30
JERALD J. BERNSTEIN
saltwater resulted in a cessation of the spontaneous firing rate associated
with a hyperpolarization and a resumption of the spontaneous firing rate
with the return of membrane potential to its earlier level.
It is of particular interest that there was antidromic inhibition of the
preoptic neuroendocrine cells ( via hypophysial stimulation ) and orthodromic excitation of preoptic neuroendocrine cells via olfactory nerve
stimulation. The antidromic inhibition constituted electrophysiological
evidence for inhibitory recurrent collateral axons synapsing on the preoptic neuron of origin. In addition, IPSPs could be produced with
stimuli that elicited only a low threshold potential in some of the
neurohypophysial tract fibers. It would appear then that the neurosecretory cells of the preoptic nucleus of the thalamus of the fish are not only
neurosecretory in function but also servc as functional units in a neural
center. It is interesting to note that Hara and Gorbman (1967) found
that the olfactory system decussates within the preoptic area of the
goldfish brain and that stimulation of the ipsilateral olfactory tract resulted in suppression of the contralatcral olfactory bulb.
The relationship between the olfactory tract and the activation of
spike potentials in the preoptic nucleus (Kandcl, 1961) has led to interesting work on the function of the olfactory-preoptic relationship within
the goldfish. Infusion of 0.1% NaCl over the nasal epithelium of the goldfish induced inhibition in some units in the preoptic nuclcus (pars
parvocellularis), excited some units in this area, and did not affect other
units (Jasinski et al., 1967). Infusion of 0.1% NaCl solutions into the
nasal cavity or emersion of the goldfish in a solution of this percentage
for up to 7 days had little to no effect on the accumulation of neurosecretory granules in the hypothalamo-hypophysial tract. However, relatively short stimulation (60 sec) of the olfactory tract resulted in complete degranulation of the neurosecretory neurons of the nucleus
preopticus. In general, neurons of specimens sacrificed immediately
following stimulation contained more degranulated neurons than those
fixed after a short delay. Olfactory stimulation for longer than 1 min
did produce clear and consistent degranulation of the cells examined.
The axons of neurons examined were located in the nucleus preopticus (pars parvocellularis and pars magnocellularis) as well as juxtosoma1 axons in most specimens. The cytological change of the axons
included the disappearance of the characteristic Herring bodies and loss
of stainability. The fuchsin stainable granules were dcpleted in one-half
of the axons examined. Regranulation was in the distal part of the neurosecretory axons in the hypothalamo -hypophysial tract after olfactory
tract stimulation. This was not true in the neurohypophysis proper where
no consistent change was found in the amount of neurosecretory sub-
JERALD J. BERNSTEIN
saltwater resulted in a cessation of the spontaneous firing rate associated
with a hyperpolarization and a resumption of the spontaneous firing rate
with the return of membrane potential to its earlier level.
It is of particular interest that there was antidromic inhibition of the
preoptic neuroendocrine cells ( via hypophysial stimulation ) and orthodromic excitation of preoptic neuroendocrine cells via olfactory nerve
stimulation. The antidromic inhibition constituted electrophysiological
evidence for inhibitory recurrent collateral axons synapsing on the preoptic neuron of origin. In addition, IPSPs could be produced with
stimuli that elicited only a low threshold potential in some of the
neurohypophysial tract fibers. It would appear then that the neurosecretory cells of the preoptic nucleus of the thalamus of the fish are not only
neurosecretory in function but also servc as functional units in a neural
center. It is interesting to note that Hara and Gorbman (1967) found
that the olfactory system decussates within the preoptic area of the
goldfish brain and that stimulation of the ipsilateral olfactory tract resulted in suppression of the contralatcral olfactory bulb.
The relationship between the olfactory tract and the activation of
spike potentials in the preoptic nucleus (Kandcl, 1961) has led to interesting work on the function of the olfactory-preoptic relationship within
the goldfish. Infusion of 0.1% NaCl over the nasal epithelium of the goldfish induced inhibition in some units in the preoptic nuclcus (pars
parvocellularis), excited some units in this area, and did not affect other
units (Jasinski et al., 1967). Infusion of 0.1% NaCl solutions into the
nasal cavity or emersion of the goldfish in a solution of this percentage
for up to 7 days had little to no effect on the accumulation of neurosecretory granules in the hypothalamo-hypophysial tract. However, relatively short stimulation (60 sec) of the olfactory tract resulted in complete degranulation of the neurosecretory neurons of the nucleus
preopticus. In general, neurons of specimens sacrificed immediately
following stimulation contained more degranulated neurons than those
fixed after a short delay. Olfactory stimulation for longer than 1 min
did produce clear and consistent degranulation of the cells examined.
The axons of neurons examined were located in the nucleus preopticus (pars parvocellularis and pars magnocellularis) as well as juxtosoma1 axons in most specimens. The cytological change of the axons
included the disappearance of the characteristic Herring bodies and loss
of stainability. The fuchsin stainable granules were dcpleted in one-half
of the axons examined. Regranulation was in the distal part of the neurosecretory axons in the hypothalamo -hypophysial tract after olfactory
tract stimulation. This was not true in the neurohypophysis proper where
no consistent change was found in the amount of neurosecretory sub-