Effects of reducing submandibular blood flow on secretory responses to parasympathetic stimulation in anaesthetized cats.
Submandibular secretory responses to stimulation of the parasympathetic chorda-lingual nerve were investigated in five anaesthetized cats before, during and after withdrawal of blood (ca 20 ml kg-1) in order to investigate the consequences of a reduced blood flow through the gland. Stimulation at different frequencies (2, 4, 6 and 8 Hz) evoked a frequency-dependent increase in the flow of submandibular saliva, sodium concentration, electrolyte and protein output. When the blood pressure was reduced (by about 50%) there was a significant reduction in submandibular blood flow and the secretion of both saliva and protein during stimulation. Under each set of conditions the flow of saliva was linearly related to the blood flow through the gland. It is concluded that submandibular secretory responses to electrical stimulation of the parasympathetic innervation can be significantly attenuated when the blood flow through the gland is reduced under the conditions employed in this study. (+info)
P2X purinoceptor-mediated excitation of trigeminal lingual nerve terminals in an in vitro intra-arterially perfused rat tongue preparation.
A novel in vitro intra-arterially perfused adult rat tongue-nerve preparation was used to explore the possible actions of P2X purinoceptor agonists (ATP and alpha,beta-methylene ATP (alpha, beta-meATP)) on sensory nerve terminals innervating the rat tongue. We made whole-nerve recordings of the trigeminal branch of the lingual nerve (LN), which conducts general sensory information (pain, temperature, touch, etc.), and the chorda tympani (CT), which conducts taste information. Changes in LN and CT activity following intra-arterial application of P2X agonists were compared. In seven preparations, bolus close-arterial injection of ATP (30-3000 microM, 0.1 ml) or alpha,beta-meATP (10-300 microM, 0.1 ml) induced a rapid (< 1 s after injection), dose-related increase in LN activity that decayed within a few seconds. The minimal concentration of ATP (100 microM) required to elicit a response was about 10-fold higher than that of alpha,beta-meATP (10 microM). Bolus injection of ATP or alpha,beta-meATP induced a moderate decrease in firing frequency in three of seven CT preparations. LN responses to P2X agonists showed signs of rapid desensitisation with the peak frequency of discharge being smaller when the agonists were applied at short intervals. Suramin (200 microM) or PPADS (200 microM) applied by intra-arterial perfusion each antagonised the rapid increase in LN activity following application of alpha,beta-meATP (100 microM). Capsaicin (10 microM, 0.1 ml, n = 5 preparations) was injected intra-arterially to desensitise nociceptive fibres. This was found to block (n = 2) or greatly reduce (n = 3) the excitatory effects of alpha,beta-meATP (100 microM, 0.1 ml) on LN activity, implying that only capsaicin-sensitive nociceptive fibres in LN were responsive to P2X agonists. In contrast to the consistent excitatory responses in LN activity following fast application of P2X agonists as bolus, a variable and moderate change in discharge rate of LN and no change in CT activity (n = 5) was observed after applying ATP (100-300 microM, n = 21) or alpha,beta-meATP (100-300 microM, n = 14) by intra-arterial perfusion. The variable responses in LN activity to slow perfusion in contrast to close-arterial bolus injection are consistent with activation of the rapidly desensitising P2X3 receptors. In summary, ATP and alpha,beta-meATP preferentially activate general sensory afferent fibres (LN) but not taste fibres (CT). We suggest that the increase in whole-nerve activity of LN following application of P2X agonists represents activation of nociceptive fibres which possess P2X3 receptors. Our data indicate that ATP and P2X3 receptors may play a role in nociception, rather than taste sensation in the tongue. (+info)
Enhancement of gustatory neural response to salts following adaptation of frog tongue to quinine-HCI.
After a frog tongue was adapted to 0.001 M quinine-HCl(Q-HCl), a change in the gustatory neural responses to salts was investigated. The initial phasic response to a variety of salt solutions such as 0.1 M NaCl, KCl, LiCl, MgCl2 and CaCl2 was greatly potentiated as a result of the Q-HCl adaptation. A weaker enhancement of the response to salts was observed after the tongue was adapted to deionized water, compared with the control response to salts during Ringer adaptation. Therefore, the Q-HCl-induced enhancement of salt responses is due to the summated effect of Q-HCl solute and water solvent. Concerning the enhancing mechanism of Q-HCl, it is postulated that the membrane potential of some salt-sensitive taste cells will be displaced in the hyperpolarizing direction during the Q-HCl adaptation, and that large depolarization, which may be related to the enhanced nerve response, will be produced by applying salts after Q-HCl. (+info)
Submandibular secretory and vascular responses to stimulation of the parasympathetic innervation in anesthetized cats.
