Electrical and mechanical properties of smooth muscle cells of the guinea pig biliary system

Inhibitory NANC neurotransmission in choledocho-duodenal junction of rabbits--a possible role of PACAP

The pharmacological properties of non-adrenergic non-cholinergic (NANC) inhibitory neurotransmission were investigated in the rabbit choledocho-duodenal junction (CDJ), using the microelectrode and tension recording methods. L-NAME (10(-4) M) and apamin (5 X 10 (-6) M) suppressed NANC relaxation evoked by electrical field stimulation (EFS) in the presence of atropine and guanethidine (each 10(-6) M) to a similar extent (to about 40% of the initial control). However, combined application of L-NAME (10(-4) M) and apamin (5 X 10(-6) M) did not abolish it. EFS also evoked biphasic inhibitory junction potentials (IJPs) consisting of initial fast and slow sustained components in the presence of atropine and guanethidine (each 10(-6) M). Apamin (5 X 10(-8)-5 X 10(-6) M) dose-dependently suppressed the initial fast component by about 70%. In contrast, L-NAME (10(-4) M) did not affect either the amplitude of IJP or the resting membrane potential. PACAP-38 (> 10(-8) M) dose-dependently hyperpolarized the smooth muscle membrane of rabbit CDJ followed by a slow repolarization to the original level. After pretreatment with apamin (5 X 10(-7) M), PACAP-38 (10(-6) M) failed to evoke membrane hyperpolarization. During repolarization in the continued presence of PACAP-38, the amplitude of initial fast component of IJP was reduced to about 40-60% of control value, while that of the slow one was unaffected. A similar suppression of initial fast component of IJP (about 40% of the control value) also occurred after application of PACAP (6-38), a PACAP antagonist, or prolonged treatment with monoclonal antibodies to PACAP-27 or PACAP-38. Furthermore, the substantial part of residual fast IJP in the presence of PACAP (6-38) was suppressed by desensitization to alpha,beta-methylene ATP (10(-3) M). These results indicate that in rabbit CDJ NANC relaxation consists mainly of apamin- and L-NAME-sensitive components, which occur in a membrane potential dependent (through membrane hyperpolarization) and independent fashion, respectively. It has further been suggested that PACAP, together with a smaller contribution of ATP, may be involved as the principal apamin-sensitive transmitter in NANC relaxation of this muscle.

Gallbladder emptying and cholecystokinin and pancreatic polypeptide responses to a liquid meal in patients with diabetes mellitus

To investigate gallbladder motility and its regulation in patients with diabetes mellitus (DM), we examined the gallbladder response to an intraduodenal test meal by measuring the temporal course of plasma cholecystokinin (CCK) and pancreatic polypeptide (PP) levels. Eighteen patients with type 2 DM and 7 healthy subjects (controls) were enrolled. The gallbladder volume was calculated by the sum-of-cylinders method from ultrasonographic images, and plasma CCK and PP were measured by radioimmunoassays. No significant difference was found in either the gallbladder response or in the CCK response between patients with DM and controls. However, the fasting plasma PP level of patients with DM was more than tenfold higher than that of controls. The integrated PP response (IPPR) of patients with DM to the test meal was 8.3-fold higher than that of controls. When patients with DM were grouped according to whether they had been treated with insulin or not, the fasting plasma PP of patients with DM without insulin treatment was significantly higher than the level in those treated with insulin. These results suggest that overproduction of PP-like immunoreactive substance(s) may occur in patients with DM, but the high plasma PP immunoreactivity does not appear to be related to the fasting gallbladder volume or to gallbladder emptying and filling.

Nerve-mediated contractile and electrical activity of the guinea-pig choledocho-duodenal junction

The intrinsic motor innervation of the guinea-pig choledocho-duodenal junction was investigated by recording the contractile and intracellular electrical activity of smooth muscle from different regions of this tissue. Electrical transmural nerve stimulation evoked phasic contractions in rings of muscle from the ampulla (0.45 s-1) and tonic contractions in rings of muscle from the choledochal sphincter. Intracellular microelectrode recordings from muscle strips from these two regions revealed that excitatory junction potentials (peak amplitude 7 mV) evoked by transmural nerve stimulation were more conspicuous in muscle strips from the choledochal sphincter, but inhibitory junction potentials (peak amplitude 13 mV) were of larger amplitude in muscle strips from the ampulla. Contractions and membrane depolarization evoked by transmural nerve stimulation were sensitive to 1.4 microM atropine and abolished by 3.1 microM tetrodotoxin. Histological studies on the choledocho-duodenal junction also revealed that the distribution of smooth muscle was non-uniform along the tissue. These results suggest that the two regions may have different functions in the motility of the choledocho-duodenal junction.

Long term haemodynamic, pulmonary function and symptomatic effects of pirbuterol in COPD

Haemodynamic studies at rest and during exercise together with radionuclide ventriculography, pulmonary function and clinical well-being assessment were evaluated in ten patients with COPD and secondary pulmonary hypertension (mean PAP 25 mm Hg), before and after 6 months therapy with pirbuterol 20 mg thrice daily. Despite the continued pharmacological action of pirbuterol on the heart and systemic circulation during peak pirbuterol levels at 6 months, no significant effect on the pulmonary circulation was observed. Seven patients reported an improvement in the level of fatigue, the partial pressure of carbon dioxide fell significantly (6.5 +/- 0.9 to 6.1 +/- 0.9 kPa: P less than 0.01) and there was a slight bronchodilator effect [forced expiratory volume in 1s (FEV1) 0.60 +/- 0.18 to 0.71 +/- 0.2 1s-1: P less than 0.02] after 6 months. The drug was generally well tolerated but three patients with pre-existing biliary tract disease developed obstructive jaundice.