176
A. M. PERKS
pressin into Astyanux mexicanus led to a loss of glycoprotein from basophylic cells in the adenohypophysis, and they interpreted this as a possible release of adrenocorticotropic hormone ( ACTH) into the circulation. However, it is not certain that the pituitary-adrenal axis is activated
in all species (Chavin, 1959). Another possible indication of effects on
the adenohypophysis comes from suggestions that neurohypophysial peptides may cause the release of gonadotropins; Bacon and Ball have noted
that mammalian pars nervosa extracts appear to cause the maturation of
free-spawning minnows ( Bacon, 1951, 1952; Ball and Bacon, 1954). However, despite the highly suggestive nature of the anatomical connections
between the neurohypophysial system and the adenohypophysis, there is
still little physiological evidence for any functional relationship between
the two regions.
There are a number of lines of evidence which suggest a possible
connection between the neurohypophysis and reproduction in teleosts.
Most of the evidence comes from observations of seasonal changes in the
histology of the system, and it is often assumed that reproductive cycles
are the most likely correlate. Polenov (1960) has seen seasonal variations
in the preoptic nucleus of the carp and sazan; however, the pars nervosa
of this species was consistently full of material. Other workers have seen
seasonal changes in the granular content of the neurohypophysis of Salmo
salar and Anguilla anguilla, and these changes may have been correlated
with migratory activity (Arvy et al., 1959; Leatherland et al., 1966).
Perhaps the most interesting correlation has been that with the process of
mating or spawning. In Salvelinus bucomuenis pluvius, neurosecretion
within the neurohypophysis increased in quantity until the time of
spawning, when it was found concentrated around the blood vessels of
the pars nervosa; after spawning, it had decreased in quantity (Honma
and Tamura, 1965). In Fundulus heteroclitus, Sokol (1961) noted a
similar loss of neurosecretion in both the male and female specimens
during the reproductive season, but W. H. Sawyer and Pickford (1963))
using pharmacological methods, were able to confirm this only in the case
of the females. They made the notable observation that, in the females,
there was a preferential depletion of 4 Ser, 8 Ile oxytocin, with no change
in the arginine vasotocin content of their glands. The significance of these
results has been increased by Wilson and Smith‘s recent observations
(1968; Wilson, 1968) on specimens of Oncorhynchus tschawytscha, which
were collected, “spent out,” after spawning. Although these glands contained an unusually high hormonal activity, they also showed an unusually low proportion of 4 Ser, 8 Ile oxytocin as compared to those of
other teleosts. This was true of both sexes. It suggested that 4 Ser, 8 Ile
oxytocin might have been lost preferentially during spawning. Unfor-
A. M. PERKS
pressin into Astyanux mexicanus led to a loss of glycoprotein from basophylic cells in the adenohypophysis, and they interpreted this as a possible release of adrenocorticotropic hormone ( ACTH) into the circulation. However, it is not certain that the pituitary-adrenal axis is activated
in all species (Chavin, 1959). Another possible indication of effects on
the adenohypophysis comes from suggestions that neurohypophysial peptides may cause the release of gonadotropins; Bacon and Ball have noted
that mammalian pars nervosa extracts appear to cause the maturation of
free-spawning minnows ( Bacon, 1951, 1952; Ball and Bacon, 1954). However, despite the highly suggestive nature of the anatomical connections
between the neurohypophysial system and the adenohypophysis, there is
still little physiological evidence for any functional relationship between
the two regions.
There are a number of lines of evidence which suggest a possible
connection between the neurohypophysis and reproduction in teleosts.
Most of the evidence comes from observations of seasonal changes in the
histology of the system, and it is often assumed that reproductive cycles
are the most likely correlate. Polenov (1960) has seen seasonal variations
in the preoptic nucleus of the carp and sazan; however, the pars nervosa
of this species was consistently full of material. Other workers have seen
seasonal changes in the granular content of the neurohypophysis of Salmo
salar and Anguilla anguilla, and these changes may have been correlated
with migratory activity (Arvy et al., 1959; Leatherland et al., 1966).
Perhaps the most interesting correlation has been that with the process of
mating or spawning. In Salvelinus bucomuenis pluvius, neurosecretion
within the neurohypophysis increased in quantity until the time of
spawning, when it was found concentrated around the blood vessels of
the pars nervosa; after spawning, it had decreased in quantity (Honma
and Tamura, 1965). In Fundulus heteroclitus, Sokol (1961) noted a
similar loss of neurosecretion in both the male and female specimens
during the reproductive season, but W. H. Sawyer and Pickford (1963))
using pharmacological methods, were able to confirm this only in the case
of the females. They made the notable observation that, in the females,
there was a preferential depletion of 4 Ser, 8 Ile oxytocin, with no change
in the arginine vasotocin content of their glands. The significance of these
results has been increased by Wilson and Smith‘s recent observations
(1968; Wilson, 1968) on specimens of Oncorhynchus tschawytscha, which
were collected, “spent out,” after spawning. Although these glands contained an unusually high hormonal activity, they also showed an unusually low proportion of 4 Ser, 8 Ile oxytocin as compared to those of
other teleosts. This was true of both sexes. It suggested that 4 Ser, 8 Ile
oxytocin might have been lost preferentially during spawning. Unfor-