Submandibular secretory responses to stimulation of the parasympathetic chorda-lingual nerve in anaesthetized cats have been investigated before, during, and after intracarotid infusion of endothelin-1 (ET-1), which reduced blood flow through the gland by 64+/-7%. Stimulation at different frequencies (2, 4, 8, and 16 Hz) evoked a frequency-dependent increase in the flow of submandibular saliva, sodium concentration and output, and output of both potassium and protein. The reduction in submandibular blood flow, which occurred in response to the infusion of ET-1, was associated with a decreased flow of saliva and a diminished output of both sodium and protein. The flow of saliva was linearly related to submandibular blood flow both in the presence and absence of ET-1. It is concluded that submandibular secretory responses to electrical stimulation of the parasympathetic innervation can be significantly attenuated by reducing the blood flow through the gland by ET-1 infusion, just as it is when the blood flow is reduced by hypotension. (+info)
Two phases of chorda-lingual induced vasodilatation in the cat's submandibular gland during prolonged perfusion with Locke solution.
The effect of stimulation of the chorda-lingual nerve on the venous flow has been studied in cat submandibular glands perfused with Locke solution for 2-4 hr. When trains of pulses at 25 Hz were given for 1-5 sec, two distinct phases of vasodilatation were observed: a rapid initial phase of high amplitude and a slower developing more prolonged phase of smaller amplitude. Repeated stimulations did not lead to a reduction of the vasodilatory response. A close relationship was found between the duration and magnitude of the second phase of vasodilatation and the duration and magnitude of the post-stimulatory, active reuptake of potassium. When the active reuptake of potassium was prevented either by ouabain (which inhibits active transport) or by atropine (which abolishes the stimulation induced loss of potassium) the second phase of vasodilatation was severely reduced, while the initial phase remained virtually normal. It is concluded that the initial phase of vasodilatation probably is mediated by vasodilator nerve fibres. The second phase is perhaps causally related to the post-stimulatory, active transport of cations. An involvement of bradykinin formation is highly unlikely under the given experimental conditions. (+info)
Oral and pharyngeal reflexes in the mammalian nervous system: their diverse range in complexity and the pivotal role of the tongue.
The oral cavity and pharynx are anatomically separate but functionally integrated regions of the head. The two regions are involved in complex motor responses that include feeding, chewing, swallowing, speech, and respiration. The multiple sensory receptors that innervate these two regions provide the first link in reflexes that control muscles of the entire head, upper gastrointestinal tract, and airway. Most of the reflexes affect the diversity of muscles that compose the tongue, which is vital to all stages of feeding and which continually affects the patency of the airway. Oral-pharyngeal reflexes are evident in the mammalian fetus and continually emerge as the animal or human matures. Some of the first reflexes in the oral region are geared toward nourishment. As the central nervous system matures and the oral and pharyngeal regions develop morphologically, new reflexes develop. Many of these reflexes are protective both of the tissue in the oral cavity, such as the tongue, and of the upper airway in preventing aspiration. While simple reflexes can be evoked in isolation, most reflexes combine with more complex oral and pharyngeal responses such as chewing and vocalization. Oral-pharyngeal reflexes demonstrate a range in complexity. Some sensory stimuli will evoke a series of responses, as is often evident in the infant, and other stimuli will evoke a complex multiple-level recruitment of muscles in a sequence, as in pharyngeal swallowing. Certain sensory inputs evoke an entire motor behavior pattern, such as taste avoidance or facial expression. The oral-pharyngeal reflexes are critical to maintaining life and ultimately serve functions that the oral and pharyngeal regions have in common, such as communication, feeding, and breathing. (+info)
Effects of prolonged reduction in blood flow on submandibular secretory function in anesthetized sheep.
Submandibular vascular and secretory responses to parasympathetic chorda-lingual (C-L) stimulation were investigated in anesthetized sheep before, during, and after an intracarotid (ic) infusion of endothelin-1 (ET-1). Stimulation of the peripheral end of the C-L nerve at 4 and 8 Hz produced a frequency-dependent reduction in submandibular vascular resistance (SVR) associated with a frequency-dependent increase in submandibular blood flow, salivary flow, and Na+, K+, and protein output from the gland. During stimulation at 4 Hz, ic ET-1 significantly increased SVR (P < 0.01), without significantly affecting either the aortic blood pressure or heart rate. Submandibular blood flow (SBF) was reduced by 48 +/- 4% and the flow of saliva by 50 +/- 1%. The effect on blood and salivary flow persisted for at least 30 min after the infusion of ET-1. The reduction in SBF was associated with a diminution in the output of Na+,K+, and protein in the saliva (P < 0.01). These effects persisted for 30 min after the infusion of ET-1 had been discontinued and were linearly related to the flow of plasma throughout. (+info)
Branch of mylohyoid and lingual nerves on submandibular and submental triangles.
The mylohyoid nerve (MN) displays several branches in the posterior, intermediate, and anterior region of the mylohyoid muscle (MM) as it courses on the internal surface of the mandibular body. Branches in the intermediate region were found in 66% of the cases (272 out of 413 sides). In the submandibular triangle, one or two large branches of the MN communicated with the lingual nerve at submandibular triangle and submental triangle in 1.45% of the cases (6 out of 413 sides). These distributions of nerve supply are an important in the operations of radical neck dissection on the submandibular triangle. (+info)