Acta biologica Academiae Scientiarum Hungaricae最新文献

The serotoninergic neuron system of the midbrain and hypothalamus was previously shown to inhibit the basal secretion of the TRH-TSH-thyroid axis. The aim of the present study was to investigate the influence of the serotoninergic system on the TSH response of the adenohypophysis to specific loads. Serum TSH levels were determined 7 days after thyroidectomy or the beginning of thiouracil administration. Animals were simultaneously treated either by intrahypothalamic implantation of serotonin-containing needles or by intraventricular or daily subcutaneous injections of the same drug. The thiouracil-induced goitre formation and increase in serum TSH concentration were significantly diminished by serotonin treatment. Similarly, the thyroidectomy-induced rapid rise in TSH blood level was also remarkably inhibited in the serotonin-treated animals. Serotonin was proved to influence rather TRH-output than pituitary TSH secretion, since exogenous TRH, injected to serotonin-pretreated animals had the same TSH-mobilizing potency as found in the not premedicated group. It is concluded that besides the inhibition of the basal secretion of the TRH-TSH-thyroid axis by serotonin, there is an integrative role of the serotoninergic system in the mediation of the reactivity of this circuit in reply to specific influences loading pituitary-thyroid function.

Nausea of vestibular origin can be used instead of poisoning in the conditioned taste aversion (CTA) paradigm. In an attempt to establish the forms of vestibular stimulation best suited for inducing CTA in rats, effectiveness of 2 h rotation (Exp. 1) was compared with tonal asymmetry elicited by unilateral microinjection of 5.0 microliters of 25% KCl into the vestibular complex (Exp. 2), by unilateral electrical stimulation of vestibular nuclei (100 Hz, 1 ms, 100-200 microA, 15 min--Exp. 3) or by 10 min polarization of labyrinth through electrodes inserted in the external auditory meati (Exp. 4). Nystagmus, deviation of the head and leaning towards the blocked and away from the stimulated side were typical symptoms. When the above stimuli were applied within 10 min after saccharin drinking, galvanic stimulation was ineffective, but electrical stimulation or chemical blockade of vestibular nuclei elicited marked CTA to saccharin, considerably stronger than CTA induced by rotation. It is concluded that direct interference with the activity of vestibular nuclei elicits CTA more effectively than the stimulation of the labyrinth and is, therefore, well suited for the analytical research into the mechanisms of CTA.

Synapse is the most common and generally accepted structural basis for the interaction between neurons. It provides a "one-to-one" communication system between neurons. However, there is another possibility for interneuronal communication: when one neuron communicates with many others without making synaptic contact. In the past few years neurochemical, morphological and pharmacological evidence has been obtained that some neurotransmitters may be released from non-synaptic sites, for diffusion to target cells more distant than those seen in conventional synaptic transmission. The non-synaptic interneuronal communication between neurons plays a physiological role in the presynaptic modulation of chemical neurotransmission. This would be a transitional form between the classical neurotransmission and the broadcasting of neuroendocrine secretion.

Dorsal root fibers were labelled with cobalt and their terminals were identified in an oval-shaped area and in its lateral extension of the dorsal horn. These areas receive mainly cutaneous afferents. A number of labelled terminals exhibited either an electron lucent and swollen, or an electron dense and shrunken form of degeneration. The majority of the labelled terminals could be classified into three groups. Type A terminals were small, less than 2 microns in diameter, and lightly stained. Type B terminals were larger and neurofilaments and an electron dense material resulted in a dark staining of the bouton. Type C terminals contained medium size granulated vesicles. The type A and type B terminals were frequently found in postsynaptic positions. The presynaptic profiles contained spheric or elliptic vesicles, or they exhibited the structural characters of presynaptic dendrites. Preterminal dorsal root fibers, identified on account of their cobalt label, were also found in postsynaptic positions to the same kinds of presynaptic profiles. It is concluded that cobalt labelling is sufficiently selective for a reliable identification of dorsal root terminals. No correlation was found between the different forms of degeneration and the different types of terminal boutons. The possible functional significance of the postsynaptic relation of dorsal root fibers and terminals to a variety of presynaptic profiles is discussed.

If applied locally around a peripheral sensory nerve, Formyl-Leurosin, a semi-synthetic diindol alkaloid of Vinca rosea--that, just like other mitotic spindle inhibitors, induces blockade of axoplasmic transport via inhibiting microtubular function--causes transganglionic degenerative atrophy of central terminals of primary nociceptive neurons in the substantia gelatinosa Rolandi of the spinal cord. In contrast, if applied to dorsal roots, Formyl-Leurosin fails to induce such alterations. Based upon these observations it is postulated that blockade of retrograde axoplasmic transport, rather than that of the orthograde one, is the decisive factor in the pathomechanism of transganglionic degenerative atrophy.

Incorporation of 3H-uridine by RNA in Tetrahymena was differently influenced by insulin, glucagon, follicle-stimulating hormone (FSH), thyrotropic hormone (TSH), adrenocorticotropic hormone (ACTH) and chorion-gonadotropic hormone (PMSG). TSH caused it to increase considerably and durably after an initial depression, while glucagon caused it to rise over the control throughout. Insulin, and especially PMSG, depressed the incorporation of label considerably, the latter to 3-6% of the control value by 120 min. ACTH and FSH accounted for an initial depression of RNA synthesis which, however, returned to normal 30 min after treatment. Remarkably, while the chemically similar hormones acted differently, insulin and glucagon showed the same trend of positive and negative influence, respectively.