28
JERALD J. BERNSTEIN
anius, optic tectum, cerebellum, and neurohypophysis ( Ariens Kappers
et al., 1960).
B. Photosensitivity of the Pineal Organ
Dodt (1963) has studied the photosensitivity of the pineal organ of
the rainbow trout, Salmo irideus, by recording with steel electrodes during photic stimulation, Stimulation by white light elicited an inhibition
of the spontaneous discharge of the organ following a 30-msec delay
between onset of stimulus and inhibition of discharge. Following offset
of light pulses of 0.1 sec duration there was a resumption of the spontaneous discharge. Light pulses of 0.65 sec duration resulted in a transient inhibitory effect. Thus, illumination of the pineal gland elicited
both inhibitory and excitatory changes within the gland. In addition, the
pineal gland could also dark adapt and demonstrated a 5.0-log unit loss
of threshold after 30 min of dark adaptation. The pineal gland also had
a spectral sensitivity of the inhibitory response which was highest in the
blue-green range and declined on either side of this spectrum. Sensitivity function of the absorption spectrum demonstrated a visual pigment with a maximal absorption of 505 mp. Electrophysiological findings
compared favorably with the two visual pigments found in the lateral
eye of the rainbow trout with a maximum at 505 and 533 mp (Bridges,
1956). It is interesting to contemplate that the only known visual pigment with an absorption spectrum at 507 mp is rhodopsin (Dodt, 1963).
C. Electrical Activity of Neurosecretory Cells
There appears to be morphological similarity between the teleost and
mammalian neuroendocrine system (Lederis, 1964; Palay, 1957, 1960).
However, the systems are not identical in function. The posterior pituitary hormone differed somewhat in its structure in the two classes
(Sawyer et al., 1960) and did not influence renal tubular absorption of
water in fish as it did in higher vertebrates (Pickford and Atz, 1957).
In teleosts the posterior pituitary hormone facilitated sodium ion influx
across the membranes of the gills of freshwater fish (Maetz, 1963; Maetz
and Julien, 1961; Meier and Fleming, 1962). The cells studied for neuroendocrine function were located in the preoptic nucleus of fish. In fish,
the preoptic nucleus does not differentiate into supraoptic and paraventricular nuclei as in higher forms. The neurons of this nuclear mass produce the hormones of the neural lobe of the pituitary in fish (Pickford
and Atz, 1957). This nucleus and its outflow, the hypothalamic pituitary
JERALD J. BERNSTEIN
anius, optic tectum, cerebellum, and neurohypophysis ( Ariens Kappers
et al., 1960).
B. Photosensitivity of the Pineal Organ
Dodt (1963) has studied the photosensitivity of the pineal organ of
the rainbow trout, Salmo irideus, by recording with steel electrodes during photic stimulation, Stimulation by white light elicited an inhibition
of the spontaneous discharge of the organ following a 30-msec delay
between onset of stimulus and inhibition of discharge. Following offset
of light pulses of 0.1 sec duration there was a resumption of the spontaneous discharge. Light pulses of 0.65 sec duration resulted in a transient inhibitory effect. Thus, illumination of the pineal gland elicited
both inhibitory and excitatory changes within the gland. In addition, the
pineal gland could also dark adapt and demonstrated a 5.0-log unit loss
of threshold after 30 min of dark adaptation. The pineal gland also had
a spectral sensitivity of the inhibitory response which was highest in the
blue-green range and declined on either side of this spectrum. Sensitivity function of the absorption spectrum demonstrated a visual pigment with a maximal absorption of 505 mp. Electrophysiological findings
compared favorably with the two visual pigments found in the lateral
eye of the rainbow trout with a maximum at 505 and 533 mp (Bridges,
1956). It is interesting to contemplate that the only known visual pigment with an absorption spectrum at 507 mp is rhodopsin (Dodt, 1963).
C. Electrical Activity of Neurosecretory Cells
There appears to be morphological similarity between the teleost and
mammalian neuroendocrine system (Lederis, 1964; Palay, 1957, 1960).
However, the systems are not identical in function. The posterior pituitary hormone differed somewhat in its structure in the two classes
(Sawyer et al., 1960) and did not influence renal tubular absorption of
water in fish as it did in higher vertebrates (Pickford and Atz, 1957).
In teleosts the posterior pituitary hormone facilitated sodium ion influx
across the membranes of the gills of freshwater fish (Maetz, 1963; Maetz
and Julien, 1961; Meier and Fleming, 1962). The cells studied for neuroendocrine function were located in the preoptic nucleus of fish. In fish,
the preoptic nucleus does not differentiate into supraoptic and paraventricular nuclei as in higher forms. The neurons of this nuclear mass produce the hormones of the neural lobe of the pituitary in fish (Pickford
and Atz, 1957). This nucleus and its outflow, the hypothalamic pituitary