Japanese carp, Cyprinus carpio, Hidaka and Yokota (1967)
recorded the pattern of response from palatine nerves to increasing
molarities of sucrose. The response appeared to summate and rise to a
maximum level, reaching asymtote with increasing sucrose molarities.
This was a typical response when increasing molarities of all the sweet
substanccs were utilized except glycine ( sucrose, dextrose, and levulose ) .
hlixtures of glycine and sucrose produced responses which were smaller
in magnitude than the sum of the responses produced by the two substances separately. As the concentration of sucrose in the glycine mixture
increased, a synergistic effect resulted in larger than normal responses.
Mixing glycine with various concentrations of dextrose, sucrose, and
levulose yielded comparable results. There appearcd to be a competitive
inhibition of the receptive sites for sweet substances.
Prestimulation of the chemoreceptors of the carp palatal organ with
mercuric chloride resulted in the complete loss of response to subsequent
stimulation with dextrose, sucrose, and levulose. The response to glycine
was only partially depressed, and the response to sodium chloride usually
was not affected. Occasionally, the response to sodium chloride stimulation was augmented by pretreatment with mercuric chloride. Thcse
data indicated that there were at least two types of chemoreceptors.
Using carp, Konishi and Zotterman (1961) classified the groups of
nerve fiber responses from the glossopharyngeal (Cr.N.IX) nerve fibers
59
Bardach et al., 1967; Fujiya and Bardach, 1966; Hidaka and Yokota,
1967; Konishi et al., 1966; Konishi and Zotterman, 1961, 1963; Tateda,
1961, 1961; Teichmann, 1962; Tester, 1963). Recordings of chemoreceptive function have been made from palatine nerves (Cr.N.IX) of ostariophysid fish, nerves from barbels (Cr.N.VII), and nerves (spinal nerve 3 )
from the modified fin rays of the hake Urophysis chum and sea robin
Prionotus carolinus (Bardach and Case, 1965). The palatine nerve fibers
in Japanese and Swedish carp, Cvprinus carpio, were found to respond
to salt (sodium chloride solution), acid, sugars, and to a broad gustatory
spectrum. Broad spectrum gustatory fibers which comprise the large
majority of axons in the palatine nerve responded differently in the
Swedish carp and the Japanese carp when the same solution stimulated
these chemoreceptors. For instance, an extract of earthworm resulted
in a massive response from nerve fibers in the Japanese carp and only a
moderate response in the Swedish carp (Konishi and Zotterman, 1963).
It is interesting that there was no response of the taste receptors to
water, unless animals were previously adapted to isotonic salt solutions
( Konishi and Zotterman, 1963). In addition, there were chemoreceptors
which were specific for sodium chloride and responded to changes in
the ionic environment ( Hidaka and Yokota, 1967).
Using Japanese carp, Cyprinus carpio, Hidaka and Yokota (1967)
recorded the pattern of response from palatine nerves to increasing
molarities of sucrose. The response appeared to summate and rise to a
maximum level, reaching asymtote with increasing sucrose molarities.
This was a typical response when increasing molarities of all the sweet
substanccs were utilized except glycine ( sucrose, dextrose, and levulose ) .
hlixtures of glycine and sucrose produced responses which were smaller
in magnitude than the sum of the responses produced by the two substances separately. As the concentration of sucrose in the glycine mixture
increased, a synergistic effect resulted in larger than normal responses.
Mixing glycine with various concentrations of dextrose, sucrose, and
levulose yielded comparable results. There appearcd to be a competitive
inhibition of the receptive sites for sweet substances.
Prestimulation of the chemoreceptors of the carp palatal organ with
mercuric chloride resulted in the complete loss of response to subsequent
stimulation with dextrose, sucrose, and levulose. The response to glycine
was only partially depressed, and the response to sodium chloride usually
was not affected. Occasionally, the response to sodium chloride stimulation was augmented by pretreatment with mercuric chloride. Thcse
data indicated that there were at least two types of chemoreceptors.
Using carp, Konishi and Zotterman (1961) classified the groups of
nerve fiber responses from the glossopharyngeal (Cr.N.IX) nerve fibers