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R S Schmidt

Publications and source records attributed to R S Schmidt.

At least 19 recordsLinked to original sources
PubMed1993

Anuran calling circuits: inhibition of pretrigeminal nucleus by prostaglandin.

Neural correlates of mating calling and pulmonary respiration were recorded from isolated brain stems of male Northern leopard frogs (Rana p. pipiens) before and after exposure of the brain stems to prostaglandin F2 alpha (PG) or saline. Diffusion of PG (but not saline) from a pipette directly over the pretrigeminal nuclei abolished "calling" temporarily. Similar application of PG nearby had no effect. Exposure of only the anterior 1/2 of the brain stem, containing the pretrigeminal nuclei but not the pulmonary respiration generator, to PG (but not saline) abolished generation of slow waves by the pretrigeminal nucleus portion of the mating calling pattern generator. Exposure of only the posterior 1/2 of the brain stem, containing the pulmonary respiration generator but not the pretrigeminal nuclei, to PG had no effect on the correlates of pulmonary respiration. These results are consistent with the hypothesis that the inhibition of calling by PG is through an effect largely, perhaps exclusively, on the pretrigeminal nuclei.

Animals↗
PubMed1992

Neural correlates of frog calling: production by two semi-independent generators.

The anterior preoptic nuclei of the isolated brainstem of male, Northern leopard frogs (Rana p. pipiens) were stimulated electrically and neural correlates of mating calling recorded from the rhombencephalic mating calling pattern generator. Lesions of discrete areas of the brainstem showed that the mating calling generator is separable into two generators, the pretrigeminal nucleus and the classical pulmonary respiration generator (which is approximately co-extensive with the motor nuclei IX-X). Each of these still can produce pulses when isolated from the other. Their interaction changes the expiratory phase of breathing into the vocal phase of calling. All stages of intermediates between these phases could be seen. An updated and simplified model of call production and evolution is presented.

Animal Communication↗
PubMed1990

Origin of anuran calling: description of toad releasing.

Electromyographic electrodes were implanted in forelimb muscles of male American toads (Bufo americanus). Toads then were allowed to clasp an artificial clasp object incorporating a pair of solenoids that, when activated, produced a stimulus simulating the side vibrations normally associated with release signalling by conspecific males. Electromyographic activity, in response to the release stimulus, was recorded. The adductor muscle contracted immediately after stimulus onset (causing intensified clasping), responding to the stimulus as a displacement threat. Then the abductor muscle contracted (causing rapid unclasping, or releasing), responding to the stimulus as a release signal. These techniques have provided a better understanding of releasing than has been possible with natural objects (i.e., living males).

Animal Communication↗
PubMed1990

Releasing (unclasping) in male American toads: a neural substrate in the lateral subtoral tegmentum.

Release signals (chirps and side vibrations) are given by a male toad being clasped by another toad. These signals trigger immediate releasing (i.e. unclasping) by the clasping toad. First, small electrolytic lesions in the lateral subtoral tegmentum of male American toads abolished releasing, i.e. these toads persisted in clasping release-signaling males. Second, stimulation of this area caused bilateral abduction of the forelimbs, as occurs in normal releasing. Third, neural responses, resulting from tactile stimulation of either thumbpad, could be recorded from this region. Supposedly, similar stimuli would be generated by the release vibrations of the sides given by a male being clasped. These data are consistent with the participation of the lateral subtoral tegmentum in the detection of release signals and in the triggering of releasing. Release signaling was probably an important step in the evolution of anuran vocalizations. The midbrain tegmentum may contain primitive circuits for the detection of stimuli eliciting anuran acoustic behaviors.

Animals↗
PubMed1989

Anuran mating calling circuits: inhibition by prostaglandin.

Male American toads (Bufo americanus) were induced to mating call in response to electronically simulated, conspecific mating calls. The injection of prostaglandin (PG) F2 alpha caused suppression of mating call answering. Neural correlates of mating calling were triggered by electrical stimulation of the anterior preoptic nucleus in the isolated brainstem of male, Northern leopard frogs (Rana p. pipiens). The addition of PGF2 alpha to the bath completely abolished the correlates of mating calling without changing the correlates of pulmonary respiration. The suppression of mating calling shown here, along with the suppression of release signalling described by Diakow and Nemiroff (1981), supports the hypothesis of a close interrelation between the neural circuits of these two calls. The suppression of the neural correlates of mating calling in an isolated preparation shows a central site of action of the PG. The retention of normal correlates of pulmonary respiration, even after suppression of mating calling correlates, suggests that the generation of mating calling patterns involves the extension and pulsing of the expiratory phase of breathing.

