Background and objective: To elucidate the effects of various degrees of hypotension induced by the calcitonin gene-related peptide (CGRP) on the splanchnic circulation, we investigated the renal and hepatic blood flow during hypotension induced by either the calcitonin gene-related peptide or sodium nitroprusside in the isofluraneanaesthetized dog.

Methods: Anaesthesia was maintained with 1.3% isoflurane in oxygen. After the baseline period, mean arterial pressure was reduced to 60 mmHg in the CGRP60 and nitroprusside groups, and to 50 mmHg in the CGRP50 group. The splanchnic organ blood flow was measured by hydrogen clearance.

Results: The cardiac index in the CGRP60 group increased (P < 0.01), but in the CGRP50 group it decreased (P < 0.01), and in the nitroprusside group it remained unchanged during hypotension. Mean pulmonary artery and pulmonary capillary wedge pressures in the CGRP60 group remained unchanged, but in the CGRP50 and nitroprusside groups they decreased (P < 0.01) during hypotension. Cardiac contractility in the CGRP60 group remained unchanged, whereas in the CGRP50 and nitroprusside groups it was reduced (P < 0.01) during hypotension. Renal blood flow in the CGRP60 group was relatively well maintained but in the CGRP50 and nitroprusside groups it was reduced (P < 0.01) throughout the observation. Hepatic blood flow in all three groups was reduced (P < 0.01) during hypotension. The reductions in hepatic blood flow between the Calcitonin gene-related peptide groups were associated with a dose-dependent decrease in mean arterial pressure.

Conclusions: The results suggest that calcitonin gene-related peptide acts as an arteriolar vasodilator at low doses but as a vasodilator of the arteriolar and venous systems at higher doses, and that profound hypotension induced by the calcitonin gene-related peptide may impair splanchnic circulation.

Immunohistochemistry of normal eccrine sweat glands was performed on paraffin sections of human skin. Immunoreactivity (ir) for neuron specific enolase, S100 protein (S100), regulatory peptides, nitric oxide synthase type I (NOS-I) and choline-acetyltransferase (ChAT) was found in small nerve bundles close to sweat glands. In the glands, secretory cells were labelled with anticytokeratin antibody. Using antibodies to S100, calcitonin gene-related peptide (CGRP) and substance P (SP) a specific distribution pattern was found in secretory cells. Granulated (dark) and parietal (clear) cells were immunopositive for CGRP, and S100 and SP, respectively. Immunoreactivity was diffuse in the cytoplasm for CGRP and S100, and peripheral for SP. Myoepithelial cells were not labelled. Electron microscopy revealed electron dense granules, probably containing peptide, in granulated cells. Using antibodies to NOS-I and ChAT, ir was exclusively found in myoepithelial cells. Immunoreactivity for the atrial natriuretic peptide was absent in sweat glands. These results provide evidence for the presence of both regulatory peptides involved in vasodilation and key enzymes for the synthesis of nitric oxide and acetylcholine in the secretory coil of human sweat glands. It is suggested that human sweat glands are capable of some intrinsic regulation in addition to that carried out by their nerve supply.

Retrograde tracing with Fluoro-Gold was used to identify the complete population of knee joint afferents in the lumbar dorsal root ganglia of adult female Wistar rats. There was an average of 581±31 (mean±S.D.) afferents supplying each joint. These were found distributed from L1 to L5 with the great majority localised in the L3 and L4 ganglia. Electron microscopy of the posterior articular nerve of the knee revealed an average of 103±15 (mean±S.D.) myelinated and 513±39 unmyelinated axonal profiles. Since about 50–60% of the unmyelinated profiles would be expected to be sympathetic efferents, these numbers are consistent with the numbers of afferents found by Fluoro-Gold retrograde tracing and suggest that the posterior articular nerve contains about 50% of the total number of knee joint afferents in the rat. Immunohistochemistry revealed that an average of 10% of identified joint afferents expressed substance P-like immunoreactivity and that 33% expressed calcitonin gene-related peptide-like immunoreactivity.