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The effects of morphine on the release of noradrenaline from the mouse vas deferens
Abstract:
Electrical field stimulation of the mouse vas deferens (TO and C57/BL strains) caused the release of noradrenaline into the bathing medium. 2 Phenoxybenzamine (30 muM) or phentolamine (36 muM) plus cocaine (13 muM) caused a considerable increase in the noradrenaline output. 3 In the vasa deferentia from TO mice the output per pulse of noradrenaline was constant at frequencies of stimulation from 0.5 to 15 Hz whereas in the vasa deferentia from C57/BL mice the output per pulse of noradrenaline increased two-fold from 1.5 to 15 Hz. 4 Morphine (2 muM) inhibited the contractions of the vasa deferentia from TO mice. This effect was greater at low (0.1-1 Hz) than at high (10 Hz) frequencies of stimulation. Morphine (2 muM) did not inhibit the response of the tissue to exogenous noradrenaline. 5 Morphine (1 muM) reduced the noradrenaline output from the vasa deferentia of TO mice stimulated at 1.5 Hz but did not reduce the noradrenaline output at 15 Hz. At 1.5 Hz the reduction of noradrenaline output was reversed by naloxone (0.05 muM). 6 Morphine (5 muM) did not inhibit the uptake of [3H]-noradrenaline into the vasa deferentia from TO mice. 7 Only in high concentrations (ID50 30.88 muM) did morphine inhibit the contractions of the vasa deferentia from C57/BL mice. 8 Normorphine (100 muM) did not reduce the noradrenaline output from vasa deferentia of C57/BL mice.
Insights
Electrical stimulation releases noradrenaline from mouse vas deferens. Morphine affects contractions and noradrenaline release differently in TO and C57/BL mice, with naloxone reversing some effects.
Area of Science:
- Neuropharmacology
- Physiology
Background:
- The vas deferens is a key component of the male reproductive system.
- Noradrenaline is a critical neurotransmitter involved in smooth muscle contraction.
Purpose of the Study:
- To investigate the effects of electrical field stimulation on noradrenaline release from mouse vas deferens.
- To examine the modulatory role of morphine and related compounds on vas deferens function and noradrenaline release in different mouse strains.
Main Methods:
- Electrical field stimulation of isolated mouse vasa deferentia (TO and C57/BL strains).
- Measurement of noradrenaline output using biochemical assays.
- Assessment of smooth muscle contractions in response to stimulation and exogenous agonists.
- Pharmacological manipulation using phenoxybenzamine, phentolamine, cocaine, morphine, and naloxone.
Main Results:
- Electrical stimulation released noradrenaline; alpha-adrenergic blockers and cocaine increased output.
- Noradrenaline output per pulse varied with stimulation frequency between TO and C57/BL mice.
- Morphine inhibited contractions in TO mice, particularly at lower frequencies, and reduced noradrenaline release at low frequencies, an effect reversed by naloxone.
- Morphine had minimal effect on C57/BL mouse vas deferens contractions and did not inhibit noradrenaline uptake.
Conclusions:
- Mouse vas deferens releases noradrenaline upon electrical stimulation, with strain-dependent frequency-dependent characteristics.
- Morphine exhibits differential effects on vas deferens contractility and noradrenaline release, suggesting complex interactions with opioid receptors and neurotransmitter systems.
- Naloxone can antagonize morphine-induced inhibition of noradrenaline release, indicating an opioid-mediated mechanism.