The Neuroendocrine System in the Intestinal Tract and Pancreas of Antarctic Fish
251
insulin-, glucagon-, PP- and somatostatin-IR cells in the Brockmann body
in C. antarcticus, P. macropterus, N coriiceps and P. antarcticum was
similar to that found in most other teleosts [6,24,27]. Glucagon-IR cells
are located at the periphery while somatostatin 14-IR and insulin-IR are
situated in the central portion. Different endocrine cell associations can be
seen in smaller islets: insulin-IR cells can be found at the periphery, while
somatostatin- and PP-IR cells can be detected throughout the islet. In the
large islet of C. antarcticus, PP-IR cells are fewer than that observed in
nothotheniids and in Serranus cabrilla [24]. The pancreatic endocrine
cells appear very early during the embryonic development and a large islet
with insulin, glucagon and somatostatin-IR cells can be observed in 20
mm long P. antarcticum larvae (Fig. 5; Tagliafierro et aI., unpublished).
Intestinal and Pancreatic Nerves
In the gut of C. hamatus, C. antarcticus, P. macropterus, N coriiceps, P.
antarcticum, T bernacchii and T newnesi and in the pancreas of C.
antarcticus, P. macropterus, N coriiceps and P. antarcticum, many
peptidergic nerve elements were seen [22,23,25,26]. Their presence,
distribution and frequency are only partially similar to those found in
other teleosts [27].
VIP, PHI and PACAP immunoreactivity was present both in the
endocrine cells and nerve elements (Fig. 6); nevertheless, VIP- PHI- and
PACAP-IR nerve elements are less common than in the gut and pancreas
of some other teleosts such as S. cabrilla and D. annularis (Figs. 7,8)
[5,26]. In the blood vessel wall of the Antarctic species no VIP
immunoreactivity was found, while numerous CCK- and serotonin-IR
nerves were instead seen. It has been demonstrated that gastrinlCCK and
serotonin stimulate smooth muscle motility and exert a constrictor role on
blood vessels influencing the blood flow [28]. Sub P-IR fibers were
particularly numerous in the myenteric plexus (Fig. 9) often surrounding
nonIR neuron cell bodies; serotonin-IR fibers were present in the blood
vessel wall and in the lamina propria beneath the intestinal epithelium.
Most of these IR nerve fibers were of the extrinsic type, at least in
channichthyids where few IR neuron somata were seen. In C. antarcticus
insulin-IR nerve terminals and neuron cell bodies were also detected (Fig.
10). Insulin immunoreactivity in C. antarcticus has been confirmed by the
in situ hybridization method (Tagliafierro, unpublished). In the
Brockmann body of the notothenioids, we detected only few VIP-,
PACAP- and PHI-IR fibers, while we saw many in S. cabrilla and in D.
annularis, as was the case in other teleosts and in mammals [29,30]. VIP,
P ACAP and PHI belong to the same family and are candidate messengers
251
insulin-, glucagon-, PP- and somatostatin-IR cells in the Brockmann body
in C. antarcticus, P. macropterus, N coriiceps and P. antarcticum was
similar to that found in most other teleosts [6,24,27]. Glucagon-IR cells
are located at the periphery while somatostatin 14-IR and insulin-IR are
situated in the central portion. Different endocrine cell associations can be
seen in smaller islets: insulin-IR cells can be found at the periphery, while
somatostatin- and PP-IR cells can be detected throughout the islet. In the
large islet of C. antarcticus, PP-IR cells are fewer than that observed in
nothotheniids and in Serranus cabrilla [24]. The pancreatic endocrine
cells appear very early during the embryonic development and a large islet
with insulin, glucagon and somatostatin-IR cells can be observed in 20
mm long P. antarcticum larvae (Fig. 5; Tagliafierro et aI., unpublished).
Intestinal and Pancreatic Nerves
In the gut of C. hamatus, C. antarcticus, P. macropterus, N coriiceps, P.
antarcticum, T bernacchii and T newnesi and in the pancreas of C.
antarcticus, P. macropterus, N coriiceps and P. antarcticum, many
peptidergic nerve elements were seen [22,23,25,26]. Their presence,
distribution and frequency are only partially similar to those found in
other teleosts [27].
VIP, PHI and PACAP immunoreactivity was present both in the
endocrine cells and nerve elements (Fig. 6); nevertheless, VIP- PHI- and
PACAP-IR nerve elements are less common than in the gut and pancreas
of some other teleosts such as S. cabrilla and D. annularis (Figs. 7,8)
[5,26]. In the blood vessel wall of the Antarctic species no VIP
immunoreactivity was found, while numerous CCK- and serotonin-IR
nerves were instead seen. It has been demonstrated that gastrinlCCK and
serotonin stimulate smooth muscle motility and exert a constrictor role on
blood vessels influencing the blood flow [28]. Sub P-IR fibers were
particularly numerous in the myenteric plexus (Fig. 9) often surrounding
nonIR neuron cell bodies; serotonin-IR fibers were present in the blood
vessel wall and in the lamina propria beneath the intestinal epithelium.
Most of these IR nerve fibers were of the extrinsic type, at least in
channichthyids where few IR neuron somata were seen. In C. antarcticus
insulin-IR nerve terminals and neuron cell bodies were also detected (Fig.
10). Insulin immunoreactivity in C. antarcticus has been confirmed by the
in situ hybridization method (Tagliafierro, unpublished). In the
Brockmann body of the notothenioids, we detected only few VIP-,
PACAP- and PHI-IR fibers, while we saw many in S. cabrilla and in D.
annularis, as was the case in other teleosts and in mammals [29,30]. VIP,
P ACAP and PHI belong to the same family and are candidate messengers