Animals↗
PubMed1989

Mating call phonotaxis in female American toad: lesions of anterior preoptic nucleus.

Lesions of the preoptic area and immediately adjacent septal area were made in female American toads, Bufo americanus. The ability to show mating call phonotaxis (MCP) was then tested for. The intensity of MCP was found to decrease as the degree of damage to the anterior tip of the anterior preoptic nucleus (APON) increased. The APON is known to concentrate androgens and to be essential for mating calling by male anurans. Perhaps the APON is involved also in the detection of the elevated levels of prostaglandin associated with MCP. Even in lesioned toads in which phonotaxis was nearly absent, there was an occasional MCP response that seemed entirely normal. Therefore, the APON is not involved in generating or guiding the motor mechanisms of phonotaxis.

Animals↗
PubMed1988

Mating call phonotaxis in female American toads: lesions of central auditory system.

Female American toads were tested for mating call phonotaxis (prostaglandin-induced) after brain lesions. The pretrigeminal nucleus, all of the telencephalon (except the preoptic area and immediately adjacent septal area), the dorsal thalamus (including all of the anterior nuclei and most of the central nuclei), the optic tectum, and the dorsal and medial parts of the torus were removed without interferring with the hormonal sensitization, acoustic triggering, or production of phonotaxis. These lesions removed most of the forebrain and much of the midbrain auditory areas. These data are compared with similar lesion data on the triggering mechanisms for three other anuran acoustic behaviors. The lateral subtoral tegmentum may have a basic, special importance in the triggering of all four behaviours.

Animals↗
PubMed1984

Mating call phonotaxis in the female American toad: induction by hormones.

Gravid, female American toads are known to move toward conspecific mating calls. This behavior, as well as ovulation, often can be induced by the injection of human chorionic gonadotropin (HCG). It was found that HCG-induced phonotaxis could be terminated by the injection of indomethacin (an inhibitor of prostaglandin synthesis) and then reinstated by the injection of prostaglandin F2 alpha. A drug regimen was devised that allowed elicitation of phonotaxis, indistinguishable from that induced by HCG and in the absence of ovulation. This involved the administration of prostaglandin F2 alpha and arginine vasotocin (or mesotocin) following progesterone priming. It has not been determined whether the peptide is really essential.

Abdominal Muscles↗
PubMed1983

Neural correlates of frog calling. Masculinization by androgens.

Neural correlates of mating calling can be recorded from isolated brainstems of male, Northern leopard frogs after the circuits for this behavior have been triggered by electrical stimulation of the preoptic area. Correlates can be evoked reliably and by a stimulus of low amplitude. However, such correlates can be evoked only rarely from female brainstems, and then only by a much larger stimulus. The sensitivity to triggering in female brainstems can be masculinized by previous treatment of the intact frog with testosterone propionate or dihydrotestosterone, but not by estradiol benzoate. This suggests that the action of the androgens is direct and does not require aromatization to estrogens. Comparisons with other studies suggest that the androgen effect may be mainly on posterior parts of the calling circuits (i.e., call pattern generator or motoneurons), rather than on the preoptic area trigger of the generator.

Androgens↗
PubMed1982

Masculinization of toad pretrigeminal nucleus by androgens.

The magnocellular portion of the pretrigeminal nucleus (a structure involved in vocalization) of male toads contains large cells than does the female nucleus. Testosterone propionate injections caused essentially complete, and dihydrotestosterone injections incomplete, mascullinization of the female nucleus. Estradiol benzoate injections had little or no effect. The androgen effects are therefore largely direct rather than involving extensive aromatization of androgen to estrogen.

Animals↗
PubMed1982

Sexual dimorphism in succinic dehydrogenase staining of toad pretrigeminal nucleus.

The anuran (toad and frog) pretrigeminal nucleus is probably involved in the production of vocalizations, including the male mating call. This nucleus is especially obvious when stained by the succinic dehydrogenase method. In the American toad, a striking sexual dimorphism is shown by such staining. The male nucleus contains numerous, large cells that stain intensely. Such cells are smaller and infrequent in females.

Animals↗
PubMed1980

Catecholaminergic neurons of treefrog isthmotrigeminal tegmentum.

Neurons that take up 3H-noradrenaline were detected, by autoradiography, around the ventral tip of the isthmic nucleus in treefrogs. No uptake was detected in the adjacent pretrigeminal nucleus, suggesting that this is not homologous to the locus coeruleus.

Animals↗